Well, if I listened to graphs, the answer is clear. ;)

However, I suspect that this test compared flat, unadorned, completely reflective side-walls with fairly-well treated, absorbent ones. This is certainly demonstrative but extreme, imho. Most cases fall in between these extremes. In addition, the use of wall-hangings and decorations can provide diffusion (rather than absorption) and ameliorate what you demonstrate.

Also, Toole's statements are based, not only on measurements, but on statistical samplings of listener opinion and, even then, he is not dismissive of treating the sidewalls. He discusses a trade-off in imaging specificity for soundstage width and immersion and this trade-off spans the continuum between what I assume are the two extremes you tested.

Another variable is the radiation characteristic of the speakers.

So, I do not think that this is a situation in which all the "right" is on either side.
radiation = off axis performance??

radiation = off axis performance??Yes, unless you are considering something nuclear.

Would 1/2" Linacoustic be acceptable for walls?

~Josh

Generally, you don't want to cover "the walls" but hit the "first reflection points" and thicker is better, say 4 inches, to get coverage of more frequencies, without making the room too dead.

Well most of the people who think early reflections are bad are the people profiting off of it...

Also Toole is just going by his research, not personal opinion. But he doesn't say that attenuating first reflections is bad, he just says that you can if you want, but there are no real downsides to leaving them reflective, only upsides. I would suggest reading his book and deciding for yourself. I think you can find it on Google Books or on Harman's site (not his book but a research paper).
I have read it (and I have an opinion based on my own experience). I am asking if you can cite two or three other researchers whose data is telling them that first lateral reflections are good in a multichannel home theater.

I suspect that this test compared flat, unadorned, completely reflective side-walls with fairly-well treated, absorbent ones.

Yes, I measured this in my living room with and without absorbers at the side-wall reflection points.

Toole's statements are based, not only on measurements, but on statistical samplings of listener opinion

I understand, but I don't know if the listeners were sophisticated or random. A lot of the "general public" will prefer a "smiley face" EQ curve, for example.

--Ethan

A quick question if possible. I am picking out carpet for my HT.
What are the most important things I need to be concerned about?
Type of carpet ( deep pyle, shagg, etc.)
Pad, thickness and type.
I am limited here sense moisture may be a problem.

A quick question if possible. I am picking out carpet for my HT.
What are the most important things I need to be concerned about?
Type of carpet ( deep pyle, shagg, etc.)
Pad, thickness and type.
I am limited here sense moisture may be a problem.

Nothing to do with acoustics, but DARK!

A quick question if possible. I am picking out carpet for my HT.
What are the most important things I need to be concerned about?
Type of carpet ( deep pyle, shagg, etc.)
Pad, thickness and type.
I am limited here sense moisture may be a problem.

Floyd Toole recommends clipped-pile carpet with 40oz/sq yd felt underlay.

I have read it (and I have an opinion based on my own experience). I am asking if you can cite two or three other researchers whose data is telling them that first lateral reflections are good in a multichannel home theater.

Floyd Toole recommends clipped-pile carpet with 40oz/sq yd felt underlay.
How's it going, mike2060, on finding two or three researchers other than Toole who think lateral first reflections in a multichannel home theater are a good thing?

How's it going, mike2060, on finding two or three researchers other than Toole who think lateral first reflections in a multichannel home theater are a good thing?

I don't know of many other researchers in this industry. I do know that Toole has used data from experiments done over the last 30-40 years though. He doesn't pull this stuff out of his ass. Let me guess, you must be like 60 years old because old people NEVER change their opinions.

How about this? Show ME two or three people who actually have research backing them up saying first reflections are bad. You seem to be the one without someone credible backing them up (And no, Ethan Winer's graph doesn't count as one as it's certainly not enough proof).

I don't know of many other researchers in this industry. I do know that Toole has used data from experiments done over the last 30-40 years though. He doesn't pull this stuff out of his ass. Let me guess, you must be like 60 years old because old people NEVER change their opinions.
I will be 60 in June. But it's not that I don't ever change my opinion, it's just that I don't easily change an opinion that is based on my personal experience the first time someone steps out from the conventional wisdom with a new idea.

Have you ever listened to a home theater system with and without treatments at the front side first reflection points?

I am in the planning phase of my HT. I have been looking around why/whether there is such a thing as too low of a RT60. I understand you want the RT60 balanced as well as you can for all frequencies. It also seems that for music listening, it might be better to have a minimum RT60 to make it sound more "live".

I am planning on running my HT off my PC. There are settings to add reverb/"environmental settings" so that for music listening I could add reverb if music sounds bad. For movies, I could opt to add that or not....but it seems for movies you might want a low RT60, especially for outdoor scenes that would normally have no reverb/echos.

I also took a look at this site where he mentions anechoic being an ideal for a HT. http://www.lenardaudio.com/education/17_cinema_6.html

Any thoughts or info you could direct me to? TIA!

Have you ever listened to a home theater system with and without treatments at the front side first reflection points?

Yes I have. I have trouble understanding dialogue on some movies with first reflection points treated. But is your opinion of what it sounds like based on what you are told by others? Like if you are told 1st reflections are bad is that going to make you think that whatever you hear without treatment is bad? Maybe you should try without treatment for a couple of weeks and see how you feel based on the knowledge that first reflections may not be bad. Then you will be able to compare without bias.

I am in the planning phase of my HT. I have been looking around why/whether there is such a thing as too low of a RT60. I understand you want the RT60 balanced as well as you can for all frequencies. It also seems that for music listening, it might be better to have a minimum RT60 to make it sound more "live".

I am planning on running my HT off my PC. There are settings to add reverb/"environmental settings" so that for music listening I could add reverb if music sounds bad. For movies, I could opt to add that or not....but it seems for movies you might want a low RT60, especially for outdoor scenes that would normally have no reverb/echos.

I also took a look at this site where he mentions anechoic being an ideal for a HT. http://www.lenardaudio.com/education/17_cinema_6.html

Any thoughts or info you could direct me to? TIA!

This can give you a recommended RT time for your room:

http://www.bobgolds.com/Mode/RoomModes.htm

The smaller a room is the shorter the RT time is going to be. So a small room is generally going to sound deader than a large room even when furnished and treated.

That's an interesting mode calculator. It isn't very user friendly, but I should be able to figure it out.

I guess my question is not what is the recommended RT60 for my room, but why can't I go less than that? ....especially if I can add reverb for music if I want?

Yes I have. I have trouble understanding dialogue on some movies with first reflection points treated. But is your opinion of what it sounds like based on what you are told by others? Like if you are told 1st reflections are bad is that going to make you think that whatever you hear without treatment is bad? Maybe you should try without treatment for a couple of weeks and see how you feel based on the knowledge that first reflections may not be bad. Then you will be able to compare without bias.
:rolleyes: Hey now, the only "bias" I have is my own experience. And being nearly sixty give me a lot of experience.

I asked you if you had done it because I have done it. To my ears, the front sound stage is much more well-defined with those front left and right absorbers. And, perhaps counter-intuitively, the surrounds integrate better with the front soundstage with those absorbers.

Perhaps your room has other problems? ;)

....especially if I can add reverb for music if I want?
With what would you add "reverb?"

With what would you add "reverb?"

I would be using a HTPC and the sound card allows you to add "ambiance". You can make it sound like a concert hall, a shower, etc. I assume it is adding reverb with different time delays and reflection percents.

Maybe this is not how it usually done (or it is not done). I am not an audio expert/purist so maybe I just don't know better. :rolleyes:

erka and mike2060 Thank you for your response.
I was concerned becuase I remember reading one of the many posts saying to also treat your floor becuase it has a 1st reflection point as well.

Mike, I did know individuals were using felt, however with my possible moisture problem I was wondering if the pads with a moisture barrier will be a acouticval problem.

I wasn't that concerned about it till I went and priced carpet for the room. At $2000 for the room I thinking I should get my best option.

I would be using a HTPC and the sound card allows you to add "ambiance". You can make it sound like a concert hall, a shower, etc. I assume it is adding reverb with different time delays and reflection percents.

Maybe this is not how it usually done (or it is not done). I am not an audio expert/purist so maybe I just don't know better. :rolleyes:
Just a guess here, but I don't think the Acoustical Treatments thread is frequented by people who have recently added reverb electronically to what they were listening. :)

:rolleyes: Hey now, the only "bias" I have is my own experience. And being nearly sixty give me a lot of experience. Me. too, and I am even older than you are!

I asked you if you had done it because I have done it. To my ears, the front sound stage is much more well-defined with those front left and right absorbers. And, perhaps counter-intuitively, the surrounds integrate better with the front soundstage with those absorbers.The problem with anecdotal arguments is that they are not reliably generalizable. My experience with similar experiments confirms your first finding but confutes your second one.

I am not arguing with Ethan's measurements, although they, too, are anecdotal but objective. I have no doubt that there is interference between direct sound and its reflections as he has demonstrated. Heck, that is a large part of what gives a room or a concert hall its unique sound.

What is open for discussion/analysis/experiment is whether those reflections, particularly in a MCH system, are advantageous or not. Our observations conflict. Toole's are based on a much larger sample size but, again, under a single set of controlled circumstances. OTOH, it is only his approach, imho, that can lead to a reliable conclusion if it was to be extended to a more generalizable result. For example, Ethan rightly wonders how the subjects were selected. Toole does offer some info on that but the ears on this forum may not demand the same things as does the general population.

Perhaps we need someone like Sean Olive to re-examine the issue.

The problem with anecdotal arguments is that they are not reliably generalizable. My experience with similar experiments confirms your first finding but confutes your second one.

I am not arguing with Ethan's measurements, although they, too, are anecdotal but objective. I have no doubt that there is interference between direct sound and its reflections as he has demonstrated. Heck, that is a large part of what gives a room or a concert hall its unique sound.

What is open for discussion/analysis/experiment is whether those reflections, particularly in a MCH system, are advantageous or not. Our observations conflict. Toole's are based on a much larger sample size but, again, under a single set of controlled circumstances. OTOH, it is only his approach, imho, that can lead to a reliable conclusion if it was to be extended to a more generalizable result. For example, Ethan rightly wonders how the subjects were selected. Toole does offer some info on that but the ears on this forum may not demand the same things as does the general population.

Perhaps we need someone like Sean Olive to re-examine the issue.
Hmmm, I don't think I've ever been "confuted" before ... :)

Do you make a distinction between spaces where "content" is created and heard (or recorded) and spaces where content is reproduced? And I guess that is only most germane, IMO, for music that was originally performed live. Movie soundtracks and a lot of pop music are creatures of the studio. My experience there is that the best concerts I have ever heard where the band sounded live exactly as they did on the album.

Jeff

Hmmm, I don't think I've ever been "confuted" before ... :)Take that!

Do you make a distinction between spaces where "content" is created and heard (or recorded) and spaces where content is reproduced? And I guess that is only most germane IMO for music that was originally performed live.

JeffThe physics is the same but the goals are different. I hope you will grant that home listening rooms should not be completely dead but, rather, have controlled acoustics different from those of performance spaces. What we are discussing, I think, is not how or why reflections interact but how much (and of what kind) is desirable in a listening room.

I have to admit that I do not have an answer. Consequently, my rooms are ad hoc projects.

I've been confused about this issue since first hearing of Toole's results, as they go against my own experience. Listening with and without first reflection absorption in 5 separate dedicated rooms has left me with absolutely no doubts.

I've been confused about this issue since first hearing of Toole's results, as they go against my own experience. Listening with and without first reflection absorption in 5 separate dedicated rooms has left me with absolutely no doubts.

Wait... I'm interested in your conclusions. You say you've been confused. Then you say you have absolutely no doubts. So what DID your ears tell you in those dedicated rooms?

toole in his writings seems to suggest that is listeners are trained to do so. (visit the harman site and read dr olives musings on the subject)
given that each of us has a different set of ears, listening in a different room, to different non-reverbated sounds, that there is no good single answer. returning to the harman site, search out the pics of their listening room. looks very little like our own h/t i'll wager.(compare harman to mr winers demo room - there is a lot of difference, and the harman room(s) is(are) what dr toole is, in great measure, basing his findings upon)
regarding age, i am 69, and have my hearing checked once a year - i cannot hear above 5khz. this IS a factor when comparing treatments and results, imo!
at any rate i have been unable to discern a difference in my room with the movement of the front treatments. controlling the bass is a related, but different issue.
for me it continues to be a work in progress.
walt

The listeners were widely varied in most of his test. Some had no clue, some were trained, some were audiophiles, etc.

Ethan's graph just shows that reflections cause comb filtering which does not indicate how it will actually sound with our ears considering the sound being high frequencies and having a high Q.

erkq,

Sorry I didn't express that very well :rolleyes:

What I should have said is that my own testing has proven to me beyond any doubt that first reflection absorption is a good thing.

I am therefore confused by the Toole test results which contradict my own experience.


One example was at a high end shop listening to B&W 800s with untreated side walls. Something wasn't right so my friend and I grabbed large cushions, sat the shop owner in the sweet spot, and then walked forward along the side walls to the first reflection points. The look on his face was priceless !! This example is very telling to me, as the shop owner thought we were mad and was convinced he had an optimal setup. He was not expecting any improvement.

erkq,

Sorry I didn't express that very well :rolleyes:

What I should have said is that my own testing has proven to me beyond any doubt that first reflection absorption is a good thing.

I am therefore confused by the Toole test results which contradict my own experience.


One example was at a high end shop listening to B&W 800s with untreated side walls. Something wasn't right so my friend and I grabbed large cushions, sat the shop owner in the sweet spot, and then walked forward along the side walls to the first reflection points. The look on his face was priceless !! This example is very telling to me, as the shop owner thought we were mad and was convinced he had an optimal setup. He was not expecting any improvement.

Yeah... I have no doubt. I'm a big fan of taking the room out of the equation... especially the small rooms we have in our homes.

Yeah... I have no doubt. I'm a big fan of taking the room out of the equation... especially the small rooms we have in our homes.
+1, but nowhere near the point of anechoism. Is that a word? :)

Just a guess here, but I don't think the Acoustical Treatments thread is frequented by people who have recently added reverb electronically to what they were listening. :)

Maybe so, but I bet they listened to music that had electronic reverb added in the recording and/or production.

My question was why a low RT60 was bad for HT? Is it just bad for music listening?

Would a low RT60 room sound as "bad" as headphones?

Listening with and without first reflection absorption in 5 separate dedicated rooms has left me with absolutely no doubts.

Same here, except many dozens of rooms. :eek:

If someone has actually tried it both ways in their own room and prefers the sound with no absorption, that's fine with me. At least they actually tried it! But as a general rule, I think it's bad advice to tell others to avoid absorption at reflection points because, well, because it just sounds lousy! :D

--Ethan

Ethan's graph just shows that reflections cause comb filtering which does not indicate how it will actually sound with our ears

Graphs can very much predict what something will sound like, at least when one understands the relation between frequencies and perceived sound. If you happen to live anywhere near me in western CT, you're welcome to visit for some fun audio demos and experiments.

--Ethan

If you happen to live anywhere near me in western CT, you're welcome to visit for some fun audio demos and experiments.

Don't do it! You'll end up a puppet like the two in the back of the room...:D

Frank

Maybe so, but I bet they listened to music that had electronic reverb added in the recording and/or production.

My question was why a low RT60 was bad for HT? Is it just bad for music listening?

Would a low RT60 room sound as "bad" as headphones?
Well, it would be "electronic" by definition, but it would not have been produced by any electronics that a homeowner is likely to own. But, in any case, that is different. Individual elements are "wet" or "dry" and mixed together. What would be added in the home would be overall and be on top of what is in the recording.

It is very easy to over-dampen a home theater. I am struggling a bit with that myself right now and am looking at swapping some absorption for diffusion.

Jeff

Kal/Jeff - Toole is older than both of you. ;)

In his research on this, I rather suspect Sean was doing more than sitting in the wings. OTOH, the arm waving is focused on "Toole says this" ignoring that it really should be "Toole says this under the following circumstances".

This is an interesting read. Albeit confusing :D :eek::eek:

My VERY slowly HT project has long been planned for 1st reflection treatment with 1" of OC703, including ceiling.

And since there are two rows with four seats, the 1st reflection points are "all over the place", leaving me to plan for treating 4 feet up on side walls from screen wall and 2/3 back into the room.

I guess I will test it when done. I can always remove the OC703 from the frames and leave them empty.

Jacob

I doubt you'll want them empty (unless your off axis response is bad). You'll likely want diffusion.

Kal/Jeff - Toole is older than both of you. ;)But, together, we are older.

In his research on this, I rather suspect Sean was doing more than sitting in the wings. OTOH, the arm waving is focused on "Toole says this" ignoring that it really should be "Toole says this under the following circumstances".Agreed.

I doubt you'll want them empty (unless your off axis response is bad). You'll likely want diffusion.

Diffusion on the first reflection points on the side walls?
And what kind?

I am considering a mix of diffusion and absorption on the REAR wall - diffusion center at ear height, and absorption around that.

But on side walls, I thought I was too close for diffusion.

I am considering a mix of diffusion and absorption on the REAR wall - diffusion center at ear height, and absorption around that.

Toole recommends the other way around - having absorption in the middle and diffusion on the sides. If there is enough space from seat to the diffuser depending on what type you're going for. Another option is vertical strips of absorption on the rear wall (wider in middle, gap, thinner, gap, thinner etc - talking width of panel not thickness).

Some highly regarding people on the forum seem to use a BAD type panel for treating first reflection points, assuming the speakers have good off axis response (refer discussion a few posts ago). Others also use these types of treatment around your surrounds

Kal ... OT. You do OK in the resent weather event (I was in Pound Ridge and Mt. Kisco during it .... nasty, nasty.)

Kal ... OT. You do OK in the resent weather event (I was in Pound Ridge and Mt. Kisco during it .... nasty, nasty.)
I resented that weather, too. Had to drive through it Sat night to get from Ridgefield, CT to Manhattan. Three detours due to downed trees or flooded roads. Coming home the next morning was an adventure as well' the Sawmill was closed in at least two places. By the end of the play, every trash bin in Times Square was stuffed with busted umbrellas.

Kal ... OT. You do OK in the resent weather event (I was in Pound Ridge and Mt. Kisco during it .... nasty, nasty.)No problemo! It seems to have hit Westchester hard but all we had was rain and little wind. Our stream was a roiling torrent as a result and the noise was wild and wonderful but that's all. Of course, for all the money spend in the last 2 years on rearranging the drainage on the property, I am happy with that.

Thanks for asking.

I resented that weather, too.

Hahaha... pretty subtle jab at misspelling.

Hahaha... pretty subtle jab at misspelling.
Well, either I thought that's what he meant or it wasn't subtle enough. :)

I took the Sawmill on Friday from Pound Ridge to Manalapan (where I had the accident).

I took the Sawmill on Friday from Pound Ridge to Manalapan (where I had the accident).
Ouch.

Guys,

Need your help. I'm looking at adding some panels on the front screen wall behind my L and R.

Given that I'm not really in a position to treat my entire front screen wall or build a false wall at this point.

Is there a happy medium that would ALSO allow me to put something behind my 110" 16:9 screen to help in the process?

What would you reccomend in terms of thin material behind a fixed screen? I have a Carada 110" BW. (A Non AT Screen)

Wasn't sure if there was a best practice here or if such a thing existed, or if it would even be beneficial. Screen wall is single Drywall against foundation.

Thanks!

I'm a little confused I think, but I'd just add a 2" or 4" panel behind each speaker (assuming that you've treated the corners already). If that's all you have room for then it'll have to do. Am I missing something?

Frank

Breaking in with hopefully a simple question, I read through a few pages but most of this is over my head. For those who are creating a HT from scratch I can see how you are able to put the different kinds of material in the walls. However, I’m going to be converting a portion of a finished basement into a HT so the exterior walls already have regular insulation and drywall which I won’t be messing with.

I’ve attached a quickie floor plan of what I have and or plan to do. I’ll be able to put sound absorption material behind the screen and speakers and in the new wall that will be built. On the remaining walls I was planning on adding acoustic panels (and from my reading of this thread I should use cotton batting) above a 36” chair rail.

Is that going to work? I don’t plan on covering the walls in fabric panels just a chair rail with decorative panels below with paint above.

^^^^

For the most part, not the most prudent thing to do. May I suggest taking a look through this thread some more, or if timing is essential, or things continue to remain confusing, consider hiring an acoustical consultant to layout the room and treatment strategy for you. Best wishes! :)

Floyd Toole recommends clipped-pile carpet with 40oz/sq yd felt underlay.

I'm converting a living room that has hardwood flooring, and I don't want to damage it by installing wall-to-wall carpet. So I think I am stuck with some kind of carpet tiles.

Does anyone have an opinion about whether the thickness of the carpet tiles matters? Or is it mostly the underlayment that provides acoustic benefits in a traditional carpet setup?

Thinner carpet tiles are cheaper, so that is my preference all else being equal. And I would be willing to add a throw rug at the first reflection point if that would take care of any thin tile downsides.

Thanks for any advice!

I'm converting a living room that has hardwood flooring, and I don't want to damage it by installing wall-to-wall carpet. So I think I am stuck with some kind of carpet tiles.

Does anyone have an opinion about whether the thickness of the carpet tiles matters? Or is it mostly the underlayment that provides acoustic benefits in a traditional carpet setup?

Thinner carpet tiles are cheaper, so that is my preference all else being equal. And I would be willing to add a throw rug at the first reflection point if that would take care of any thin tile downsides.

Thanks for any advice!
I used a throw rug with heaviest padding I could find underneath.

Breaking in with hopefully a simple question, I read through a few pages but most of this is over my head. For those who are creating a HT from scratch I can see how you are able to put the different kinds of material in the walls. However, I’m going to be converting a portion of a finished basement into a HT so the exterior walls already have regular insulation and drywall which I won’t be messing with.

I’ve attached a quickie floor plan of what I have and or plan to do. I’ll be able to put sound absorption material behind the screen and speakers and in the new wall that will be built. On the remaining walls I was planning on adding acoustic panels (and from my reading of this thread I should use cotton batting) above a 36” chair rail.

Is that going to work? I don’t plan on covering the walls in fabric panels just a chair rail with decorative panels below with paint above.

Although we go back and forth about treating first reflection points with absorption, treating a bunch of non first reflection points (ie, below the chair rail) is probably a deprecated approach for most situations.

What the heck am I talking about? Here are some good short explanations of a good starting point:

http://www.realtraps.com/rfz.htm

http://www.gikacoustics.com/news_020209.html

Well I am not confused, maybe i don't understand "deprecated" (obsolescent and in the process of being phased out)
I was under the impression, from the start of this thread through the majority. That a person is in general suppose to use from floor up to 44" 1" Insul-Shield and from there to ceiling nothing or batting if doing a full cloth wall. Front wall was entirely 1" Insul-Shield.
What is the good practice for room acoustic in a home theater? If its not what is stated in the beginning of the thread maybe that should be revised.
I'm about to begin my wall covering and acoustics. Do I need a new plan?
All the talk of first reflection points is very interesting but, like wise I need a concrete direction to go.

The person who posted at the start of this thread did so about 7 years ago, and hasn't been back to this thread in almost that much time (as a poster).

Those two links in my post are the best practices out there. Some people argue for even less absorption.

But almost no one calls for thin (1") in all the places your are talking about.

From personal experience and based on data here and elsewhere, you want thicker panels (say 3 or 4 or 5 inches), and less wall coverage.

----

Two things you want to pay attention to for the best sound (in terms of room treatments):

1. Bass trapping
2. Absorption of first reflection points (though in larger rooms, diffusion can work instead of, or in tandem with, absorption).

Well, I am confused. In post #5 of this thread the poster asks: "1) Is 1" Insul-Shield (or equivalent) adequate for the front wall, or should it be increased to 2" if possible?"

In post #6 Dennis Erskine answers "I would not use the 2" material...it will very likely be too absorptive."

Has this advice changed since the thread started?

Well, I am confused. In post #5 of this thread the poster asks: "1) Is 1" Insul-Shield (or equivalent) adequate for the front wall, or should it be increased to 2" if possible?"

In post #6 Dennis Erskine answers "I would not use the 2" material...it will very likely be too absorptive."

Has this advice changed since the thread started?

Whumf trust me your not the only one. I thought I had everything planned and figured. Now I'm lost and about to say screw it. you would think after reading and researching for nearly 1 year I 'd have a clue.

I'm not sure why the moderator hasn't change or updated the beginning and posted recomended procedure to acoustically treat your room.
I believe it would decrease their amount of repeated inquaries on topics, I'm sure they are tired of answering, if they would post a procedure to acoustically treat your room.

Yes I know everyroom is different but maybe there is a common practice.

1) Measure RT60
a) What to do with this?
2) Find 1st reflection points ( all surfaces )
a) Method - mirrior.
b) Treatment of 1st reflection points - Clueless
3) Building absorbtion panels and total wall treatment.
a) Materials - list of exceptible material
b) Absorbtion material - OC703, Insul-Shield ect, and thickness
4) Bass traps
a)
5)ect.

Just an Idea, and no this isn't correct. I'm throwing out a starting point and I'm sure theres lots of things that could be included.

whumpf and belzarreth, those are all good questions and the information is all "out there." You can probably get a question or two at a time answered here, but no one on a forum thread can start you at the basics and bring you the whole way through all the variables and have you be able to design a theater at the end.

As for changing information, the *thinking* on how to treat rooms has changed over the years. When I research a new topic, I always make sure that the content is relatively recent. And there seems to be different schools of thought on some things.

Jeff

Well I thought this would be the thread for these questions and information, if not could you lead me to them. I do not mind reading and learning; which i've tried for the last year, however, going through 200 pages of posts which goes all directions is very miss leading and unfortunitly dishearting.
I have asked questions here and other forums which has lead me to the general practice of what was first listed.
If a person follows the listed procedure is it detrimental to the acoustics of the room, better than a cement basement?

There is a reason the experts get paid a few thousand dollars (and up) to design good acoustic spaces for home theater: It's complicated and a specialized skill set.

However, there are some basics that you can follow, and get good results -- without hiring an expert. The links I provided will NOT steer your wrong, and are an improvement over what you describe as your plan.

If you prefer a video, try this. A 15 minute investment and you'll be miles ahead of most people when it comes to understanding and implementing good home theater acoustic treatment.

http://www.realtraps.com/video_setup.htm

--------

If you want to get some written details about the variations of the best practices, here are some great links to check out:

http://www.audioholics.com/education/acoustics-principles/

I agree with nathan_h's suggestion...those links are a good place to start. I've been trying to learn about this subject too and found some of those articles very helpful.

Another resource...I also just started reading the Floyd Toole book that has been discussed here. I skipped ahead to the practical recommendations and have found them very clearly explained so far.

Well I thought this would be the thread for these questions and information, if not could you lead me to them. I do not mind reading and learning; which i've tried for the last year, however, going through 200 pages of posts which goes all directions is very miss leading and unfortunitly dishearting.
I have asked questions here and other forums which has lead me to the general practice of what was first listed.
If a person follows the listed procedure is it detrimental to the acoustics of the room, better than a cement basement?
'Nother one for you (http://forum.studiotips.com/) ....

I used a throw rug with heaviest padding I could find underneath.

Thanks pepar. So from your pictures it looks like you left the rest of the room as hardwood?

Then I should be fine with a similar approach. I'll probably still cover the whole room with the thin carpet tiles (for light control), then do a throw rug and pad in between the screen and the front row.

Thanks pepar. So from your pictures it looks like you left the rest of the room as hardwood?

Then I should be fine with a similar approach. I'll probably still cover the whole room with the thin carpet tiles (for light control), then do a throw rug and pad in between the screen and the front row.
The floor is wood, but not really much of it is exposed due to the carpeted riser. BTW, the next "chapter" is as of now un-written, but the rug was removed and I am looking at replacing some absorption with diffusion.

Hello, working on treating my theater room and I want to make sure I am doing the right things. Some of you have already provided great advice, thanks. I am treating behind my screen wall, attempting to reduce noise transmitting to the living room above, and absorb sound for the best sound reproduction from behind the screen into the main room. I have installed safe and sound insulation to reduce noise carrying upward, and it has worked well, see pics attached.

Next question I Have, what should I do, if anything, to the concrete block wall behind the screen? I was thinking a linacoustic RC type product, do I need it?

Thank you for your help, obviously I will be doing more reading. I not sure what my new direction will be but I'm sure it will envolve taking measurements and much more time.

Count me in among the confused. I have also done much reading and based a lot of my treatments on the first 50 to 100 pages of this thread. Obviously, as the thread goes on differing opinions start to emerge, which sometimes contradict each other. I personally took what I thought was a consensus approach to start with - couple of 1" OC703 panels on side walls, behind L/R speakers, and bass traps in the corners. I went with the 1" panels because they look better and the original purpose was to treat high-frequency reflections. Some people reccommend 2" or even 4" (wouldn't that be a bass trap?), on the walls which would look ridiculuous if you are not building from scratch and using panels.

Anyway, so far I like the results and will wait and see before doing any further work.

Count me in among the confused. I have also done much reading and based a lot of my treatments on the first 50 to 100 pages of this thread. Obviously, as the thread goes on differing opinions start to emerge, which sometimes contradict each other. I personally took what I thought was a consensus approach to start with - couple of 1" OC703 panels on side walls, behind L/R speakers, and bass traps in the corners. I went with the 1" panels because they look better and the original purpose was to treat high-frequency reflections. Some people reccommend 2" or even 4" (wouldn't that be a bass trap?), on the walls which would look ridiculuous if you are not building from scratch and using panels.

Anyway, so far I like the results and will wait and see before doing any further work.
Thicker absorbers reach lower frequency-wise. The sound hitting the first reflection points is full range, so the absorber should be as full range as possible. Beyond the first reflections, the concern is that absorbing the highs/mid-highs and not the mids/mid lows will result in a dead, boomy room. (Bass traps are needed for the lows/low lows.) Once you put "looking better" above "working better", you have gone off track, IMO.

Four inch panels might be an odd thing to see and could even encroach into the room space, if not physically then certainly visually. But the benefit of bumping the 1" to 2" seems to me to outweigh the additional 1" of thickness.

Just my $.02.

Jeff

Count me among the confused as well.
I based my plan (not done yet) on the first 150 pages as well, when concensus seemed to be something like:
- 1st reflection treatment with absorbtion (1" OC703) from floor and up to 4' - from screen and two thirds back into room.
- 2" OC703 on whole front wall behind false screen wall
- Bass traps in corners - as many corners as possible.
- As this is an attic room, I have sloping walls, starting from 5' up the side walls. Therefore, I will treat the sloping walls as well with 2" OC703 in 3.5" deep frames, each panel measuring 40" x 6" on the inside. They will be mounted as vertical strips, with 8" of air between each panel. The will give 1st reflection absorption and crude difussion.
- I also consider 2-3 QRD Diffusor (from Real Traps) for the center back wall - with 6" absorption (OC703) as fallback - the QRDs are expensive...

The whole discussion about using a mirror etc to find first reflections seems to me to be for HT with two seats or something like that - for a dedicated HT room with multiple seats and two rows or more, the first reflection points are going to be all over the place. :eek:
I have two rows of four seats, second row on a riser.
1st reflections from the three identical front speakers pretty much include most of the sidewall as described above in plan... ;)

Now, my room is small - 13.4' x 20' x 8'. It's my understanding (based on this thread, Real Traps and GIK homepages etc) that diffusion works best in larger rooms (or rather, when the listener is far away from the diffusor).

When Dennis Erskine now mentions diffusion for 1st reflection points, instead of absorption - does that go for a small room like mine as well? :confused:

And what kind of diffusion products for this specific task? :confused:

Cheers from Denmark, :)
Jacob

1) Measure RT60
a) What to do with this?
2) Find 1st reflection points ( all surfaces )
a) Method - mirrior.
b) Treatment of 1st reflection points - Clueless
3) Building absorbtion panels and total wall treatment.
a) Materials - list of exceptible material
b) Absorbtion material - OC703, Insul-Shield ect, and thickness
4) Bass traps
a)
5)ect.

Just an Idea, and no this isn't correct. I'm throwing out a starting point and I'm sure theres lots of things that could be included.

I'd make #4 your #1. An RT60 of a small room is not very useful...if you really want to know what things look like across the broad bandwidth at a particular place in the room, then shooting with room EQ Wizard, Fuzzmeasure or whatever, will tell you that and also allow you to generate a waterfall measurement so you can see what your ringing times look like. If you want to go a step further you can use an Energy Time Envelope (ETC) that'll tell you in fairly precise way where your problems are in terms of frequency and position.

Frank

If "what to do with waterfall" pops into your mind :), the idea is to get everything to "ring down" at the same time. Anything that rings way beyond the average is a problem.

Thicker absorbers reach lower frequency-wise. The sound hitting the first reflection points is full range, so the absorber should be as full range as possible. Beyond the first reflections, the concern is that absorbing the highs/mid-highs and not the mids/mid lows will result in a dead, boomy room. (Bass traps are needed for the lows/low lows.) Once you put "looking better" above "working better", you have gone off track, IMO.

Four inch panels might be an odd thing to see and could even encroach into the room space, if not physically then certainly visually. But the benefit of bumping the 1" to 2" seems to me to outweigh the additional 1" of thickness.

Just my $.02.

Jeff

It was my understanding that ringing was a bigger problem than low freq 1st reflections :confused:
Therefore, I plan to have a 4" panel to the sides of the 1st row (primary), and 1" panels between that and the screen wall. The two sidewall surround speakers (MK-SS150 tripoles) will be mounted above this 4" panel (=90 degrees to 1st row).

I also plan for a 4" OC703 panel in ceiling right above 1st row, to counter ringing as well.

When Dennis Erskine now mentions diffusion for 1st reflection points, instead of absorption - does that go for a small room like mine as well?
I believe he'd said it does apply; however, I believe he'd also say that depends on the quality of the off axis response of your speakers.

I believe he'd said it does apply; however, I believe he'd also say that depends on the quality of the off axis response of your speakers.

My speakers are known for good off axis response - its a key concept for the company - but whether this measures up, I don't know ;) I think part of the concept is the rear radiation ports, which I guess I nullify with the front wall treatment anyway :rolleyes:

So where does that leave me?

My speakers are known for good off axis response - its a key concept for the company - but whether this measures up, I don't know ;) I think part of the concept is the rear radiation ports, which I guess I nullify with the front wall treatment anyway :rolleyes:

So where does that leave me?

Hi Jacob,

How do you know this? I am sure Dennis "he'd also say" would also say (:))...never, ever believe what the manufacturer has told you. It may or may not be true for your particular speakers. You need to test your individual speakers to make sure their off-axis is response is good. Best wishes! :)

Hi Jacob,

How do you know this? I am sure Dennis "he'd also say" would also say (:))...never, ever believe what the manufacturer has told you. It may or may not be true for your particular speakers. You need to test your individual speakers to make sure their off-axis is response is good. Best wishes! :)

How do I measure this (my self) and what does the result mean, i.e.
good off axis response => x treatment of 1st reflection points?
bad off axis response => y treatment of 1st reflection points?

thanks :)

Jacob

Count me in among the confused. I have also done much reading and based a lot of my treatments on the first 50 to 100 pages of this thread. Obviously, as the thread goes on differing opinions start to emerge, which sometimes contradict each other. I personally took what I thought was a consensus approach to start with - couple of 1" OC703 panels on side walls, behind L/R speakers, and bass traps in the corners. I went with the 1" panels because they look better and the original purpose was to treat high-frequency reflections. Some people reccommend 2" or even 4" (wouldn't that be a bass trap?), on the walls which would look ridiculuous if you are not building from scratch and using panels.

Anyway, so far I like the results and will wait and see before doing any further work.

Count me among the confused as well.
I based my plan (not done yet) on the first 150 pages as well, when concensus seemed to be something like:
- 1st reflection treatment with absorbtion (1" OC703) from floor and up to 4' - from screen and two thirds back into room.
- 2" OC703 on whole front wall behind false screen wall
- Bass traps in corners - as many corners as possible.
- As this is an attic room, I have sloping walls, starting from 5' up the side walls. Therefore, I will treat the sloping walls as well with 2" OC703 in 3.5" deep frames, each panel measuring 40" x 6" on the inside. They will be mounted as vertical strips, with 8" of air between each panel. The will give 1st reflection absorption and crude difussion.
- I also consider 2-3 QRD Diffusor (from Real Traps) for the center back wall - with 6" absorption (OC703) as fallback - the QRDs are expensive...

The whole discussion about using a mirror etc to find first reflections seems to me to be for HT with two seats or something like that - for a dedicated HT room with multiple seats and two rows or more, the first reflection points are going to be all over the place. :eek:
I have two rows of four seats, second row on a riser.
1st reflections from the three identical front speakers pretty much include most of the sidewall as described above in plan... ;)

Now, my room is small - 13.4' x 20' x 8'. It's my understanding (based on this thread, Real Traps and GIK homepages etc) that diffusion works best in larger rooms (or rather, when the listener is far away from the diffusor).

When Dennis Erskine now mentions diffusion for 1st reflection points, instead of absorption - does that go for a small room like mine as well? :confused:

And what kind of diffusion products for this specific task? :confused:

Cheers from Denmark, :)
Jacob

When I read this thread last year from the beginning, I printed it all off and read it during my commute; don't worry, I take a commuter train (2 hours a day)!. For some reason, I cannot absorb technical details and complex information while reading on the computer. Perhaps that is becuase whenever I am at a computer, I am frequently interrupted.

Anyway, this allowed me to fully concentrate on the subject matter and highlight & save the good parts. I started to figure out who was knowledgeable and realized there were differing opinions. I simply collected the relevant posts on various subjects so I could see all opinions when it came time to make my design/purchase decisions for acoustic treatments.

I employed this same technique when I initially read through the Audyssey thread, and then subsequently created the setup guide for my own edification / sanity. When folks asked where I got the information from, I could pull up the relevant post.

To make a long story short, it is difficult in long threads (spanning years) to assimilate the information by simply searching or reading on the computer. Unless, of course, one has a photographic memory. To complicate matters, then Dr. Toole comes out with a new book, and we find ourselves some elements of design / treatment. This is the nature of our hobby, I guess.

Mark

And then we have to remember that some of the articles we read are about 2 channel music rooms and some are about 5.1 or 7.1 home theater rooms.
In general home theater rooms are much more absorbent. As 2 channel needs the reflections to help with the stereo illusion.

And then we have to remember that some of the articles we read are about 2 channel music rooms and some are about 5.1 or 7.1 home theater rooms.
In general home theater rooms are much more absorbent. As 2 channel needs the reflections to help with the stereo illusion.

Ahh, but what is a home theater setup if not an enhancement upon two channels for multiple listeners? Food for thought. Best wishes! :)

Count me among the confused as well.
I based my plan (not done yet) on the first 150 pages as well, when concensus seemed to be something like:
- 1st reflection treatment with absorbtion (1" OC703) from floor and up to 4' - from screen and two thirds back into room.
- 2" OC703 on whole front wall behind false screen wall
- Bass traps in corners - as many corners as possible.
- As this is an attic room, I have sloping walls, starting from 5' up the side walls. Therefore, I will treat the sloping walls as well with 2" OC703 in 3.5" deep frames, each panel measuring 40" x 6" on the inside. They will be mounted as vertical strips, with 8" of air between each panel. The will give 1st reflection absorption and crude difussion.
- I also consider 2-3 QRD Diffusor (from Real Traps) for the center back wall - with 6" absorption (OC703) as fallback - the QRDs are expensive...

The whole discussion about using a mirror etc to find first reflections seems to me to be for HT with two seats or something like that - for a dedicated HT room with multiple seats and two rows or more, the first reflection points are going to be all over the place. :eek:
I have two rows of four seats, second row on a riser.
1st reflections from the three identical front speakers pretty much include most of the sidewall as described above in plan... ;)

Now, my room is small - 13.4' x 20' x 8'. It's my understanding (based on this thread, Real Traps and GIK homepages etc) that diffusion works best in larger rooms (or rather, when the listener is far away from the diffusor).

When Dennis Erskine now mentions diffusion for 1st reflection points, instead of absorption - does that go for a small room like mine as well? :confused:

And what kind of diffusion products for this specific task? :confused:

Cheers from Denmark, :)
Jacob

My room is similar to yours (17'x12.5'x7.5' -- nice of you to translate into feet rather than use metrics...) but even a little smaller.

I have two rows of seats: one couch for each. The second row couch is on a riser.

Using the mirror method I was able to cover the side wall first reflection points for all three front speakers for almost all sitting positions with just two 2'x'4 panels on each of the side walls.

That, plus bass trapping in every corner and under the screen (ie, where the screen wall meets the floor), please two more panels on the back wall, and heavy carpet on the floor, have really made things solid and clear. Yet most of the wall space is still uncovered.

I'm glad to see others were having the same difficulties. :confused:
Wouldn't it be relevant for those individuals with lots of experience to each make a proposed summary of a method to acoustically treat a HT.
Even if they were opposing views. Individuals could choose which they feel best fits their needs and ask questions in this forum based on those summaries.


I'd make #4 your #1. An RT60 of a small room is not very useful...if you really want to know what things look like across the broad bandwidth at a particular place in the room, then shooting with room EQ Wizard, Fuzzmeasure or whatever, will tell you that and also allow you to generate a waterfall measurement so you can see what your ringing times look like. If you want to go a step further you can use an Energy Time Envelope (ETC) that'll tell you in fairly precise way where your problems are in terms of frequency and position.

Frank

Weasel9992 thank you for your response to my list, I quickly wrote that up with out much thought.
I was just trying to give ideas to enhance the thread. I spend time also on the diy screen thread which employs this method.

2 channel needs the reflections to help with the stereo illusion.

To my ears, avoiding small-room reflections improves stereo imaging, and also makes the music sound larger and wider. When you allow reflections in a typical domestic size room, those reflections drown out the "larger room" reverb that's present in many recordings. So the net result from reflections in a small room is a smaller sound.

--Ethan

To my ears, avoiding small-room reflections improves stereo imaging, and also makes the music sound larger and wider. When you allow reflections in a typical domestic size room, those reflections drown out the "larger room" reverb that's present in many recordings. So the net result from reflections in a small room is a smaller sound.

--Ethan

Big +1 from me.

Frank

To my ears, avoiding small-room reflections improves stereo imaging, and also makes the music sound larger and wider. When you allow reflections in a typical domestic size room, those reflections drown out the "larger room" reverb that's present in many recordings. So the net result from reflections in a small room is a smaller sound.

--Ethan

Big +1 from me.

Frank
How do you reconcile your experience wrt this with Dr Toole's recent work?

I must admit to being confused by this ...

Jeff

How do you reconcile your experience wrt this with Dr Toole's recent work?



I cannot speak for the others, but for me: I have tried it both ways in several rooms (good rooms, bad rooms, and everything in between), and it typically sounds better (clearer stereo image and soundstage details, I hear more of a small room when the recording is creating a small room sound and more of a large room when the recording is creating a large room sound) to me when treating first reflection points, especially lateral ones, with thick absorption. Some rooms and some speakers benefit more from this.

How do you reconcile your experience wrt this with Dr Toole's recent work?

I must admit to being confused by this ...

Jeff

I'll admit in turn that it's not necessarily an objective statement on my part...more of a subjective observation. It's not my intention to contradict Toole...I'm not that arrogant yet. :)

Frank

I'll admit in turn that it's not necessarily an objective statement on my part...more of a subjective observation. It's not my intention to contradict Toole...I'm not that arrogant yet. :)
I've read his paper - at least the part that is in English - and I am still not sure that his work was done with/applies to a residential-sized room with a multichannel system. I, rightly or wrongly, thought it was for 2-channel systems ... reproducing "symphonic" music.

Jeff

To my ears, avoiding small-room reflections improves stereo imaging, and also makes the music sound larger and wider. When you allow reflections in a typical domestic size room, those reflections drown out the "larger room" reverb that's present in many recordings. So the net result from reflections in a small room is a smaller sound.
--Ethan
For 2 channel stereo music Siegfried Linkwitz prefers a more reflective room.

http://www.linkwitzlab.com/stereo%20reproduction.htm

Sure. Stereo relies on room reflections for any sense of envelopment. MCH provides that from the surround channels.

How do you reconcile your experience wrt this with Dr Toole's recent work?

I wouldn't even try. :D

Seriously, all I can go by is my ears and my own experience. And of course hard measurements showing a much flatter response with all early reflections absorbed.

--Ethan

One possible way to reconcile that is even Toole's recent work, as quoted here a few moons ago, I haven't read it myself, said that for critical listening, killing early reflections aided imaging, but casual listeners in a casual setting preferred having the envelopment of the early reflections... so it seems to me this would come down to reference vs preference...

One possible way to reconcile that is even Toole's recent work, as quoted here a few moons ago, I haven't read it myself, said that for critical listening, killing early reflections aided imaging, but casual listeners in a casual setting preferred having the envelopment of the early reflections... so it seems to me this would come down to reference vs preference...

Interesting post Greg. That sounds very reasonable.

Frank

One possible way to reconcile that is even Toole's recent work, as quoted here a few moons ago, I haven't read it myself, said that for critical listening, killing early reflections aided imaging, but casual listeners in a casual setting preferred having the envelopment of the early reflections... so it seems to me this would come down to reference vs preference...I see this as preference vs. preference since the sense of envelopment is a component of the original event.

One possible way to reconcile that is even Toole's recent work, as quoted here a few moons ago, I haven't read it myself, said that for critical listening, killing early reflections aided imaging, but casual listeners in a casual setting preferred having the envelopment of the early reflections... so it seems to me this would come down to reference vs preference...
Greg, I think the context here is critical listening. When I am in a casual setting, I prefer a margarita and could give a sh*t about acoustics. :)

Jeff

Interesting post Greg. That sounds very reasonable.
Thanks. It's a shame, though, that I just made it up and don't have the foggiest clue what I'm talking about. :D
I see this as preference vs. preference since the sense of envelopment is a component of the original event.
Wouldn't that depend on the recording in question? And therefore the intent of the artist? More to the point, I think, is that accurate imaging is not necessarily the same thing as envelopment.
Greg, I think the context here is critical listening. When I am in a casual setting, I prefer a margarita and could give a sh*t about acoustics. :)
Understood, but I think you mean that you "couldn't" give a... ;)

More to the point, I think, is that accurate imaging is not necessarily the same thing as envelopment.

Hi Greg,

I am not 100% sure what you are referring to, but I think you may be referring to focus rather than imaging. IMHO, imaging can be defined as both focus and/or envelopment, and the combination of the two contribute to recreating a believable soundstage in three dimensional space if properly employed. Best wishes! :)

That's probably fair ... I may not be doing a very good job of articulating what I mean here, but haven't we all heard systems (which of course include the room and it's reflections) that sound as if the sound is all around you, but in a random, as opposed to your focussed, way?

The first time I head such a thing I was rather impressed. Now I much prefer listening to a system that produces focussed imaging, as you say. But I could see the uninitiated, as I once was, who may still be unaware that such a thing is possible, being preferring random envelopment to a system that just sounds two dimensional. We're all aware of the success of a company that claims to have invented that sort of random envelopment...

Those speakers are great for casual listening!!!

:p
I'm so ashamed I have a friend who works there.

I see this as preference vs. preference since the sense of envelopment is a component of the original event.

Wouldn't that depend on the recording in question? And therefore the intent of the artist? Perhaps but my focus and concern is always about the accurate reproduction of a real event (and mostly classical music). If the program content was studio-created, your distinctions might be relevant.

More to the point, I think, is that accurate imaging is not necessarily the same thing as envelopment.
I am not 100% sure what you are referring to, but I think you may be referring to focus rather than imaging. IMHO, imaging can be defined as both focus and/or envelopment, and the combination of the two contribute to recreating a believable soundstage in three dimensional space if properly employed.Amen.

I am not 100% sure what you are referring to, but I think you may be referring to focus rather than imaging. IMHO, imaging can be defined as both focus and/or envelopment, and the combination of the two contribute to recreating a believable soundstage in three dimensional space if properly employed.
You listened well in class, Grasshopper. Now, more wax on, wax off. :)

ahhh...sank you Master! :D

Perhaps but my focus and concern is always about the accurate reproduction of a real event (and mostly classical music). If the program content was studio-created, your distinctions might be relevant.

That's fair enough. Perhaps the distinction I'm making is more between the believable and, um, other...

A little input would be appreciated. I searched, but didn't quite get what I needed.

I work in a manufacturing facility that produces polyurethane foam. We simply make the foam, then ship it to customers who fabricate it to their needs. We produce everything from low density foams (more open cell structure) to high density ones (more closed).

I have virtually unlimited access to these, and can have my guys cut them to whatever size I wish. My question is, would any of this be effective in a cheap DIY solution to acoustic paneling? I can also have them covered with whatever material would work. I'm aware that I can experiment with it, but would really rather know if it would be worth the trouble. Thanks.

Yes, in fact, one of the big names in acoustic panels (Auralex) uses foam almost exclusively, and it works.

It is not as effective as fiberglass -- meaning thicker panels are needed for the same impact.

I cannot tell you whether low density or high density is better (though there is a difference in the acoustic properties).

And you want to make very sure that the foam you get is fire-retardant because a lot of industrial foams, like packing materials, are very flammable and therefor dangerous to hang on your walls/ceiling.

Thanks for the response, Nathan. That gives me some hope in using it.

Yes, I'm all too familiar with fire retardant foam. It's one of our big concerns and several of our grades can't get used if they fail the tests.

I have both roxul and oc 703, if I use burlap material to cover the panels, do I have to wrap them with cotton batting before I wrap them with burlap?

Trying to keep the fiberglass fibers within the panels? Any suggestions.

I have both roxul and oc 703, if I use burlap material to cover the panels, do I have to wrap them with cotton batting before I wrap them with burlap?

Trying to keep the fiberglass fibers within the panels? Any suggestions.

No, you don't. If it'll make you feel better you can, but it's really not necessary.

Frank

A little input would be appreciated. I searched, but didn't quite get what I needed.

I work in a manufacturing facility that produces polyurethane foam. We simply make the foam, then ship it to customers who fabricate it to their needs. We produce everything from low density foams (more open cell structure) to high density ones (more closed).

I have virtually unlimited access to these, and can have my guys cut them to whatever size I wish. My question is, would any of this be effective in a cheap DIY solution to acoustic paneling? I can also have them covered with whatever material would work. I'm aware that I can experiment with it, but would really rather know if it would be worth the trouble. Thanks.

sb1 - take a look at this RPG link to their Skyline diffuser which looks to me like it might be made out of high density polyurethane foam:

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

Does this look like the same stuff you have access to? If so then you may wish to build a Skyline diffuser but would need something to cut the varying depth cells with . . . If you're interested then PM me and I can send you the best calculator I found and a write up on how to do it . . .

This is probably wacky, but I figure if anybody would know, it would be somebody subscribed to this thread. I need to mount a speaker in a location that has no 2x4 wall studs (there's a pocket door) and am considering mounting it on a pipe flanged between the ceiling and the floor. Besides making the pipe strong enough to hold the speaker, would there be any bad vibrations of the pipe caused by the speaker?

Jeff

This is probably wacky, but I figure if anybody would know, it would be somebody subscribed to this thread. I need to mount a speaker in a location that has no 2x4 wall studs (there's a pocket door) and am considering mounting it on a pipe flanged between the ceiling and the floor. Besides making the pipe strong enough to hold the speaker, would there be any bad vibrations of the pipe caused by the speaker?

Sure...it's possible. It's hard to say if it's likely or not without knowing what speaker it is and what you're doing with it. If it's a satellite, then it's probably fine though.

Frank

Sure...it's possible. It's hard to say if it's likely or not without knowing what speaker it is and what you're doing with it. If it's a satellite, then it's probably fine though.

Frank
Full range, but crossed like the others in the system at 80Hz or maybe 100Hz. Material costs will be negligible, so I might as well try it and find out. I'll just go with a 2" OD steel pipe.

Thanks,

Jeff

Full range, but crossed like the others in the system at 80Hz or maybe 100Hz. Material costs will be negligible, so I might as well try it and find out. I'll just go with a 2" OD steel pipe.

Thanks,

Jeff

Try filling the pipe with sand to add mass to reduce resonances and put some thick/firm rubber (e.g. carpet underlay) at any points where the speaker touches the pipe, again to absorb and prevent any engery transfer.

Try filling the pipe with sand to add mass to reduce resonances and put some thick/firm rubber (e.g. carpet underlay) at any points where the speaker touches the pipe, again to absorb and prevent any engery transfer.

+1 for all that. A hollow pipe seems like it would be an instant problem to me.

Frank

Try filling the pipe with sand to add mass to reduce resonances and put some thick/firm rubber (e.g. carpet underlay) at any points where the speaker touches the pipe, again to absorb and prevent any engery transfer.
The sand adds a bit of potential drama to the process, but should be easy to do. The shock mounting of the speaker might be a bit tricky. I was thinking of U-bolting a flat mounting surface onto the pipe and then attaching the Omnimount to that.

http://www.averagingpitottubes.com/imges/brackets/175pd.gif

I don't thing I could put rubber between the bracket and the pipe and not have it get squeezed out and fairly quickly. Might be able to custom cut a layer or two of old tire inner tube to the outline of the Omnimount though and place it between the plate and the mount. Interesting.... and thanks!

Jeff

I am considering some possible room treatment in the future. I was hoping I could photo the room and send the pics for evaluation to someone experienced in acoustical treatments. Anyone that has recommendations feel free to share.

Thanks, Rob

How do I compare and evaluate the performance of the plethora of diffusors on the market?

Jeff

I am considering some possible room treatment in the future. I was hoping I could photo the room and send the pics for evaluation to someone experienced in acoustical treatments. Anyone that has recommendations feel free to share.

Thanks, RobMost of the regular players in this business will do this for you. Note that their recommendations, while helpful and useful, will include only their products. As a result, it will still be necessary for you to make a difficult comparison.

Also, pix are useful but a precise diagram of room, major features, equipment and listening position(s) should also be supplied.

Try:
www.realtraps.com
www.gikacoustics.com
www.acousticsciences.com
www.auralex.com

How do I compare and evaluate the performance of the plethora of diffusors on the market?

Jeff

Jeff - armed with a little bit of knowledge you will be better apt to critique or evaluate the various types. Have you read Toole's latest book or this text book written by RPG's CEO and Prof Trevor Cox http://www.amazon.ca/Acoustic-Absorbers-Diffusers-Theory-Application/dp/0415471745/ref=sr_1_2?ie=UTF8&s=books&qid=1270254199&sr=1-2?

Firstly, where do you think you want to put diffusion as that'll dictate whether it should be 1D or 2D which will narrow your choices down . . . 1D is recommended for scattering sound latterly (horizontally) and should be placed on the front wall and side walls in front of the listening seat to widen the apparent sound stage width. 2D should be placed on the rear parts of the side walls and rear wall to create a sense of listener envelopment.

Common 1D types include QRD and hemi-cylindrical (and others?) while 2D would include Skylines and derivations thereof.

Secondly, you want the diffuser to work as broad range as possible so as not to act as a low pass filter and throw off your spectral balance that you paid dearly for in your selection of speakers ;) HF effectiveness for:
* Skylines is determined by the size of the block (not the depth) with small sizes allowing for higher freq diffusion effectiveness. I could only find 1.5" *1.5" blocks of wood for my Skyline which will work up to and likely beyond 4.5KHz which is higher than the highest note on a piano. Even George Massenberg's famous 'Studio C' uses 1"*1" sized blocks which will take it up to 6.75KHz or so . . .
* Hemi-cylindrical diffusers is a funtion of how hard the outer material is (so as not to absorb mid/high frequencies) and the angle of incidence; the max diffusion occurs head-on (meaning perpendicular) to the centre of the hemi.
* QRD is determined by the thickness of the wells with thinner being better.

The diffuser should work down to your room's transition (or Schroeder) frequency which is about 300Hz. LF effectiveness for:
* Skyline is determined by the max cell depth which should be a substantial % of the 300Hz freq wavelength. 50% would mean a depth of 22.6". Of course you could opt for 25% (11.3") or even 14% (6.5") but it would mean less and less effectiveness at 300Hz . . .
* Hemi-Cylindrical is determined by the length of the radius or strickly speaking the 'Sagita' which is that part of the radius that sticks out from the wall into the room when the hemi's arc is less than 180 degrees. The farther out into the room the radius extends the lower the depth it diffuses to. The same calculations would apply as above meaning a radius of 6.5" will only be about 14% of the 300Hz freq wavelength and be less effective than a 11.3" or 22.6" radius.
* QRD well depths determine the LF limits. I've only seen one manufacturer which makes a 15" well depth. Good on them!

Lastly, the diffusion and scattering coefficients are useful metrics for evaluation purposes except that they haven't been standardized nor widely accepted or mandated for inclusion as part of a company's stock marketing collateral for their respective diffusers lines . . .

Hope this tid bit of education has helped.

How do I compare and evaluate the performance of the plethora of diffusors on the market?

Jeff
Add me to the list of persons desiring diffusor evaluation!

And which kind is better for a small HT with 7 feet to 1st reflection points and 8 feet to rear wall?

Jacob

1D is recommended for scattering sound latterly (horizontally) and should be placed on the front wall and side walls in front of the listening seat to widen the apparent sound stage width. 2D should be placed on the rear parts of the side walls and rear wall to create a sense of listener envelopment.

Common 1D types include QRD and hemi-cylindrical (and others?) while 2D would include Skylines and derivations thereof

Kevin, if 1D should be placed in front of the listen e.g. the first reflection point, then why are we seeing an increase in the use of BAD style panels at first reflection points, they are 2D aren't they?

Also, why does Toole advocate absorbers on the front wall and not diffusion? or are you just saying that IF you/I determined we wanted diffusion at those points the ones you outline are the most appropriate?

also, why does toole advocate absorbers on the front wall and not diffusion?
sbir

Kevin, if 1D should be placed in front of the listen e.g. the first reflection point, then why are we seeing an increase in the use of BAD style panels at first reflection points, they are 2D aren't they?

Also, why does Toole advocate absorbers on the front wall and not diffusion? or are you just saying that IF you/I determined we wanted diffusion at those points the ones you outline are the most appropriate?



"why are we seeing an increase in the use of BAD style panels at first reflection points, they are 2D aren't they" I might imagine that any number of reasons could account for what you call the "increased use of BAD-style panels at 1st reflection points, including better/smarter RPG marketing, cost savings of combining diffusion & absorption within a single tool, combined diffusion/absorption functionality means less clutter of devices within a room and higher WAF, flavour of the month etc etc. ;) The RPG BAD panel and BAD ARC are 1-D devices that only scatter sound in one dimension based on the panel's flat or ARC's hemi-cylindrical shape.

Regarding your 2nd question: Toole does in fact recommend absorption in the centre of the front and rear walls to deal with the pressure maxima of the bass nodes similar to what Dennis called SBIR (adjacent boundry effect). His recommendation is within a HT environment, whereas my comment was within a stereo music listening environment - sorry, I likley forgot to mention that assumption up front. my bad. Yes you are correct that IF you wish to put diffusion on the front/side walls then the 1D types that diffuse laterally are the ones most often recommended so as to add spaciousness by widening the apparent source width, which is commohnly seen as a positive thing.

Hope this tid bit of education has helped.
Yes, it does. Thank you. I'll need to bookmark it and return later. Sitting in the parking lot outside the Starbucks in Dickson City isn't conducive to the focus necessary to properly digest all the meat there. :)

Add me to the list of persons desiring diffusor evaluation!

This video lets you hear a variety of diffusors and other surfaces, close-up as if you were in the same room:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

--Ethan

Thanks all Kevin and Dennis, thats clarrified that for me. Most useful. I was sure BAD's were 2D.....*slap self in head*

There in lies the problem when I want my room for both stereo and HT, well it may not be a problem, I guess we'll see how it goes and then make a judgement on completion :(

But treating the first side reflections with both a BAD and a QRD would be useful (seperately of course) and then I just see which one works better?

Have we reached agreement on what is classified as "absorptive"? i.e. fiberous v membrane? at the points where Toole states it should be (middle of front and rear walls)?

There are more than one variety of "BAD" type panels. Clearly there are the RPG BAD Panels. Kinetics has their own similar version and Quest Acoustical has a PerfSorb product, which frankly, I like a lot better than the other two.

This video lets you hear a variety of diffusors and other surfaces, close-up as if you were in the same room:

All About Diffusion (http://www.realtraps.com/video_diffusors.htm)

--Ethan
And they are helpful, Ethan. But it is like understanding spelling of a foreign language without comprehending the syntax. The video really doesn't aid in coming up with A Plan based on what someone hears and measures in their room.

It does show that that YOU understand the various treatments. ;)

Jeff

Jeff - armed with a little bit of knowledge you will be better apt to critique or evaluate the various types. Have you read Toole's latest book or this text book written by RPG's CEO and Prof Trevor Cox http://www.amazon.ca/Acoustic-Absorbers-Diffusers-Theory-Application/dp/0415471745/ref=sr_1_2?ie=UTF8&s=books&qid=1270254199&sr=1-2?

Firstly, where do you think you want to put diffusion as that'll dictate whether it should be 1D or 2D which will narrow your choices down . . . 1D is recommended for scattering sound latterly (horizontally) and should be placed on the front wall and side walls in front of the listening seat to widen the apparent sound stage width. 2D should be placed on the rear parts of the side walls and rear wall to create a sense of listener envelopment.

Common 1D types include QRD and hemi-cylindrical (and others?) while 2D would include Skylines and derivations thereof.

Secondly, you want the diffuser to work as broad range as possible so as not to act as a low pass filter and throw off your spectral balance that you paid dearly for in your selection of speakers ;) HF effectiveness for:
* Skylines is determined by the size of the block (not the depth) with small sizes allowing for higher freq diffusion effectiveness. I could only find 1.5" *1.5" blocks of wood for my Skyline which will work up to and likely beyond 4.5KHz which is higher than the highest note on a piano. Even George Massenberg's famous 'Studio C' uses 1"*1" sized blocks which will take it up to 6.75KHz or so . . .
* Hemi-cylindrical diffusers is a funtion of how hard the outer material is (so as not to absorb mid/high frequencies) and the angle of incidence; the max diffusion occurs head-on (meaning perpendicular) to the centre of the hemi.
* QRD is determined by the thickness of the wells with thinner being better.

The diffuser should work down to your room's transition (or Schroeder) frequency which is about 300Hz. LF effectiveness for:
* Skyline is determined by the max cell depth which should be a substantial % of the 300Hz freq wavelength. 50% would mean a depth of 22.6". Of course you could opt for 25% (11.3") or even 14% (6.5") but it would mean less and less effectiveness at 300Hz . . .
* Hemi-Cylindrical is determined by the length of the radius or strickly speaking the 'Sagita' which is that part of the radius that sticks out from the wall into the room when the hemi's arc is less than 180 degrees. The farther out into the room the radius extends the lower the depth it diffuses to. The same calculations would apply as above meaning a radius of 6.5" will only be about 14% of the 300Hz freq wavelength and be less effective than a 11.3" or 22.6" radius.
* QRD well depths determine the LF limits. I've only seen one manufacturer which makes a 15" well depth. Good on them!

Lastly, the diffusion and scattering coefficients are useful metrics for evaluation purposes except that they haven't been standardized nor widely accepted or mandated for inclusion as part of a company's stock marketing collateral for their respective diffusers lines . . .

Hope this tid bit of education has helped.
Thanks again, Kevin. I will check the linked book. I have read Toole's paper on reflections (I forget the title right now) and ... wow, are these guys ever "proud" of this book! I have Geddes's book sitting here to go through after I finish one from Tom Holman. Not sure I'll be dropping $150 on the one you linked though ...

I recently changed my front speaker locations to be very close to ear level and can reduce the left and right front absorbers from 48" x 48" to 24" x 48". Above that, on the now exposed carpeted wall above them, I'd like to add 1D diffusors. I do have 48" x 96" absorber on the front ceiling that could be trimmed down in size, too. And I have an absorber on the rear wall. I'd consider replacing that with some sort of diffusion, but the addition of that absorber made the largest improvement in the sound quality of my theater, so I have some anxiety about doing that.

I'll read your excellent Diffusors 101 post and decide on what I might want to try. I think it would be 1D everywhere but the ceiling.

Jeff

Not sure I'll be dropping $150 on the one you linked though ...
Jeff

It's more of a text book and not really a "guide" to anything. I have found some useful equations in it for other purposes in modelling, but you really start getting into the nitty gritty of things. Chris's (Audyssey) book is even worse. Those books are really geared for folks seeking a MS in Acoustical Engineering. If you love differential equations, those books are for you, but most things you need to know can be found in the Master Handbook of Acoustics and to some degree, Toole's book, but I found Toole's book to be more of a compilation of his work (almost autobiographical of a life's work) rather than a true "how to" book. If I were to point out a specific useful book to people, it would be the Master Handbook of Acoustics. Best wishes! :)

It's more of a text book and not really a "guide" to anything. I have found some useful equations in it for other purposes in modelling, but you really start getting into the nitty gritty of things. Chris's (Audyssey) book is even worse. Those books are really geared for folks seaking MS's in Acoustical Engineering. If you love differential equations, those books are for you, but most things you need to know can be found in the Master Handbook of Acoustics and to some degree, Toole's book, but I found Toole's book to be more of a compilation of his work (almost autobioraphical of a life's work) rather than a true "how to" book. If I were to point out a specific useful book to people, it would be the Master Handbook of Acoustics. Best wishes! :)
Differential equations are why I did not become an Electrical Engineer. :o

Thanks. I'll muddle through.

Jeff

I am a newbie here when it comes to acoustics and I have upgraded my speakers and now am interested in acoustical treatment...
We own a smaller house that I remodeled and plan on only staying a few more years but would like to get some suggestions/help on the room from hell we use for the HT....
There is alot of openings and windows and would like to get any helpful ideas on waht to do to get the most sound from the room.
I am enclosing a drawing of the room with the furniture and equipment...any and all recommendations are GREATLY appreciated!

Note: I have two subs and due to wife and room constraints the subs are both up front but I am planning on getting two more and putting them on the opposite rear wall corners as well.

wow what a thread fellas

would like to get any helpful ideas on waht to do to get the most sound from the room.

The basics are:

* Proper setup, including placing things symmetrically for good imaging.

* Bass traps to even out the low end, and remove boominess at some bass frequencies and nulls at others.

* Absorption at the side-wall and ceiling reflection points to improve clarity.

Much more here:

How to Setup a Room (http://www.realtraps.com/video_setup.htm)

--Ethan

Note: I have two subs and due to wife and room constraints the subs are both up front but I am planning on getting two more and putting them on the opposite rear wall corners as well.

Just to add to Ethan's wisdom, I'd try some different locations for those subs. The corners might not be the best place for them. Try positioning them using prime numbers...like 1/5th the width of the room and 1/7th the length. Just a thought. :)

Frank

Quick question regarding front wall treatments.

I use in-wall speakers for my fronts... should I still treat the front wall for absorbtion??
What should I be doing to avoid causing issues with the in-wall speakers (do I need to leave a certain amount of space around them with no treatments, etc...).

Also, I've read through the thread... but there is just a ton of information. I know diffusers are preferred on the rear wall. But, can I use the same acoustic treatment panels I apply in the front; to the back if I cannot do actual diffusers at this time? Or would I be better off using a rockwool type material for the front/side walls and a batting type material for the rear walls?

Ok, one last question for now. I know it's not recommended to treat the ceiling, but for aesthetics I need to do something. One reason is I get a good amount of light reflected onto the ceiling when I use the projector and I would like to eliminate this. Is there a material I can buy for the ceiling to wrap with the same fabric as the rest of my panels that will not cause any issues?

I know these are newbie questions, but that's exactly what I am with regard to acoustic treatments.

Thanks in advance for any assistance!

EDIT: This room is purely for home theater, no 2 channel audio going on.

This is a great thread with lots of information!

I understand that the first priority should be to treat the corners with bass traps. However, that doesn't seem to apply when the room is not symmetric, which is my case.

This is the listening area (length: 19ft, width: 12ft, height: 8ft), which has a large opening on the left side. On the right side, there is a window up front and a sliding glass door on the back.

http://i590.photobucket.com/albums/ss347/lromand/Family%20Room/IMG_7885.jpg

Here’s a view of the left-side opening:

http://i590.photobucket.com/albums/ss347/lromand/Family%20Room/IMG_7898.jpg

My budget is somewhere between $300 and $600 and aesthetics are important.

I’m thinking the best option is 4”-deep decorative panels in the front wall behind the speakers. Does that sound like a good plan? What would you guys do?

The basics are:

* Proper setup, including placing things symmetrically for good imaging.

* Bass traps to even out the low end, and remove boominess at some bass frequencies and nulls at others.

* Absorption at the side-wall and ceiling reflection points to improve clarity.

Much more here:

How to Setup a Room (http://www.realtraps.com/video_setup.htm)

--Ethan

I am stuck with where I can put my subs due to wife and room constraints...
I have been looking into bass traps and am planning on picking some out as well as something as a reflection absorption but I do have problems with room opening and placement of those!
I have already contacted Real Traps...are you psychic?

Just to add to Ethan's wisdom, I'd try some different locations for those subs. The corners might not be the best place for them. Try positioning them using prime numbers...like 1/5th the width of the room and 1/7th the length. Just a thought. :)

Frank

I have my subs 8 1/4" from each side wall and 6" from the front walls (rear of sub)...I am limited since I have a room opening near the left sub...and due to room constraints and wife, corners are the only place until we move, to put them!

What would you guys do?
I would take some scans of the room response to see where best to put that budget, and consider a DIY approach as opposed to buying commercial ones, to help stretch that budget.

If this helps...here is what I am working with (and stuck with...) I did notice this thread in Home Theater Shack and would like to build these bass traps but due to the window being so close to the front speakers/sub, I would either have to do something narrower or treat with additional wall treatments...from the pics does anyone have suggestions...on the room and what I could do...until we move in a couple years!

If this helps...here is what I am working with (and stuck with...) I did notice this thread in Home Theater Shack and would like to biuld these bass traps but due to the window being so close to the front speakers/sub, I would either have to do something narrower or treat with additional wall treatments...from the pics does anyone have suggestions...on the room and what I could do...until we move in a couple years!

Is there an attic or another room above the ceiling?
If its an attic look into Infinite baffle subwoofer. For more information on IB subs go to http://ibsubwoofers.proboards.com/index.cgi?board=general.

Is there an attic or another room above the ceiling?
If its an attic look into Infinite baffle subwoofer. For more information on IB subs go to http://ibsubwoofers.proboards.com/index.cgi?board=general.

No, there was attic directly above but I had put in a room/dormer up there.
However, all the walls and ceilings are insulated..used R13 in walls and R30 in ceiling joists. Under the house is a skirted crawl space...no basement or anything!

I already own subs....

I apologize for bumping my own post, but I'm really looking to get the ball rolling on my treatments. The part I'm most concerned with is how to treat the front wall since I use in wall speakers. But, any help with anything would be extremely appreciated.

Thanks!

Quick question regarding front wall treatments.

I use in-wall speakers for my fronts... should I still treat the front wall for absorbtion??
What should I be doing to avoid causing issues with the in-wall speakers (do I need to leave a certain amount of space around them with no treatments, etc...).

Also, I've read through the thread... but there is just a ton of information. I know diffusers are preferred on the rear wall. But, can I use the same acoustic treatment panels I apply in the front; to the back if I cannot do actual diffusers at this time? Or would I be better off using a rockwool type material for the front/side walls and a batting type material for the rear walls?

Ok, one last question for now. I know it's not recommended to treat the ceiling, but for aesthetics I need to do something. One reason is I get a good amount of light reflected onto the ceiling when I use the projector and I would like to eliminate this. Is there a material I can buy for the ceiling to wrap with the same fabric as the rest of my panels that will not cause any issues?

I know these are newbie questions, but that's exactly what I am with regard to acoustic treatments.

Thanks in advance for any assistance!

EDIT: This room is purely for home theater, no 2 channel audio going on.

I use in-wall speakers for my fronts... should I still treat the front wall for absorbtion?

Probably not. Even with normal speakers, the front wall is not usually the most important place to worry about:

Front Wall Absorption (http://www.realtraps.com/art_front-wall.htm)

What should I be doing to avoid causing issues with the in-wall speakers (do I need to leave a certain amount of space around them with no treatments, etc...).

The basics of acoustic treatment are bass traps in corners plus absorbers at the side-wall and ceiling reflection points. So again, absorbers on the front wall are not usually needed.

Also, I've read through the thread... but there is just a ton of information.

Not only too much info, but conflicting and often wrong info. :eek:

I know diffusers are preferred on the rear wall. But, can I use the same acoustic treatment panels I apply in the front; to the back if I cannot do actual diffusers at this time?

Yes, absorption works well on the rear wall.

I know it's not recommended to treat the ceiling, but for aesthetics I need to do something.

Actually, the ceiling reflection points are very important to treat! More here that may help:

How to set up a room (http://www.realtraps.com/art_room-setup.htm)
Early Reflections (http://www.realtraps.com/rfz.htm)

I know these are newbie questions, but that's exactly what I am with regard to acoustic treatments.

Tons more info here:

Acoustics FAQ (http://www.ethanwiner.com/acoustics.html)
RealTraps Articles (http://www.realtraps.com/articles.htm)
RealTraps Videos (http://www.realtraps.com/videos.htm)

--Ethan

If this helps...here is what I am working with (and stuck with...) I did notice this thread in Home Theater Shack and would like to build these bass traps but due to the window being so close to the front speakers/sub, I would either have to do something narrower or treat with additional wall treatments...from the pics does anyone have suggestions...on the room and what I could do...until we move in a couple years!

Stu, you might want to try something like this (http://www.gikacoustics.com/gik_artpanel.html). It's easier to make them fit into a room like yours aesthetically speaking.

Frank

Probably not. Even with normal speakers, the front wall is not usually the most important place to worry about:

Not only too much info, but conflicting and often wrong info. :eek:


--Ethan

Thanks a bunch, this will be a huge help!

And yes, one of the issues I've run in to while going through this thread is a TON of conflicting information. It's hard to decide what really makes sense and what doesn't. I'll check out all of the links.

But, I do have one more quick question regarding the front walls. I do want to get some sort of fabric up there so it will tie in with the rest. Since I do not want absorption, could I just use a thin foam batting covered in fabric... or could that be detrimental to my sound?

Thanks again!

could I just use a thin foam batting covered in fabric... or could that be detrimental to my sound?

You could just glue the fabric directly to the sheet rock. Nothing else is needed. I'd avoid thin batting because that will absorb very high frequencies possibly skewing the balance in the room. The best type of absorption is broadband, working over as wide a range of frequencies as possible.

--Ethan

Hi Guys,

Sorry in advance for the large post. I finally got to spend some time futzing with REW.

Room - 26 x 16 x 8.
Gear Onkyo 805
Klipsch Icons
Klipsch Sub 10
Emotiva Side and Rear Surrounds.

Room has it's own sets of challenges. Mostly asymetry of the front wall between the Left and Right front stage. There is also pergo at the main stage. Carpeting covers the back half of the room and listening position. GIK 242 Panels along left and right side walls at reflection areas.

Let me know how these initial graphs look to you guys and if it looks remotely accurate or if I'm missing something completely. The stuff at 80hz is bothering me a bit. Look at that big azz null. Couple people have mentioned potential phasing issues. I just did the default sweep with all speakers connected. Sub turned on.

I need some fellow super geeks to tell me how to interpret this stuff better than I can.

First one is with no smoothing turned on

http://chriskir.smugmug.com/Other/Home-Theater/4-10-2010mainspeakersweep/834043243_B8NsE-O.jpg

Second with smoothing
http://chriskir.smugmug.com/Other/Home-Theater/mainspeakersweep4-11-2010/834058248_vmW4S-O.jpg

A waterfall I generated.
http://chriskir.smugmug.com/Other/Home-Theater/waterfallcorrected-4-11-2010/834058242_obRrY-O.jpg

Update

Green Graph shows what happens when sub is turned OFF!

http://chriskir.smugmug.com/Other/Home-Theater/greenlinesubturnedoff/834387026_vnyTq-O.jpg

To determine if that is a modal null, move the microphone at least 3 feet in a diagonal direction and measure again. If you have your cross over set to 80 hz, that could be because your sub is 180 degrees out of phase from your mains at 80 Hz.

Are you not using a crossover to direct all low frequencies to your sub? If so, this is just asking for phase interaction problems. There are solutions, but they can be quite tricky.

hi everyone, i am looking for some bass traps and absorbers to help treat my movie room. i've looked at sites lite realtraps, gik, etc. though they have great stuff, i just simply can't afford them.

can you point me to some diy alternatives that can be done cheaply? thanks!

hi everyone, i am looking for some bass traps and absorbers to help treat my movie room. i've looked at sites lite realtraps, gik, etc. though they have great stuff, i just simply can't afford them.

can you point me to some diy alternatives that can be done cheaply? thanks!
Try here (http://forum.studiotips.com/viewforum.php?f=8&sid=8b25b1940334ae6735555c7b8dc9e8b7). Linked in my sig is the process I went through to add treatments ...

Jeff

thanks pepar.

the bass trap diy instruction is awesome.

question, is owens 703 still the preferred material for diy bass trap? is this something i can easily obtain at a local lowes or home depot? if there are better materials, please do tell. thanks!

thanks pepar.

the bass trap diy instruction is awesome.

question, is owens 703 still the preferred material for diy bass trap? is this something i can easily obtain at a local lowes or home depot? if there are better materials, please do tell. thanks!
Seven-O-three or something like it (http://www.bobgolds.com/AbsorptionCoefficients.htm). I think it's a safe bet that home improvement stores do NOT have these materials. The pink-n-fluffy stuff is not the same. These acoustical treatment materials come from the "HVAC world" and to buy them - DIY ;) - you need to get them from an HVAC insulation distributor such as this one (http://www.spi-co.com/directory.html).

Jeff

Pepar-

I commented on that link in another thread but maybe this is a better place for it.

I assumed that the OC703 and JM814 were superior to the Linacoustic RC since they are twice as dense (3 pcf vs 1.5 pcf). That's not the case though according to the data from your link. I added the Knauf (http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_insulation_board.aspx) numbers in the table below directly from their website.

No OC locally, but I was able to find the Knauf sheets locally for $68 for 20 sheets of 1" or 10 sheets of 2". Is this price reasonable?

Also, given the data below, wouldn't linacoustic be the product of choice since it shows as being equivelent in performance and I'm guessing a roll of linacoustic is a lot easier to work with than the OC703?

Product thickness density 125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
OC 703, plain 1" (25mm) 3pcf (48kg/m3) 0.11 0.28 0.68 0.9 0.93 0.96 0.7
JM Linacoustic RC 1" (25mm) 0.08 0.31 0.64 0.84 0.97 1.03 0.7
JM 814 1" (25mm) 3pcf (48kg/m3) 0.06 0.29 0.75 0.99 1.04 1.02 0.75
Knauf Insulation board 1" (25mm) 3pcf (48kg/m3) 0.08 0.23 0.62 0.88 0.96 0.99 0.65

Pepar-

I commented on that link in another thread but maybe this is a better place for it.

I assumed that the OC703 and JM814 were superior to the Linacoustic RC since they are twice as dense (3 pcf vs 1.5 pcf). That's not the case though according to the data from your link. I added the Knauf (http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_insulation_board.aspx) numbers in the table below directly from their website.

No OC locally, but I was able to find the Knauf sheets locally for $68 for 20 sheets of 1" or 10 sheets of 2". Is this price reasonable?
FWIW, about two years ago I paid $125 for a bundle of 2" 703 consisting of twelve sheets x 24" x 48". I'm pretty sure that the 3pcf stuff is what is recommended by the experts.

Jeff

Pepar-

I commented on that link in another thread but maybe this is a better place for it.

I assumed that the OC703 and JM814 were superior to the Linacoustic RC since they are twice as dense (3 pcf vs 1.5 pcf). That's not the case though according to the data from your link. I added the Knauf (http://www.knaufusa.com/products/building_insulation/commercial_building_insulation/knauf_insulation_board.aspx) numbers in the table below directly from their website.

No OC locally, but I was able to find the Knauf sheets locally for $68 for 20 sheets of 1" or 10 sheets of 2". Is this price reasonable?

Also, given the data below, wouldn't linacoustic be the product of choice since it shows as being equivelent in performance and I'm guessing a roll of linacoustic is a lot easier to work with than the OC703?
Where I use the J-M Linacoustic product, I think installation was more easily accomplished with it than 703.

Jeff

Where I use the J-M Linacoustic product, I think installation was more easily accomplished with it than 703.

Jeff

Did you fasten it in any fashion or just use spray adhesive. Am I interpreting the numbers correctly in that the Linacoustic is equivalent in performance to the rigid insulation boards?

Did you fasten it in any fashion or just use spray adhesive. Am I interpreting the numbers correctly in that the Linacoustic is equivalent in performance to the rigid insulation boards?
I used drywall screws. :) It's behind a false wall and it is the 2" Linacoustic.

Rigid insulation board? Which product it that on the charts?

Rigid insulation board? Which product it that on the charts?

I was referring to OC703, JM814, or the Knauf equivalent. (all the other guys on my chart besides the Linacoustic)

I was referring to OC703, JM814, or the Knauf equivalent. (all the other guys on my chart besides the Linacoustic)
It is a wee bit more absorbent at 125Hz, but neither are very effective in that area making bass traps a necessity anyway. I think the 250Hz number is more important and that is where the 703 is about 33% more absorbent. And the 703 is 14% more absorptive at 500Hz. My room, anyway, needed 200Hz to 500Hz absorption and my guess is that so do a lot of others.

http://www.peparsplace.com/storage/703_RC_comparison.JPG

Should the ceiling and/or floor behind the screen wall be treated as well?

Should the ceiling and/or floor behind the screen wall be treated as well?
My main concern when treating behind my false wall was comb-filtering. That is said to be less of an issue with the woven screen I have now over the micro-perforated one I had previously, but the front wall is also a first reflection point and I would have treated there anyway.

Sorry for the blather; I covered the ceiling but not the floor ... one of the two parallel surfaces. I am not an acoustician, though, so that is only my opinion.

Jeff

this is sad. can't get OC 703 anywhere locally. home depot requires a 60/80 piece minimum for special orders.

none of the OC distributors in my areas carry the 700 series. they too would have to special order. this stinks.

my only option is online order for 2-3x the price. ahhh....

btw, i assume that you can use OC 703 for both bass trap (corncers) as well as absorbers (sidewalls/ceilings)?

this is sad. can't get OC 703 anywhere locally. home depot requires a 60/80 piece minimum for special orders.

none of the OC distributors in my areas carry the 700 series. they too would have to special order. this stinks.

my only option is online order for 2-3x the price. ahhh....

btw, i assume that you can use OC 703 for both bass trap (corncers) as well as absorbers (sidewalls/ceilings)?
Shipping charges will kill you, too, by ordering online. Where are you located?

06110

LOL. This is a ripoff.

One of my local distributors quoted me $258+tax for a bundle (12 pieces) of 2x24x48 OC 703.

this is sad. can't get OC 703 anywhere locally. home depot requires a 60/80 piece minimum for special orders.

none of the OC distributors in my areas carry the 700 series. they too would have to special order. this stinks.

my only option is online order for 2-3x the price. ahhh....

btw, i assume that you can use OC 703 for both bass trap (corncers) as well as absorbers (sidewalls/ceilings)?

Yeah... I've been trying to find a source on and off for years. I'm in 95472.

06110
Closest in CT is Stratford. http://www.spi-co.com/directory.html

One in Chester, NY, too.

Call and get a quote.

Yeah... I've been trying to find a source on and off for years. I'm in 95472.
Benecia, CA down around the bay.

http://www.spi-co.com/directory.html

Benecia, CA down around the bay.

http://www.spi-co.com/directory.html

Totally cool! Thanks so much. I can drive my truck there and pick up a bunch. :D:D

Closest in CT is Stratford. http://www.spi-co.com/directory.html

One in Chester, NY, too.

Call and get a quote.

thanks pepar. man that is going to be one long drive.

btw, i want the "PLAIN" type right?

they also have the ASJ (white) and FKS (silver). not sure what the differences are.

EDIT: i called and was quoted $54 for 6 piece (woot). the other two types were $80/85.

btw, i want the "PLAIN" type right?

they also have the ASJ (white) and FKS (silver). not sure what the differences are.

EDIT: i called and was quoted $54 for 6 piece (woot). the other two types were $80/85.

Yes, get the plain. ASJ and FRK are different kinds of facings. The plain is unfaced.

FWIW, about two years ago I paid $125 for a bundle of 2" 703 consisting of twelve sheets x 24" x 48". I'm pretty sure that the 3pcf stuff is what is recommended by the experts.

Jeff

I just bought mine from the exact same place as Pepar and was charged $168.92 for 2 bundles of 2" 703, After reading this I'm getting worried that I ordered the right stuff! It should be in this week, but with surgery in the morning I doubt I'll pick it up till next week.

thanks pepar. man that is going to be one long drive.
C'mon, man. CT is just not that big. :rolleyes: ;) :)

I just bought mine from the exact same place as Pepar and was charged $168.92 for 2 bundles of 2" 703, After reading this I'm getting worried that I ordered the right stuff! It should be in this week, but with surgery in the morning I doubt I'll pick it up till next week.
Yes, I should reiterate that my purchase was at the beginning of '08. Today, $168 seems like a good deal. Two fifty-eight, not so much. :)

btw, i want the "PLAIN" type right?

they also have the ASJ (white) and FKS (silver). not sure what the differences are.

EDIT: i called and was quoted $54 for 6 piece (woot). the other two types were $80/85.
Killer price if that's 2" x 24" x 48" for unfaced.

Jeff

C'mon, man. CT is just not that big. :rolleyes: ;) :)

you have no idea. we're only allowed to drive 55mph. ;)

Killer price if that's 2" x 24" x 48" for unfaced.

Jeff

yes, that's a bundle of 6 pc 2" x 24" x 48" plain.
unfortunately, it's currently out of stock. they need to put in an order.

yes, that's a bundle of 6 pc 2" x 24" x 48" plain.
unfortunately, it's currently out of stock. they need to put in an order.
Hmmm, I wonder how much they charge WHEN THEY HAVE SOME? :)

I just bought mine from the exact same place as Pepar and was charged $168.92 for 2 bundles of 2" 703, After reading this I'm getting worried that I ordered the right stuff! It should be in this week, but with surgery in the morning I doubt I'll pick it up till next week.

That's not too bad...that works out to about $85 for 12 boards of 2" 703. It's more than Pepar paid a few years ago, but it's still a pretty great price.

Frank

Hmmm, I wonder how much they charge WHEN THEY HAVE SOME? :)

lol. you could be surprised.

i just called back to place an order and the guy said their other branch has some in stock. he's going to get them transfer some over.

the new price? $71 for 96 sf of OC 703 2" x 24" x 48" (or 12 pieces).

i plan on having my brother pick them up on Fri so we'll see.

lol. you could be surprised.

i just called back to place an order and the guy said their other branch has some in stock. he's going to get them transfer some over.

the new price? $71 for 96 sf of OC 703 2" x 24" x 48" (or 12 pieces).

i plan on having my brother pick them up on Fri so we'll see.
Be aware that 24" x 24" x 48" is TWO FEET x TWO FEET x FOUR FEET! :) Up close and personal, it is HUGE. I can tell you that it was real struggle to get two of them into an SUV.

C'mon, man. CT is just not that big. :rolleyes: ;) :)

you have no idea. we're only allowed to drive 55mph. ;)Yeah. I tend to drive a little faster and I run out of state every Sunday night!

Yeah. I tend to drive a little faster and I run out of state every Sunday night!
Are they chasing you?

Yeah. I tend to drive a little faster and I run out of state every Sunday night!

Are they chasing you?I didn't say that I get run out of state but, rather, at cruising speed, I am very quickly at the border and into NY. ;)

I didn't say that I get run out of state but, rather, at cruising speed, I am very quickly at the border and into NY. ;)
Oh, Kal, I would have thought that they were chasing you to get you back. ;)

Oh, Kal, I would have thought that they were chasing you to get you back. ;)They're chasing me all right. After decades of getting away (with it), I got speeding tix in CT and NY in recent months. It is hard to slow down.

They're chasing me all right. After decades of getting away (with it), I got speeding tix in CT and NY in recent months. It is hard to slow down.

What do you drive? I feel like me BMW 335xi has a bullseye on it. Even with my V1.

What do you drive? I feel like me BMW 335xi has a bullseye on it. Even with my V1.Nothing notable. MB C320 Station Wagon(!)

What do you drive? I feel like me BMW 335xi has a bullseye on it. Even with my V1.

Try an M5. The cop who pulled me over knew a lot about it. He was a car nut. Part of my protestation was "but it won't even DO 65 in 2nd." He said, "Yeah it will" and smiled like he knew I was trying to put one over on him.

BTW, I was in a 50mph zone.

Try an M5. The cop who pulled me over knew a lot about it. He was a car nut. Part of my protestation was "but it won't even DO 65 in 2nd." He said, "Yeah it will" and smiled like he knew I was trying to put one over on him.

BTW, I was in a 50mph zone.My best experience was a while back when a cop stopped me as I was leaving the Cross County Expwy. He cited me for speeding and changing lanes without signaling. I immediately responded by challenging the latter as I am an assiduous signaler and never fail at that. In a surprise, he immediately backed off and reduced the whole ticket failure to signal which is a misdemeanor and not reported to the insurance company. Cheap, too.

What do you drive? I feel like me BMW 335xi has a bullseye on it. Even with my V1.
Electronic countermeasures (http://www.laserveil.com/).

They're chasing me all right. After decades of getting away (with it), I got speeding tix in CT and NY in recent months. It is hard to slow down.

They've really gotten bad in recent months, haven't they?
That's why I love the get-out-of-jail-free card my nephew the State Trooper gave me...

Dang I love that kid!

what is everyone using as fabric for the panel? i've been hearing a bit about the JoAnn's grill cloth?

do you have the exact product number for this? i went to JoAnn, asked an old lady there about it but she looked like she had no idea what i was talking about.

what is everyone using as fabric for the panel? i've been hearing a bit about the JoAnn's grill cloth?

do you have the exact product number for this? i went to JoAnn, asked an old lady there about it but she looked like she had no idea what i was talking about.

It's a little on the pricey side, but Guilford of Maine FR701 material is very popular.

thanks, that is indeed pricey.

i have a 50% off coupon from JoAnn and was hoping to pick up some of this 'grill cloth'

thanks, that is indeed pricey.

i have a 50% off coupon from JoAnn and was hoping to pick up some of this 'grill cloth'

I mean, just about anything that's breathable will work. I'm not sure Joann's would sell something quite as specific as grill cloth. I've never seen in there...I could be wrong of course.

Frank

I mean, just about anything that's breathable will work. I'm not sure Joann's would sell something quite as specific as grill cloth. I've never seen in there...I could be wrong of course.

Frank
Yeah, make sure to get the right thing. Half off something that doesn't work is no bargain!

Jeff

Guys,

Treating the screen wall with GIK 242s behind the L and R tower speakers.

Towers = 41"
Panels = 49"

Is there a general rule of thumb of the fraction of speaker height for my specific placement? What do you reccomend? 1/3 above?

Having the top of the panel flush with the top of the screen would be nice, but not required.

Also - What tips and tricks have people used for their ceiling mounted panels?

Hey all,

I need some help in the treatment of sound for my entertainment room. I have attached the layout of the room. Cant do much with windows, glass door which leads to the balcony and the in-wall fitted cupboard. But I can cover the windows and the glass door with thick curtains. The floor will be carpeted wall-to-wall. The only other option as I see fit are to mount two sound deadning panels at the back and right wall from the seating position. Where I live, sound proofing is a mute concept and therefore most of the pro material is unavailable. I'll need some basic solutions to put the wall mounts in place.

I was thinking of using 1 inch thick, 3 x 2 ft plywood panels with normal 1 - 1.5 inch thick foam glued to it. To round it off, thin piece of decorative cloth covering the foam nailed/stapled at the back of plywood.

I need ideas on the size of the plywood (or whether plywood is a good option or is there another surface I can use?) and type of foam to glue to the plywood.

I will also use two down facing lights above each panel to make it look attractive.

Looking forward to ideas.

Zeeshan

173123

Count me among the confused as well.
I based my plan (not done yet) on the first 150 pages as well, when concensus seemed to be something like:
- 1st reflection treatment with absorbtion (1" OC703) from floor and up to 4' - from screen and two thirds back into room.
- 2" OC703 on whole front wall behind false screen wall
- Bass traps in corners - as many corners as possible.
- As this is an attic room, I have sloping ceiling, starting from 5½' up the side walls. Therefore, I will treat the sloping ceiling as well with 2" OC703 in 3.5" deep frames, each panel measuring 40" x 6" on the inside. They will be mounted as vertical strips, with 8" of air between each panel. The will give 1st reflection absorption and crude difussion.
- I also consider 2-3 QRD Diffusor (from Real Traps) for the center back wall - with 6" absorption (OC703) as fallback - the QRDs are expensive...

The whole discussion about using a mirror etc to find first reflections seems to me to be for HT with two seats or something like that - for a dedicated HT room with multiple seats and two rows or more, the first reflection points are going to be all over the place. :eek:
I have two rows of four seats, second row on a riser.
1st reflections from the three identical front speakers pretty much include most of the sidewall as described above in plan... ;)

Now, my room is small - 13.4' x 20' x 8'. It's my understanding (based on this thread, Real Traps and GIK homepages etc) that diffusion works best in larger rooms (or rather, when the listener is far away from the diffusor).

When [many people - edit] now mention diffusion for 1st reflection points, instead of absorption - does that go for a small room like mine as well? :confused:

And what kind of diffusion products for this specific task? :confused:

Cheers from Denmark, :)
Jacob


Add me to the list of persons desiring diffusor evaluation!

And which kind is better for a small HT with 7 feet to 1st reflection points and 8 feet to rear wall?

Jacob

Would any one care to sum it up ? :D

My room is similar to yours (17'x12.5'x7.5' -- nice of you to translate into feet rather than use metrics...) but even a little smaller.

I have two rows of seats: one couch for each. The second row couch is on a riser.

Using the mirror method I was able to cover the side wall first reflection points for all three front speakers for almost all sitting positions with just two 2'x'4 panels on each of the side walls.

That, plus bass trapping in every corner and under the screen (ie, where the screen wall meets the floor), please two more panels on the back wall, and heavy carpet on the floor, have really made things solid and clear. Yet most of the wall space is still uncovered.

thanks for sharing your experiences! :)

Jacob b

I have a question for the experts regarding the "double bass array", discussed here:

http://www.avsforum.com/avs-vb/showthread.php?t=837744

Does it cancel room modes from all 3 directions (front/back wall, side/side wall, and floor/ceiling), or just the front/back modes? I know the description says that it works on all modes, but I'd appreciate a bit more explanation.

Thanks,
John

All modes. By having subwoofer arrays in both front and back, you create waves which travel only from front to back, essentially eliminating widthwise and heightwise modes. If you look up the "image source method" for modeling acoustic shoeboxes, you'll see that the speakers are reflected in side walls, ceiling, and floor. This makes, with proper subwoofer placement, perfect symmetry for not exciting these modes.

So all that's left are the lengthwise modes. That's where the DBA really does its magic. Any wave that hits the back wall gets automatically "sucked up" by the rear subwoofers, eliminating all reflection. This obviously requires careful level adjustment. But it works!

- Terry

Guys,

Treating the screen wall with GIK 242s behind the L and R tower speakers.

Towers = 41"
Panels = 49"

Is there a general rule of thumb of the fraction of speaker height for my specific placement? What do you reccomend? 1/3 above?

Having the top of the panel flush with the top of the screen would be nice, but not required.

Also - What tips and tricks have people used for their ceiling mounted panels?

1/3 above works great.

For ceiling hanging, I like to use #8 sheet rock anchors and #8 hooks, then use zip ties to secure the panel to the hooks.

Frank

I'm in the process of finishing up my basement theater; completed the fabric install over the weekend. I have been using an acoustic plan that Brian Pape put together for me with the standard 2" treatement (Linacoustic) covering the front wall, 1" treatment from floor to ceiling on the side walls about four feet back from the front for first reflections, and then 5' high the rest of the way to the back wall. The back wall is covered with 2" of OC 703 for bass absorbtion, and then a foil scrim over that to reflect the highs and mids. I also have two floor to ceiling bass traps in the front corners made up of 2' square pieces of 5" thick cotton.

I haven't had much time to actually sit and listen to things during construction, although I did some two channel listening when I first finished up the acoustic treatments and was pretty impressed with how things sounded, especially the "soundstage." Vocals were dead center and clear. However, last night I "listened" to some of the Eagles "Hell Freezes Over" concert DVD in multi-channel DTS (I don't have the projector hung yet so I just listened), and I have to say I was somewhat disappointed. The center channel material, mainly vocals, seemed almost muted. As I was contemplating this while sitting in a chair, I put my hands behind my head and noticed it sounded a bit clearer. I then "cupped" my hands behind my ears, and the sound seemed much more dynamic. Long story to my question, but is my room too dead, or is there something else that's going on? One concern is that the ceiling is only 7' as this is a basement build in an older home. Could that be contributing to it?

After all of this work I'm really hoping I haven't screwed things up.:confused: I also realize that the "HFO" DVD is not exactly audiophile quality.

Brian was one of the experts I consulted (and bought from) when putting together my room, and his advise was very helpful.

I'll let others weigh in on whether you have perhaps too much thin treatment, and not enough thick (broadband) treatment, but I assume Brian received detailed measurements of your room, including furniture and speaker layout, and made the recommendations based on those details.

The real way to tell if the room is too dead is to measure it. There are some tools discussed in this and other threads, some of which require your laptop, a mic + preamp + some free software. Other options probably exist if, for example, you have an iPhone and want to buy an app for that.

That said, while I don't know the DVD you are speaking about, one thing about a good room is that you will readily hear imperfections in recordings now. I know that poor ADR in movies and TV shows is now glaringly apparent in my room.... whereas before it was masked by the poor room.

All modes. By having subwoofer arrays in both front and back, you create waves which travel only from front to back, essentially eliminating widthwise and heightwise modes. If you look up the "image source method" for modeling acoustic shoeboxes, you'll see that the speakers are reflected in side walls, ceiling, and floor. This makes, with proper subwoofer placement, perfect symmetry for not exciting these modes.

So all that's left are the lengthwise modes. That's where the DBA really does its magic. Any wave that hits the back wall gets automatically "sucked up" by the rear subwoofers, eliminating all reflection. This obviously requires careful level adjustment. But it works!

- Terry

Thanks, Terry. I'm in the process of building one of these things, with 4 15" drivers on the front and back walls, respectively. Further, these drivers will be mated to ported, closet sized enclosures, about 140 cubic feet per wall. Each box of 4 drivers will be tuned to around 14hz, using the "large and low tuned" guidlines (LLT) found at hometheatershack.com.

I also saw that you ran a simulation on a double bass array a few years ago and concluded that it wasn't a "magic bullet", but was pretty good.

http://www.avsforum.com/avs-vb/showthread.php?t=942585

In this simulation, did you run the exact same output signal through both the front and back walls (with delay and 180 degrees of phase shift), or did you go further and adjust the rear wall signal to compensate for losses from simulated room objects/people?

Thanks,
John

All modes. By having subwoofer arrays in both front and back, you create waves which travel only from front to back, essentially eliminating widthwise and heightwise modes. If you look up the "image source method" for modeling acoustic shoeboxes, you'll see that the speakers are reflected in side walls, ceiling, and floor. This makes, with proper subwoofer placement, perfect symmetry for not exciting these modes.

So all that's left are the lengthwise modes. That's where the DBA really does its magic. Any wave that hits the back wall gets automatically "sucked up" by the rear subwoofers, eliminating all reflection. This obviously requires careful level adjustment. But it works!
Terry, does your answer apply to any front/back sub setup or just the one with subs in the wall, aka DBA?

Brian was one of the experts I consulted (and bought from) when putting together my room, and his advise was very helpful.

Yes, Brian's been great, and I haven't bounced (no pun intended :)) this phenomena off of him at this point. I'm also not completed with the room as there is no carpet in there yet, nor furniture. I'm hoping that it will all come together when that happens.

With acoustics design, in a conventional room, there is no need to "hope". You can come up with a very solid plan with very predictable results. I would definitely share your impressions with him.

The center channel material, mainly vocals, seemed almost muted. As I was contemplating this while sitting in a chair, I put my hands behind my head and noticed it sounded a bit clearer. I then "cupped" my hands behind my ears, and the sound seemed much more dynamic.

Are you able to easily remove some of your treatments? You might try removing the panels for the first reflections. Toole presents very good evidence in his book Sound Reproduction (http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?ie=UTF8&s=books&qid=1271825591&sr=1-1) for not treating first reflections as it adds to the spaciousness and speech intelligibility. I know when I added treatments for the first reflections I immediately got the "muted" impression that you got. I removed those treatments as I didn't like it and then read Toole's book which sealed it for me. He also states that if you do want to treat the first reflections to use at least 4" absorption or you'll throw off the spectral balance.

Are you able to easily remove some of your treatments? You might try removing the panels for the first reflections. Toole presents very good evidence in his book Sound Reproduction (http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_1?ie=UTF8&s=books&qid=1271825591&sr=1-1) for not treating first reflections as it adds to the spaciousness and speech intelligibility. I know when I added treatments for the first reflections I immediately got the "muted" impression that you got. I removed those treatments as I didn't like it and then read Toole's book which sealed it for me. He also states that if you do want to treat the first reflections to use at least 4" absorption or you'll throw off the spectral balance.

There are many products currently on the market that address this issue, and it isn't quite as black and white as broadband absorption or bare wall. You may also want to consider using a Perfsorber or Binary Amplitude Diffsorber. These products preserve much of the higher frequency energy but also treat for frequencies that cause smearing due to path differences. The timing difference is a main source of reduced speech intelligibilty. Toole is correct in the fact that absorbing the higher frequencies is less desirable, but using some type of diffusion/absorber combination is preferable IMHO. Best wishes! :)

There are many products currently on the market that address this issue, and it isn't quite as black and white as broadband absorption or bare wall. You may also want to consider using a Perfsorber or Binary Amplitude Diffsorber. These products preserve much of the higher frequency energy but also treat for frequencies that cause smearing due to path differences. The timing difference is a main source of reduced speech intelligibilty.

Toole actually devotes an entire chapter in his book to countering this very argument.

Toole is correct in the fact that absorbing the higher frequencies is less desirable, but using some type of diffusion/absorber combination is preferable IMHO. Best wishes! :)

You'll have to forgive me if I give much more weight to the opinion of the guy who presents mountains of evidence and studies (many his own) in a 500+ page book versus a guy on an internet forum. :)

I just finished stapling all of the fabric on over the treatments so removing anything would be a real cramp, and a bit premature.

I think that I've got to do some more serious listening with a variety of recordings to get a better idea; like I said, 2-chanel sounds pretty good. And I've got to talk to Bryan as well. He based the design on some very specific room measurements I gave to him when I started. I could always experiment with placing some hard surface material against the walls (plywood, or something) to see what difference it might make. I was just curious as to the phenomena of things sounding better with my hands cupped behind my ears, and what that might indicate as far as room acoustics go.

I guess I could always figure out some kind of headband to wear that would push my ears forward :-).

Good idea.

Here's a couple of more thoughts:

1. About Toole: There are dozens of pages of experts in various topics here on AVS talking about the particularities of the Toole results, including important clarifications from his co-researchers. Luckily, you can try it both ways and see what works for you. There is no single correct answer. Your results on the face of it contradict Toole -- since you like the two channel sound with the side treatments -- and fall in line with how much music and film soundtracks are mastered.

2. Related to #1 perhaps, in terms of trying things out: You may be used to hearing music reproduced in sub-optimal ways (it was true of me) so give any change a few weeks of listening before making a decision. And in the end, trust your ears.

I posted this on a separate thread and am hoping someone can help. I would really like the best treatment for controlling bass. Right now (totally un-treated), it is boomy (sp?), not tight etc. I have read many threads on this subject, however, the below has me confused.


Thank you,

B.


Hi,

I have been reading about room treatments for some time (read: eyes are bleeding) and frankly I am confused. I am building a small dedicated home theater that is 16x10x8. It has a soffit all around the perimeter. I have Klipsch THX Ultra 2 "horn" loaded speakers behind an acoustically transparent screen. I have two of the KSW 12" subs. Most of the information I have read suggests that a smallish room will need to control bass more than say a larger room. I was planning on making a couple of the "super chunk" type traps for behind the screen, however, after having read your comments here it seams as though I may do a better job with cotton. Is this so? If so, how would you suggest I apply this material? Behind the screen?

Second, someone also mentions that having "horn" loaded speakers negate the need for first reflection point treatment (perhaps I am inferring incorrectly). This is the first I have read of this. Care to elaborate?

Thank you,

B.

Hello, My basemant just got finalized by the inspector so I'm getting ready for the treatment of my HT.
Front wall and 1st reflection obsorbtion I see most people using OC703, I can not get this in my area, I have spent many hours wasting sales time requesting information.
What can I get, 3" rock wool, and an OEM product that is the same as oc703.
I also found Knauf duct liner and Plenum http://www.knaufusa.com/products/commercial__industrial/air_handling_insulation/knauf_duct_liner_e-m.aspx

It seem the 2" duct liner would be better for obsorbtion than oem or rock wool.
The knauf duct liner is the same price as rock wool or oem, $1.00 square ft.
Should I go with the Knauf duct liner?

2. Related to #1 perhaps, in terms of trying things out: You may be used to hearing music reproduced in sub-optimal ways (it was true of me) so give any change a few weeks of listening before making a decision. And in the end, trust your ears.

I think you're right; I need to give it some time and a lot more testing before I get too concerned. Thanks for your time and thoughts Nathan.

Toole actually devotes an entire chapter in his book to countering this very argument. You'll have to forgive me if I give much more weight to the opinion of the guy who presents mountains of evidence and studies (many his own) in a 500+ page book versus a guy on an internet forum. :)

You were offering an opinion, I was offering an alternative opinion. Toole's book is not the be all end all. There are many theories and opinions (including other piles of evidence) that deal with lateral reflections. Why don't you try reading other people's work, including Dr. D'Antonio, or other opinions before you jump to definitive conclusions. Best wishes! :)

You'll have to forgive me if I give much more weight to the opinion of the guy who presents mountains of evidence and studies (many his own) in a 500+ page book versus a guy on an internet forum. :)
I respect Floyd Toole, but there are equally experienced professionals who disagree with him. They are just not as vocal about it. Floyd likes to stir the pot! :D And there are some things he can say in his book which he cannot say in a refereed journal paper, because he simply doesn't have the scientific proof.

- Terry

I respect Floyd Toole, but there are equally experienced professionals who disagree with him. They are just not as vocal about it. Floyd likes to stir the pot! :D And there are some things he can say in his book which he cannot say in a refereed journal paper, because he simply doesn't have the scientific proof.

Exactly. Nothing but respect for Floyd Toole, but just know that there's a lot of debate about his findings.

Frank

Exactly. Nothing but respect for Floyd Toole, but just know that there's a lot of debate about his findings.

Frank
I must admit to be experiencing the debate .. in my own head. I know what I heard before, during and after adding FRP absorbers to my room, but yet here's this respected researcher whose findings contradict what I've heard.

Jeff

I must admit to be experiencing the debate .. in my own head. I know what I heard before, during and after adding FRP absorbers to my room, but yet here's this respected researcher whose findings contradict what I've heard.

Jeff

There is absolutely nothing wrong with approaching this in an empirical manner. My recommendation is to try all suggestions and physically understand what is happening before formulating an opinion. I have formulated my own opinion based on this idea. It does not mean mine is absolutely the correct one. I believe the point here is to stick with what you feel you is best, but always remain open minded about new methods, scientific evidence or ideas. The mark of a good scientist. Best wishes!:)

You were offering an opinion,

Nope. I was giving him an option, and the reasoning behind the option, to help him figure out why he didn't like his sound. The opinion is Toole's and backed up by Toole.

I was offering an alternative opinion.

Exactly. So I give way more weight to Toole's than yours. When your book comes out I'll give you more weight. :)

Toole's book is not the be all end all. There are many theories and opinions (including other piles of evidence) that deal with lateral reflections. Why don't you try reading other people's work, including Dr. D'Antonio, or other opinions before you jump to definitive conclusions. Best wishes! :)

You jumped to conclusions that I haven't done any other reading. Toole's opinion just happened to match up with what I liked in my room. And I discovered that before I even read Toole's book.

yet here's this respected researcher whose findings contradict what I've heard.

There are respected researchers on both (several?) sides of this debate. And when one digs into how the conclusions were drawn, one can get a sense of how to weight the apparently contradictory conclusions.

I don't want to beat a dead horse but the proof is in the listening, and one answer does not fit all people and situations.

For me, in addition to listening tests (ie, living with each scenario), I also researched a bit about how the recordings I listen to were mastered -- both in terms of the room the creation took place in, the treatments and specs for how the sound is reproduced, and in terms of speaker placement, etc. I am trying to hear what the sound designer and mastering engineers intended and heard -- and not, for example, a more spacious soundstage than they heard or intended.

Of course, even with that goal and process, there is more than one way to get there -- and many many ways to get "close" (which is what I'd say I have done, rather than getting a perfect simulacrum, based on feedback from a professional engineering and a pro musician who have experienced my system).

The big question that is foremost in my mind with Dr Toole's research on this - and maybe I missed it in his paper - is what was the content his research subjects listened to - music or cinema? If music, classical or pop?

Beyond that, I've done everything I can to remove the room's "environment" from the system's sound so that the artist's "environment" could be heard and he is saying the room adds something desirable.

Jeff :confused:

Nope. I was giving him an option, and the reasoning behind the option, to help him figure out why he didn't like his sound. The opinion is Toole's and backed up by Toole. Exactly. So I give way more weight to Toole's than yours. When your book comes out I'll give you more weight. :) You jumped to conclusions that I haven't done any other reading. Toole's opinion just happened to match up with what I liked in my room. And I discovered that before I even read Toole's book.

You are certainly entitled to your opinion. Best wishes! :)

Beyond that, I've done everything I can to remove the room's "environment" from the system's sound so that the artist's "environment" could be heard and he is saying the room adds something desirable.

From reading Toole's book, one of his main points is there is a spaciousness to music that needs to be recreated during playback. The two channel stereo playback needs the early reflections to increase the spaciousness to sound more like the original music and to what sounds natural to us. He states that it is up to the listener to decide whether to treat early reflections for multichannel since multichannel can recreate the spaciousness. People can agree or disagree with his findings... I'm just stating what he concludes.

From reading Toole's book, one of his main points is there is a spaciousness to music that needs to be recreated during playback. The two channel stereo playback needs the early reflections to increase the spaciousness to sound more like the original music and to what sounds natural to us. He states that it is up to the listener to decide whether to treat early reflections for multichannel since multichannel can recreate the spaciousness. People can agree or disagree with his findings... I'm just stating what he concludes.
I know, I know. :)

You seem a good interpreter, so let me follow up with an observation that spaciousness, if even a small home theater can add such a thing, comes from the reflections and resulting reverberant field arriving after the 20ms or so time frame during which reflections are interpreted as part of the direct sound event, but are delayed enough so that they confuse instead of merging.

So, what sayeth Dr Toole on first reflections, early reflections and reverberance? :)

I know, I know. :)

You seem a good interpreter, so let me follow up with an observation that spaciousness, if even a small home theater can add such a thing, comes from the reflections and resulting reverberant field arriving after the 20ms or so time frame during which reflections are interpreted as part of the direct sound event, but are delayed enough so that they confuse instead of merging.

So, what sayeth Dr Toole on first reflections, early reflections and reverberance? :)

Actually, I didn't do a good job. There is way more involved than just the spaciousness. Needless to say he spends a large part of the book on the precedence effect. It is more complex than "does the reflection arrive before or after 20ms?" There really is no way I could summarize it. Even if you don't end up agreeing with him, I'd recommend getting the book. If anything one gains perspective on the whole issue... by an expert, not from joe schmoes like myself.

Actually, I didn't do a good job. There is way more involved than just the spaciousness. Needless to say he spends a large part of the book on the precedence effect. It is more complex than "does the reflection arrive before or after 20ms?" There really is no way I could summarize it. Even if you don't end up agreeing with him, I'd recommend getting the book. If anything one gains perspective on the whole issue... by an expert, not from joe schmoes like myself.
jeff schmoe vs. frank schmoe? :)

I have his paper, but very little of it is in English.

Terry, does your answer apply to any front/back sub setup or just the one with subs in the wall, aka DBA?
Only DBA. The sound sources have to be on a grid which is no coarser than 1/2 the highest wavelength between centers. Otherwise, you will not get this nice unidirectional flow of waves from front to back. So with anything above subwoofer frequencies, this gets impractical pretty quickly! Also, with higher frequencies, such a front to back wave flow is not desirable. You want these sounds bouncing around and coming from different directions for a variety of reasons.

People talk about competing ideas to Toole's work and say they've "got proof", but I am yet to see a reference (as in a scientific paper not Ethan’s video) - can someone point me in the right direction to the following issue -

- Toole says you need membrane absorbers in corners due to an argument around particle velocity v pressure

Obviously there are quite a few people that use fibrous absorbers over membrane traps. I need to understand the maths behind that versus Toole's point of view.

Hi Elill,

I don't have any specific reference to guide you to other than a simple physics text book (many answers to understanding audio can be found in one), but the physics is easy enough to understand. Here is how I usually explain it to people. Do you understand the process of reverse osmosis? If you do, understand that it only works when the water on one side is under pressure. The membrane is just big enough to allow water molecules to pass through while leaving the minerals behind due to their size. In essence, that is what is going on along a boundary. Particles are at their slowest speed...indeed...maybe even close to zero. However, they have a bunch of other particles piling up behind them with continued energy input. Since the particles have nowhere to go due to the boundary...the pressure begins to increase. So, we have high pressure, but very slow if not zero velocity. Away from the boundary, it is just the opposite...higher velocity...lower pressure (although the particles are actually at their slowest on the peaks and nulls (think of a pendulum). So, frictional based absorbers work best when the particle is moving (hence the term frictional implying velocity), membrane type absorbers work best when there is higher pressure. This, of course, is an explanation in its simplest form, but I think explanation enough. It really is simple physics. Best wishes! :)

Thanks SMB, I get that, so why do people put frictional absorbers in corners then?

Frictional absorbers are low cost and more readily available in comparison and they are effective...just not as effective as membranes. Best wishes! :)

How much "less effective" are they? this is what I have been trying to quantify

Elill,

For textbooks covering this subject in general, see "Room Acoustics," by Heinrich Kuttruff, chapter 6, and "Acoustic Absorbers and Diffusers," by Cox, chapters 5-7.

Something to bear in mind about membrane absorbers is they are inherently tuned to some range of optimal frequencies. This is not a free choice, but is greatly constrained by the depth of the absorber.

- Terry

Significantly less effective for low frequencies! Still effective for high frequencies. A general target is a frictional (velocity type) absorber needs to have a depth equal to, or greater than, a 1/4 wavelength. Some of these corner frictional absorbers have a vinyl barrier between a couple of layers of the fuzzy stuff...that creates a pressure type absorber. In fact if you take two layers of 1" fuzzy stuff and put it on a wall, you'll get absorption down to frequency "x". If you now put a very thin sheet of vinyl or plastic between those two layers, the absorber suddenly starts performing more like 4" of fuzzy stuff.

Let me give you a slightly better mental picture of pressure vs velocity. Find a very solid wall. Concrete for example. Stand 3 meters from the wall. Now run as fast as you can directly toward this wall. When you hit the wall, your velocity is zero but you're feeling a lot of pressure.

Thanks Terry, I have the Cox book somewhere, I'll have a read....again.

So if I were to go down the DIY treatment route, it'd be "give it a go" take some measurements, see if it worked, repeat if/until desired results are acheived.

OR

Alternatively I can just buy off the shelf products which have been tested and "proven".....DIY isn't looking like a good option especially when its only about $1k cheaper for the entire room.....again the curse of buying stuff here...

That said I'll file that suggestion Dennis, it could work well on the under side of my soffits, I had planned on stuffing 100mm or 4" there, so this might save a little height - cant hurt right?

I did a chem. major so SMB's explanation makes perfect sense....not quite as exciting as your suggestion to run at a wall though :D

Yes, SierraMikeBravo gave a very good explanation, as did Dennis.

Don't assume that off-the-shelf products are "proven." They may just have "proven sales," which ain't the same thing! :D

let me give you a slightly better mental picture of pressure vs velocity. Find a very solid wall. Concrete for example. Stand 3 meters from the wall. Now run as fast as you can directly toward this wall. When you hit the wall, your velocity is zero but you're feeling a lot of pressure.

lol! :D