It's not clear if those numbers were predicted or actually measured. Small rooms don't really have true reverb, so I'm not sure the same metrics can be applied.

I don't have a lot of personal experience with dipoles, though of course I've heard them. When people used to ask me if they should put absorption on the front wall, I'd always tell them to ask their speaker maker and report back. Finally someone did, and the speaker maker told them that absorption there is good. I don't recall which brand of speaker it was though. Then a few months later I visited a customer with a pair of dipoles, and the speaker maker's rep was there. The rep told me he always recommends front-wall absorption.

If anyone reading this who has dipoles, and is local to me (near Danbury CT), and wants to experiment and run a few tests, send me an email from my company's web site:

www.realtraps.com/contact.htm

Then we can report the results here.

--Ethan


I'd be willing, but I am about 100 miles away from you.

Pitting against what the room may contribute to sound appears very fashionable. Taken to the nth degree then, nothing could be better than listening to headphones or having ones he-man rig set up outdoors. It's the sort of specious logic leading some to advocate extensive absorption, in order that the room may not overlay the intended reverb of, say, a subway station or a concert hall.

Granted, a room will usually have an adverse effect on bass tightness, and hence an area where headphones will trump rooms. All other vilification of the room is largely baloney, in my opinion. Of course a well set up room shouldn't be excessively reverberant or have flutter echo issues. For one, distances in such a room are typically so short that it is unlikely reflections will ever overpower reverberation and reflection cues in recorded material. The psycoacoustic Haas or precedent effect with these shorter reflections may actually enhance accurate musical reproduction. If anything, a room with a good balance of reflective/absorptive/ diffusive or scattering surfaces will flatter the output of competent wide dispersion loudspeakers, be they monopole, dipole or omnipole. This is not so because of a taste that has veered to loudspeaker inaccuracy. A mastering engineer's need for clinical evaluation is not the same as that of the end consumer whose goal is simply the most profound enjoyment. The latter also aims for accuracy. However it is accuracy in the context of a wide polar radiation in a well balanced, somewhat lively room, that imparts the most satisfying and enriching reproduction. The mix engineer may have tweaked all the placement cues expediently and efficaciously, but the full musical glory to realize may be for the end consumer with his stellar dipoles in a sensible, "neutral" room. The contribution of a room in such a scenario does not militate against the intentions of the recording and mastering crew.

Indeed, it's interesting to note what sort of loudspeakers earn the highest accolades by the most respectable writers in audio journalism. (please don't refer to stereophile, or I'll prematurely pop an aneurysm)

http://theaudiocritic.com/blog/index.php?op=ViewArticle&articleId=33&blogId=1

Tumara Baap

Going back to the top of this thread, the following products were listed as good choices for acoustic board:

Owens Corning Select Sound Black Acoustic Board
Owens Corning Fiberglas 703 Series duct insulation.
Johns Manville Insul-Shield
Johns Manville Linacoustic Permacoate rolls.
Certainteed Certpro Acoustaboard Black
Knauf Duct board EI-475
Knauf Duct liner EM

I am hoping someone can suggest where to get one of these products in Canada (Burlington, Ontario area (west end of Toronto)). Failing that, I am willing to drive to Buffalo NY to pick it up. I tried to track down the O/C Black Acoustics board, with no luck.

Thanks.

Going back to the top of this thread, the following products were listed as good choices for acoustic board:

Owens Corning Select Sound Black Acoustic Board
Owens Corning Fiberglas 703 Series duct insulation.
Johns Manville Insul-Shield
Johns Manville Linacoustic Permacoate rolls.
Certainteed Certpro Acoustaboard Black
Knauf Duct board EI-475
Knauf Duct liner EM

I am hoping someone can suggest where to get one of these products in Canada (Burlington, Ontario area (west end of Toronto)). Failing that, I am willing to drive to Buffalo NY to pick it up. I tried to track down the O/C Black Acoustics board, with no luck.

Thanks.



Do a search for Ottawa Fibre - ofigroup.com I think is the site- they have products similar and I read a thread here a few weeks back from someone in TO area that was using it in his home therater.

Also - you can look on bob golds side for the coefficients that compare all products including the ottawa fiber stuff to see how close or how far off it is from the others.

That's what I'm going with if I ever get around to building my theater and not blasting the money on other toys in the meantime......

Lewis

All other vilification of the room is largely baloney, in my opinion. Of course a well set up room shouldn't be excessively reverberant or have flutter echo issues. For one, distances in such a room are typically so short that it is unlikely reflections will ever overpower reverberation and reflection cues in recorded material.

I agree with much of that, but with a few caveats:

Once all of the early reflection points are treated with absorption (or possibly diffusion), other sources of ambience are not particularly damaging. But in the case of dipole speakers, reflections off the front wall are early too. The main problem is not Haas as far as I'm concerned - rather, it's the horribly skewed frequency response from all those separate comb filtering sources.

--Ethan

Of course I'm no expert on this, but I've often wondered why the best dipoles garner the sort of praise they do. What Ethan sees as needless higher frequency SBIR, David Greisinger of Lexicon probably views through the prism of Interaural Cross Correlation and Interaural Time Delay. Maybe the secret to the rich expansive sound of the best dipoles has to do with our binaural hearing mechanism's ability to revel in the chaos of room comb filtering and the brain's skill at extracting sublime beauty out of it. Just a thought.

Tumara Baap

Just thought I'd add no disrespect intended towards any one individual at Stereophile or any other audio medium. I do have a problem with exotic cable sniffing culture. That said I note that the tradition breaking NHT Xd monopole got its due respect in Stereophile. This is a sharp counterpoint to what was meted out to the excellent Paradigm Active 20 a few years ago. Thankfully, there are a few brainy ones who carry their weight around.

Ethan and Tumara,

I see the issue of rear radiation of a dipole speaker as distinct from its directivity. The rear radiation could be absorbed or diffused to eliminate comb filtering, and no change to the front directivity pattern will occur. Of course, it will change the sound to something you may no longer like. :(

In the sweet spot, which is fairly confined for a dipole, the sound will be minimally affected by the room. In fact, it is less affected by the room at low frequencies than a monopole. A benefit of the "figure eight" dipole directivity pattern is that it has zero side radiation, even at lowest frequencies. If you oriented the dipole so that it is aligned with the front-to-back axis of room, there will be no excitation of the widthwise and heightwise axial room modes. This is true to the extent that the speaker is acting as an ideal dipole. And there are dipole subwoofers, too!

Ethan, to better understand dipole speakers in familiar recording studio terms, think "ribbon microphone" (the kind Johnny Carson used throughout his career). This is just a dipole speaker run in reverse! :D In fact, you can make a dipole speaker using a similar ribbon, but it can't move much air so it produces very little bass.

- Terry

Terry,

> Ethan, to better understand dipole speakers in familiar recording studio terms, think "ribbon microphone" <

Indeed, and I already mentioned that in my post #1983 above. :D

Also, to be completely accurate, what you're talking about is a Figure 8 pattern. This is not unique to ribbon microphones.

--Ethan

Maybe the secret to the rich expansive sound of the best dipoles has to do with our binaural hearing mechanism's ability to revel in the chaos of room comb filtering and the brain's skill at extracting sublime beauty out of it.

As one who agrees with Occam, for now I'll stick with comb filtering as the most plausible explanation. :cool:

BTW, comb filtering can be perceived as an improvement in sound quality. If a comb filter null aligns with an "obnoxious" frequency such as the tubby region around 250 Hz or the harsh range around 3 or 4 KHz, the presence of the null might be considered an improvement. Likewise for a comb filter peak that falls on the fullness range around 80 to 120 Hz.

I also mentioned this in the comb filtering video on my company's web site in the context of recording with microphones. Sometimes you'll see recording engineers obsess with tiny changes in microphone placement, especially when recording pianos. I'm convinced this is often a matter of finding peak/null frequencies that complement the instrument more than anything else.

--Ethan

Terry,

> Ethan, to better understand dipole speakers in familiar recording studio terms, think "ribbon microphone" <

Indeed, and I already mentioned that in my post #1983 above. :D

Also, to be completely accurate, what you're talking about is a Figure 8 pattern. This is not unique to ribbon microphones.

--Ethan
Sure, I never meant to imply the a ribbon microphone is the only type which can exhibit a figure eight pattern. Two cardioid capsules facing in opposite directions will do the same. I mentioned a ribbon microphone because it was the first of this type, and has had a long history in professional recording and broadcasting.

As far as I know, figure eight pattern == dipole. I don't think that it is possible to achieve this directivity pattern in any other way.

- Terry

Aren't the "teeth" on a comb filter close together and usually thought of as being at higher frequencies (than 250Hz)? Of are you referring to peaks and nulls in the bass region as being part of the comb?

I don't have 4 solid corners in my room. In a couple I have windows. I won't really need to access these.

Wll bass traps still work well if I have it straddling a room corner and some of it is covering the window?

There are more corners than just vertical room corners. Ceiling to Wall. I want to maximize with the space I have though.

Aren't the "teeth" on a comb filter close together and usually thought of as being at higher frequencies (than 250Hz)? Of are you referring to peaks and nulls in the bass region as being part of the comb?

The higher frequencies are certainly what I had in mind discussing the inaudibility or even positive effects of room comb filtering.

I suppose the "teeth" can show up elsewhere, like the SBIR distortion in bass when a loudspeaker playing full range without a sub is placed a few feet away from the wall behind.

As far as I know, figure eight pattern == dipole. I don't think that it is possible to achieve this directivity pattern in any other way.

A regular cone driver not mounted inside a box?

--Ethan

Aren't the "teeth" on a comb filter close together and usually thought of as being at higher frequencies (than 250Hz)?

Yes, "usually thought of" is the case, but it's not really correct. As TB pointed out, SBIR is also comb filtering. Whatever the cause, comb filtering starts at some low frequency and repeats indefinitely at regular intervals. With acoustic comb filtering caused by reflections, the pattern repeats only at frequencies that are reflected. So for a wall covered with one inch thick 703 the peaks and nulls start low but stop when the 703 kicks in.

--Ethan

A regular cone driver not mounted inside a box?

--Ethan
Correct. That's most easily understood as an acoustic doublet == dipole. There is sound radiating from the front and back with opposite phase.

Here are my completed Bass Traps and Acoustic Panels. I built 2 2'x2'x2" panels for my early reflection points and 2 2'x4'x4" bass traps for my corners. Also I built 1'x2'x2" panels and placed them behind my Left and Right front speakers, those the panels are not covered with fabric yet. Now the traps and the early reflection panels and consist of owens corning 703 fiberglass framed in pine lumber. The back of the panels are covered in black gardening fabric, which does let air pass but very ugly although it was free from my father. The front of the panel and sides are covered in Guilford of Maine fabric. The difference in audio clarity is dramatic. High freq's are tamer. Bass is tighter. And surround affects are more pinpoint. So here are the photos:
http://img243.imageshack.us/img243/4788/img8993lq0.th.jpg (http://img243.imageshack.us/my.php?image=img8993lq0.jpg)http://img81.imageshack.us/img81/4052/img8996bv3.th.jpg (http://img81.imageshack.us/my.php?image=img8996bv3.jpg)http://img85.imageshack.us/img85/3165/cornertrapms3.th.jpg (http://img85.imageshack.us/my.php?image=cornertrapms3.jpg)http://img85.imageshack.us/img85/4732/backpanelzl9.th.jpg (http://img85.imageshack.us/my.php?image=backpanelzl9.jpg)http://img167.imageshack.us/img167/1935/leftpanelbo9.th.jpg (http://img167.imageshack.us/my.php?image=leftpanelbo9.jpg)
Also, you can click my signature for more photos.

Here are my completed Bass Traps and Acoustic Panels. I built 2 2'x2'x2" panels for my early reflection points and 2 2'x4'x4" bass traps for my corners. Also I built 1'x2'x2" panels and placed them behind my Left and Right front speakers, those the panels are not covered with fabric yet. Now the traps and the early reflection panels and consist of owens corning 703 fiberglass framed in pine lumber. The back of the panels are covered in black gardening fabric, which does let air pass but very ugly although it was free from my father. The front of the panel and sides are covered in Guilford of Maine fabric. The difference in audio clarity is dramatic. High freq's are tamer. Bass is tighter. And surround affects are more pinpoint. So here are the photos:
http://img243.imageshack.us/img243/4788/img8993lq0.th.jpg (http://img243.imageshack.us/my.php?image=img8993lq0.jpg)http://img81.imageshack.us/img81/4052/img8996bv3.th.jpg (http://img81.imageshack.us/my.php?image=img8996bv3.jpg)http://img85.imageshack.us/img85/3165/cornertrapms3.th.jpg (http://img85.imageshack.us/my.php?image=cornertrapms3.jpg)http://img85.imageshack.us/img85/4732/backpanelzl9.th.jpg (http://img85.imageshack.us/my.php?image=backpanelzl9.jpg)http://img167.imageshack.us/img167/1935/leftpanelbo9.th.jpg (http://img167.imageshack.us/my.php?image=leftpanelbo9.jpg)
Also, you can click my signature for more photos.

It is kind of hard to see and maybe you did, but are you sure you have the thinner panels in the first reflections? Did you use a mirror to find those spots? The one side panel looks kind if high on the wall.



Glenn

It is kind of hard to see and maybe you did, but are you sure you have the thinner panels in the first reflections? Did you use a mirror to find those spots? The one side panel looks kind if high on the wall.



Glenn
Yes my fronts are high and I did use the mirror trick before and after placing the panels.

It is kind of hard to see and maybe you did, but are you sure you have the thinner panels in the first reflections?
Thinner? I probably missed something along the way here, but isn't thicker better so that first reflection absorption extends as low as possible?

Thinner? I probably missed something along the way here, but isn't thicker better so that first reflection absorption extends as low as possible?
For early lateral reflections which create image shift problems, there is no need to go below 1 kHz. Perceptually, this is a high frequency phenomenon.

- Terry

For early lateral reflections which create image shift problems, there is no need to go below 1 kHz. Perceptually, this is a high frequency phenomenon.

- Terry
Thanks, that makes sense. What about skewing the decay unfavorably toward the upper bass by not using the "opportunity" - no additional HF would be removed - to trap some upper bass?

Thanks, that makes sense. What about skewing the decay unfavorably toward the upper bass by not using the "opportunity" - no additional HF would be removed - to trap some upper bass?
Sure, I never pass up an opportunity to absorb lower frequencies if a room needs it (which a room typically does). Side wall absorbers can do double-duty here. Note that effective treatment of decay times typically requires many square feet of absorption, not just the "spot" absorption necessary to handle early reflections.

- Terry

For early lateral reflections which create image shift problems, there is no need to go below 1 kHz. Perceptually, this is a high frequency phenomenon.

- Terry

Surely there's more to it than just an effect on image shift. Also affected (adversely by absorption) is image size. The thickness would also determine the tonality of what's heard (affected adversely by thinner panels). There may also be reason to believe that absorption smothers important spatial cues.

It increasingly seems to me that absorption seems to have a benefit only when listening to mediocre speakers. The Holy Grail of top performance probably lies in attaining perfection in polar response. What's called for is not only a respectable off-axis performance (and a subsequent absence of absorption for this prowess to be realized), but a darn good robust showing in a loudspeaker's extreme off-axis performance. Very few loudspeakers could pull this off well.

A must reading should be the highly regarded Siegfried Linkwitz' ebullient 2007 update of his pet project:
http://www.linkwitzlab.com/orion++.htm
Also very informative is an older Mix Magazine article summarizing the work of Professor David Moulton at Sausalito Audio Works.
http://www.sawonline.com/wp_mix_article1.shtml

Tumara Baap

Thanks, that makes sense. What about skewing the decay unfavorably toward the upper bass by not using the "opportunity" - no additional HF would be removed - to trap some upper bass?

Sure if you can fit them and afford them, then thicker panels are better. But someone should never think that using thicker panels in the early reflections is going to give enough bass control. I always assume people have plenty of bass trapping in the corners. :D

Glenn

Surely there's more to it than just an effect on image shift. Also affected (adversely by absorption) is image size. The thickness would also determine the tonality of what's heard (affected adversely by thinner panels). There may also be reason to believe that absorption smothers important spatial cues.

It increasingly seems to me that absorption seems to have a benefit only when listening to mediocre speakers. The Holy Grail of top performance probably lies in attaining perfection in polar response. What's called for is not only a respectable off-axis performance (and a subsequent absence of absorption for this prowess to be realized), but a darn good robust showing in a loudspeaker's extreme off-axis performance. Very few loudspeakers could pull this off well.

A must reading should be the highly regarded Siegfried Linkwitz' ebullient 2007 update of his pet project:
http://www.linkwitzlab.com/orion++.htm
Also very informative is an older Mix Magazine article summarizing the work of Professor David Moulton at Sausalito Audio Works.
http://www.sawonline.com/wp_mix_article1.shtml

Tumara Baap
This is the Dedicated Theater Design and Construction area, so we should take a cue from that. It is important to remember that any Holy Grail is for a specific ideal listening purpose: 2 channel music, for example. Choose another purpose, and you get a different Grail, and potentially, a completely different engineering solution.

Another must read, and a good example of this, is everything at the ambiophonics site:
http://www.ambiophonics.org

It comes to a very different conclusion regarding speaker polar response and the use of room treatments. Its rooms are deader than home theaters, and its speakers directional criteria are not the polar response, at least in the normal sense. Compared to other approaches to sound reproduction (high-end two channel music, livish room; high-end movie surround sound, deadish room), it is completely sideways. But its purpose is to create an extremely realistic spacial music experience for a single listener only. And it only needs two channels of source material (old stereo recordings) to do this!

- Terry

I need advice:

As you can see in this picture, I have three cabinet cavities across the planned screen wall and one on the front of the right wall. The right front corner (where the TV hole is now) is going to be squared off. The cabinets are going away. The screen will be flush with that wall.

http://www.meyerzone.net/meyerht/pics/DSC_8306.JPG

Options:

a) remove the cabinets completely and drywall the wall.

b) remove the cabinet fronts and leave them flush to the wall. Fill them with cotton or 703. They'll be covered by GOM or equivalent when I treat my front wall. Essentially free bass traps in non-ideal positions. No implication that they would be the only bass traps (I'm still looking at soffit and corner possibilities).

General plan for now is dead front wall, first reflections left and right, carpet. I'm using CARA to model how much further absorption/diffusion I'll need.

Thoughts?

Paul Meyer
Bee Cave, TX

(see MeyerHT (http://www.meyerzone.net/meyerht/) for more pictures and details of my project)

I am thoroughly enjoying the discourse between TumaraBaap and Terry Montlick. Having waded through the Toole paper so graciously provided by the former, I know from where he comes.

Absolutely not to take anything away from Dr Toole, but I still need to reconcile his direction - he didn't present it as a conclusion - on absorption with my own senses. And my senses tell me that reducing/eliminating the first (and strongest) reflections will improve imaging. I know that when I added my absorbers (2" OC SelectSound Black) to the first reflection points, I achieved nearfield listening vis-a-vis the LCR speakers at my main seating positions. How can anything be better than nearfield listening? How can letting the room affect what the artist/engineer/producer mixed be better?

pepar,

Again, I think the consequences of side reflections with regard to imaging are dependent upon the specific purpose of the reproduction. Is it for multichannel home theater, for which there are reference theaters which one would like to match? Or is it for conventional stereophonic playback, which has no such reference environments?

Indeed, for the latter, side reflections can be beneficial if done properly, as they can widen the front sound stage (which was Tumara Baap's point). This sense of widening can be accomplished without image shifting or smearing if you play by the correct psychoacoustic rules. This means that the reflections should be below the threshold for such shifting or smearing, but still be audible. Side wall diffusers -- rather than absorbers -- can work very well for this purpose.

- Terry

...although, Floyd Toole's recent work suggests that the choice of diffusion and absorption (quantity and type) should be dependent upon the quality of the off axis response of the speakers.

pepar,

Again, I think the consequences of side reflections with regard to imaging are dependent upon the specific purpose of the reproduction. Is it for multichannel home theater, for which there are reference theaters which one would like to match? Or is it for conventional stereophonic playback, which has no such reference environments?
My multi-channel home theater match a reference theater? Nah, that's not my goal. I think a good home theater goes way beyond any "movie theater." If I'm in the nearfield of "proper" speakers - I'm basically using what a lot of studios use (M&K 150s) - then I'm hearing exactly what the mixdown team did. Am I missing something? How is this not As Good As It Gets?

I am thoroughly enjoying the discourse between TumaraBaap and Terry Montlick.

Of course, I'm merely a health professional. Terry is an acoustician. I seek concepts and answers from other audio professionals, and largely base my own beliefs on their credibility. I listen to a 7.1 channel system with wide dispersion active loudspeakers myself but otherwise have very limited exposure to the best systems. Frankly, I doubt I'll have the time to fully peruse through extensive links as the one provided by Terry (gracias by the way...will check it out). I don't always have an answer for the ever inquisitive Honcho of this thread either ;-) So take what I have to say with a grain of salt.

However, my thoughts on this: If a Theater/Music enthusiast wants to choose seven wide dispersion loudspeakers such as the NHT Xd over the ample competition, design a room with broadband absorption on the center portion of the backwall and ceiling, go with extensive bass trapping, and otherwise eschew the thin panel absorption elsewhere that seems to be the acoustic norm, it would indeed be a stride taken with the grail in mind. I concede that with multi channel systems, one can get away with directional loudspeakers or poor loudspeakers plus lots of early reflection absorption. The more the channels, the more the leeway with that approach. But that doesn't amount to respective stereo and muli-channel speaker/room systems being at an absolute tangent in their quest for perfection. In that vein proprietary 10 channel surround formats such as by Audyssey try to make up for the dearth of reflection cues in a 5.1 or 7.1 channel formats, especially the front soundstage. Linkwitz' system, already enriched with sonic energy from the front soundstage thanks to its inherent dipole design with excellent polar radiation raises the bar with four wide dispersion omnipoles utilizing a surround format similar to Chesky's six speaker setup. Granted the role of reflections in a multi channel system are far from established. But there seems nothing incompatible with an *accurate* wide dispersion loudspeaker system/lively room combo and multi channel formats either. The NHT Xd owner just might as well be making a precocious move to reference systems of the future based on such central ideas...
Tumara Baap

Am I missing something? How is this not As Good As It Gets?
Yup. Room size.

Of course, I'm merely a health professional. Terry is an acoustician. I seek concepts and answers from other audio professionals, and largely base my own beliefs on their credibility. I listen to a 7.1 channel system with wide dispersion active loudspeakers myself but otherwise have very limited exposure to the best systems. Frankly, I doubt I'll have the time to fully peruse through extensive links as the one provided by Terry (gracias by the way...will check it out). I don't always have an answer for the ever inquisitive Honcho of this thread either ;-) So take what I have to say with a grain of salt.

However, my thoughts on this: If a Theater/Music enthusiast wants to choose seven wide dispersion loudspeakers such as the NHT Xd over the ample competition, design a room with broadband absorption on the center portion of the backwall and ceiling, go with extensive bass trapping, and otherwise eschew the thin panel absorption elsewhere that seems to be the acoustic norm, it would indeed be a stride taken with the grail in mind. I concede that with multi channel systems, one can get away with directional loudspeakers or poor loudspeakers plus lots of early reflection absorption. The more the channels, the more the leeway with that approach. But that doesn't amount to respective stereo and muli-channel speaker/room systems being at an absolute tangent in their quest for perfection. In that vein proprietary 10 channel surround formats such as by Audyssey try to make up for the dearth of reflection cues in a 5.1 or 7.1 channel formats, especially the front soundstage. Linkwitz' system, already enriched with sonic energy from the front soundstage thanks to its inherent dipole design with excellent polar radiation raises the bar with four wide dispersion omnipoles utilizing a surround format similar to Chesky's six speaker setup. Granted the role of reflections in a multi channel system are far from established. But there seems nothing incompatible with an *accurate* wide dispersion loudspeaker system/lively room combo and multi channel formats either. The NHT Xd owner just might as well be making a precocious move to reference systems of the future based on such central ideas...
Tumara Baap
Wow, you've obviously given this a lot of thought, so who besides you would be best suited to execute it? I'll gladly provide you with server storage space for the blog of your new project!

Yup. Room size.
In the nearfield (of a room with smooth bass response), there is no spoon, er . . room.

But, if you're in the nearfield to the extent the room effects are not audible, then you don't really care about the room, reverberent field, surround channels, etc. Equally to the point, the more in the nearfield you are, the more critical that you have exactly the same speakers as the engineer used during the mix...the closer to the speaker the greater the impact of speaker differences on the mix and what you hear.

But, if you're in the nearfield to the extent the room effects are not audible, then you don't really care about the room, reverberent field, surround channels, etc.
That's exactly my point. It's in fourth place in having one-to-one control of our eardrums, just behind in-ear monitors, and high quality on- and around-ear headphones. You are there.

Equally to the point, the more in the nearfield you are, the more critical that you have exactly the same speakers as the engineer used during the mix...the closer to the speaker the greater the impact of speaker differences on the mix and what you hear.
Exactly the same speakers or very good and very close? I would think it more comes down to the skills of the artist, producer and engineer in creating a believable environment (in their mix). If it's a hackneyed mix, it will be (painfully) obvious to the listener.

If I'm in the nearfield of "proper" speakers - I'm basically using what a lot of studios use (M&K 150s) - then I'm hearing exactly what the mixdown team did.

Not necessarily. You'd have to put your ears literally next to the loudspeakers to be close enough to overcome the room effects. Now that would be nearfield! :D

--Ethan

Not necessarily. You'd have to put your ears literally next to the loudspeakers to be close enough to overcome the room effects. Now that would be nearfield! :D

--Ethan
Or we could just wait for the HeaDMI interface.

Or we could just wait for the HeaDMI interface.Only if you have your head retrofitted to be compatible with HeadDCP! :p

Why not just wear headphones. Then you would never have to worry about room acoustics and bass traps. I wonder what the first reflection points between headphones and ears would be? :)

Why not just wear headphones. Then you would never have to worry about room acoustics and bass traps. I wonder what the first reflection points between headphones and ears would be? :)Cute. My personal issue with headphones is that they simply cannot recreate the soundstage on stereo or mch recordings unless they are binaural recordings or subjected to lots of reprocessing.

Why not just wear headphones. Then you would never have to worry about room acoustics and bass traps. I wonder what the first reflection points between headphones and ears would be? :)
Ethan: Are you following this? There could be a whole new untapped market for wee lit'l traps and diffusors. And you'll need wee wee WEE lit'l microphone capsules for testing.

"My mommy said not to put traps in my ears . . . "

:D

A major problem with headphone imaging is that center channel sound often appears to be coming from your brainstem. :)

- Terry

A major problem with headphone imaging is that center channel sound often appears to be coming from your brainstem. :)- TerrySome people listen only with their brainstems. :rolleyes:

Some people listen only with their brainstems. :rolleyes:
In the end, it all goes through the brainstem.

I had hoped to stop with this silliness, but . . :)

Ethan: Are you following this? There could be a whole new untapped market for wee lit'l traps and diffusors. And you'll need wee wee WEE lit'l microphone capsules for testing.

"My mommy said not to put traps in my ears . . . "

:D

We sell them!!!! It is called the GIK Cuetip. Just mount them in all corners of the headphones. :D

Glenn

My screen wall if covered in rigid fiberglass. MY false wall is only 2 feet deep.

All the fiberglass is currently spaced out about 1.5", with 2" fiberglass. I'm very limited in space back there. So could I double up on fiberglass in some places back there (where the speakers aren't). So half would 2" spaced 1.5". The other half would be 4" spaced 1.5".


Or does it all have to be the same thickness.

S2G-Unit:
The difference in absorption between {4" spaced 1.5} vs {2" spaced 1.5} is relatively minor. Pretty much no change at all above 250hz.
The 4" will do more absorption in frequencies lower than that, but not a lot more, and not a lot lower.
The significant change would be from about 50hz to 200hz. With 50hz moving from about 0.02 to 0.10, and 100hz moving from about 0.20 to 0.40, and 200hz moving from about 0.40 to 0.70. (source: ChrisW's spreadsheet, 0 degree incidence not diffuse)

OK perfect,

So would it be ok to have some 2 thick and some 4 thick all behind the screen? Do they all have to be the same thickness?

Last thing for Bob, Terry or Ethan and Bpape.
I used to have a bookshelf in the room along the wall. I did not dry wall over the space it fit in. I did not want the long walls would to be perfectly parallel (would have more echo I think). The size is approx 24"W x 13"Dx 7'H.

I'm guessing I could make 2 small floor to ceiling superchunks in the right?
But it would not be symmetrical to the other side of the room.

Some times ago (back to 2005) Easley posted a First Point of Reflection Calculator.

Somebody can send me a copy ?

I've used the mirror method to calculate first point of reflections, but a tool can be useful to confirm my findings.

bye
Emanuele

I've used the mirror method to calculate first point of reflections, but a tool can be useful to confirm my findings.

This article on my company's site explains how to calculate the reflection points without needing a mirror:

http://www.realtraps.com/art_room-setup.htm

--Ethan

This article on my company's site explains how to calculate the reflection points without needing a mirror:

http://www.realtraps.com/art_room-setup.htm

--Ethan

thanks Ethan, I'll read it.

bye
Emanuele

This article on my company's site explains how to calculate the reflection points without needing a mirror:

http://www.realtraps.com/art_room-setup.htm

--Ethan


Ethan,
may I use the same formula you suggest for wall reflection, also for calculating the first reflection on ceiling ?
Because I have my central channel lower than my ear, so just going at half the way between my ear and that channel doesn't work.

Another question: my sofa is really close (10 cm) to rear wall.
May I use just absorber here or you think it's better diffusion ?
Or may I mix it, using absorber just rear my head and diffusion upper ?

thanks
Emanuele

may I use the same formula you suggest for wall reflection, also for calculating the first reflection on ceiling ?

Sure.

> my sofa is really close (10 cm) to rear wall. May I use just absorber here or you think it's better diffusion ? <

That's the worst place to sit. But if you have no other choice, then you want the thickest absorption there you can manage.

--Ethan

If you have some room behind the couch down low, you'll find that some good thick absorbtion there will also help considerably.

Bryan

Has anyone here used RPG Flutter Free for a rear wall?

I'd like some thoughts on an optimum treatment, please. Particularly what absorption spectrum to shoot for.

The room is about 22'x13'x8', not counting the AV alcove in the front wall. (It used to be a fireplace.) Standard drywall construction, floor on joist. Viewing position is about room center, and the rear is broken up by another alcove and hallway openings to each side. Most of the floor is covered by area rugs. Subs are close to the midpoints of the side walls. There is 100 sq ft of acoustic panels (2" 6.0 pcf JM Whispertone with a 2" air gap) on the front sidewalls, from before the first reflection points past and surrounding the side speakers.

The ex-fireplace alcove at the front is flanked by windows. To hide the equipment when not watching, and cover the windows when watching, I have installed two sliding panels, each 7'6" x 3'4" (48 sq ft). The panels are wood-frame, open front and back, and will be covered by fabric. They are built to accept 4" of something. The question is what?

Before I put in the side panels there was a definite slap echo. That's largely gone and the room is not hideously live, but the live front wall (windows and glass TV screen) doesn't help. So I need some mid-high absorption up there. The primary need is for bass absorption. The floor tends to ring at around 40 Hz. There are acoustic decouplers under the subs, but response is still uneven.

Bob Golds tables for 4" OC700 show these numbers
Product thickness mounting density 125hz 250hz 500hz 1KHz 2KHz 4KHz

701, plain 4" (102mm) on wall 1.5 pcf 0.73 1.29 1.22 1.06 1.00 0.97
701, plain 4" (102mm) 16" air 1.5 pcf 0.87 1.14 1.24 1.17 1.18 1.28
703, plain 4" (102mm) on wall 3.0 pcf 0.84 1.24 1.24 1.08 1.00 0.97
703, plain 4" (102mm) 16" air 3.0 pcf 0.65 1.01 1.20 1.14 1.10 1.16
705, plain 4" (102mm) on wall 6.0 pcf 0.75 1.19 1.17 1.05 0.97 0.98
705, plain 4" (102mm) 16" air 6.0 pcf 0.59 0.91 1.15 1.11 1.11 1.19
703, FRK 4" (102mm) on wall 3.0 pcf 0.88 0.90 0.84 0.71 0.49 0.23
705, FRK 4" (102mm) on wall 6.0 pcf 0.65 0.52 0.42 0.36 0.49 0.31
1240 4" (102mm) A 4.0 pcf 0.88 1.14 1.17 1.08 1.06 1.10
1260 4" (102mm) A 6.0 pcf 0.99 1.01 1.10 1.03 1.03 1.05
1280 4" (102mm) A 8.0 pcf 1.11 0.91 1.07 1.03 1.06 1.07

"Differences in coefficients of less than 0.15 are not significant."

1) Does it make sense to use FRK (faced) to keep from eating too much of the mid/highs? Or is there enough coverage to matter?

2) Ethan Winer reports that increasing density increases bass absorption (up to a point). Yet, at least with the 700 series, the data appears to illustrate the opposite trend. Might he have been working at lower frequencies?

3) Like the density correlation, the air gap seems to have a contrary influence. (Gap behind mine will be 2-4".)

4) Can we extrapolate these numbers below 125Hz with any confidence?

Anything other significant factors, like cost and availability? (OC705 seems hard to come by, for instance.)

DMF

Bob is adamant elsewhere that increasing density increases bass absorption Really?
I guess that's true in the fairly thin (0.5" to 2"-ish).
What increases bass absorption is deeper/thicker material. Anything over a foot deep, consider much less dense.

BTW, Eric Desart did a really nice graph with comments based on the data on my page and others.

1) Does it make sense to use FRK (faced) to keep from eating too much of the mid/highs? Or is there enough coverage to matter?Depends on what else is in the room, and where you're placing these. For example, FRK covered are probably not appropriate at the first reflection points.

Oops. It was Ethan Winer's site. "My own tests in a certified acoustics lab confirm this, showing denser types of rigid fiberglass absorb as much as 40 percent more than less dense types at 125 Hz and below." here (http://www.ethanwiner.com/acoustics.html#rigid%20fiberglass)

When my panels are open they butt into the corner, adjacent to the 2" panels.

IMO, since it's on the front wall, FRK/FSK is not recommended. We want the front wall dead in the mids and highs.

Bryan

Bryan, how does 4" mineral wool compare acoustically to 705? How is it to handle?

Mineral wool is more 'crumbly' than 705. It's OK to handle but a bit itchy and very dusty.

To me, for the front wall application, I'd stay with 703.

Bryan

Oops. It was Ethan Winer's site. "My own tests in a certified acoustics lab confirm this, showing denser types of rigid fiberglass absorb as much as 40 percent more than less dense types at 125 Hz and below." here (http://www.ethanwiner.com/acoustics.html#rigid%20fiberglass)

Also see my Density Report:

www.ethanwiner.com/density/density.html

--Ethan

Mineral wool is more 'crumbly' than 705. It's OK to handle but a bit itchy and very dusty.

To me, for the front wall application, I'd stay with 703.

Bryan

From what I understand, OC 703 and 705 tend to hold their shape better than mineral wool. This would make 703 or 705 better for panels. But what about superchunk style traps? These devices are easy to build, easy to place, easy to stack up and are very effective absorbers. The downside is that the mass closest to a wall has little air particle velocity and contributes little to absorption. Cost then becomes a consideration with 703 or 705 as the raw material. But wastage isn't a big issue if using the far less expensive and easily procured mineral wool boards. Since the device is a solid mass block, rigidity of the starting panels shouldn't be an issue either.
This is how I am planning to do my corner traps. I'll dress up the mineral wool superchunks with weed fabric, and incorporate them behind the layers of stage velour at the proscenium. They'll be out of sight and provide superb broadband absorption.
Tumara Baap

. . . what about superchunk style traps? These devices are easy to build, easy to place, easy to stack up and are very effective absorbers. The downside is that the mass closest to a wall has little air particle velocity and contributes little to absorption. Cost then becomes a consideration with 703 or 705 as the raw material. But wastage isn't a big issue if using the far less expensive and easily procured mineral wool boards. Since the device is a solid mass block, rigidity of the starting panels shouldn't be an issue either.
This is how I am planning to do my corner traps. I'll dress up the mineral wool superchunks with weed fabric, and incorporate them behind the layers of stage velour at the proscenium. They'll be out of sight and provide superb broadband absorption.
The Studiotips (http://forum.studiotips.com/viewforum.php?f=8) SuperChunks seems to me to be the easiest and most economical way to DIY yourself into some seriously effective bass traps. Not everyone's theater can accommodate the 34" cut, but even the 24" cut seems quite effective.

OC 703/705 can be difficult to find at a price reasonable enough to meet the "most economical way to DIY" criteria I mentioned above; many acoustical treatment companies and individuals sell it, but one needs to get to the "source" for the best pricing. The original, and still by far the largest, use of this material is HVAC insulation. Sooo, the source is a distributor of HVAC materials. I am fortunate enough to live a mere 30 mins from the corporate headquarters of just such a company, Specialty Products & Insulation (http://www.spi-co.com/index.html), but they have locations all over the U.S. I know from reading here and on other forums, this company is well known among home theater enthusiasts.

As you get thicker, density has less of an effect. Doing a solid chunk style absorber is thick enough that 703 is plenty dense and easy to work with - not to mention being half the price of 705.

Bryan

Hi all!

I have a lot of problems with echos and reverberations. Even during normal conversations I can hear my voice get distorted. Not to mention clapping my hands or snapping my fingers.

Now I am new to room acoustics and unfortunately there is no professional within a 100miles of where I live in Germany.

So could you guys give me some tips as to where to start and what to do?

I can post some pictures if that helps. It's currently a living room/music/HT room as I do not own a house yet. I looked into buying absorbers but they are so expensive I do not want to just spend 1k on absorbers and end up with the same poor sound I left off with.

Ok guys,
I have bass traps in all 4 corners of my HT room. I also have a small indentation in the room, where a bookshelf was (13"Dx28"W). I have already put 2 superchunks in that space. Should I instead just fill the caivity completly instead of having 2 superchunks there? More mass?

I've got tons of Fiberglass left.

Hi all!

I have a lot of problems with echos and reverberations. Even during normal conversations I can hear my voice get distorted. Not to mention clapping my hands or snapping my fingers.

Now I am new to room acoustics and unfortunately there is no professional within a 100miles of where I live in Germany.

So could you guys give me some tips as to where to start and what to do?

I can post some pictures if that helps. It's currently a living room/music/HT room as I do not own a house yet. I looked into buying absorbers but they are so expensive I do not want to just spend 1k on absorbers and end up with the same poor sound I left off with.
Absorption can be overdone. It's common to treat only the first reflection points - all of them - and see what that does. I can't imagine that NOT making a HUGE improvement. Front wall and back wall are first reflection points along with ceiling, floor and left/right front sidewalls. A nice thick rug can be used on the floor.

HT-Naimee:

Flutter echo (that twang you hear when you snap your fingers) is the easiest of acoustic problems to get rid of.

The easiest way is to let a woman loose in the room. By the time they're done decorating usually flutter echo is gone.


The next thing to work on is knowing that flutter echo is caused by sound bouncing back and forth between large parallel surfaces. In this case 'large' can be as small as 4'x4'. These surfaces are usually wall-wall, or floor-ceiling.

The next thing to know about flutter echo is that the annoying sound you are hearing isnot actually the sound that's going past. What you're hearing is the interaction of two higher frequency waves, causing a 'beat' like lower frequency to be heard. This is really great because it's easier to absorb higher frequencies than lower ones.

All you need to do is to stop flutter is to put something that will either:
a) reflect the sound away from the other parallel surface (e.g. a diffuser, an unevenly shapped armoir, a book case, etc)
b) absorb the high frequency sound

For (b) you can use anything soft. Even thin drapes. Or a lot of big plants.

As an experiement, hang a couple of comforters/duvets or sleeping bags on a wall (wall-wall flutter). If you have friends handy, they can hold it in place. If not you can temporarily hold it in place with anything from broom handles, to a horizontal piece of wood attached to the wall.
Cover the floor in carpet/rug(s) (floor-ceiling flutter).

If the problem is floor-ceiling or front-wall-back-wall, then treating one surface is fine.
For left-wall-right-wall, you probably want to maintain symmetry, so treat both surfaces equally.


Using 1" of rigid fiberglass (eg Linacoustic) is better than a comforter, particularly at the first reflection points, because rigid fiberglass's absorption is more even above 1000hz. Ignoring imaging, optimally you want reflections to have the same tonality as the speaker -- and if you can't get that then you want the reflections absorbed/diffused into insignificance.
DIY 2'x4'x2" absorbers are easy to make. I've done woodworking since I was quite young, so that's how I did it. But you can also buy bags to cover rigid fiberglass, which isn't any harder than putting on a shirt.

S2G-Unit:
Post a scale floor plan.

I have a lot of problems with echos and reverberations. Even during normal conversations I can hear my voice get distorted ... So could you guys give me some tips as to where to start and what to do?
Start here:

http://www.ethanwiner.com/acoustics.html

Understand that obvious echoes are only half the story. Just as important is getting the bass range correct. But you may not notice the bass problems until after you tame the mids and highs.

I do not want to just spend 1k on absorbers and end up with the same poor sound I left off with.
If you get good acoustic treatment you will greatly improve the sound at all frequencies.

--Ethan

Thank you both for your interest and help. First thing tomorrow morning (it's 10:30pm now) I will take some pictures and post them.

I will try to read up everything I can by then. I hope you two will be able to help me with this.

By the way, if it is ceiling to floor (laminate floor and bare white ceiling), will it suffice to "treat" the floor or is it necessary to treat the ceiling?

I hope the pictures will be able to help analyze my room.

Room is 3.4m x 5.6m . I am firing across the room and sitting against the rear room. Not ideal acoustically, but for some reason it still sounds best (and is the best and currently only way to position the system).

Looking forward to your views and thanks again!

Alex

By the way, if it is ceiling to floor (laminate floor and bare white ceiling), will it suffice to "treat" the floor or is it necessary to treat the ceiling?
Doing the floor, two side walls, and maybe one other wall (might be pointless with your configuration) is usually quite enough.

Also, beware reflective surfaces between you and the speakers. No glass coffee tables. ;)

By the way, if it is ceiling to floor (laminate floor and bare white ceiling), will it suffice to "treat" the floor or is it necessary to treat the ceiling?From a flutter perspective, it is not nessessary to treat the ceiling if the floor is carpeted. "If the problem is floor-ceiling or front-wall-back-wall, then treating one surface is fine."

Also, beware reflective surfaces between you and the speakers. No glass coffee tables. This is a different effect -- comb filtering. For it to be flutter you'd have to be leaning over the table (without a pillow).
Although comb filtering is easy to detect with real time analyzer equipment, most people do not hear it.

I do not know what effect precisely I have, nor whether I only have one sole effect causing the sonical problems.

Unfortunatly I had to go to university early this morning and was unable to take any pictures.

My room is more or less bare, though. No curtains (I don't like them), one big carpet on the laminate floor (between me and the speakers) which is about 1-2cm thick, but quite "rigid". The walls are more or less empty with only a few picture frames but nothing really diffusing.
I hope to be able to take some pictures when I get home tonight.

I do not know what effect precisely I have, nor whether I only have one sole effect causing the sonical problems.

Unfortunatly I had to go to university early this morning and was unable to take any pictures.

My room is more or less bare, though. No curtains (I don't like them), one big carpet on the laminate floor (between me and the speakers) which is about 1-2cm thick, but quite "rigid". The walls are more or less empty with only a few picture frames but nothing really diffusing.
I hope to be able to take some pictures when I get home tonight.

I have a lot of problems with echos and reverberations. Even during normal conversations I can hear my voice get distorted. Not to mention clapping my hands or snapping my fingers.
Let me first say I agree with the advice already given from Ethan and the others, but I'll try to make this less technical. Based on your quote above, I would not bother with reflection points - yet. What you need to do is fill your room with stuff (preferably soft stuff). Get a couch or loveseat, hang things on the walls. I know you said you don't like drapes, but get something - acoustical panels would be wonderful.

Sound needs to be absorbed or it will keep bouncing around until it loses all its energy - soft things tend to absorb sound. After you fill the room, then you should begin thinking about bass treatment, frequency response measurements and the rest. Take it slow and you'll notice a great improvement - then immerse yourself in this thread, Ethan's site and other online material. Don't try to do it all at once.

Good luck!

is it necessary to go from the floor to ear level on the side walls? Also any acoustic experts, please check out my thread in this forum, I need help putting up my panels. Thanks!

Please note that I posted this message outside the thread a few days ago, but didn't receive a response. Maybe this is the better place for help.

Thanks

--------------------------------------------------------------------------------

Dear home theater gurus,

I’m in the process of planning a new house and, of course, home theater. I’ve spent many hours on the forum, and now have a vague sense of my options. I’m hoping some of you can take a few minutes to help me firm things up re acoustical treatments. (I’ve posted a separate question re noise isolation.)

The room layout is in the image below. The is about 18’ long, from the screen wall to the rear wall. The room will be about 13.5’ wide. The ceiling will be 8’ high. I'll have one or two rows of sofas or large home theater chairs, no closer that 2' to the back wall.

http://home.comcast.net/~bjolish/Home_theater_sketch_1.jpg

Please also note that the screen wall will have an opening to the closet, so that I can access the DVD player, receiver, etc. The opening will be below the screen, about 12” high and about 8’ long (and would be closed with glass doors). (I’ve planned the closet equipment shelf opening so as to avoid IR repeaters, see the cable box channel display, easily load DVD’s, etc.) The closet will have a vent to an exterior room. There are also a door and window in the rear wall.

The projector will be mounted on a rear wall shelf. The speakers will all be wall- mounted KEF KHT6000s (6.2 configuration). I’m not sure where the sub should sit.

Here’s my acoustical treatment strategy:

Font wall: I know the general rule is to treat the front wall with lots of absorptive material, but I’m wondering if this would be a mistake given that the KEF 6000s are specifically designed to be wall-mounted—i.e., their design probably already compensates for rear-wall reflections.

Rear wall: Curtains backed with thick blackout shades along entire wall, for diffusion and light control. I know having the rear seats so close to the rear wall is not ideal, but I want to maximize seating. Should I add more diffusion behind the curtains (e.g. with some foam products from partsexpress.com)?

Side walls: 1” OC 703 velcroed to the walls to 48” from floor (i.e., to ear level). Note, however, that the LEF 6000s will be wall mounted. Does that mean I should adjust the OC 703 on the walls? If so, how?

The whole wall would then be covered by a light curtain (i.e., like at a modern movie theater). Hopefully I can use something inexpensive and pre-made (i.e., not GOM)--maybe a thin velvet. I don’t want to make the room too dead, but I don’t see how the thin curtain material would be any more absorptive than the cotton batting lots of people are using on the walls.

Ceiling: No treatment.

Floor: Wood subfloor (over concrete slab) with pad and carpet.

Rear corners: Bass traps, consisting of 2 layers of OC 703 at 45 degree angle to wall. They would start about 4’ up, and extend to the ceiling. I don't think I can fit 2’ wide panels, but I assume any width is better than nothing. Should I stuff the traps with something to add mass?

2 final miscellaneous questions:
Projector shelf: I’m planning on a Panasonic PT-AX100U, which is supposed to be pretty quite. Nonetheless, would it do any good fine to line the inside bottom of the shelf with OC 703? I don’t think I need to bother with an entire hush box.

Subwoofer: I’d like to keep the subwoofer (or maybe 2 subwoofers) away from the front wall, so that the kids can use the area. I know I’m supposed to do the subwoofer seating position test for optimal placement, but at this point can anyone opine on whether it may be OK to place the sub(s) along the rear walls, about 4’ from the corner?

Thanks to all who take the time to help. I’m eager to for your feedback.

OK, sorry for the delay but now I hopefully have the info needed to judge my room.

Here is the layout. As you can see I am using half of the room for my music. I tried using the lenght of the room but that was not satisfactory at all. I quite like it the way it is now....except for the reverberations/echoes ;)

http://img107.imageshack.us/img107/4871/18236523jj5.jpg (http://img107.imageshack.us/my.php?image=18236523jj5.jpg)

First of the front speakers. Please ignore that tiny old TV but mine died on me and I am currently looking for a 50"-60" flatscreen. So, ignore that part :rolleyes: :)

http://img359.imageshack.us/img359/3531/45094971lm7.jpg (http://img359.imageshack.us/my.php?image=45094971lm7.jpg)


In the left part of the picture you can see a big cupboard. Wooden, more or less even surface.

Next the far corner. On the layout picture this would be left and you can see the cupboard on the right.

http://img359.imageshack.us/img359/110/56292130zw2.jpg (http://img359.imageshack.us/my.php?image=56292130zw2.jpg)

Moving further (counter-clockwise)

http://img359.imageshack.us/img359/9715/83436694qk7.jpg (http://img359.imageshack.us/my.php?image=83436694qk7.jpg)

And arriving at the listening position or rather the wall opposite te fronts. You can see the rear left speaker at the bottom.

http://img359.imageshack.us/img359/5899/30626298ir9.jpg (http://img359.imageshack.us/my.php?image=30626298ir9.jpg)

And further (you can just see the top of my rack with my DVDP in the bottom left corner.

http://img359.imageshack.us/img359/3781/80736501ht6.jpg (http://img359.imageshack.us/my.php?image=80736501ht6.jpg)

1. Get the sub out of the corner.
2. Move the front speakers out away from the front wall a bit
3. Get the listening position away from being right up against the wall.

Those are all the 'free' things you can do to improve the sound.

Bryan

1. Get the sub out of the corner.
Two subs actually. But they are not being used for stereo and the bass is fine.

2. Move the front speakers out away from the front wall a bit
These speakers (Naim Audio Allae) are made to be up against walls and you can adjust the amount of bass they do by moving them closer or away. I like the amount of bass they give that close and the reverberations do not change when moved away (tried it :( ).

3. Get the listening position away from being right up against the wall.
Well, I tried moving away about 30-50cm but it didn't change the problem. It only looks bad and feels weird sitting in the room like that. Unfortunately not a cure for my problems.

Those are all the 'free' things you can do to improve the sound.

Bryan
Unfortunately I think those will be the tweaks once the vital room acoustics have been dealt with :(

HT-Naimee:

What happens if you rotate your viewing 90 degress
by putting the TV under the shelf instead of under the photos.
That'll give you more symmetry, and air behind your head.

Two subs in the new front corners may be fine. (Floyd Toole sub paper)

I tried turning 90° (I think I mentioned it before), but unfortunatly it actually made the sound worse. The reverberations remained more or less the same (impossible to say without measuring). But the music lost its life and everthing sounded dull to me.

On top of the poor sound, it also looked pretty awefull :)

I guess I would really be interested in all of your views on where to install treatments and how much I would need to kill off all reverberations.

I would really be interested in all of your views on where to install treatments and how much I would need to kill off all reverberations.

It's all explained in my Acoustics FAQ:

http://www.ethanwiner.com/acoustics.html

--Ethan

I know this sounds over simplified, but after looking at your pictures you have nothing on your walls. You need soft stuff to absorb the sound. I'd definitely go to www.realtraps.com and get at least two MicroTraps (2' by 4'). It's not enough to make your room perfect, but you will be amazed at how an under $300 investment can impact on your sound quality.

I can honestly say that the <$300 for the MicroTraps will have a significantly greater impact on your audio quality than buying $15,000 Tannoy Definitive speaker system.
---------------------------------------------------------------------------------------------------
What I'm about to say is a generalization, I'm not picking on HT-Naimee. I am continually amazed that people will spend thousands of dollars on their audio gear and for some reason wince at a sub $300 investment in traps.

Or take that same $300 and build 12 of your own panels.

I know this sounds over simplified, but after looking at your pictures you have nothing on your walls. You need soft stuff to absorb the sound. I'd definitely go to www.realtraps.com and get at least two MicroTraps (2' by 4'). It's not enough to make your room perfect, but you will be amazed at how an under $300 investment can impact on your sound quality.

I can honestly say that the <$300 for the MicroTraps will have a significantly greater impact on your audio quality than buying $15,000 Tannoy Definitive speaker system.
---------------------------------------------------------------------------------------------------
What I'm about to say is a generalization, I'm not picking on HT-Naimee. I am continually amazed that people will spend thousands of dollars on their audio gear and for some reason wince at a sub $300 investment in traps.

OK. So the two walls I could work with are the one behind the listening position and the wall to my left, where the two brwon picture frames are.

Now my question would be, how much do I need and what sizes? Would I really need to cover the entire far wall and all of the wall behind me or will I just need three or four absorbers overall with each the size of those picture frames?

OK. So the two walls I could work with are the one behind the listening position and the wall to my left, where the two brwon picture frames are.

Now my question would be, how much do I need and what sizes? Would I really need to cover the entire far wall and all of the wall behind me or will I just need three or four absorbers overall with each the size of those picture frames?
It depends on the quality/accuracy you want to achieve. But covering 25% of the wall area with wideband absorption is not at all unreasonable. Front wall and side walls toward the front of the room are prime areas. Every room is different, but 2" thick mineral wool or other dense porous absorber should make a dramatic difference.

Regards,
Terry

Font wall: I know the general rule is to treat the front wall with lots of absorptive material, but I’m wondering if this would be a mistake given that the KEF 6000s are specifically designed to be wall-mounted—i.e., their design probably already compensates for rear-wall reflections.
If speakers could compensate for room acoustics, we wouldn't need sound treatments. Disabuse yourself of this notion. The only time you'd worry about nearby wall treatments is if the speaker configuration is that of a dipole. Rear (high frequency) radiators rely on reflections.

The whole wall would then be covered by a light curtain (i.e., like at a modern movie theater). Hopefully I can use something inexpensive and pre-made (i.e., not GOM)--maybe a thin velvet. I don’t want to make the room too dead, but I don’t see how the thin curtain material would be any more absorptive than the cotton batting lots of people are using on the walls.
First off, the material needs to be fire resistant/flame retardant. It isn't the acoustic properties that make (e.g.) GOM expensive, it's the fire rating. You don't have to use it, but use something equally safe.

Second, the cloth covering is not intended to absorb anything. Quite the opposite - it's intended not to absorb anything. Likewise it's intended not to reflect anything either. The absorptive material underneath will be pointless if energy is reflected by the covering fabric before it ever gets there.

OK, now, if I were to make my own of mineral wool, glas-wool, say 2" thick, would I be allowed to squeeze it or would it need to remain as loosly as possible?

And is it important at which height I hang the absorbers? e.g. how about one lonish one (2m x 0.50m) over the wooden door, one on the door itself and then one big one behind my listening position?

You won't be able to squeeze it, it's already compressed and set in a resin. My frames were a little too small for your standard 2x4 slab, and I literally had to break down the ends to get it to fit (though it's in there good now).

If you're thinking of using the fluffy stuff, you're thinking of the wrong material.

Please read Ethan's FAQ on placement. Yes, height is crucial.

OK, now, if I were to make my own of mineral wool, glas-wool, say 2" thick, would I be allowed to squeeze it or would it need to remain as loosly as possible?

And is it important at which height I hang the absorbers? e.g. how about one lonish one (2m x 0.50m) over the wooden door, one on the door itself and then one big one behind my listening position?

OK, I will have to go to our shops again and look around. Most stuff was the fluffy kind rather than rigid. Maybe I overlooked it.

Did I miss the part in Ethan's text where to place the absorbers? By the way, Ethan, very nice work! Now I just need to find the German fibreglass stuff that corresponds to 703 and need to know where to hang the absorbers.

OK, I will have to go to our shops again and look around. Most stuff was the fluffy kind rather than rigid. Maybe I overlooked it.

Did I miss the part in Ethan's text where to place the absorbers? By the way, Ethan, very nice work! Now I just need to find the German fibreglass stuff that corresponds to 703 and need to know where to hang the absorbers.
Search the web for a Knauf dealer and ask them to order you Knauf Black Acoustical Board (http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_black_acoustical_board.aspx). Sound absorption coefficients are at the bottom of the page, but I would definitely recommend the 2" product.

If I remember correctly you need to buy a minimum of one carton (six sheets). Each sheet is 2' x 4' - so you'll get 48 sq. ft. of coverage. I would expect to pay around $300 per carton, but its been a while since I ordered any and building materials have skyrocketed in price so I tried to build that into my estimate.

They also sell some very absorptive Insulation Board (http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_insulation_board.aspx) - so find a local dealer and price it out. This stuff will require you put some fabric around it to give it a clean look, the black stuff looks pretty sharp framed with some cheap molding.

Of course you can just order nice looking absorbers over at realtraps.com, but this is definitely an option.

This is my first post reguarding acoustical treatments so please be kind, I really am quite new to this area.

About 6 months ago I moved from a condo to a home where I have no worries about sound levels anymore. Finally I can do anything I like with the rooms. Until the weather gets nicer outside I have moved my 'theater' into a small 12x11 room. It's somewhat crowded but ok for 2 people to watch movies or 1 person to listen to music, very small sweetspot.

After spending the last month really tweaking out the htpc side of things I finally have a decent source for music, but that's another story. The problem I have now, is things seem to 'ring' when at fairly high volumes. I don't know how else to explain it, but I really believe I can hear a slight ringing in my ears and it's really taking away from the effect I am trying to achieve.

This problem is why I am making the post in this forum. As the room serves multiple purposes I can't do much with the position of equipment or furniture, it's also my office.

Here is a picture of the front wall
http://gallery.avsforum.com/data/501/DSCN2123.JPG
It is about 8.5' before getting to the door on the right side.
The curtains on the left side are double doors going out to the balcony. They take up about 1/2 of the side wall.
What I was thinking about was using some kind of treatment on the wall below the screen, just need to know what would work best there. I really can't move the speakers further out into the room, as it's quite shallow to begin with, can go a few more inches if needed. From the picture you can see that I have run all the wires for the speakers through the walls to the server closet.

Would building panels with the 703 stuff that I read about on here, that take up the entire bottom portion of the wall, below screen, help here?

Here is the rear wall
http://gallery.avsforum.com/data/501/backwall2.jpg
There is about 6-8" between the wall and the seats when reclined. Curtains cover up a window, just have not gotten around to cutting the curtains down yet.
Rear speaker will be placed on a shelf up where the backplate is located. Problem I ran into is the corners are not square so I could not use 'off the rack' corner shelves, yeah really sucks....

I was thinking about using the same 703 stuff below a 'chair rail' level, though not sure if that would help. Should I also put some panels up above the chairs?

Here is the side wall with the desk
http://gallery.avsforum.com/data/501/side11.jpg
Same problem with rear speaker, walls not being square. No idea at all what to do in this part of the room. The first door on the left goes to the 'server closet' that holds all the gear including computers. Far left door is exit to the room.

Also not sure what to do reguarding bass traps in the room. It's already quite crowded, but could use something for sure.

I am open to any advice here as I am not sure where to start this project, and it's been sitting like this for a few months now. Definately time to kick it in gear.

As to equipment I am using the following
infocus 7210
monitor audio gr 10's x4
I have 2 gr60's that I put in the bedroom for now as it was overkill for such small room, though with treatments I hope to bring them back.
Velodyne dls
sunfire mkII
denon 5800
denon 3910
htpc with hd setup

This is my first post reguarding acoustical treatments so please be kind, I really am quite new to this area.

About 6 months ago I moved from a condo to a home where I have no worries about sound levels anymore. Finally I can do anything I like with the rooms. Until the weather gets nicer outside I have moved my 'theater' into a small 12x11 room. It's somewhat crowded but ok for 2 people to watch movies or 1 person to listen to music, very small sweetspot.


If you could sketch up an overhead view, that would be helpful. I like "Room Arranger" for simplicity of use. Google it.

In replying to a post with big pics, unless your reply deals specifically with the pics, please consider deleting them from your reply as they scroll the thread onto the next page very quickly . . .

If you could sketch up an overhead view, that would be helpful. I like "Room Arranger" for simplicity of use. Google it.
Here it is
http://gallery.avsforum.com/data/501/room_diagram.png
each square is 12 inches, room is almost exactly 12x11x8.5high I would have put text on each item but the program doesn't seem to allow it. Hope that between the diagram and the actual pics that it's clear what I am dealing with.

In replying to a post with big pics, unless your reply deals specifically with the pics, please consider deleting them from your reply as they scroll the thread onto the next page very quickly . . .
Not sure if you mean me....
If you do, yeah the pics are kinda important to describe what I am dealing with. It's so difficult to work and describe such a small room without them, esp with so much going on in such a small space.

I was able to track down a local dealer for the rigid fiberglass today. Pickup tomorrow. Only thing is not sure if to go with 1" or 2" 6lb or 7lb board insulation. I believe the brand was 'kanuff" spelling wrong I'm sure....

From what I gather in this very long thread, I may be better off going with 1" with a 1" space between the insulation and the wall vs. going with 2" flush mounted. As the stuff is only like $3/sq' I figure it's cheap enough that I can't loose either way. My biggest problem I see myself is that my first reflection points on the side walls both have doors there. One going to server closet, and the other is going to the balcony, covered by drapes. Expert advice on placement and types is def going to be needed in such a small room.

The first thing I want to tackle is the 'ringing' I hear at fairly loud volumes. It's not terrible but definately there. I would say it's in the upper middle range. I find myself getting fatigued listening to long in here, esp late night with jazz prior to bed, though I do listen to just about anything in here. I want a huge soundstage, well as big as possible for such a small room. I want the vocals to be crystal clear, and I really want to feel like I'm actually there. Of course everyone says that....

Afte that I'll tackle the bass. Believe it or not, it's not to bad, though there are definately some peaks and valleys in play. Esp around 40 and 80 hz. I was thinking about a softit in the back by the projector and turning it into a bass trap, if that would even work, no idea. Also as my rear walls are not square, hence the speakers still not mounted, I could use floor-ceiling corner traps with the speaker inside. Of course the side with the desk would only go from the desk up as not possible below desktop.

Well that's about all I can think of. I'll leave it up to the experts now.

Not sure if you mean me....
Nope, not you - you needed the pics. It was the next poster who has now edited his post and removed them.

Here it is

each square is 12 inches, room is almost exactly 12x11x8.5high I would have put text on each item but the program doesn't seem to allow it. Hope that between the diagram and the actual pics that it's clear what I am dealing with.

Well, seeing as how no one else has chimed in yet (thread must be getting a little stale)...

First, if you're using room arranger, the text is called "labels", in the object properties.


Between windows, doors, and your screen, you don't have a whole lot of wall left. Assuming you don't want to reorient the room 180 degrees, block out that window w/ your screen, and get rid of that desk, I suppose your positioning is about as good as it gets. You could center up the screen as much as possible, and move your right channel whenever you want to enter/exit the room, but I'm sure that will get old quick.

It looks like your seating is a little far back. Assuming you like your seating distance/screen size, I'd move your L/R out a bit to give them some breathing room, even up the distance between the seating position and your L/C/R, and give you a 45 degree listening angle.

That ringing is probably flutter echo, so you've got to damp your parallel surfaces.

Since your emphasis is is on the big sound stage (which, as the former owner of a 12x12x10 I can tell you is a losing battle): Put 2" over as much of the front wall as you can, spaced out 2" if you can. Get some sound reflective curtains for that back window (thick manmade fibers, even vinyl), and hang diffusors to the right and left of it. A couple tall bookcase paked with thrift store books would work on the cheap.

See where that gets you. If the ringing is still there, you'll need to add more diffusion/absorption, probably absorption. New carpet with a thick pad? More fiberglass?

Anyone else have thoughts?

Thank you eugovector for the input.

Your right about the placement of equipment/furniture. I tried just about everything I could think of prior to placing things where they are at now. This was the best scenario I could come up with.

I found a company that sells the 703/705 in both 1" and 2" thick panels. Will drive down tomorrow and pick up a bunch. From everything I have read in this thread and other sources I think I am going to go with the 1" 705 and space it 1" away from the wall. I'm initially going to start by covering the entire front wall below the screen with this. In the future I may rebuild my screen so that I can place it behind there as well.

As to the rear walls, I can probably go with corner traps from the desk to ceiling on the left side, and floor to ceiling on the opposite side. Seems concensis is to use 705 for the bass traps. I may even have enough room between the bass traps to place a small 2x6 705 panel on the back corners and rear windows.

the hardest part has been figuring out which materials to go with for the panels, and wether or not to purchase it with facing or without.

Another idea I had was to build a triangle bass trap along the front wall ceiling all the way across the room. I can't go an entire 2' triangle but could probably come close to 16" or so. Heck it may even look kind of cool, who knows.

Curious if I should do any treatment on the side walls at all. As the reflection points both have doors there, one wall being my closet, and the other being the balcony doors, there is no way to properly place panels. I can easily put them further toward the back of the room on the side walls though. Just not sure if it would have any effect at all, or if it would harm the sound.

I don't want to kill the room, dead, but it does need to be toned down. It's just as important to me to maintain a semblance of a soundstage as well.

If I'm barking up the wrong tree, or going to far with ideas, please let me know.

Well I ran out today and purchased 50 of the 2x4 2" 6lb '705' panels to see if they would help out or not. Wish they had at least some 1" in stock but no luck there so I bought what I could get my hands on.

I figured that before taking the time to build/stain and cover the panels that I would try setting them around the room first to see if they made any difference. First I started by placing 8 panels around the room, listened for awhile, wasn't exactly blown away by the change so I made some changes.

I read about people cutting them into triangles and stacking them into a corner. So a few hrs later I had one big pile ready. Really only having one corner in the room available I decided to start there.
http://gallery.avsforum.com/data/501/705corner.JPG
The sound change wasn't really all that evident. I wonder If I should continue all the way up the wall or not. Takes a lot of time and energy cutting these suckers, so if people here believe it wont help I'd like to hear before going through the motions.

If it is worth it, was thinking about leaving the rear speaker there, filling in the sides, and just continuing up the wall until I reach the ceiling. Of course if it does sound better, then I will build enclosers and wrap them to make it look right.

I also tried laying a few across the front to see if there was an effect
http://gallery.avsforum.com/data/501/705front.JPG
I may only be imagining things but it does seem to help a little bit with the harshness. It's not a huge change like I was hoping for, but there is a little.

Also, do you guys think it would help if I rebuilt my screen so that I could place this stuff behind it as well?

If I can find a scenario where this stuff really helps the room out, then I will build 1x2 frames for them, router edges, and stain them, probably deep mohogany. Will use french cleats on the back so that they are sticking about an inch out from the walls.

As I'm not getting many replies I just wanted to show that I'm serious about trying this, and doing everything I can think of from reading the threads. Any expert advice is GREATLY appreciated.

50 panels? Good God!! what did that run you. I only bought 12 of the 703 for $120, and I thougt that was a good deal. Are you getting this stuff really cheap?

Before we go any further, please be careful when cutting and stacking that fiberglass. If you get a bunch of those fibers in your lungs you're not going to like it. It won't kill you, but you're not going to like it.

I'm not sure what you mean by staining the fiberglass. I framed mine and covered it with a thin, natural fiber (cotton) fabric. Check out the walmart bargin shelf. You can also affix it directly to the panels w/ 3m spray adhesive.

On to the room. First you should understand what you're doing, and how sound works. With the fiberglass in the corner, you are taming room modes. Google that one if you're not familiar with it. Fiberglass in the corner will smooth out bass a little, should help shorten bass reverb time a bit. With as much fiberglass as you have, you might as well use the leftovers for this purpose.

One of your original problems was flutter echo. If you clap your hands, and you get a pringy reverb, this is flutter echo. It's cause by sound bouncing back and for between parallel surfaces, so anywhere you have 2 flat, reflective surfaces, you want to hang fiberglass on atleast one of those surfaces. Like I recomended, the front wall should be as dead as possible. Given that your room is so small and you have that screen taking up a lot of your front wall, you'll want to deaden or diffuse the first reflection points on the back wall, the space right behind your ears.

Putting fiberglass behind your screen won't do a damn thing unless your screen is perforated, or otherwise acoustically trandparent.

What to listen for? Do a clap test, then hang your fiberglass, then repeat the clap test. The results should be quite evident. That same improvement will carry over to music and movies. Dialogue should be clearer. You should be able to hear quiet details in music that were masked by room reverb before. All of these things I notice after hanging only 9 2x4 2" 703 panels in my 15.2x13.8x8 room.

If you feel the room is too dead. Take down a panel or two from the side or back walls. Like that better? Then hang the panels you just took down in another room, or make super chunk bass traps out of them.


Well I ran out today and purchased 50 of the 2x4 2" 6lb '705' panels to see if they would help out or not. Wish they had at least some 1" in stock but no luck there so I bought what I could get my hands on.

I figured that before taking the time to build/stain and cover the panels that I would try setting them around the room first to see if they made any difference. First I started by placing 8 panels around the room, listened for awhile, wasn't exactly blown away by the change so I made some changes.

I read about people cutting them into triangles and stacking them into a corner. So a few hrs later I had one big pile ready. Really only having one corner in the room available I decided to start there.

The sound change wasn't really all that evident. I wonder If I should continue all the way up the wall or not. Takes a lot of time and energy cutting these suckers, so if people here believe it wont help I'd like to hear before going through the motions.

If it is worth it, was thinking about leaving the rear speaker there, filling in the sides, and just continuing up the wall until I reach the ceiling. Of course if it does sound better, then I will build enclosers and wrap them to make it look right.

I also tried laying a few across the front to see if there was an effect

I may only be imagining things but it does seem to help a little bit with the harshness. It's not a huge change like I was hoping for, but there is a little.

Also, do you guys think it would help if I rebuilt my screen so that I could place this stuff behind it as well?

If I can find a scenario where this stuff really helps the room out, then I will build 1x2 frames for them, router edges, and stain them, probably deep mohogany. Will use french cleats on the back so that they are sticking about an inch out from the walls.

As I'm not getting many replies I just wanted to show that I'm serious about trying this, and doing everything I can think of from reading the threads. Any expert advice is GREATLY appreciated.

Dreamhost,

Just read your other thread. Since you don't seem to be afraid of throwing a little money at a problem, and you mention boominess, take out what your bass traps can't help with the Behringer FBD and Room EQ Wizard. Google it.

50 panels? Good God!! what did that run you. I only bought 12 of the 703 for $120, and I thougt that was a good deal. Are you getting this stuff really cheap?

Before we go any further, please be careful when cutting and stacking that fiberglass. If you get a bunch of those fibers in your lungs you're not going to like it. It won't kill you, but you're not going to like it.

I'm not sure what you mean by staining the fiberglass. I framed mine and covered it with a thin, natural fiber (cotton) fabric. Check out the walmart bargin shelf. You can also affix it directly to the panels w/ 3m spray adhesive.

On to the room. First you should understand what you're doing, and how sound works. With the fiberglass in the corner, you are taming room modes. Google that one if you're not familiar with it. Fiberglass in the corner will smooth out bass a little, should help shorten bass reverb time a bit. With as much fiberglass as you have, you might as well use the leftovers for this purpose.

One of your original problems was flutter echo. If you clap your hands, and you get a pringy reverb, this is flutter echo. It's cause by sound bouncing back and for between parallel surfaces, so anywhere you have 2 flat, reflective surfaces, you want to hang fiberglass on atleast one of those surfaces. Like I recomended, the front wall should be as dead as possible. Given that your room is so small and you have that screen taking up a lot of your front wall, you'll want to deaden or diffuse the first reflection points on the back wall, the space right behind your ears.

Putting fiberglass behind your screen won't do a damn thing unless your screen is perforated, or otherwise acoustically trandparent.

What to listen for? Do a clap test, then hang your fiberglass, then repeat the clap test. The results should be quite evident. That same improvement will carry over to music and movies. Dialogue should be clearer. You should be able to hear quiet details in music that were masked by room reverb before. All of these things I notice after hanging only 9 2x4 2" 703 panels in my 15.2x13.8x8 room.

If you feel the room is too dead. Take down a panel or two from the side or back walls. Like that better? Then hang the panels you just took down in another room, or make super chunk bass traps out of them.

Panels were just under $20 each, so not to bad. I got them somewhat local, 50 mile drive, so no shipping involved. They didn't have any 703 in stock, only had 2" 705 so I bought what they had.

Your right about the lungs. Took long cold shower to stop the itching, totally sucked, and I've only just begun.

Do you think continuing the corner trap all the way to the ceiling would help? I was going to leave the rear speaker where it's at and just continue adding 705 above it. Just got tired of cutting this stuff. Will continue it up this weekend if it's advised. I just wish I could do the other corners. I do have enough that I could do the entire ceiling circ like I did the corner, though I have never seen that done before.

I am NOT going to leave it as is. If I like the effect I was trying to say that I would build enclosures for all the 705, and stain the enclosure itself where you would see the wood boarders. Think speaker cabinet with cloth grill, only the cloth would cover the 705. I want to keep this room looking as nice as possible.

So far I have noticed a substantial increase in perceived bass in the room. I literally jumped up to turn off the buttkickers, only to find they were already off. The room is still a bit boomy, but it's def tighter.

I put two large panels on the front wall below the screen, temp covered in fabric just sitting there, and it has indeed cleared up the front stage. Hands down the biggest difference though was putting a sheet on top of the coffee table. I was cutting it there, and noticed sound was kinda cool, so sat back and wow..... big difference.

Even without treating the side walls, the harshness is now gone, or close to it. I'm certain that I am pushing such a small room beyond it's volume capability. I'll keep bringing in pieces and putting them around the room until I find a level I like. Then I'll build the frames etc.

Question about framing the panels:
As I have 2" I know that I still want an airgap between the panel and the wall, prob close to an inch. Now if I use wood that is 3" wide and have the panel in the front part, that leaves the back 1" open, but the sides of the wood would be touching the walls. Is that optimal?
Or should I just build the frame 2" thick and then th 705 would fill it up, and then just use a crossbrace french cleat to keep it away from the wall?
Hope this makes sense.... photoshop is not on this computer so can't diagram it out to well.

Dreamhost,

Just read your other thread. Since you don't seem to be afraid of throwing a little money at a problem, and you mention boominess, take out what your bass traps can't help with the Behringer FBD and Room EQ Wizard. Google it.

Should I go that route, or just purchase a Audyssey setup? It's only $2500 plus install, so not talking a ton of $ here. Never heard of the Behringer FBD before.

Should I go that route, or just purchase a Audyssey setup? It's only $2500 plus install, so not talking a ton of $ here. Never heard of the Behringer FBD before.

Honestly, if you're willing to spend that type of money I would go ahead and contact Terry from HAA.

He's a specialist and can not only recommend good treatments but also back it up with graphs etc. to show you the difference.

Should I go that route, or just purchase a Audyssey setup? It's only $2500 plus install, so not talking a ton of $ here. Never heard of the Behringer FBD before.

Dude, I need your problems for a day.

Yeah, you've already spent $1000 on fiberglass. Just hire somebody.

Eugo.

What you've done and heard only a little improvement is simply because there just isn't enough there yet. Doing half of one room corner isn't going to give a significant improvement in bass control For what you're doing, save some money and use 703 instead of 705 - will work just fine in a solid chunk like that.

As for the front wall, you need to do the whole thing. It's not just boundary effects but also killing surround reflections off the front wall mucking things up.

Bryan

Eugo.

What you've done and heard only a little improvement is simply because there just isn't enough there yet. Doing half of one room corner isn't going to give a significant improvement in bass control For what you're doing, save some money and use 703 instead of 705 - will work just fine in a solid chunk like that.

As for the front wall, you need to do the whole thing. It's not just boundary effects but also killing surround reflections off the front wall mucking things up.

Bryan
No go on the 703 as I already have all the 705 I would ever need.
As to having only done 1/2 of 1 corner, do you think it would be more effective to carry that all the way to the ceiling? As the room is so small that would equate to about 1.5% of the entire room volume.

I'm going out today to pickup a mic adaptor so that I can take some frequency sweeps of the room. I'm curious if there is a formula involved with bass traps and how much vs. density to help with the problem tones? MEaning that if I have a hole at say 80hz, is there a formula to follow that tells me exactly how much of the 705 to use and where and in what configuration? Obviosly I am quite new to this acoustic stuff but eager to learn.

...I have all the pieces, the Lincoustics, the poly batting, and the furring strips, etc.

I have 84" high ceilings.

I have heard 1/2 way up from floor is Lincoustic, remainder is poly batting.

Question: I am rather tall, can I extend the lincoustic to 48 inches? Remainder finished with poly batting of course.
Reasoning-Lincoustics comes in 48" rolls. one less cut... :)

I plan on putting the chair rail moulding about 1/3 of the distance from floor-ie black GOM lower ~1/3, burgundy GOM ~ upper 2/3.

Question: Will that make the walls look weird if the moulding is not located at the lincoustic/poly batting seam?

Won't the 1" furring strips elimate this wierd interface?

Thanks for the advice,
Best,
Tom
Chinaclipper

This weekend, I will be making (2) 36" x 18" x 4" panels to mount in the corners of my room.

They will be wrapped in batting, and covered with Burlap across the front. They will not have frames of any kind. But I can attach small wood strips if needed.

Does anyone have any ideas on how I can mount them straddling the upper corners?

See pics attached.

http://i38.photobucket.com/albums/e127/esthomps/Home%20Theater%202/HomeTheater1-7.jpg

http://i38.photobucket.com/albums/e127/esthomps/Home%20Theater%202/HomeTheater.jpg

Thanks

I'm curious if there is a formula involved with bass traps and how much vs. density to help with the problem tones? MEaning that if I have a hole at say 80hz, is there a formula to follow that tells me exactly how much of the 705 to use and where and in what configuration? Obviosly I am quite new to this acoustic stuff but eager to learn.
Unfortunately, no. But your speakers are so close to one wall and your chairs so close to another, I can't imagine not having some significant acoustical issues. Boundary interference effects are strongest under these circumstances, as are room mode peaks.

I would start by putting the 2" fiberglass over all of the wall right behind the seating, and over all of the wall behind speakers and screen. Putting fiberglass behind your screen will only affect low frequencies, but you say you have problems in this area. Flutter echo is a higher frequency phenomenon, and can only occur when you have parallel surfaces with both you and the sound source between them. Since your speakers are below the screen, there can't be any audible flutter echo between the screen and the back wall.

Regards,
Terry

As to having only done 1/2 of 1 corner, do you think it would be more effective to carry that all the way to the ceiling?

Yes.

I'm curious if there is a formula involved with bass traps and how much vs. density to help with the problem tones? MEaning that if I have a hole at say 80hz, is there a formula to follow that tells me exactly how much of the 705 to use and where and in what configuration? Obviosly I am quite new to this acoustic stuff but eager to learn.

No, no formula. IF you are eager to learn, you should read this whole thread, as well as Ethan's FAQ and the information on Room EQ Wizard, The Behringer BFD, and and anything else that googling "acoustic treatment" and "Room Acoustics" turns up.


Look before you leap.

Does anyone have any ideas on how I can mount them straddling the upper corners?

That's always a tough one. Maybe long picture wire or nylon fishing line? Of course, that's the whole point of DIY - the fun of figuring out what to do and how to do it.

--Ethan

rockemsockem:

Does anyone have any ideas on how I can mount them straddling the upper corners?

There's a few ways. There's some ideas in this thread (http://forum.studiotips.com/viewtopic.php?t=2857).

My house building is about to start. My media room is 3.5 x 5.9m.

I was hoping to have a multipurpose/minimalist room with stealthed equipment, stealthed motorized screen, etc. So is there any way to improve the room for both 2ch and surround without it looking like a dedicated room? Is it even possible to improve the sound to a certain extent for both 2ch and surround or is any benefit for one a hinderance to the oher?

I can always move my 2ch setup into a different room so what are the best "bang for the buck" treatments I can do for surround without doing large parts of the room?

My house building is about to start. My media room is 3.5 x 5.9m.

I was hoping to have a multipurpose/minimalist room with stealthed equipment, stealthed motorized screen, etc. So is there any way to improve the room for both 2ch and surround without it looking like a dedicated room? Is it even possible to improve the sound to a certain extent for both 2ch and surround or is any benefit for one a hinderance to the oher?

I can always move my 2ch setup into a different room so what are the best "bang for the buck" treatments I can do for surround without doing large parts of the room?

The more bass traps you put into the room the flatter the response will be. Most rooms are going to take quite a few bass traps to get it to a point of "HEAVEN", but there is no reason why starting with 4 bass traps with one in each corner and panels for the first reflection points will not help a lot.

Glenn

what are the best "bang for the buck" treatments I can do for surround without doing large parts of the room?

There's no good answer. As Glenn said, even four bass traps, one in each wall-wall corner, will help. But if your goal is truly excellent sound you'll need a lot of acoustic treatment. There's no way around that.

You can hide treatments behind faux fabric walls etc, but it's more expensive. So you have to balance cost, appearance, and audio quality. Personally, I don't mind the look of acoustic treatment. I think it looks cool! And when you dim the lights to watch a movie or listen to a great CD, how many panels you see is irrelevant.

--Ethan

By the way, does anybody have good suggestions for modelling corner bass traps in a program like CARA?

CARA works on the concept of surfaces with absorption coefficients applied to each area of the surface. I can easily model the angled front of the corner trap as the new wall surface, but what absorption coefficient would I apply across it's face? In reality, it seems like the absorption would actually vary across the face (more bass absorption in the middle, where it's deeper).

Has anyone measured/estimated the average absorption coefficient equivalent across the front surface of a superchunk style corner bass trap?

I finally made it to the end of this Thread. I now have enough information to be dangerous. I would like to thank Dennis, Ethan, Terry, pepar,BasementBob and bpape. I hope to complete my theatre in the next 90 days. I will be posting questions as we proceed.

Thanks
Guy

Dennis, Ethan, Terry, pepar, BasementBob, bpape and others I really need some input...




I was not sure whether or not to post here in the Acoustical Treatment thread and after consideration I felt that this issue would in all probability full under acoustic treatment... so here goes...

I have a theater room that I would consider Quasi- dedicated as there is an opening through a wall into another room and I will also ultimately be acoustically treating this room to some degree with the requisite first reflection and bass absorption treatments.

The theater room is 12.5 ft. wide and 21 ft. long with a shed type slanted ceiling which rises from an 8 ft high wall on the right to a 10 ft. high wall on the left. The theater room has a 5 ft. wide X 3 ft. high opening which is centered on the left wall and is 3.5 ft. off the floor and opens into a 8 ft. wide X 11 ft. long galley style kitchen.

There is also a 5 ft. wide X 3.5 ft. high glass window centered on the right side wall opposite the left side wall opening and has a blackout cellular shade installed running in light control tracks.

The two rooms can be completely sealed off from the rest of the house via doorways so in essence the two sealed rooms are only linked together via the 3 ft. X 5 ft. opening and I was wondering how to effectively handle and work with this opening and the opposing window?

Remember, I will ultimately be placing acoustic panels within the room to some degree and the window on the right side wall already has the cellular blackout shade installed.

Should I install some wooden blinds over the opening into the kitchen? Would this help contain some of the High/ Mid frequency sound and help in room acoustics?

Should I also place similar wooden blinds over the cellular shade treated glass window on the right side of the room for symmetry?

Basically, how is this opening on the left side of my theater going to possibly impact my in room acoustics and how should I deal with it?

Any and all suggestions will be greatly appreciated!


...Glenn :)

By the way, does anybody have good suggestions for modelling corner bass traps in a program like CARA?

CARA, or even an actual ray-tracer, will not produce correct results if you just plug in the geometry and absorption coefficients. The reason is that at low frequencies (where the size of the surface is comparable to or smaller than a wavelength) diffusion, in the sense of diffraction/scattering, will become a significant factor at the edges of the absorber. The simple ray model is no longer a correct description, because rays effectively bend into the absorber near boundaries. They are no longer straight. This causes the effective surface area to be significantly greater at low frequencies than geometric acoustics would predict.

Regards,
Terry

Glenn -- I am too stupid to visualize your room, even though you've given an extensive textual description. :) Can you post some kind of diagram or plan?

Thanks,
Terry

CARA, or even an actual ray-tracer, will not produce correct results if you just plug in the geometry and absorption coefficients.
...
Regards,
Terry

Thanks, Terry, good input.

Is CARA completely useless below a certain frequency (say 200 Hz)? Or is it useful but it under/overestimates the effectiveness of bass traps? Is there a way to compensate? A rule of thumb for fudging the geometry or the coefficients up or down to roughly compensate for the edge effects/bending?

If not, I'll just plan on using CARA for higher frequency stuff: localization, speech intelligibility, etc. and drop in as many bass traps as the room can handle without looking too silly.

Thanks, Terry, good input.

Is CARA completely useless below a certain frequency (say 200 Hz)? Or is it useful but it under/overestimates the effectiveness of bass traps? Is there a way to compensate? A rule of thumb for fudging the geometry or the coefficients up or down to roughly compensate for the edge effects/bending?

CARA is one of two general classes of geometric acoustic modeling programs: image source modelers and ray tracers. CARA is an image source modeler. Professional programs are pure ray tracers or hybrids which use the image source technique for the first few reflections and ray tracing for the rest. More about this later.

With all geometric modelers, you have the absorption diffraction problem. I know of one technique to deal with it, which I developed myself. I started writing this up for a professional journal last year. But then I realized it is worth much more to me as trade secret who's use is part of what my clients pay for than as a journal paper. Sorry!


If not, I'll just plan on using CARA for higher frequency stuff: localization, speech intelligibility, etc. and drop in as many bass traps as the room can handle without looking too silly.
There are many tricks of the trade which turn geometric modelers from amusing curiosities which draw pretty diagrams into useful prediction tools. One of the biggest issues is correct absorption coefficients. The "book values" measured in the lab simply don't cut it in many cases, and they have to be tuned through experience to reflect realistic field conditions. So its often a case of "garbage in -- garbage out."

Another issue which is particular to CARA is sufficient computation time to yield accurate results. An image source modeler is very efficient for purely rectangular rooms, and can yield results as good as any ray tracer for these. But add any more complex room geometry (furniture, for example), and the accuracy plummets for the same computation time. This is why professional programs don't use the pure image source technique.

So take the CARA results with a very large grain of salt. IMO, it is a good qualitative tool for interactively learning some of the effects which rooms have on sound. But as a serious prediction tool, it is lacking. Which is not to say that if you had a pro tool like ODEON, for example, you would necessarily get great results. The proper use of complex prediction software requires experience. There are elements of uncertainty, sensitivity to particular conditions, and interpretation which can take years to learn. If is somewhat akin to using a CAD architecture program. You can draw pretty buildings with it, but this does not automatically make you an architect! :)

Regards,
Terry

Glenn,

> I was wondering how to effectively handle and work with this opening and the opposing window? <

From an acoustics standpoint you can probably just ignore the window and the opening. This assumes neither is at a reflection point, which may or may not be the case.

> Should I install some wooden blinds over the opening into the kitchen? Would this help contain some of the High/ Mid frequency sound and help in room acoustics? <

Are you asking about sound isolation between rooms, or sound quality inside the room?

--Ethan

Ethan,

Sound isolation between the two rooms is not an issue at all, I am speaking strictly in an acoustical sense.

I was curious as to any possible acoustical anomolies that might be created such as additional ringing, slap echo or a general break down in the acoustic bubble and or envelopment issues particularly on the left side of the room where the opening is into the kitchen.

My thinking was that maybe some wooden blinds installed over the opening might help contain and or allow some of the sound to bounce around the room a little better. If that strategy would help and in the interest of balance/symmetry I thought that maybe I should also install similar blinds over the cellular blackout shade treated window which is directly across the room on the opposing right side wall.

Remember, the 3 ft. X 5 ft. opening is on the left side of the room and the 3 ft. X 5 ft. window is directly opposite the opening on the right side wall like mirrors of each other... I hope that makes sense.

The total room length is 21 feet and the opening and window are about centered on the side walls. My 3 abreast theater seats are just within the back third of the room and when sitting upright my head is about 6 to 6.5 feet from the back wall.

A cursory examination appears to place the opening and window just behind the first side wall reflection point and I might be able to adjust that somewhat via seating and speaker placement changes.

I am probably reading to much into this, and I know of course that I should set everything up and listen and evaluate the sound before passing any real judgements! I am sure however that I will be installing room treatments in the form of first reflection/ broadband absorption and bass absorption as I do have some slap echo that I can hear and the room will definitely require some taming.


...Glenn :)

Glenn,

> My thinking was that maybe some wooden blinds installed over the opening might help contain and or allow some of the sound to bounce around the room a little better. <

With acoustics, what matters is the big stuff. If you have a window and you cover it with wood blinds, that won't have much affect whether the blinds are open or closed. Maybe if the slats were really wide and you opened them partway. But mostly, a large reflecting surface is a large reflecting surface.

> A cursory examination appears to place the opening and window just behind the first side wall reflection point and I might be able to adjust that somewhat via seating and speaker placement changes. <

There you go.

--Ethan

For an HT/MC Music Room, would it be a good idea to cover the entire front wall with 4" 703? Would this make a good bass trap? Or, would it be better to place the traps in the corner and use a thinner material, (1" or 2") on the rest of the wall? Which would provide more bass trapping?

Thanks.

Craig

The latter. Put the thicker stuff in corners and at room boundaries (straddling corners and places where floor/ceiling and walls meet), with thinner 2" panels at specific points arond the room. Don't cover every wall.

Agreed mostly.

How thick you go on certain parts of the front wall will depend on what you're needing to do in terms of SBIR control. For pure reflection control, 1-2" is fine.

Bryan

Agreed mostly.

How thick you go on certain parts of the front wall will depend on what you're needing to do in terms of SBIR control. For pure reflection control, 1-2" is fine.

Bryan
Should acoustical measurements be taken before the 2" - 4" decision is made? The front wall in question here is behind a false wall, so no aesthetics are harmed by doing whatever there. It was my recommendation to use 4" instead of 2" thinking that it may reduce the need for chunky-style traps in the listening/viewing are by reaching lower in frequencies absorbed. Is my thinking wrong? If so, why?

pepar:

lower in frequencies

Please define 'low', in hz range, that you mean. (To me, when I write 'low', what I mean is the typical-HT-room-volume's modal problems range, which would be in the 15hz to 115hz.)

Then define the % increase in normal incidence absorbtion at 125hz (and lower) to 1khz, and % increase in diffuse absorption at 125hz to 1khz, of going from 2" to 4" mounted on the wall.

Then cost justify it, including mounting technique differences. This is all from a 'how good is it as an absorber' point of view, not from a is it needed for some-specific-room point of view.

(also remember the ITU/EBU rule "Early reflections are defined as reflections from boundary surfaces or other surfaces in the room which reach the listening area within the first 15 ms after the arrival of the direct sound. The levels of these reflections should be at least 10 dB below the level of the direct sound for all frequencies in the range 1 kHz to 8 kHz.")

Please define 'low', in hz range, that you mean. (To me, when I write 'low', what I mean is the typical-HT-room-volume's modal problems range, which would be in the 15hz to 115hz.)
His room sounded tubby and to me that's 125Hz to 250Hz, maybe 300Hz. Note that I said "lower in frequency" not "low frequency."

Then define the % increase in normal incidence absorbtion at 125hz (and lower) to 1khz, and % increase in diffuse absorption at 125hz to 1khz, of going from 2" to 4" mounted on the wall.
Incidence absorption? Is that different from plain ol' absorption? :) Is is a straight calculation, e.g. 4" 703, plain, has ~5x the absorption (.84 vs .17) at 125Hz of 2" 703, plain?

Then cost justify it, including mounting technique differences. This is all from a 'how good is it as an absorber' point of view, not from a is it needed for some-specific-room point of view.
I know what I paid for plain 2" 703, but I've never priced 4". If it was much more, then couldn't one simply use two layers of 2"? On your last sentence - huh?

(also remember the ITU/EBU rule "Early reflections are defined as reflections from boundary surfaces or other surfaces in the room which reach the listening area within the first 15 ms after the arrival of the direct sound. The levels of these reflections should be at least 10 dB below the level of the direct sound for all frequencies in the range 1 kHz to 8 kHz.")
Wrong it may have been, but my thinking was that he'd get more absorption in the range that sounded, to me, like it was a problem.

pepar:

I'm just muttering in general terms -- not about any specific room. :)

'normal incidence' is an angle, in this case straight into the face. There aren't many published results about these. But there's a lot of theory, and calculation tools. ChrisW's spreadsheet for example.

'diffuse absorption' is sound coming from everywhere, and is the style for all the results at this page: http://www.bobgolds.com/AbsorptionCoefficients.htm

Wrong it may have been, but my thinking was that he'd get more absorption in the range that sounded, to me, like it was a problem. You're not nessessarily wrong -- you may be 100% right. I was just hoping you'd make me some graphs of the expected difference between the two absorbers you're considering to see what you think the actual difference is between them.
I figure moving from 2" to 4" of 703 gives a
a) diffuse: 400% increase in diffuse absorption at 125hz, and a 20% increase in diffuse absorption at 250hz, and no increase above that frequency. (see bottom of graph)
b) normal: well, I'll do the graphs I was hoping for

http://www.bobgolds.com/AbsorberModeVsBassTrap/2vs4inchAndNormalVs70degreeAndAngleVsDiffuse.GIF

His room sounded tubby and to me that's 125Hz to 250Hz, maybe 300Hz. Note that I said "lower in frequency" not "low frequency."Yep, I see a reasonable change in the 125hz to 300hz range moving from 2" to 4" in the normal and grazing and diffuse coefficients. (16000rayls/m may not represent 703, and neither may a computer simulation)

So, how many square feet of this do you think this specific room will need to make a perceptable difference? Where do you want to put it, and what side effects will it have?

pepar:

I'm just muttering in general terms -- not about any specific room. :)
Roger that. :) craig john and I have a specific room in mind.

'diffuse absorption' is sound coming from everywhere, and is the style for all the results at this page: http://www.bobgolds.com/AbsorptionCoefficients.htm
Roger that as well. (That's you, right, you're da Bob in bobgolds?) :cool:
. . . what you think the actual difference is between them.
I figure moving from 2" to 4" of 703 gives a
diffuse: 400% increase in diffuse absorption at 125hz, and a 20% increase in diffuse absorption at 250hz, and no increase above that frequency.

Yep, I see a reasonable change in the 125hz to 300hz range moving from 2" to 4" in the normal and grazing and diffuse coefficients. (16000rayls/m may not represent 703, and neither may a computer simulation)

So, how many square feet of this do you think this specific room will need to make a perceptable difference? Where do you want to put it, and what side effects will it have?
Thanks, and that's exactly what I had in mind. The "where" is behind his false wall. Can you point me to information and/or calculations for determining in advance how much it would take to make a perceptible difference and what "side effect" it would have? (I suppose I should be looking for negative side effects?)

Perceptable
a) changing any reflection at some frequency band by 6db
b) halving RT60 at some frequency band
c) increasing the absorption in some frequency band by 30%

There's lots of side effects. One, from an RT60 perspective would be that if the room sounds good now with little absorption (no draps, no cloth couch, no carpet), and you cover an otherwise bare front wall with absorption that does a much larger job of absorbing 500hz to 8khz, than it does from 15 hz to 300 hz, you might create more problems than cures.

Perceptable
a) changing any reflection at some frequency band by 6db
b) halving RT60 at some frequency band
c) increasing the absorption in some frequency band by 30%

There's lots of side effects. One, from an RT60 perspective would be that if the room sounds good now with little absorption (no draps, no cloth couch, no carpet), and you cover an otherwise bare front wall with absorption that does a much larger job of absorbing 500hz to 8khz, than it does from 15 hz to 300 hz, you might create more problems than cures.
Right now, it does not sound good. There's carpet and a large comfy sectional, but otherwise it is plaster walls and ceiling.

Here is a pic of my J-M Linacoustic-lined false wall cavity - http://www.peparsplace.com/assets/images/HT_009.jpg. My room sounds good, but I need to add traps to control the 125Hz to 250Hz range. I would have lost no more mids and highs by using 4" in my false wall cavity instead of the 2" I did use and I'd have less of a problem - or maybe NO problem - in that range. That is what's at the root of my thinking. :)

"Should acoustical measurements be taken before the 2" - 4" decision is made? The front wall in question here is behind a false wall, so no aesthetics are harmed by doing whatever there. It was my recommendation to use 4" instead of 2" thinking that it may reduce the need for chunky-style traps in the listening/viewing are by reaching lower in frequencies absorbed. Is my thinking wrong? If so, why?"

Yes. IMO we set up speakers and tweak location to get the smoothest response. Then based on what's left and what's being reinforced by SBIR, we deal with it accordingly. This is more of an iterative way to go about it but it works well in real rooms where there isn't always enough space to do what we'd like.

If we could get by with just 4" on the front wall and that was all that was needed, you'd be correct - assuming that you're not making the SBIR issues worse. You may in fact not WANT to deal with the really lower frequencies as they're already relatively flat in which case we'd go thinner. Also, the corners provide better efficiency over a number of different axial, tangential, and oblique modes where the front wall is going to deal with less of those and less efficiently.

Bryan

pepar:

One should define 'sounds good' a bit better.

For example
I had my room like this
http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1089.jpg
and when I played the end credits to We Were Soldiers DVD, with the men's choir, I was in acoustic heaven. Room support was fantastic. I litterally stopped what I was doing and couldn't stop listening. I played that bit over and over, turned the volume up, showed that bit to all of my friends and relatives. It was fantastic. Easilly the best sound I've ever heard, anywhere.

But that layout wasn't what I wanted.
And the imaging was off and speach inteligibility seemed low.

I tried different speaker positions and treatment layouts.

http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1192.jpg

http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1195.jpg

http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1190.jpg

and although the last one above sounded really great,
what I ended up building was a little different:

http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1248.jpg

That's 4" thick rockwool, with a 4" airgap behind it.
And I can tell you without a shadow of a doubt, it's not that heavenly room support I had before. It's dull and lifeless.

(for more about this and some more detailed acoustic observations regarding each picture please see
http://www.bobgolds.com/LivingRoomPlasma/Construction/home.htm
at 2006/12/01 about 60% of the way down)

Speach inteligibility is pretty good though.

I had some imaging problems, pod race from Star Wars I couldn't tell left from right. Room geometry takes care of left speaker off the left wall, and right speaker off the right wall. But the problem turned ot to be left speaker off right wall, which a right side wall absorber took care of and solved the imaging. Pod race is better with good imaging.

I've been meaning to do some ETF tests and tweaks, but I haven't gotten around to it.

That room will never be optimal acoustically due to other constraints -- and I haven't tried more or less surface area, nor more or less absorbtive material, in that front wall yet. Although I built it so I could fiddle.


A year ago I had the same speakers in the basement (five concrete surfaces walls and floor) and even with two subwoofers never had any bass. Upstairs in the living room (above pictures) I've got bass to burn. I'm hearing things I've never heard before and really enjoying them.


My point is 'sounds good' can actually be a bad thing.

With my lifeless room now, I've tried a bunch of the DSP modes on my receiver (DSP pretend to be a church, DSP pretend to be a concert hall, DSP pretend to be a rock studio, ...) and I've found that while I can get some of that heavenly sound with that particular spot in We Were Soldiers (although not nearly the stop dead in your tracks as if you've fallen under a spell like the first time you fall in love and think that all's right in the world that I had with the two other layouts), if I leave that DSP setting on there's some DVDs that I can't understand speach with -- but I turn off the DSP modes (output 'STRAIGHT') and it clears up immediately.

If we could get by with just 4" on the front wall and that was all that was needed, you'd be correct - assuming that you're not making the SBIR issues worse. You may in fact not WANT to deal with the really lower frequencies as they're already relatively flat in which case we'd go thinner. Also, the corners provide better efficiency over a number of different axial, tangential, and oblique modes where the front wall is going to deal with less of those and less efficiently.
OK, that gets my attention; thicker on a wall isn't as effective as corners. So that is a point in favor of saving money on 2" on the front wall and spending it on more effective corner treatments. In fact, that is probably the tipping point in favor of that.

pepar:

One should define 'sounds good' a bit better.
I have nearfield listening at all six listening positions. Once I tame the under 300Hz range, I will be a happy camper. So, actually, I misspoke. The room doesn't sound good, the system does, and the room is not in the way.


I had my room like this and when I played the end credits to We Were Soldiers DVD, with the men's choir, I was in acoustic heaven. Room support was fantastic. I litterally stopped what I was doing and couldn't stop listening. I played that bit over and over, turned the volume up, showed that bit to all of my friends and relatives. It was fantastic. Easilly the best sound I've ever heard, anywhere.

But that layout wasn't what I wanted. And the imaging was off and speach inteligibility seemed low.
Not sure what you mean by "room support." And in light of poor imaging and low intelligibility, it's obvious your room's support was interfering. Perhaps the room's signature was complementary to a choir, but not other sounds. This is exactly why I prefer nearfield listening.

I tried different speaker positions and treatment layouts. and although the last one above sounded really great, what I ended up building was a little different:

http://www.bobgolds.com/LivingRoomPlasma/Construction/IMG_1248.jpg

That's 4" thick rockwool, with a 4" airgap behind it.
And I can tell you without a shadow of a doubt, it's not that heavenly room support I had before. It's dull and lifeless. Speach inteligibility is pretty good though.

I had some imaging problems, pod race from Star Wars I couldn't tell left from right. Room geometry takes care of left speaker off the left wall, and right speaker off the right wall. But the problem turned ot to be left speaker off right wall, which a right side wall absorber took care of and solved the imaging. Pod race is better with good imaging.

I've been meaning to do some ETF tests and tweaks, but I haven't gotten around to it.

That room will never be optimal acoustically due to other constraints -- and I haven't tried more or less surface area, nor more or less absorbtive material, in that front wall yet. Although I built it so I could fiddle.


A year ago I had the same speakers in the basement (five concrete surfaces walls and floor) and even with two subwoofers never had any bass. Upstairs in the living room (above pictures) I've got bass to burn. I'm hearing things I've never heard before and really enjoying them.


My point is 'sounds good' can actually be a bad thing.
To the extent that a room has a noticeable "sound" at all, yes. See my response above.

With my lifeless room now, I've tried a bunch of the DSP modes on my receiver (DSP pretend to be a church, DSP pretend to be a concert hall, DSP pretend to be a rock studio, ...) and I've found that while I can get some of that heavenly sound with that particular spot in We Were Soldiers (although not nearly the stop dead in your tracks as if you've fallen under a spell like the first time you fall in love and think that all's right in the world that I had with the two other layouts), if I leave that DSP setting on there's some DVDs that I can't understand speach with -- but I turn off the DSP modes (output 'STRAIGHT') and it clears up immediately.
DSP, IMO, is worse than worthless. Artists, engineers and producers go to great length to create an ambiance. Monkeying with that can only degrade what the creators intended. If a particular DSP setting, or room environment, enhances a particular recording - We Were Soldiers for example - but nothing else, then it is likely that We Were Solders is not "right" either.

Dennis, Ehtan, and anyone else

I am doing a Ht room and i line around Memphis, TN. I have the room sheetrocked and want to get the acoustics right. My room is small 10 (width)x16 (length)x8.5(height). My room "T''s out in the back to 25 foot wide for about 4 feet.

I will sit around 12 feet from the front and thus 4 feet from the back.

Here are my thoughts:

1) Acoustic panels behind the front left and right placed on the sheetrock.
2) Acoustic panels atthe first reflective points (using mirror suggestion)
3) Basss traps in the corners in the front and in the back corners (the room is shaped in a "T" shape. SHould I put bass traps in the corbers created by the "T" as well.
4) Should i consider diffusors on the back walls or acoustic shields for absorbtion.

I mentioned where i live in case you could recommend someone locally I could have come and help me.

It seems that acoustic shields behind the front speakers is very important as well as shields at the first reflective points in relation to where the listener is sitting.

thanks for the help!

Dax

Dax,

> Here are my thoughts: <

That all sounds about right. You can't have too many bass traps, so plan on plenty for best results.

> SHould I put bass traps in the corbers created by the "T" as well. <

Maybe. If you stand back there in the "wings" do you hear bass build up in the corners? If so, traps there might help.

> 4) Should i consider diffusors on the back walls or acoustic shields for absorbtion. <

Good diffusors cost more than good absorbers, whether DIY or commercial, so it comes down to how much you're willing to spend.

> I mentioned where i live in case you could recommend someone locally I could have come and help me. <

It's not clear if you're looking for DIY advice or a commercial solution. I help customers all over the world by email and photos etc.

--Ethan

Re: cost of diffusers, you can make inexpensive polycylindrical diffusers out of bent sheets of practically anything hard and relatively flexible. They are as good as the modern "well-type" diffuser in nearly all situations.

Both types of diffusers have the drawback of needing a lot of depth -- much more than an absorber of equivalent frequency effectiveness.

- Terry

I would not use the 2" material...it will very likely be too absorptive.

The fill out is polyester batting. Don't use styrofoam.


Dennis, you sound pretty firm on not using styrofoam. Is there a valid reason, if it is fire rated.

Re: cost of diffusers, you can make inexpensive polycylindrical diffusers out of bent sheets of practically anything hard and relatively flexible. They are as good as the modern "well-type" diffuser in nearly all situations.

Both types of diffusers have the drawback of needing a lot of depth -- much more than an absorber of equivalent frequency effectiveness.

- Terry

Terry,

Can you offer any pointers on building "bent-sheet" diffusers such as what radius of curvature is needed to be effective and what the orientation of the arc should be?

I have my theater room sheetrocked and painted. Almost my whole front wall will be covered with the screen.

I keep hearing that shielding the front wall is big but what about my situation?

Should I treat all the areas around the screen or go ahead and treat behind the screen as well?

What should I use? Anything I can get at Lowes or Home Depot? Can I paint it to match the other walls in my theater room (brown).

I was goign to put acoustic shields right behind the front, left, and center channels. Would this not be enough treatment for my front wall.

The dimension are 9.5'wideX16'long.

Thanks for your advice

I have my theater room sheetrocked and painted. Almost my whole front wall will be covered with the screen.

I keep hearing that shielding the front wall is big but what about my situation?

Should I treat all the areas around the screen or go ahead and treat behind the screen as well?

What should I use? Anything I can get at Lowes or Home Depot? Can I paint it to match the other walls in my theater room (brown).

I was goign to put acoustic shields right behind the front, left, and center channels. Would this not be enough treatment for my front wall.

The dimension are 9.5'wideX16'long.

Thanks for your advice

Start by reading this whole thread. This question has been asked and answered severall times.

Short version:

What about your situation?
Depends on if your screen is perforated.
OC 703 or similar. No. No.

i have read all the thread but i still am confused on how I am going to treat my front wall that has a non-perforated screen that takes up most of that front wall.

Should I go ahead and put OC 703 on the whole wall ebfore my screen goes up even though the scren will cover msot of it up??

i have read all the thread but i still am confused on how I am going to treat my front wall that has a non-perforated screen that takes up most of that front wall.

Should I go ahead and put OC 703 on the whole wall ebfore my screen goes up even though the scren will cover msot of it up??

No, the screen will reflect high frequencies and make the absorption ineffective and narrowband.

Terry,

Can you offer any pointers on building "bent-sheet" diffusers such as what radius of curvature is needed to be effective and what the orientation of the arc should be?
You have a lot of flexibility here. :D

A larger arc will diffuse down to lower frequencies. To a first approximation, a radius of curvature r will be effective at diffusing frequencies whose wavelengths are less than 2 pi r. This is not a sharp boundary -- you approach the maximum diffusion at maybe 3 or 4 times this frequency. To get the frequency for a particular wavelength in feet, just divide it into 1130 feet per second, the speed of sound. How much of a circular arc you use will depend on how much depth you are willing to allow. Varying the spacing and radius of curvature for multiple diffusers is a good idea.

One nice thing about polycylindrical diffusers is that, unlike the now-common discrete varying depth type of diffuser, they have no high frequency limit on the sounds they will effectively diffuse. As for orientation, it depends on the specific purpose of the diffusion. If it is to maintain a broad sound stage, then vertical orientation is often preferable. On the other hand, horizontal orientation will improve the uniformity of reverberation decay if you have a very uneven balance of horizontal and vertical absorption -- "dead" walls and "live" ceiling and floor, for example.

- Terry

Terry,

> polycylindrical diffusers ... are as good as the modern "well-type" diffuser in nearly all situations. <

That's wrong on so many levels I'm not even sure where to start. :eek: But I'll try.

The main advantage of QRD diffusors is they actually diffuse, versus curved plywood that merely deflects. There is a difference, and that difference affects how well each device reduces comb filtering.

But don't take my word for it. :D Here's a recent quote from Jeff Szymanski, who I'm sure you know of:

Having heard some truly awful acoustical artefacts from things like polys and pyramidal "diffusers," I can conclude that proper diffusers are a much better way to go.

And this is from recording studio designer Wes Lachot, another big proponent of QRD diffusors over curved plywood:

To my ears, sitting on a couch in front of a diffusor array sounds much better [than absorption]. Of course you hear some phase effects if you move your head left to right, but it still beats having a black hole behind your head (or a big flat reflector).

It was explained to me once by one of the inventors of QRDs that phase distortion is inherently part of the sound of QRDs. In fact, without comb filtering effects, QRDs could not do what they do, which is accomplished through the deft use of constructive and destructive interference techniques.

--Ethan

Anyone know of any good sites dealing a DIY 2D Quad Diffuser? I found this page, with a link to the infamous BBC paper that looks helpful: http://www.mhsoft.nl/DiffusorCalculator.html

Some people have used wood, but that seems aweful heavy. ANyone have ideas for a hard foam that would reflect well, hold it's shappe, weigh little, cost less, and come in nice, long, square lengths?

Terry,

> polycylindrical diffusers ... are as good as the modern "well-type" diffuser in nearly all situations. <

That's wrong on so many levels I'm not even sure where to start. :eek: But I'll try.

The main advantage of QRD diffusors is they actually diffuse, versus curved plywood that merely deflects.
Sorry, but this distinction is incorrect. It is wrong on so many levels I don't know where to start. :eek: :D

Since I tried to get you to read some of the acoustics literature and failed, let's look at some commercial diffusers. RPG makes diffusers, right? And D'Antonio and Cox know a thing or three about such things, right?

Have a look at these RPG diffuser products:

http://www.rpginc.com/products/monoradial/index.htm
http://www.rpginc.com/products/opticurve/index.htm
http://www.rpginc.com/products/chaos/index.htm

Either these curved pieces of plywood are diffusers, or RPG has some of the greatest scam artists in the world. :D

- Terry

You have a lot of flexibility here. :D

A larger arc will diffuse down to lower frequencies. To a first approximation, a radius of curvature r will be effective at diffusing frequencies whose wavelengths are less than 2 pi r. This is not a sharp boundary -- you approach the maximum diffusion at maybe 3 or 4 times this frequency. To get the frequency for a particular wavelength in feet, just divide it into 1130 feet per second, the speed of sound. How much of a circular arc you use will depend on how much depth you are willing to allow. Varying the spacing and radius of curvature for multiple diffusers is a good idea.

One nice thing about polycylindrical diffusers is that, unlike the now-common discrete varying depth type of diffuser, they have no high frequency limit on the sounds they will effectively diffuse. As for orientation, it depends on the specific purpose of the diffusion. If it is to maintain a broad sound stage, then vertical orientation is often preferable. On the other hand, horizontal orientation will improve the uniformity of reverberation decay if you have a very uneven balance of horizontal and vertical absorption -- "dead" walls and "live" ceiling and floor, for example.

- Terry

Thanks for the tips. Now to find some time to build a few. One point of clarification on horizontal and vertical orientation. Is this diffuser oriented vertically or horizontally?

http://www.rpginc.com/products/monoradial/index.htm

Thanks for the tips. Now to find some time to build a few. One point of clarification on horizontal and vertical orientation. Is this diffuser oriented vertically or horizontally?

http://www.rpginc.com/products/monoradial/index.htm
Vertically, at least according to my convention.

- Terry

Terry,

> http://www.rpginc.com/products/monoradial/index.htm <

The first sentence on that page begins "Overhead canopies are used in auditoriums..."

> http://www.rpginc.com/products/opticurve/index.htm <

Under Applications the recommended uses are "Arenas, Atriums, Auditoriums, Cinemas and Home Theaters, Conference Rooms, Music Rehearsal Rooms, Performing Arts Facilities, Recording and Broadcast Studios, Restaurants"

Yes, home theaters are listed, but that's not the primary intention. Also, this is not a simple curved piece of plywood!

> http://www.rpginc.com/products/chaos/index.htm <

Likewise for the above link.

> Sorry, but this distinction is incorrect. <

It seems to me you are either intentionally trying to mislead - for motives I can't fathom - or you just don't understand the considerable difference between a poly and what RPG is selling on those pages.

I say we need another face-off test in person, with the results reported publicly here. :D

Only this time we'll measure the improvements in comb filtering, and maybe also the subjective audible difference, between a simple poly and a real diffusor. I'll even make the trek out to your place this time. You game?

I'll also make this (hopefully) final point:

Curved wood has been around for a long time as a way to avoid flutter echo. It works well for that, especially in large rooms like the big recording studios Everest shows in his Master Handbook of Acoustics. But curved wood is not useful for reducing comb filtering, which is a much bigger problem in small listening rooms and home theaters than in larger spaces.

If anyone likes, I'll be glad to post a dozen photos of very high-end million dollar plus recording studio control rooms. In almost every case you will see QRD style diffusors on the rear wall, and you won't see curved plywood there in any of them.

I was recently at the Hit Factor / Criteria recording studio where I was invited to speak on small room acoustics. In their most expensive Studio A they had a row of QRD well diffusors lining the entire rear wall. I'll guess they had $20,000 worth of diffusors in that room. Now ask yourself why a multi-million dollar facility that puts sound quality above all else would invest so heavily in QRD diffusors rather than curved plywood which would have cost much less.

--Ethan

> Sorry, but this distinction is incorrect. <

It seems to me you are either intentionally trying to mislead - for motives I can't fathom - or you just don't understand the considerable difference between a poly and what RPG is selling on those pages.

I say we need another face-off test in person, with the results reported publicly here. :D

No way! I have no interested in debating you, as you are far more skilled at this technique than I am. If you would like to declare yourself "the winner" on this basis, go right ahead. :)

My interest is in promoting the understanding and practice of acoustics. If an "Acoustics Specialist" doesn't know what a diffuser is, this ain't my problem. End of discussion.

- Terry

If you would like to declare yourself "the winner" on this basis, go right ahead. :)
Woo hoo! I won! :cool:

> My interest is in promoting the understanding and practice of acoustics. <

That's my interest too, and I've been doing it for, oh, 20 to 30 years now. :D

> If an "Acoustics Specialist" doesn't know what a diffuser is, this ain't my problem. <

Why do you feel you must insult me? Have I ever insulted you, or questioned your competence? Why do you feel you have to do that to me? Not just here, but elsewhere on the 'net I've seen you make disparaging remarks about me. And not just once or twice. Why do you do that? :mad: We're not even competitors fer crying out loud! I'm sorry our previous comparison of traps versus EQ didn't pan out well for you, but that's not my fault. What the heck did I ever do to you?

--Ethan

Woo hoo! I won! :cool:

> My interest is in promoting the understanding and practice of acoustics. <

That's my interest too, and I've been doing it for, oh, 20 to 30 years now. :D

> If an "Acoustics Specialist" doesn't know what a diffuser is, this ain't my problem. <

Why do you feel you must insult me? Have I ever insulted you, or questioned your competence? Why do you feel you have to do that to me? Not just here, but elsewhere on the 'net I've seen you make disparaging remarks about me. And not just once or twice. Why do you do that? :mad:

It seems to me you are either intentionally trying to mislead - for motives I can't fathom - or you just don't understand the considerable difference between a poly and what RPG is selling on those pages.
This seems to me to be questioning of my competence or ethics. :mad: Only you could simultaneously argue that bent plywood isn't a diffuser at all, and bent plywood is not as good a diffuser as a QRD. This is why arguing with you on any matter of acoustics is so futile.

So please quit playing the innocent, wronged party minding his own business. And learn what a diffuser is, for God's sake.

- Terry

Ethan and Terry,

Out of respect for the valuable expertise that both of you possess (and that I have availed myself of), and to keep a positive vibe in this thread, could you edit your past couple post to keep things friendly, and take any other discourse to private messaging.

I'm not blowing smoke up your rears when I say this. I'm devouring everything on acoustics that I can, and this thread has some of the best info that I've found on a subject that few people want to tackle (most would rather just buy more expensive speakers for their crappy rooms). I love disagreement, but bickering could turn people off.

Finally, I for one, hope that both of you continue to contribute your honest opinions to this thread.

Thanks,

Marshall

If everyone follows one simple rule - no disrespectful posts - much space- and bandwidth-wasting banter could be avoided. Differing opinions are to be expected, but questioning someone's professionalism is out of line.

If Ethan removes his first "That's wrong on so many levels I'm not even sure where to start" message and subsequent ones, I will be happy to delete mine and forget the whole matter.

- Terry

Anyone have any thoughts on this:

http://remixmag.com/mag/remix_diy_acoustics/index.html

Bass Trap:

Buy a large rubber 30- or 40-gallon trash can at least 3 feet tall and without any holes in its bottom, sides or lid; then, line its circumference with bats of high-density mineral insulation (same as used for the absorbers), and loosely zigzag one or two more bats inside, being careful to leave large air pockets. Caulk around the rim of the trash can, as well as the lip of the lid, with nonhardening acoustical caulking or weather sealant, and put the lid on the can. Duct-tape the lid so that it won't accidentally come undone when you move or bump into it, and feel free to drape a decorative fabric over it. Because bass frequencies collect most in corners, bass traps are often placed in the two front corners of the room. And because bass is omnidirectional, placing them asymmetrically if space is tight won't diminish their performance one bit.

Anyone have any thoughts on this:

http://remixmag.com/mag/remix_diy_acoustics/index.html

Bass Trap:

Buy a large rubber 30- or 40-gallon trash can at least 3 feet tall and without any holes in its bottom, sides or lid; then, line its circumference with bats of high-density mineral insulation (same as used for the absorbers), and loosely zigzag one or two more bats inside, being careful to leave large air pockets. Caulk around the rim of the trash can, as well as the lip of the lid, with nonhardening acoustical caulking or weather sealant, and put the lid on the can. Duct-tape the lid so that it won't accidentally come undone when you move or bump into it, and feel free to drape a decorative fabric over it. Because bass frequencies collect most in corners, bass traps are often placed in the two front corners of the room. And because bass is omnidirectional, placing them asymmetrically if space is tight won't diminish their performance one bit.

Sounds like a silly idea. Not only do the air pockets serve no purpose, neither does caulking the lid.

Sounds like a silly idea. Not only do the air pockets serve no purpose, neither does caulking the lid.To say nothing of the high WAF of adding several trash cans to the family room.

To say nothing of the high WAF of adding several trash cans to the family room.

Well they said you could drape a cloth covering over them ("could" implies they haven't, and just have garbage cans full of fiberglass in their home theaters)

But would it work? Not seriously considering it, just curious what people's thoughts are.

I have no idea how effective it is but, seems to me, that should be the responsibility of the guy who designed it. Besides, are there any acoustic standards for plastic trash cans?

To say nothing of the high WAF of adding several trash cans to the family room.
Shabby chic?

So, this is my first post on the forums and I will confess to being mostly ignorant to many of the theories discussed in this thread. I have a couple of questions about wall treatments that I have not seen answers to. I did search, with no luck, so please excuse me if I am asking something that has already been covered.

I am about 75% of the way finished with my home theatre. All of the walls in my room are insulated but I would like to block the sound a little more on the wall that is behind my tv and front channels. It seems like everyone agrees that this will benefit sound quality and that wall is common with my 2 year old's room. It sounds like insul-shield is the best stuff for the job, but I didn't have any luck at the typical home improvement stores. Lowes sells Johns Manville products but all I got was blank stares when I inquired about insul shield. Who is a common retailer for this stuff? What are some alternatives that are more readily available. Looks are not important to me as I will be hanging fabric in front of the wall anyway. What about covering the wall with acoustical ceiling tiles?

Sorry for the long post, thanks in advance for help with my noobie questions.

bd

So, this is my first post on the forums and I will confess to being mostly ignorant to many of the theories discussed in this thread. I have a couple of questions about wall treatments that I have not seen answers to. I did search, with no luck, so please excuse me if I am asking something that has already been covered.

I am about 75% of the way finished with my home theatre. All of the walls in my room are insulated but I would like to block the sound a little more on the wall that is behind my tv and front channels. It seems like everyone agrees that this will benefit sound quality and that wall is common with my 2 year old's room. It sounds like insul-shield is the best stuff for the job, but I didn't have any luck at the typical home improvement stores. Lowes sells Johns Manville products but all I got was blank stares when I inquired about insul shield. Who is a common retailer for this stuff? What are some alternatives that are more readily available. Looks are not important to me as I will be hanging fabric in front of the wall anyway. What about covering the wall with acoustical ceiling tiles?

Sorry for the long post, thanks in advance for help with my noobie questions.

bd

It's a lot I know, but please read this thread all the way through. There are several links for OC 703 and the like. SPI is a popular choice, but I didn't have one in my area so EJ Davis shipped from CT to NY for me.

Shabby chic?Shabby and trashy are quite different.

Shabby and trashy are quite different.
But many times they do hang out together.

But many times they do hang out together.Yeah. See it all the time in system pix on AVS. :p

So, this is my first post on the forums and I will confess to being mostly ignorant to many of the theories discussed in this thread. I have a couple of questions about wall treatments that I have not seen answers to. I did search, with no luck, so please excuse me if I am asking something that has already been covered.

I am about 75% of the way finished with my home theatre. All of the walls in my room are insulated but I would like to block the sound a little more on the wall that is behind my tv and front channels. It seems like everyone agrees that this will benefit sound quality and that wall is common with my 2 year old's room. It sounds like insul-shield is the best stuff for the job, but I didn't have any luck at the typical home improvement stores. Lowes sells Johns Manville products but all I got was blank stares when I inquired about insul shield. Who is a common retailer for this stuff? What are some alternatives that are more readily available. Looks are not important to me as I will be hanging fabric in front of the wall anyway. What about covering the wall with acoustical ceiling tiles?

Sorry for the long post, thanks in advance for help with my noobie questions.

bd

Welcome, Bobby. Insul-shield will do very little to nothing to keep sound from going through (and around) that wall. Insulshield and similar products are used to improve the sound in the room, not trying to keep it in. Two different goals there. I'd add a layer of green glue and another layer of drywall on that wall. Also, don't ONLY focus on that one wall.

One last thing, find a professional HVAC supplier in your area for Insulshield and similar products.

Dan

Ethan and Terry,

Out of respect for the valuable expertise that both of you possess (and that I have availed myself of), and to keep a positive vibe in this thread, could you edit your past couple post to keep things friendly, and take any other discourse to private messaging.

I'm not blowing smoke up your rears when I say this. I'm devouring everything on acoustics that I can, and this thread has some of the best info that I've found on a subject that few people want to tackle (most would rather just buy more expensive speakers for their crappy rooms). I love disagreement, but bickering could turn people off.

Finally, I for one, hope that both of you continue to contribute your honest opinions to this thread.

Thanks,

Marshall


I heartily concur... Ethan and Terry, you guys are very valuable to this forum and I enjoy and respect both of your opinions!


...Glenn :)

Dennis, you sound pretty firm on not using styrofoam. Is there a valid reason, if it is fire rated.
Fire rated styrofoam? Is there such a thing?

If everyone follows one simple rule - no disrespectful posts - much space- and bandwidth-wasting banter could be avoided. Differing opinions are to be expected, but questioning someone's professionalism is out of line.
I agree, and I apologize for coming off as combative. I will point out that I was not the first to question the other person's professionalism and competence. That's what set me off. There's some history to this and I'm frankly tired of being on the receiving end of it. But that's no excuse for me to be insulting back.

I also agree that the difference between curved surfaces and real QRD diffusors is worth exploring further. I already stated the reasons I consider a QRD to be much better than curved plywood. Not just via logical explanations and understanding of how each surface type reflects, but also based on having heard both many times.

So let's discuss, okay? I also think some measurements are in order, which is why I offered to visit Terry in person and bring along some real diffusors. Does anyone else here live near me (within a few hours) and have poly type surfaces in their room? I suppose I could fabricate one easily enough at our factory, but it probably makes more sense to have a "second opinion" for listening evaluations.

Also, Glenn Kuras at GIK told me today he thinks the subject of "poly versus QRD" deserves a thread all its own. So Glenn, or anyone else, by all means do that and we can move the discussion there if y'all agree this warrants further exploration.

--Ethan

So let's discuss, okay? I also think some measurements are in order, which is why I offered to visit Terry in person and bring along some real diffusors. Does anyone else here live near me (within a few hours) and have poly type surfaces in their room? I suppose I could fabricate one easily enough at our factory, but it probably makes more sense to have a "second opinion" for listening evaluations.

--Ethan

I live 1 hour away, Pleasant Valley, NY, but I live in a townhouse with shared walls, and have plenty of absorption but no diffusion. However, I'd love to offer a second opinion if a test ever comes about.

This work has already been done 13 years ago.

Trevor J. Cox & Y. W. Lain, "The Performance of Realisable Quadratic Residue Diffusers (QRDs)" Applied Acoustics 41 (1994) 237-246.

Anyone who is honestly interested in the subject should read this paper.

- Terry

This work has already been done 13 years ago.

Trevor J. Cox & Y. W. Lain, "The Performance of Realisable Quadratic Residue Diffusers (QRDs)" Applied Acoustics 41 (1994) 237-246.

Anyone who is honestly interested in the subject should read this paper.

- Terry

Do you have a link to that paper? I'd love to read it.

I live 1 hour away, Pleasant Valley, NY, but I live in a townhouse with shared walls, and have plenty of absorption but no diffusion. However, I'd love to offer a second opinion if a test ever comes about.

Do you have a poly on one of those walls? Or are you willing to put one on a wall?

--Ethan

Do you have a link to that paper? I'd love to read it.

I found a synopsis. The only links to the paper I've found are $$:

3. T J Cox and Y W Lam. The Performance of Realisable Quadratic Residue Diffusers (QRDs). Applied Acoustics. 41. 237-246. (1994).

The scattering performances of realisable quadratic residue diffusers (QRDs) have been tested. The scattering has been compared to (i) the original design theory of the QRD; (ii) optimum diffusion; and (iii) the performance of plane and curved reflectors. The QRDs do produce similar diffusion to that predicted by the original design theory. Only at low frequencies, however, is this close to optimum diffusion. For oblique incidence the QRD produced greater diffusion than the curved and plane panels. At normal incidence, however, the curved panel was as good as the QRD.

Terry,

This work has already been done 13 years ago.
Great. A big part of the scientific method is for others to duplicate and see if they get the same results, so another round of tests isn't necessarily redundant. This also brings up two new questions:

1) What's the punch line? Did they determine that polys are as good as QRD or not?

2) If polys were considered subjectively (or measured) to be as good as QRD diffusors in small rooms at close distances, why did Dr. D'Antonio go into business selling QRDs? His curved stuff is much more recent, no?

I'm with Eugo - ya got a link? If not, a summary is a good start.

--Ethan

Do you have a poly on one of those walls? Or are you willing to put one on a wall?

--Ethan

I really don't know how much my humble little room would tell use (14'x15x'8'), and with the shared walls, I don't get to let my system breathe fire as much as I would like for fear of disturbing the neighbors. I've certainly considered hanging a poly if I could find the time to build one, but I'm pretty happy with the 703 panels for now.

Mostly, I'd just like to be in on the fun if anyone in the area starts doing a listening test and would be more than willing to drive a ways.

A quote from the paper (stolen from a post in another thread with a similar discussion on 1/24/06 titled 'diffusion')


4.1 Normal incidence case

"In Fig. 6 two examples are given of the scattering from the three surfaces at
1.5 kHz and 7.5 kHz. The plane panel gave less uniform scattering than
either of the other two panels at all frequencies. The scattered field also has
much more pronounced minima and maxima, particularly the central
maxima at high frequencies. The result is hardly new; acousticians tend to
avoid plane reflectors in difficult areas which are likely to produce strong
specular reflections and echoes.

"Overall there seems to be little difference in the relative performances of
the curved panel and the QRD. Below about 3.5 kHz the QRD did produce
more scattering to large angles, but at the expense of having large minima at
some receiver positions. Above 3.5 kHz the amount of scattering away from
the normal direction was similar for both panels. Again the QRD had many
more, well defined minima and maxima. As illustrated in Fig. 6(a), a
particular problem for the QRD at high frequencies was that the central
maximum was large and similar to the central lobe for the plane panel.
Consequently, there seems to be a risk of strong specular reflections and
echoes from this QRD. The QRD and curved panel were constructed so that
the maximum 'depth' of the curved panel (28 cm) was of similar size to the
maximum depth of the QRD wells (35 cm). So for the same overall size in all
dimensions, and for on-axis incidence, it was possible to achieve as good if
not better diffusion with the curved panel. Curved panels are generally
cheaper to construct. So, if near normal incidence can be guaranteed, as
would be the case for reflectors over the stage area in auditoria, the curved
panel is to be preferred."

Excellent Paul, thanks!

Any others?

--Ethan

If you "toe in" the L&R front speakers, how would that effect the positioning of acoustic panels using the mirror method? It would seem that since the speaker is pointed toward the middle listening area that the reflection would be more on the wall opposite that speaker vs. right beside it.

If you "toe in" the L&R front speakers, how would that effect the positioning of acoustic panels using the mirror method? It would seem that since the speaker is pointed toward the middle listening area that the reflection would be more on the wall opposite that speaker vs. right beside it.YOur speakers are not lasers. Their output is dispersed over an angle and, as long as the postion of the drivers does not change when you change the aiming, the first reflection point should not change.

Thanks for the reply.

To apply your response to the mirror method of determining reflection points, should I only consider it a point of reflection when I can see the driver (in my case it's a 60' x 90' Horn loaded tweeter - Klipsch KL 650THX)? It seems with it being angled away from the wall that this would move your reflecting point further down the wall vs. just seeing the reflection of the speaker cabinet. Is that accurate?

Thanks,
Matt

YOu should also recall that there is no one 'point' but an area around the mirror-determined point that needs absorption.

Thanks. The reason I'm needing more flexibility in placement is because I'm trying to locate these in a somewhat uniform distance from my columns. I'm just trying to determine just "how much" flexibility I have by knowing where the most critical point is for placement and judging placement options from there. I plan to do panels approximate 1-2'W x 4'H.

So is the critical point just where I will see the Tractix Horn?

Matt

I've certainly considered hanging a poly if I could find the time to build one

Polys are pretty easy to build... even if you want to make them somewhat fancy by using a hardwood veneer or some such. These came out pretty nice and it doesn't look like too ambitous a project for most handy folks. [scroll down for a pic of a very simple design, and a link to a thread on more stylish unit]

http://forum.studiotips.com/viewtopic.php?t=48

PS: If you are trying to read up a bit on diffusion, his gentleman's work might also be of interest.

http://pcfarina.eng.unipr.it/Public/Papers/135-AES00.PDF

http://pcfarina.eng.unipr.it/Public/Papers/136-AES00.PDF

http://pcfarina.eng.unipr.it/Public/Papers/138-Sem00.PDF

http://pcfarina.eng.unipr.it/Public/Papers/150-ACTA2000.PDF

PPS: This thread had some interesting ideas on how to make a poly as well

http://forum.studiotips.com/viewtopic.php?t=2787

but my all time favorite was the guy who decided to build a poly faced bar at the back of the room. :)

Awesome, thanks.

This work has already been done 13 years ago.

Trevor J. Cox & Y. W. Lain, "The Performance of Realisable Quadratic Residue Diffusers (QRDs)" Applied Acoustics 41 (1994) 237-246.
Correction: that's Y.W. Lam. This was an error in Adobe Acrobat's OCR software when I copied and pasted it from my PDF version of the paper. I didn't notice it because my eyes were fooled as well. :)

- Terry

Thanks. The reason I'm needing more flexibility in placement is because I'm trying to locate these in a somewhat uniform distance from my columns. I'm just trying to determine just "how much" flexibility I have by knowing where the most critical point is for placement and judging placement options from there. I plan to do panels approximate 1-2'W x 4'H.

So is the critical point just where I will see the Tractix Horn?

Matt
The Klipsch THX Ultra2 speakers are designed with a wide horizontal dispersion pattern, and a narrow vertical dispersion pattern. The wide horizontal dispersion means there will be a significant amount of sound energy striking the side walls. Toeing the speakers in a little bit will reduce the amount of energy somewhat, but the first reflection point will stay physically where you see the speaker in the mirror. This is true for *each* front speaker. Therefore, there will be 3 first reflection points on each side wall, one for each of your 3 front speakers. You want to cover all 3 of them. One wide absorption panel on each side wall should do it for all 3 speakers.

Craig

The Klipsch THX Ultra2 speakers are designed with a wide horizontal dispersion pattern, and a narrow vertical dispersion pattern. The wide horizontal dispersion means there will be a significant amount of sound energy striking the side walls. Toeing the speakers in a little bit will reduce the amount of energy somewhat, but the first reflection point will stay physically where you see the speaker in the mirror. This is true for *each* front speaker. Therefore, there will be 3 first reflection points on each side wall, one for each of your 3 front speakers. You want to cover all 3 of them. One wide absorption panel on each side wall should do it for all 3 speakers.
A bit more needs to be added to this advice; there are three first reflection points on each side wall for EACH listening position. The conclusion remains the same though - one panel should do it for all of the points.

This is not only true for the side walls, but the ceiling, the front wall and the rear wall as well.

I didn't notice it because my eyes were fooled as well.

Dammit Terry, go get those eyeballs fixed. A blind acoustician is more irony than the any of us should have to put up with. :D

I know Ethan is speaking at HES (http://www.homeentertainment-expo.com/) , and if anyone else is going, we should have a meetup, maybe after one of the acoustics seminars? Anyone game?

Pepar and Craig,

Thanks for your input on the reflection point issue. How much will it matter if I have a 4"D x 12" W wood column in a reflection point area? I know it's a hard surface and it will reflect sound, but since it sticks out from the flat wall, will that help any?

Matt

The Klipsch THX Ultra2 speakers are designed with a wide horizontal dispersion pattern, and a narrow vertical dispersion pattern. The wide horizontal dispersion means there will be a significant amount of sound energy striking the side walls. Toeing the speakers in a little bit will reduce the amount of energy somewhat, but the first reflection point will stay physically where you see the speaker in the mirror. This is true for *each* front speaker. Therefore, there will be 3 first reflection points on each side wall, one for each of your 3 front speakers. You want to cover all 3 of them. One wide absorption panel on each side wall should do it for all 3 speakers.

Craig


Craig,

Since they do have a wide horizontal disperson pattern, would it be ok not to "toe in" the front speakers (assuming I treated the side walls properly)?

Thanks,
Matt

Craig,

Since they do have a wide horizontal disperson pattern, would it be ok not to "toe in" the front speakers (assuming I treated the side walls properly)?

Thanks,
Matt
I think it's common practice to aim all monopole (direct-radiating) speakers at the geographical center of the listening positions. Dipoles, too, but "directly at" is more of a concept with them; I suppose one aims the null at the geographical center. I use a special laser pointer system and a target balloon to do my speakers. Better speakers, including all THX-approved ones, have tightly controlled vertical dispersion, so it is especially important to properly aim them.

I know Ethan is speaking at HES (http://www.homeentertainment-expo.com/) , and if anyone else is going, we should have a meetup, maybe after one of the acoustics seminars? Anyone game?
I would love to meet you, and anyone else here. I'm sure I'll be hanging around several minutes before the discussion panel starts, so please come by and say Hi. Then we can hook up after and chat. I'll be the guy holding the big fat pussy cat. :D

--Ethan

http://www.ethanwiner.com/avatar.jpg

Any thoughts on having my 4"D x 12"W wood column in an area which is a first reflection point?

Thanks,
Matt

Any thoughts on having my 4"D x 12"W wood column in an area which is a first reflection point?

Thanks,
Matt

Not an expert, so grain of salt time.

For medium/high frequencies that you'll worry about for first reflections, 12" wide is plenty wide to give you a reflection from a speaker. If your reflection point for your center speaker/right ear is in the middle of the column on the right side, it would act just like a wall and should be treated as such.

If your reflection point for a given speaker/ear combo is right on the front edge, you'll get ~half a reflection (the rest will be reflected forward and not be an issue). If your point is at the back edge of the column, you'll get half (the rest will continue on and hit the wall).

Bottom line: the column complicates the calculation, but it doesn't really change anything.

Have you considered curved columns? Can you move them out of the reflection point or treat them? What about moving speakers?

The center speaker might be hidden by a fabric covered frame beneath the screen. What if I moved it towards the back of the framed area and placed some 1" 703 panels to the immediate sides and extended the panels out past the face of the speaker. This would keep it from reflecting to the side walls, but would it keep the sound of the center too localized?

Thanks,
Matt

The center speaker might be hidden by a fabric covered frame beneath the screen. What if I moved it towards the back of the framed area and placed some 1" 703 panels to the immediate sides and extended the panels out past the face of the speaker. This would keep it from reflecting to the side walls, but would it keep the sound of the center too localized?

Thanks,
Matt

Yeah, that would not be good. Basically you'll kill any horizontal dispersion of high frequencies and create a very narrow sweetspot.

Hi Matt,

Paul is right. Wood column faces at early reflection points are not a great idea. This is a trade-off: aethetics vs. acoustics. The best thing would be to face the columns with 1" fiberglass and cover with fabric.

- Terry

Thanks for all your responses. I have enough info now to weigh the options out.
Great Advice!!!!
Matt

Perhaps slip some upholstered pipe insualtion on them?

http://einsulation.com/products-fiberglass-pipe/products_fiberglass_pipe.php

Due to some of the pipes we have we had to put in a couple of soffits. We did straight 45 degree soffits on the side walls to the ceiling to conceal the pipes. I was thinking to match the room up I was going to put in bass traps in the front and rear walls and create a tray ceiling in the room. From an athetics stand point this would work, but how would this help with bass? I have room to put corner traps in 3 corners but one corner has a door too close in the rear of the room so I was leaning toward not putting corner traps in and was hoping this might help enough to offset that. or am I wasting time and money on something that really won't help much.

Any input would be great.

Thanks

Patirck:

Corner mounted bass traps are the most effective way to control low frequencies, but preserving symmetry is also important. Can you use any floor/wall or ceiling /wall corners and keep things even [left to right]?

Do the front and back in a matching soffit but with just absorbtion and cloth. Do the front 2 room corners that you can. That should be sufficient to make a difference.

If you need more, you can square off the angled soffits on the side walls again with absorbtion.

Bryan

So the traps at the front and back ceiling/wall junction aren't going to help as much as a bass trap in each of the front corners?

Also not sure what to think of this but I have a friend that works at an industrial filter plant. He was telling me that he can get me a ton of free felt (more high tech then that but easy way to explain it as felt). Some of this stuff is extremely dense. I was wondering if this might be worth looking into. It won't be expensive so I might give it a shot, but I was thinking 3 or 4 layer of this on the screen wall might help absorb some sound. Any thoughts?

So the traps at the front and back ceiling/wall junction aren't going to help as much as a bass trap in each of the front corners?

Depends... both cases are corner mounted panels and will work equally well as bass traps. And either may, or may not, also be useful for controlling SBIR and/or early reflections.

...he can get me a ton of free felt (more high tech then that but easy way to explain it as felt). Some of this stuff is extremely dense. I was wondering if this might be worth looking into.

No harm in looking into it I suppose... but you need to find out what the stuff is to make a determination. If its a medium density thermal insulation product, it probably has reasonably good acoustic absorption properties. Find out exactly what it is and look it up. Though I wouldn't settle for anything that didn't have good lab numbers... and good handling properties... as excellent materials in either semi-rigid fiberglass or rockwool are available in mosts markets for modest costs.

I would love to meet you, and anyone else here. I'm sure I'll be hanging around several minutes before the discussion panel starts, so please come by and say Hi. Then we can hook up after and chat. I'll be the guy holding the big fat pussy cat. :D

--Ethan

http://www.ethanwiner.com/avatar.jpg

Wish I could go, but will be pretty much stepping off a plane back from the UK. Would be way to much "out of town time" for me.
Hope it all works out well for you. BREAK A LEG. :p

Glenn

Wish I could go, but will be pretty much stepping off a plane back from the UK. Would be way to much "out of town time" for me.
Hope it all works out well for you. BREAK A LEG. :p

I'll try hard not to break a leg. :D

But I will mention your name when I speak on the panel. :eek:

--Ethan

I'll try hard not to break a leg. :D

But I will mention your name when I speak on the panel. :eek:

--Ethan

Would it be to much to ask for you to pass out some of our brochures also? :D

Back in February I posted (http://www.avsforum.com/avs-vb/showthread.php?p=9658701&&#post9658701) about building my first prototype panel absorber.

Well, last night I finally finished the last of five planned panels of this design, so I thought I'd share with y'all the fruits of the knowledge in this thread. So far everything is turning out pretty well. Thanks again for everyone who has posted.

The original prototype is in the center of the second shot. Note also that the panels hanging behind the sofa are shorter to leave room for a yet-to-be-built second row riser.

I will be making at least one more of similar design. It will go behind the door seen in the first shot, but it will need to be thinner and mount flush to the wall instead of spaced away like the others.

I'm also planning to do something about the corners, and I have a couple questions about that. (See next post.)

http://gallery.avsforum.com/data/501/North_Side_Wall.JPG

http://gallery.avsforum.com/data/501/South_Side_Wall.JPG

Now that I'm done with my side-wall panel absorbers, I need to turn to my corner bass trapping.

Currently I have eight 2' x 4' x 4" 8lb rockwool batts straddling the room's vertical corners. For aesthetic reasons, I'd like my corner absorbers to extend 14.25" from the corners instead of the 17" you get with a full 24" panel.

(1) Would reducing the width of the panel this much reduce the effectiveness of the absorber more than the simple reduction in the volume of the material?

and on a very related note:

(2) Would building "chunk" style absorbers using all my available material recover the absorption lost due to the width reduction?

Cheers,

Those are great looking absorbers. Are they just a wood frame/cloth over fiberglass? or are they tuned panel absorbers?

Those are great looking absorbers. Are they just a wood frame/cloth over fiberglass? or are they tuned panel absorbers?
Thanks.
They are frames & fabric around 8lb 2" rockwool.
I tried to tune them, but I couldn't figure out where to put the knobs. :D

Cheers,

I tried to tune them, but I couldn't figure out where to put the knobs. :D

I have had that problem, too! :D :D

- Terry

(1) Would reducing the width of the panel this much reduce the effectiveness of the absorber more than the simple reduction in the volume of the material?

and on a very related note:

(2) Would building "chunk" style absorbers using all my available material recover the absorption lost due to the width reduction?

Cheers,

Just so I understand correctly. You are going to build the panels that straggle the corners shorter? or are you going to build super chunks that are shorter? Sorry kind of early here. :o
It is all about coverage, so the shorter you make them the less area it has to pick up sound and it will reduce the air gap in the back. So all and all it will pick up less bass over all. How much, is really hard to tell, but if it was me I would stick with the face to be 24" across the corner. May it be super chunks or panels.

Hope that helps.

Glenn

Now "A".

In multi-channel, the entire wall behind the front speakers is treated. You want none of the back reflections to overlay the surround field or the bring the reverberent field forward (your reverberent field and surround field is created by the multi-channel processor or mix, not so much the room as is mandatory for 2-channel). Depending on speaker placement, this treatment is brought forward along the side walls. Wall treatments are floor to slightly above ear level (where exactly is also a function of front speaker heights). While one could argue the sound at their feet is of no concern, often that square footage of treatment is required to bring the room's RT60 down to the lower levels required for multi-channel playback.

If you have soffits, the bottom of the soffits is also treated...several reasons, right tricorners among them.

***
I am finishing a rather narrow home theater (11' by 20') in an unfinished part of the basement by building a 'room within a room' with 2"x4" studs, thermal insulation in the walls, and 1/2 " drywall around the walls. I plan to use two 5/8" drywall layers for the ceiling, using green glue to dampen the sound through the ceiling (plus 8" of thermal insulation above). Got a 12" soffit perpendicular to the main axis of the room about 14 ' back from the front (narrow end) wall. Rug covering concrete floor. 6 reclining seats. Set-up will include a 45" HDTV centered on the front wall. Using Klipsch spkrs for 7.1 sound (Synergy F-3 series). A front projection screen will descend for movies, covering much of the front wall.

First questions concern spkr placement for the mains and the subwoofer:

1) Should mains be placed as close to the screen as possible to minimize corner effects in this set-up (i.e., maybe 6-8 feet apart?). With the screen down, spkrs will be awfully close to the corners ... will this cause a problem?

2) Should the subwoofer be placed in the center to minimize smearing?

3) With respect to acoustic treatments in such a narrow room (and with insulation in the walls), should I use 1" batting or insul-shield around the sidewalls, up to ear height, and no treatment above that? Or something else?
More (or higher) treatment because the room is narrow?

4) Front side of soffet (i.e., side facing the speakers) should be treated, I bet...?

5) Back wall treated same as sides in this case?

-Thanks for sharing your expertise -

jchretien4

1) Should mains be placed as close to the screen as possible to minimize corner effects in this set-up (i.e., maybe 6-8 feet apart?). With the screen down, spkrs will be awfully close to the corners ... will this cause a problem?

Yes, and you'll need to adjust your seating distance. Take the distance between your speakers and multiply it by 1.25 and 0.87. That's the distance from the midpoint between your speakers that your seating distance should be.

Move your fronts forward from the front wall and screen to minimize rear boundry effects and any potential acoustic reflection off the side of the screen. Is the screen perforated, or will you have you center channel below it?

2) Should the subwoofer be placed in the center to minimize smearing?

You'll have to listen and measure to find the best place for the subwoofer. Read up on Room EQ Wizard for free software that will help tremendously.

3) With respect to acoustic treatments in such a narrow room (and with insulation in the walls), should I use 1" batting or insul-shield around the sidewalls, up to ear height, and no treatment above that? Or something else?
More (or higher) treatment because the room is narrow?

Consider building a false front wall w 2" of absorption. This will give you better acoustics, and will get the demensions of the room a little further away from being multiples of each other. How tall are your ceilings?

As far as te rest, it's hard to say w/o listening to it, but you'll want to treat the first reflections for sure, at ear height. I'd start by putting in your system and seeing what it sounds like. There's no magic acoustic bullet.

4) Front side of soffet (i.e., side facing the speakers) should be treated, I bet...?

Better yet, put in a soffit on the opposite side to keep the room symmetry.
Treat both, might even make a good place for your rear speakers if I'm doing my seating distance math correctly. What's in the soffit?

5) Back wall treated same as sides in this case?

Once again, have to listen, but it sound like you'll have a significant amount of space between you and the back wall if you do your seating distance correctly (2x screen diagonal at most. Assuming a seating distance of about 14 feet, you'll probably have 4-5 feet behind you, and you might benefit from some dispersion back there. Once again, you'll just have to give it a listen.

Center channel will be below display and screen, mounted forward about 6". Screen will not be perforated. Soffit is drywall enclosing a steel girder.

So, above ear height on the sides, I should leave alone, at least to start?

Thanks for your help -

jchretien4

Anybody know how much of a difference 1/2" vs. 3/4" OSB will make as a second floor layer with Green Glue? I'm looking at sound isolation from the room below in a new home theater (pictures of current status here) (http://www.meyerzone.net/meyerht). I'm trying to get a feel if it is worth the extra weight/expense to go for 3/4" OSB. I don't see much on the Green Glue site other than "3/4 OSB or 11/16 OSB are best, 1/2" is good". I'm trying to see if there is any more data than that. If 3/4" makes a 20%+ difference in perceived noise levels in the room below, I'm all over it. If it's a barely noticable difference, I'll go lighter.

By the way, I know this is very difficult to answer, hard to quantify, and it will vary from room to room and depend on my weakest link. For this discussion, assume the floor is my weakest link and the only path for sound getting to the room below. I'm just looking for informed gut feels.

My theater is going in an existing room in a room. The current floor is 3/4" OSB on 2x8 floor joists 16" OC with a 3" gap over the 2x6 ceiling joists in the room below. Blown in insulation on the ceiling below, R-30 pink between the floor joists.

The walls are 1/2" drywall on 2x4 studs with minimum 3" spacing to another 2x4 wall. Most of the walls and the ceiling actually face attic or roof. I'm already planning on GG/double drywall (another layer of 1/2") on the walls (5 cases of green glue up there right now).

I've just thrown GG/OSB for the floor into the plan (my wife's idea, I've been trying to avoid overdoing it). It'll cost me 12 sheets of OSB and another two cases of GG, but it'll be easy to do now that the floor is torn up.

However, I have to decided between 3/4", 11/16", or 1/2" OSB (or something else, if there are better/cheaper/lighter options) I haven't explored price yet, but the lighter the better as my wife and I have to lug it upstairs. Also, the hallway outside the room has 3/4" wood floors on top of the same subfloor. If I put 3/4" OSB, my pad/carpet will start flush with the outside floor. I'm worried about dealing with the step up on entering the room. I don't want people tripping.

Any thoughts?

Has anyone tried this product?

http://www.fibratec.com/

The blanket sounds like it could work, just waiting to see what the sound attributes are for it before I order any.

.

Just so I understand correctly. You are going to build the panels that straggle the corners shorter? or are you going to build super chunks that are shorter?
Currently I have my 4" batts straddling the corners. The room sounds OK. I could use some more absorption from 30hz to about 80hz...but then who couldn't? (See the waterfall charts in my gallery)

What I want to do is make them shorter - from the 17" of wall space they currently occupy, down to 14.25". This will reduce the front-side length from 24" down to just over 20". I know that this will reduce the effectiveness of the panel...So, I'm wondering if switching to a "super chunk" design will adequately compensate.

Therefore, what I'd like to know is how the performance of a 20" wide "super chunk" compares to that of a 24" wide panel?

Currently I have my 4" batts straddling the corners. The room sounds OK. I could use some more absorption from 30hz to about 80hz...but then who couldn't? (See the waterfall charts in my gallery)

What I want to do is make them shorter - from the 17" of wall space they currently occupy, down to 14.25". This will reduce the front-side length from 24" down to just over 20". I know that this will reduce the effectiveness of the panel...So, I'm wondering if switching to a "super chunk" design will adequately compensate.

Therefore, what I'd like to know is how the performance of a 20" wide "super chunk" compares to that of a 24" wide panel?

Look into a roomeqwizard/BFD combo. Google "Room EQ Wizard". If you pull down those two huge peaks, you'll notice a world of difference, and it'll only cost you about $150, which is much less than most eq solutions.

If you like it, throw the guy a couple bucks so he'll keep developing the program.

The more I read, the more confused I become.
Can I use 2" rockwool to deaden the entire front wall?
I am going to use 4" rockwool for bass traps in all four corners.
Can I treat the lower half of the side walls with 2" rock wool like the frontwall?
Does the rear wall get treated like the front wall or just some panels placed to help absorb and diffuse?
I will be placing quilt stuff on the outside of the rockwool before covering with GOM.
The floor will have pad and carpet over cement. The cieling will be treated with a few panels if I have the materials left over,
My room is 17X12.5X8.3,
I have a Sony 60XBR2, Rocket 760(l&r), Bigfoot, 300's (ss) and MFW-15 sub.
My seating will be about 7'&11" from front of TV(3"from wall).
Any comments or suggestions on my plans and questions are greatly appreciated.
Humbly.

The more I read, the more confused I become.
Can I use 2" rockwool to deaden the entire front wall?
I am going to use 4" rockwool for bass traps in all four corners.
Can I treat the lower half of the side walls with 2" rock wool like the frontwall?
Does the rear wall get treated like the front wall or just some panels placed to help absorb and diffuse?
I will be placing quilt stuff on the outside of the rockwool before covering with GOM.
The floor will have pad and carpet over cement. The cieling will be treated with a few panels if I have the materials left over,
My room is 17X12.5X8.3,
I have a Sony 60XBR2, Rocket 760(l&r), Bigfoot, 300's (ss) and MFW-15 sub.
My seating will be about 7'&11" from front of TV(3"from wall).
Any comments or suggestions on my plans and questions are greatly appreciated.
Humbly.

The 2" on the front wall, and 4" bass traps should be a safe bet (are you going wih superchunk or panel style?). So would treating the first reflection points from the floor to a foot or two above ear level. Beyond that, you'll want to put you system in and give it a listen. I'd say a panel on the ceiling is a safe bet also.

Beyond that, you're going to have to see how the room sounds. If it's starting to feel dead, stop. If it sounds small, try some diffusion in the back. If it's still really live, go with absorption.

eugovector;

I was going to cut the 4" into 2' triangles and stack in the corners.
So do you think treating the entire length of the side walls up to 4' would be too much?
This all completely new to me, but I have a clean slate with my garage conversion and I want to do it the best that I can.
Thanks again.

eugovector;

I was going to cut the 4" into 2' triangles and stack in the corners.
So do you think treating the entire length of the side walls up to 4' would be too much?
This all completely new to me, but I have a clean slate with my garage conversion and I want to do it the best that I can.
Thanks again.

Without hearing it it's hard to say. There are no hard and fast rules. Put in a sytem, fire it up, and then add or remove absorption, and listen some more. This isn't baking, it's a fine saute.

Dennis or whomever,
Hey guys I usually build home theaters and am currently doing a commercial acoustic job. I have mostly done fabric over 1x lumber and have started using fabric mate recently. Usually I do the lighting and audio also and am dealing with any cutting that is done myself. A large local company is doing the audio and a large electical outfit is installing about 150' of track light over my fabric. Any ideas besides glueing the fabric to lumber blocking so they don't destroy my fabric when they install the track? Thanks

eugovector,

Thanks again for your response. If you are in the neighborhood in the next few weeks, stop buy and you could help me place my treatments:). This invitation is open to everyone here at AVS, I could really use the guidance and support.
But, irregardless(really a word?), I will continue on and hope for the best. I know it has got to turn out better than my chainsaw modification to the spare bedroom. That is where everything is right now.

eugovector,

Thanks again for your response. If you are in the neighborhood in the next few weeks, stop buy and you could help me place my treatments:). This invitation is open to everyone here at AVS, I could really use the guidance and support.
But, irregardless(really a word?), I will continue on and hope for the best. I know it has got to turn out better than my chainsaw modification to the spare bedroom. That is where everything is right now.

I think starting out I would go with the bass traps in the corners, 4" panels on the back wall with 2" panels in the first reflections on the side walls. Putting panels on the front wall will help but I would not deaden it right away.
Hey I would come over but you are WAY FAR!!!!!!!!!!!! :D

Glenn

Thanks to all for your suggestions. I will be incorporating much of them in the comming days. I will let you all know how it turns out.
Thanks again.

I just got quoted a price for 1.5" insul-shield of $31.25 for 144 sqft. It comes in 2'x4' panels in a bag of 18 pieces for that price.

Now the question is just how much can I fit in my car.

eugovector,

Thanks again for your response. If you are in the neighborhood in the next few weeks, stop buy and you could help me place my treatments:). This invitation is open to everyone here at AVS, I could really use the guidance and support.
Any good Pinots nearby? :)

I just got quoted a price for 1.5" insul-shield of $31.25 for 144 sqft. It comes in 2'x4' panels in a bag of 18 pieces for that price.

Now the question is just how much can I fit in my car.

That's a great price. What company did you get this from?

eugovector,

Thanks again for your response. If you are in the neighborhood in the next few weeks, stop buy and you could help me place my treatments:). This invitation is open to everyone here at AVS, I could really use the guidance and support.
But, irregardless(really a word?), I will continue on and hope for the best. I know it has got to turn out better than my chainsaw modification to the spare bedroom. That is where everything is right now.

You're welcome. I'll be in Portland in late June, don't wait for me though.