Okay, I'll clarify - normal felt from a normal fabric store is fine. You know, like the kind he said he tested and was able to blow through easily. :D

--Ethan
:o I knew there was something that I missed.

What are your thoughts about treating the area of wall directly to the left and right of the viewing positon? I have already treated the front wall with 1" linacoustic and 4" oc 703 traps on the corners. I also have all of the first reflection points covered with 2" oc703 and things sound pretty good at this point. I do however have some extra 2" panels and didnt know if I should just stop where I am at or treat that area to the left and right of the viewer.

Any thoughts?

Thanks,
Eric

Time to put in ceiling in a small (12' x 20') theater in basement. 8' ceiling, with 12" space between joists filled with pink insulation.

I think the drop ceiling would be easier, but the drywall ceiling better for acoustics. Any thoughts?

Drywall, I know, will be more difficult to put up, and there are potential future problems if I need access to pipes, wiring, etc. But as far as noise-dampening for the rooms above, isn't drywall better?

jchretien4

Some folks do both... lay squares of drywall on top of acoustic ceiling tiles to add mass to reduce the rattles from the grid caused by large subwoofer output... also the drywall panels are fairly absorptive at lower frequencies [about 30% at 125 Hz as I recall].

Or you could use a high NRC tile and a roll insulation topper.

I wouldn't consider a drywall ceiling unless noise isolation was an issue.

Or you could use a high NRC tile and a roll insulation topper.

This can actually work really well for HT sound, low frequency isolation issues aside. It puts a lot of very wideband absorption on the ceiling, improving lower frequencies than can be readily dealt with by typical wall treatment. By itself, this wouldn't handle lengthwise and widthwise reverberation very well, typically resulting in a double-slope decay curve (fast decay from heightwise room modes and slow decay from lengthwise and widthwise modes),with a long overall reverberation time. But if you have many uneven wall surfaces to diffuse the sound upwards and all around, the reverberation decay can become smooth and clean.

- Terry

Here's my deal, I am renting a new house that has an unfinished basement; walls are concrete and ceiling is rafters. The room is 10x25 but am only gonna use about 10x20 for HT. I need something I can put up temporarily so it will look decent and sound decent until I can get a lease option on the house and do what I want with it!! I know most of the material is kinda expensive but is there anything I can "hang" up?

Thanks for any suggestions!

Is it better to use absorbtion directly to the left and right of the listening position or is it best to leave the wall untreated for proper surround effect?

Here's my deal, I am renting a new house that has an unfinished basement; walls are concrete and ceiling is rafters. The room is 10x25 but am only gonna use about 10x20 for HT. I need something I can put up temporarily so it will look decent and sound decent until I can get a lease option on the house and do what I want with it!! I know most of the material is kinda expensive but is there anything I can "hang" up?

Thanks for any suggestions!

Into the rafters in the ceiling, staple batts of fiberglass insulation, and then cover it all with acoustic fabric (doesn't have to be expensive Guildford of Maine stuff -- just anything dark and that you can blow air through).

Along the walls, especially at first reflection points, hang absorbing material -- could be acoustic foam, or buy some rigid fiberglass and cover in acoustic fabric.

One idea I've been thinking of is using curtains covering every wall floor to ceiling, of a lightweight (acoustically permeable, can blow through it) fabric -- and then putting ugly but effective treatments behind it all.

Is it better to use absorbtion directly to the left and right of the listening position or is it best to leave the wall untreated for proper surround effect?

The first reflection points on the side walls (and ceiling and floor) should be treated with absorption. Left untreated your room will destroy surround effects, not enhance them. :D

--Ethan

The first reflection points on the side walls (and ceiling and floor) should be treated with absorption. Left untreated your room will destroy surround effects, not enhance them. :D

--Ethan


I have covered the first reflection points on the side walls but they do not extend all the way to the point directly to the right and left of the the listening position. I have enough treatment to cover that area also but I am afraid of having to much absorbtion.

Into the rafters in the ceiling, staple batts of fiberglass insulation, and then cover it all with acoustic fabric (doesn't have to be expensive Guildford of Maine stuff -- just anything dark and that you can blow air through).

Along the walls, especially at first reflection points, hang absorbing material -- could be acoustic foam, or buy some rigid fiberglass and cover in acoustic fabric.

One idea I've been thinking of is using curtains covering every wall floor to ceiling, of a lightweight (acoustically permeable, can blow through it) fabric -- and then putting ugly but effective treatments behind it all.

Thanks Nathan! I am really trying to keep the cost down as with this much space I'm sure it can add up quickly.. I was also thinking of some sort of curtains with acoustical treatment behind.

I have enough treatment to cover that area also but I am afraid of having to much absorbtion.

Better too much absorption than too little. To my way of thinking, the idea that the sound of your room should influence what you hear from the speakers is misguided. Small room ambience is generally bad sounding ambience. I'm not saying to make your room totally dead. But there's a good amount of leeway with this, and generally more absorption leads to cleaner sound that is more realistic and lifelike.

--Ethan

Better too much absorption than too little. To my way of thinking, the idea that the sound of your room should influence what you hear from the speakers is misguided. Small room ambience is generally bad sounding ambience. I'm not saying to make your room totally dead. But there's a good amount of leeway with this, and generally more absorption leads to cleaner sound that is more realistic and lifelike.

--Ethan

Ok, Thanks for your expert advice Ethan. I will hang the rest of my treatments tonight.

One can easily over deaden a room...be careful. Whether or not diffusion is used, or absorption is used, on the early reflection points is based upon the quality of the off axis response of the speakers.

What is the rule of thumb for acoustics in a small, 2 channel ONLY listening room (12wx14lx8h). Is it deaden front end, liven back or do I have that in reverse? Any tips or tricks you may suggest would be highly appreciated.

My seating position is an equilateral triangle 8' apart.

Thanks!

One can easily over deaden a room...be careful. Whether or not diffusion is used, or absorption is used, on the early reflection points is based upon the quality of the off axis response of the speakers.

All of my fronts are Ascend 340s. They seem to be pretty good off axis. I added some more 2" absorbers to the left and right of the viewing postion last night and it definately made a difference. The bass seemed tigher with more clarity and the imaging was improved. I am still having problems flattening out the response on my sub but I may need to just break down and buy an EQ of some sort.

Thanks for your help guys.

I am looking for advice on a post-mortem fix for sound leaking through the A/C ducts. I spent quite a bit of money ($3,000) in double drywall + GG + insulation, so I think I must take care of this.

Unfortunately the ducts themselves were already in place when the build began, so I need a solution that will accomodate to the current state of things... Linacoustics would have been great, but not something I could apply to an enclosed ductwork...
Can someone point me in the right direction please? Anything is help... even if it just cuts the sound by half.

All of my fronts are Ascend 340s. They seem to be pretty good off axis. I added some more 2" absorbers to the left and right of the viewing postion last night and it definately made a difference. The bass seemed tigher with more clarity and the imaging was improved. I am still having problems flattening out the response on my sub but I may need to just break down and buy an EQ of some sort.

Thanks for your help guys.

You may need to get a EQ to flatten out some of the sub low frequencies, but you may want to add a few more bass traps (if you can) before hand. I may be over looking this but you only have 2 right now?

Glenn

I have a basement theater 11' wide, 20' long and 92" high. 3 walls are treated up to 42" height with OC703, which has worked well for damping refletions. the 4th wall is bookcases and heavy floor to ceiling cabinet doors (faced partially with absorption panels. The back 6 feet of the room has a 9" riser for second row seats and is stuffed with fiberglass. The ceiling is also partially absorptive due to a home built star ceiling made with FRK OC 703 with the foil facing the room and partially removed in a sort-of checkerboard pattern.

Now its time for bass trapping. There is an AC soffit running down one side of the room. When i put up the crown molding, I left some space at the back of the room for a soffit bass trap that would be about 12" in height and 16" front to back, matching the size of the AC soffit. I have some 1" FRK OC 703 left over and was thinking about cutting and gluing 4 layers of it to form an L shaped soffit, covering it with GOM to match the stuff in the room now, and mounting it to look like the existing soffit.

Questions: Will this be an effective part of a bass trapping solution for the room? Should i remove the foil from the room-facing side of the 703? (i will remove from all the other layers). Should i stuff the inside cavity with additional fiberglass, like the stuff on rolls?

I plan to span the floor/rear wall intersection with 2'x4'x4" 703 panels and perhaps put Ethan's tricorner traps in the lower rear corners. There is no place to put bass traps at the front of the room as the right front 5' of the room is an open arch, the front12' on the left is the floor to ceiling cabinets and the screen is too close to the ceiling to put anything above it (also, the WAF thing).

You may need to get a EQ to flatten out some of the sub low frequencies, but you may want to add a few more bass traps (if you can) before hand. I may be over looking this but you only have 2 right now?

Glenn

Glenn,

I have two 4" absorbers in the front two corners and I lso built two 4" triangle traps for the ceiling corners.

Very cool. Now I gotta figure out the weight thing.... I wonder if Home Depot carries balsa wood?

One homemade skyline diffuser i saw was made from stiff 2" thick exterior foam insulation - like the stuff you see at HD in 4x8 sheets. The guy cut 12 2" x 24" skyline profiles out of the stuff , then glued them together to form a 24" x 24" square. If you're careful, you can get 2 skylines out of one rectangle with one continuous cut. i think you can get hot wire cutters for that stuff at hobby shops. It would beat cutting 144 balsa sections and putting them together.

That's an interesting idea. I would have thought it would be too porous / absorbing -- but I suppose a little of that is not bad. Thanks!

Glenn,

I have two 4" absorbers in the front two corners and I lso built two 4" triangle traps for the ceiling corners.


I would put some more in first. Most rooms at minimum need 4 2x4s and really something more like 8 or more for the "wow" factor. All rooms are not the same, but 2 is a pretty small amount.

Glenn

If you have a fully treated (absorptive) front wall, and your speakers are all behind an AT screen, can you use black velvet across the rest of the entire fake screen wall? I would assume that if the black velvet is not reflective at all, then it's not any different than an acoustically transparent cloth, like speaker grill. However, I'm concerned that it may reflect some frequencies. Does anyone know if typical black velvet will reflect some sound, or if it is only absorptive and transparent across the entire frequency range?

If you have a fully treated (absorptive) front wall, and your speakers are all behind an AT screen, can you use black velvet across the rest of the entire fake screen wall? I would assume that if the black velvet is only absorptive, then it's not any different than an acoustically transparent cloth like speaker grill. However, I'm concerned that it may reflect some frequencies. Does anyone know if typical black velvet will reflect some sound, or if it is only absorptive and transparent across the entire frequency range?
If the black velvet is ONLY ABSORPTIVE, then it is not acoustically transparent and is ENTIRELY different than speaker grill cloth.

If the black velvet is ONLY ABSORPTIVE, then it is not acoustically transparent and is ENTIRELY different than speaker grill cloth.

You missed the entire point. If everything behind that passes through the material is absorbed, then, effectively, an absorbent material is no different than acoustically transparent material, because when the audio passes through the acoustically transparent cloth, it becomes absorbed.

You missed the entire point. Almost any cloth will be transparent below some frequency (not enough mass), hence a cloth really can't be only absorptive. I'm just worried about some frequencies that may be reflected by typical black velvets.
If I had read it after you edited it, I may not have. ;)

I don't know where you'd find data on reflectivity. Transmission and absorption data, yes.

pepar:

Where is there absorption coefficients on velvet ?

(velvet is certainly absorptive, and is not acoustically transparent speaker cloth)



Lindahl:
I have no idea if velvet makes a good absorber cover. Nevertheless, that's what I used.
http://www.bobgolds.com/LivingRoomPlasma/Construction/home.htm
However I used it mostly so the surrounding space would be blackest black.

I believe SandmanX did exactly what you're proposing: speakers behind an acoustically transparent screen, and the rest of the front wall covered in black velvet.
http://www.smxscreen.com/images/curved-screen/IMG_1441.jpg

Where is there absorption coefficients on velvet ?

(velvet is certainly absorptive, and is not acoustically transparent speaker cloth)
My mistake. When he said "black velvet" I thought of felt. And Ethan recently was saying that felt was OK. Again, my mistake. :o

Lindahl: It would not have mattered if I had read your edited post, I *still* would have got it wrong. :(

No prob... any acousticians want to chime in on the suitability of black velvet in this application?

Felt is fine for in front of treatments. It is most definitely not recommended in front of speakers.

Bryan

Felt is fine for in front of treatments. It is most definitely not recommended in front of speakers.

Hmm, my concern was about velvet... did you mean velvet too? Or just felt?

My room sounds okay as is, but would probably benefit, like most rooms, from acoustic treatment. Obviously, at a minimum, I would need panels or something at the first reflection points. Here is my room:

http://ericbeth.home.comcast.net/theater.html

Now I read most of this thread, but most of it deals with DIY stuff. I'm not a DIY guy, but would like some cost effective acoustic treatment.

Who can you hire to decide what treatments (basic) your room needs acoustically and who will also actually put the stuff up (or get someone to do it)?

I'm not looking to spend a fortune, but I'm not looking to spend just a few hundred either.

I'd imagine there are several folks in this thread who make treatments for a living who would love to help you out. If you're anywhere near Poughkeepsie, NY, I'll give you my opinion for what it's worth.

I'd imagine there are several folks in this thread who make treatments for a living who would love to help you out. If you're anywhere near Poughkeepsie, NY, I'll give you my opinion for what it's worth.

I'm in the Philadelphia suburbs.

Well, so much for that then. My amateur opinion based only on your pictures is to fill the space above your ceiling with the pink fluffy stuff if you haven't already. If those aren't acoustic tiles, replace them with some that are, at least at your First reflection points. For your walls, if you're not DIY, get a couple panels from one of the suppliers in this thread and hang them at you first relection points on the side walls. Bonus points if you treat your front wall. Since the room is a pretty tight fit, use Bass Trapping in your front corners, and couple that with a parametric EQ. Check out the Behringer feedback destroyer and Room EQ Wizard on hometheatershack.com, or go with Velodyne if you want simple, yet expensive.

P.S. While I'm here, is anyone elses view of this forums screwed up? Here's what my screen looks like: http://img103.imageshack.us/img103/6690/avsqn7.th.jpg (http://img103.imageshack.us/my.php?image=avsqn7.jpg)



Please PM me if you know what I'm doing wrong.

Well, so much for that then. My amateur opinion based only on your pictures is to fill the space above your ceiling with the pink fluffy stuff if you haven't already. If those aren't acoustic tiles, replace them with some that are, at least at your First reflection points. For your walls, if you're not DIY, get a couple panels from one of the suppliers in this thread and hang them at you first relection points on the side walls. Bonus points if you treat your front wall. Since the room is a pretty tight fit, use Bass Trapping in your front corners, and couple that with a parametric EQ. Check out the Behringer feedback destroyer and Room EQ Wizard on hometheatershack.com, or go with Velodyne if you want simple, yet expensive.

P.S. While I'm here, is anyone elses view of this forums screwed up? Here's what my screen looks like: http://img103.imageshack.us/img103/6690/avsqn7.th.jpg (http://img103.imageshack.us/my.php?image=avsqn7.jpg)



Please PM me if you know what I'm doing wrong.

Thanks, the ceiling tiles are acoustic and there is insulation in the ceiling joists (where possible -- as ductwork also runs through the ceiliing).

I'm most concerned with acoustic panels/fabric (wall treatments) at this point. I need someone to decide where the panels/fabric should go EXACTLY -- and who will also install them. What companies do that?

Thanks, the ceiling tiles are acoustic and there is insulation in the ceiling joists (where possible -- as ductwork also runs through the ceiliing).

I'm most concerned with acoustic panels/fabric (wall treatments) at this point. I need someone to decide where the panels/fabric should go EXACTLY -- and who will also install them. What companies do that?

Well, "exactly" is easy, you and a buddy with a mirror get get the job done. Search "mirror trick". As for hanging them, you and a handheld drill, some screws, maybe a drywall anchor or two.

As for companies, Realtraps (Ethan) and GIK Acoustics (bpape) are well represented here, offering lots of free advice in this thread. Appologies to other contributing members in the business that I didn't mention, please make yourselves known.

Well, "exactly" is easy, you and a buddy with a mirror get get the job done. Search "mirror trick". As for hanging them, you and a handheld drill, some screws, maybe a drywall anchor or two.

As for companies, Realtraps (Ethan) and GIK Acoustics (bpape) are well represented here, offering lots of free advice in this thread. Appologies to other contributing members in the business that I didn't mention, please make yourselves known.

I'm looking for a company that will actually do the installs (I don't even own a drill, nor would I know which kind to buy). From their websites I think these companies provide analysis and materials, but not installation of fabric or panels.

http://rivesaudio.com/ can help you out. They can do the analysis remotely, and then give you the details (and probably names) to talk to, locally, to get their ideas implemented.

caesar1,

Where are you located??

You might want to add your location to your visible profile.

I'm looking for a company that will actually do the installs (I don't even own a drill, nor would I know which kind to buy). From their websites I think these companies provide analysis and materials, but not installation of fabric or panels.
If you can hang a piture on your wall, you can hang an acoustic panel :) And corner bass traps just rest on your floor, no hanging. I am definitely not a DIY kind of guy and I totally understand where you are coming from here, but finding a local installer to do what you can do with a screwdriver is going to add a lot of labor costs (believe me, if I can hang a panel than anyone can, I am a real mechanical/tool idiot!).

I just worked with Glenn at GIK, emailed him pics of my room which he expertly analyzed and he came up with a game plan for basic treatment consisting of a total of 7 traps & panels with exact intructions of where to place each piece, all for about $950 delivered from the east coast to the west. I'll be setting them up when they arrive next week and am really looking forward to hearing the improvement in SQ.

Cheers,
Ross

caesar1,

Where are you located??

You might want to add your location to your visible profile.

Philadelphia suburbs.

I'm looking for a company that will actually do the installs (I don't even own a drill, nor would I know which kind to buy). From their websites I think these companies provide analysis and materials, but not installation of fabric or panels.

Who built your room for you? It's nice by the way.

Honestly, anyone with a knowledge of building a room, hanging speakers could do the work for you. I think a number of us could point you to step by step directions for making the panels and hanging them. Maybe you have a friend or family member that can help you...it would save a lot of money. I'm not very handy, so if I can do them, I know you could.

If you can hang a piture on your wall, you can hang an acoustic panel :) And corner bass traps just rest on your floor, no hanging. I am definitely not a DIY kind of guy and I totally understand where you are coming from here, but finding a local installer to do what you can do with a screwdriver is going to add a lot of labor costs (believe me, if I can hang a panel than anyone can, I am a real mechanical/tool idiot!).

I just worked with Glenn at GIK, emailed him pics of my room which he expertly analyzed and he came up with a game plan for basic treatment consisting of a total of 7 traps & panels with exact intructions of where to place each piece, all for about $950 delivered from the east coast to the west. I'll be setting them up when they arrive next week and am really looking forward to hearing the improvement in SQ.

Cheers,
Ross


They send you panels already completely made and ready -- and you just hang them on the wall with a nail (like a picture)?

Who built your room for you? It's nice by the way.



Thanks. This is a new construction home -- so I worked with the home builder on a custom partially finished basement -- including the home theater room. I gave the builder the basic specs as far as room size desired, the riser location, etc. (mostly from reading AVS) and I worked with the builder's electricians on placement of the speaker positions and projector and rack location for wiring purposes (as well as lighting).

After we closed on the house, we hired painters for the room colors (builder did every room in one basic color) and the place I bought my projector from did the projector, screen and speaker mounting.

This was my "construction" thread:

http://www.avsforum.com/avs-vb/showthread.php?t=746578&highlight=caesar1

They send you panels already completely made and ready -- and you just hang them on the wall with a nail (like a picture)?

Yes, that's the way our RealTraps panels mostly work. If you're not handy at all you can probably find someone locally to do this for you for $100. But it's not that big a deal, even if you're all thumbs. :D

--Ethan

Lindahl.

Yes - that applies to velvet also. If a material is absorbtive, it is not suitable for in front of speakers. Many of GOM's materials themselves are not suitable. There are maybe 8-10 of them that are really transparent enough to put speakers behind.

Bryan

On a DIY network show on home theaters, they showed construction using double drywall, hat channel, acoustic caulk and some other good things, but they also showed using rigid fiberglass panels BEHIND the double drywall.

They alternated every other panel so that it looks like this:

http://img.diynetwork.com/DIY/2005/01/12/dhtw103_1fg_e.jpg

More info is at http://www.diynetwork.com/diy/hi_family_room/article/0,2037,DIY_13912_3465208_02,00.html

Does this work? Is there any benefit to putting rigid fiberglass panels behind the drywall on top of the r13 batts? They described it in the actual show, as I recall, as a kind of acoustic treatment -- not just sound isolation. sort of a bass trap behind the drywall. would that work?

Does this work?
No. I'm afraid it was pure stupidity on the part of the TV show. :)

- Terry

Anybody??

I am preparing to make some changes in my home theater and would like some input. Along with lowering to a wee bit above ear level of my M&K S-150s and adding superchunk style bass traps, I am contemplating REMOVING or reducing the size of the front left & right first reflection point absorbers. They are now 4' x 4'. Lowering LCR would mean I could cover the points with 2' x 4' panels. The "removing completely" thought comes from reading Toole's June 06 AES paper (so kindly provided by TumaraBapp) and how lateral reflections are good. As I have black carpet on the wall (for light control), I would - I guess - be replacing the absorbers with diffusion.

I'd like to hear comments on what I am considering, including what diffusion I should use. Skyline LPs are so so expensive.

TIA!!

The "removing completely" thought comes from reading Toole's June 06 AES paper (so kindly provided by TumaraBapp) and how lateral reflections are good.
This has been part of Floyd Toole's stump speech for the last few years. I think he makes these overstatements to shake up the professional acoustics community from their traditional complacency and indifference toward small room acoustics.

Early reflections will improve speech intelligibility in low-quality environments. They are of great benefit in classrooms, for example. But they will also lower the accuracy of front sound stage spacial imaging for a high-quality HT room. His and Sean Olive's 1988 paper demonstrated this "image shift" phenomenon pretty clearly.

- Terry

Anybody??

I am preparing to make some changes in my home theater and would like some input. Along with lowering to a wee bit above ear level of my M&K S-150s and adding superchunk style bass traps, I am contemplating REMOVING or reducing the size of the front left & right first reflection point absorbers. They are now 4' x 4'. Lowering LCR would mean I could cover the points with 2' x 4' panels. The "removing completely" thought comes from reading Toole's June 06 AES paper (so kindly provided by TumaraBapp) and how lateral reflections are good. As I have black carpet on the wall (for light control), I would - I guess - be replacing the absorbers with diffusion.

I'd like to hear comments on what I am considering, including what diffusion I should use. Skyline LPs are so so expensive.

TIA!!

Opinions differ, and I'm not an expert, but one line of thought is that in a larger room, for two channel music, diffusion would be ideal for what you describe. It would increase the sound stage width and depth.

But for surround sound, in a more modest room, the absorption at the first reflection points will keep the imaging focussed -- and you'll hear only the sound stage in the recording, with the room adding less to the character of the recording.

The "removing completely" thought comes from reading Toole's June 06 AES paper (so kindly provided by TumaraBapp) and how lateral reflections are good.Rather than an all or nothing approach, discussing Toole's paper with a friend got me to consider which first reflections I wanted to absorb and which I wanted to diffuse.

For example, I know I don't want to hear sounds from the right speaker coming from the left wall, because it'll mess with directionality. So I'll absorb the first reflection from the opposite speaker. However, I do like it when sound from my right speaker reflects off the right wall, because it helps widen the soundstage. So I'll diffuse the first reflection from the nearby speaker. The diffusion will keep the reflection from being a mirror image and causing image shifting (where sounds from the right channel will phantom image between the right speaker and its first reflection on the right wall).

I'm undecided on what to do with the first reflections from my centre speaker. For movies, absorbtion tends to make dialogue clearer. For music (which is what I use my system for primarily) diffusion seems to work better, helping the vocalist blend more naturally with the widened soundstage rather than be a crystal clear dot in the middle of it. This sometimes works well for movies, but I'm still experimenting.

BTW, the above assumes that your speakers maintain somewhat consistent tonality off-axis. If the frequency response of the first reflections is very different than what's coming directly from your speakers, then I would absorb them (the reflections, not the speakers). Don't get me wrong, I love a wide lush soundstage, but not if it's going to make a noticeable change to the sound of instruments and vocals.

Sanjay

This has been part of Floyd Toole's stump speech for the last few years. I think he makes these overstatements to shake up the professional acoustics community from their traditional complacency and indifference toward small room acoustics.

Early reflections will improve speech intelligibility in low-quality environments. They are of great benefit in classrooms, for example. But they will also lower the accuracy of front sound stage spacial imaging for a high-quality HT room. His and Sean Olive's 1988 paper demonstrated this "image shift" phenomenon pretty clearly.
Opinions differ, and I'm not an expert, but one line of thought is that in a larger room, for two channel music, diffusion would be ideal for what you describe. It would increase the sound stage width and depth.

But for surround sound, in a more modest room, the absorption at the first reflection points will keep the imaging focussed -- and you'll hear only the sound stage in the recording, with the room adding less to the character of the recording.
My room is ~13' x 21' x 8', so it is not a large room. Going by what I heard as I installed my absorbers, the first one up - the rear wall - made a huge difference in the clarity and imaging of LCR and greatly improved surround/mains integration. The front left and right ones went up next and, while they made an improvement in both of those areas, it was incremental. The front ceiling was last and it also improved front imaging to a slightly greater degree than the left and right front absorbers. But with these, the 2" J-M Linacoustic lining the cavity behind the false wall, the six fat LaZBoys and the wall carpet to ear level all around, I feel that there is no "air" or at least not enough. The front sound stage is wide and deep, so I do not want to monkey with that.

Perhaps what I should start with is to lower LCR to close to ear level. They are higher now and aimed down at the 3D "center" of the seats and with the tight vertical dispersion - M&K S-150 THX (pre Select & Ultra) - I feel that I will get more even coverage. I already have 2' x 4' absorbers made, so it will be a simple matter to swap them with the 4' x 4' ones, and the smaller ones will be a closer match for the angles to the ears from the new location(s). And then I would like to try adding diffusion to the area above the 2' x 4' absorbers. The first reflection points will still be covered and perhaps I can increase the airiness. Have my cake and eat it, too.

Can you recommend some diffusors? I've been looking at Skyline LP, but they are very proud of them and command a price that just looks out of whack for what would seem to be a few dollars worth of styrofoam, if that. I will bite the bullet, though, if they are the right tool for the job.

Thanks for the advice.

Jeff

Rather than an all or nothing approach, discussing Toole's paper with a friend got me to consider which first reflections I wanted to absorb and which I wanted to diffuse.

For example, I know I don't want to hear sounds from the right speaker coming from the left wall, because it'll mess with directionality. So I'll absorb the first reflection from the opposite speaker. However, I do like it when sound from my right speaker reflects off the right wall, because it helps widen the soundstage. So I'll diffuse the first reflection from the nearby speaker. The diffusion will keep the reflection from being a mirror image and causing image shifting (where sounds from the right channel will phantom image between the right speaker and its first reflection on the right wall).

I'm undecided on what to do with the first reflections from my centre speaker. For movies, absorbtion tends to make dialogue clearer. For music (which is what I use my system for primarily) diffusion seems to work better, helping the vocalist blend more naturally with the widened soundstage rather than be a crystal clear dot in the middle of it. This sometimes works well for movies, but I'm still experimenting.

BTW, the above assumes that your speakers maintain somewhat consistent tonality off-axis. If the frequency response of the first reflections is very different than what's coming directly from your speakers, then I would absorb them (the reflections, not the speakers). Don't get me wrong, I love a wide lush soundstage, but not if it's going to make a noticeable change to the sound of instruments and vocals.
Thank you, Sanjay. I like the thinking behind what you suggest, but with two front speakers - three if you count center channel - and six seats that I am trying like the dickens to have all be good seats - it seems too complex and perhaps not even doable. Absorption that would catch the right speaker's sound coming from the left wall to ears in the right rear seat would also absorb the left front speaker's sound going to the left rear seat.

You have made me think; I visited my theater two times over the course of typing this post and sat in several seats to visualize the angles. :) I'd be interested in hearing any further comments you have on your experimentation.

Can you recommend some diffusors? I've been looking at Skyline LP, but they are very proud of them and command a price that just looks out of whack for what would seem to be a few dollars worth of styrofoam, if that.

I would never stoop so low as to recommend my own company's products. :D

The best diffusor would be rugged enough to withstand being bumped into without snapping into pieces, and would offer bass trapping at low frequencies where diffusion is not needed or useful.

--Ethan

The best diffusor would be rugged enough to withstand being bumped into without snapping into pieces, and would offer bass trapping at low frequencies where diffusion is not needed or useful.
Teaching me how to fish; I like that. :)

sdurani:

For example, I know I don't want to hear sounds from the right speaker coming from the left wall, because it'll mess with directionality.
I've experienced that particular one first hand -- well the left/right mirror of it.
I was watching the Star Wars Pod Race, and couldn't tell where the pods were coming from. Turned out the left speaker was bouncing off the right wall. I put an absorber by my right shoulder, and bingo imaging was MUCH MUCH better.

However, I do like it when sound from my right speaker reflects off the right wall, because it helps widen the soundstage.

I don't want on-screen action to sound like it's happening off-screen. While this may be nice for music, I find this effect to ruin the immersion aspect of movies. I can barely stand having my speakers just barely outside my screen (which will soon be remedied with an AT screen). For music, yes, an artificially wide soundstage can be nice. But this is all the more reason to have separate rooms, if it's feasible.

I like the thinking behind what you suggest, but with two front speakers - three if you count center channel - and six seats that I am trying like the dickens to have all be good seats - it seems too complex and perhaps not even doable.I can't imagine doing it successfully for multiple seats. I just do it for the sweet spot and let the other seats fall where they may. Same for time alignment, levels calibration, speaker placement, toe-in, etc. I can't do all that based on a sweet spot and then pretend the other seats are equally important.

Since there is one location from where I calibrate, that's the seat I keep in mind for the rest of the set-up. It doesn't mean the other seats sound bad, just that "all good seats" to me means all seats compromised. I'd rather have one optimized seat in there. YMMV.

Sanjay

I don't want on-screen action to sound like it's happening off-screen.Not everything in the front L/R channels is meant to be on-screen, since sound mixers vary in their approach.

There's a scene at the begining of the movie 'Speed' where a phone is ringing off-screen and the camera pans to bring it on-screen. The sound itself starts in the left channel and moves to the centre channel. If you spread your speakers way outside the screen, it sounds much more natural than having the sound of an off-screen object come from where your screen is.

There are other movies where the L/R channels define the limits of the image. For that, it would be better to have the L/R speakers within the edges of the screen. But there is no consistency. You have to choose what type of set-up you prefer, and live with it for both types of mixes. For music, yes, an artificially wide soundstage can be nice.What do you mean by "artificially" wide soundstage? Like when an orchestra sounds like it is larger than the width of my living room? I think it would sound more artificial, at least to me, if the entire soundstage was limited to the spread of my front L/R speakers. I think this comes down to personal taste, both for music and movies.

Sanjay

There's a scene at the begining of the movie 'Speed' where a phone is ringing off-screen and the camera pans to bring it on-screen. The sound itself starts in the left channel and moves to the centre channel. If you spread your speakers way outside the screen, it sounds much more natural than having the sound of an off-screen object come from where your screen is.

True, but I've found it infinitely more distracting when on-screen action sounds off-screen. It's the whole "your brain sees one thing, your ears hear another" conflicting of the senses that really rattles my cage. When the action is off screen, and the sound is on-screen, it's like pyschoacoustics kicks in, and it's a lot less distracting (maybe because the brain shifts what you thought you heard?). It could also be because the eyes are more precise in locating something than the ears, so your brain will discard the locational cues from your ears? Who knows... all I know is that I don't notice those problems. However, I do really notice the other mismatch.

What do you mean by "artificially" wide soundstage? Like when an orchestra sounds like it is larger than the width of my living room?

No, not that kind of artificial. Artificial because the sound is coming from well outside the placement, due to the wall artificially expanding it.

True, but I've found it infinitely more distracting when on-screen action sounds off-screen.I've had the opposite reaction, probably because I think of the soundstage as being a seamless circle extending around me and the screen as a window seeing only part of it. When watching a movie, I'm used to sounds continuously imaging off-screen (outside my front L/R speakers, at my sides, behind me, etc). Artificial because the sound is coming from well outside the placement, due to the wall artificially expanding it.Understood. But that's no more artificial than having phantom imaging outside your mains due to blending with the surround speakers or decorrelated sounds in the front channels or certain speaker designs or anything else that causes the soundstage to extend beyond speaker placement. Home audio is an artificial construct to begin with. I don't see why limiting the soundstage between a couple of arbitrary points (the distance between your L/R mains) is any less artificial than having the soundstage extend wider.

Sanjay

I would think the difference would involve having phantom imaging placed where they're intended to be versus where they show up by mistake due to unintended reflections.

I've had the opposite reaction, probably because I think of the soundstage as being a seamless circle extending around me and the screen as a window seeing only part of it. When watching a movie, I'm used to sounds continuously imaging off-screen (outside my front L/R speakers, at my sides, behind me, etc).

I suppose it has to do with the size of the screen. My screen almost fills my peripheral vision (2.35 AR). If I see something happen on-screen and it sounds like it's off-screen, then it destroys this immersion. Even if you consider the soundstage to be a seamless circle, around you, then only the action that happens off screen should sound like it's coming off-screen. If the sound needs to image off-screen, it should be softly matrixed (and almost always is) with the surrounds. Sound engineers mix for the theater, in which the front speakers are behind the screen. They very rarely mix on-screen action with off-screen sound.

I would think the difference would involve having phantom imaging placed where they're intended to be versus where they show up by mistake due to unintended reflections.

Yes, this is what I mean.

sdurani and Lindahl:

There's a scene at the begining of the movie 'Speed' where a phone is ringing off-screen and the camera pans to bring it on-screen. The sound itself starts in the left channel and moves to the centre channel. If you spread your speakers way outside the screen, it sounds much more natural than having the sound of an off-screen object come from where your screen is.
With a 2.35:1 aspect ratio and constant height, and most movies being 16:9, most times the left/right speaker behind an acoustically transparent screen would be outside of the image.
So, I looked it up.
"Speed (1994)" - Aspect Ratio: 2.35:1
Oh well.

I suppose it has to do with the size of the screen.Sure. If I stretched my screen to the width of the soundstage I hear, then the soundstage wouldn't extend beyond the screen. If the sound needs to image off-screen, it should be softly matrixed (and almost always is) with the surrounds.What should be done is not always what is done. There was an on-line article I read years ago where lots of soundtracks were compared in order to figure out optimal front speaker placement. Turned out that roughly half the tracks had sounds in the L/R channels for off-screen action while half used the L/R channels to define the limits of the sceen. There was no consistency in mixing philosophy. So placing the speakers within screen boundries and placing them outside the screen both had compromises, depending on soundtrack. Made it impossible to for them to conclude a right or wrong placement; they ended up going on personal preference, which included what was less distracting for each individual.

Sanjay

Turned out that roughly half the tracks had sounds in the L/R channels for off-screen action while half used the L/R channels to define the limits of the sceen.

That's not at all been my experience, but eh, oh well.

Kermie:



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

<snip>

A sabin can be defined loosly as "an open window one square foot in size".
So, if you have a material that absorbs 100% of the sound at all frequencies, and you need 413 sabins, then you'd need 413 square feet of that material.

For HF absorption, the above line
(sabins - front wall - carpet) / Left+Right+Rear wall: 30 %
means assuming you have the front wall and floor completely covered, then you should cover about 30% of the left/right/rear walls with HF absorption, assuming there's nothing else in the room.

In practice, different materials absorb different amounts per frequency band (as well as placement, diminishing returns, etc)
For example carpet tends to absorb lots of HF, and less LF.
Leather couches tend to reflect HF, and absorb more around 200hz.
Your walls tend to reflect HF, and absorb low frequency.
What you want to do is add up the sabins for each frequency band, and add (or possibly remove) material until you hit around 413 sabins.
I say 'around' because who can really tell the difference between RT60=.20 and RT60=.30.
Once you have the right amount of material in the room, then it's a question of placing it to deal with other things. You don't want to put it all on one wall for example. Imaging might be improved if you put it on the front wall and first reflection points (particularly the absorber on the right wall at the left front speaker reflection point).

http://www.bobgolds.com/AbsorptionCoefficients.htm
http://www.bobgolds.com/Sabin.htm

Hey all, apologies for not reading the whole thread but I'm looking into improving/fixing the acoustics in my HT, and at the moment, I'm trying to figure out how much absorption I need, and I'm having a little trouble narrowing down the more scientific methods to do it.

Starting with what I know, I've got a (roughly) 24x40 basement that houses my HT. Of that, roughly a 12 x 20 corner of that is closed off (half in both directions) portion, and opposite that, is a stair well (closed under solid walls, no door). So basically I've got a 12x40 "room" that makes up the HT with a stair well in the back, and that room opens up (via an 8' opening) into another
12x20 room. The two room form basically and open L but broken up by the stair well. About 7.5' ceilings.

Floor is shag carpet on pad. Walls are framed sheetrock, drop ceiling.

So I've been playing with ETF a bit, with my Galaxy 140 SPL meter as the mic and I get an RT60 of up to 3 seconds over much of the bass range (not entirely convinced the wiring is up to snuff for ETF), but that does somewhat jive with the "snap" or clap test, I can hear a snap reverberate for probably 2 seconds.

The big question I have is I see things like: "Absorbtion to achieve ITU RT60: 1112 sabins". Problem is (if I understand right) RT60 is a function of frequency, not a simple number. So I'm having a bit of trouble reconciling the two.

Is it (for example) RT60(f) = k * V / S(f)? With RT60 and Sabines being functions of frequency? Do you go through and say "I need x Sabines at this frequency and y Sabines at this other frequency?

Assuming my RT60 graph is right, and my basement is 7200ft^3, if I've got an RT60(400Hz) = 1400ms, (1400ms-200ms)=0.049*7200/S, so S = 252 Sabines currently @ 400Hz. If I want an RT60(400Hz) = 200ms, that would be 1764 Sabines? So I would need to add absorbtion "worth" ~1500 Sabines @ 400Hz? Looking at GIK 244 panels (http://www.gikacoustics.com/absorption.html), that would be about 100 panels?

Is that right, mathematically (ignoring for the moment if an RT60 of 1.4s is reasonable, or if 7200ft^3 is reasonable for my setup) or am I horribly lost?

stranger89

The big question I have is I see things like: "Absorbtion to achieve ITU RT60: 1112 sabins". Problem is (if I understand right) RT60 is a function of frequency, not a simple number. So I'm having a bit of trouble reconciling the two.

When the page says "Absorbtion to achieve ITU RT60: 1112 sabins", what it means is
1112 sabins at 63hz
1112 sabins at 125hz
1112 sabins at 250hz
1112 sabins at 500hz
1112 sabins at 1000hz
1112 sabins at 2000hz
1112 sabins at 4000hz


I believe that in a pre-build, that RT60 calculations are a useful and simple to understand metric to give you a starting point.
There are better models for pre-build.

For post-build, you'll find that your RT60 calculations will not match any measurements, and it's debateable if RT60 is something that even exists by it's definition and assumptions in a room as small as an HT.

And then there's ETF. You should talk to the author of that program for his opinions on RT60 measurements, and how to do them. ETF's RT60 measurements I never was happy with. R+D's (the successor to ETF by the same author) are supposed to be a little better. Even still, focusing on RT60 as a post-build room tuning isn't something I'd start with. ETF/R+D are great for proving lots of room hypothesis, as well as before/after changes, using measurements other than RT60.

So it assumes a flat RT60? That makes sense.

So in reality, if I've got the real, measured RT60 curve for my room, at each frequency it's:

Sabins for recommended RT60 - Sabins calculated from measured RT60 = Sabins needed

Roughly?

Thanks for the quick response :)

So it assumes a flat RT60? That makes sense.
Yes, it assumes a flat RT60.
Note that the RT60 curve doesn't have to be flat -- a little longer in the low isn't a problem. There's graphs about the acceptable limits somewhere. And I think that page lists some of them, although the wording is a bit cryptic.

(BTW, I edited the above post a bit)

The "removing completely" thought comes from reading Toole's June 06 AES paper (so kindly provided by TumaraBapp) and how lateral reflections are good.
There's a "yeah, but" here. In speaking with Floyd, he thinks this whole topic is a worthy PhD project. His recent work suggests these reflections can be good and they can be bad. Bad particularily if the off-axis response of the speakers happens to be poor. The threshold, and mechanism, between what makes them "good" and what makes them "bad" is not clearly understood (from not only the physics of what's going on; but, the psychoacoustics as well). It all rather falls into this rather broad category of small room acoustics and more specifically into the entire spectral decay issues (in small rooms). So, if anyone wants a PhD topic, here it is. (I'm tempted ;) )

And then there's ETF. You should talk to the author of that program for his opinions on RT60 measurements, and how to do them. ETF's RT60 measurements I never was happy with. R+D's (the successor to ETF by the same author) are supposed to be a little better. Even still, focusing on RT60 as a post-build room tuning isn't something I'd start with. ETF/R+D are great for proving lots of room hypothesis, as well as before/after changes, using measurements other than RT60.

Hm, for some reason I didn't get an email to about the replies... Oh well.

Thanks again the responses. As far as ETF goes, it's more a case of, I know there's something wrong, both based on my own "clap" tests (long reverb) and noticing that my system sounds increasingly harsh at higher volumes which if I'm reading this thread (http://www.avsforum.com/avs-vb/showthread.php?t=896253) right, could be attributed to the increasing audibility of decay issues at higher volumes.

So, I figured I'd play with ETF a bit to see if I can confirm some of the problems I suspect and get an idea for "where" they are and a rough magnitude of how big they are.

Oh, and in searching for "acceptable RT60 curve" I ran across this very interesting paper:
http://www.acousticsciences.com/articles/room-acoustics.pdf

Reading it now, looks like it might be exactly what I'm looking for...

There's a "yeah, but" here. In speaking with Floyd, he thinks this whole topic is a worthy PhD project. His recent work suggests these reflections can be good and they can be bad. Bad particularily if the off-axis response of the speakers happens to be poor. The threshold, and mechanism, between what makes them "good" and what makes them "bad" is not clearly understood (from not only the physics of what's going on; but, the psychoacoustics as well). It all rather falls into this rather broad category of small room acoustics and more specifically into the entire spectral decay issues (in small rooms). So, if anyone wants a PhD topic, here it is. (I'm tempted ;) )
So this is just an academic exercise? I need to formulate a plan now based on what is known now, not what might be sussed out in the future. My M&K S-150s are to have wide and even horizontal dispersion, but I still can't grok how my experience will be better by hearing a reflection delayed from 5ms to 12ms (due to the additional distance of "LCR to front side wall to my ears"). When I reduce the size of my absorbers there due to leveling out LCR vis-a-vis the listeners, I need to mount something over the newly exposed carpeted wall. What choice do I have other than diffusion? And then WHAT diffusors do I use? 1D or 2D? :confused:

stanger89:

http://www.bobgolds.com/RT60/HomeTheatreRecommendedRT60.gif

stanger89:

http://www.bobgolds.com/RT60/HomeTheatreRecommendedRT60.gif
This is relative. Is there an absolute recommendation? THX recommends 300ms midband decay.

pepar:

http://www.bobgolds.com/Mode/RoomModes.htm
calculates all these things for you, as well as the IEC and ITU RT60 ranges for frequencies (a little different than the above graph).

The ITU RT60 specification for rooms < 12,000 cu. ft is specified in the form:
Control Room Recommended RT60 = 0.3 *{(volume cu ft / 3531.34 cu ft) raised to 1/3 power}
Control Room Recommended RT60 = 0.25 * (( ProposedRoomVolume / 100 m^3 ) ^ .3333)
(1 cubic foot = 0.0283168 cubic meter)

This is the value I'd use for 500hz in the above graph.


ITU RT60
v, RT60 if V m^3, RT60 if V ft^3
i.e. if you calculate your room volume in ft^3, then go down the 1st column and find the volume of your room, and then get the RT60 from the 3rd column.
if you calculate your room volume in m^3, then go down the 1st column and find the volume of your room, and then get the RT60 from the 2nd column.
63 1.8 0.07 (shower stall - waterproof acoustical treatment required?)
1000 28.3 0.16
1250 35.4 0.18
1500 42.5 0.19
1750 49.6 0.20 (approximately 16' x 16' x 7')
2000 56.6 0.21
2250 63.7 0.22
2500 70.8 0.22
2750 77.9 0.23
3000 85.0 0.24
3250 92.0 0.24
3500 99.1 0.25
3750 106.2 0.26
4000 113.3 0.26
4250 120.3 0.27
4500 127.4 0.27
4750 134.5 0.28
5000 141.6 0.28
5250 148.7 0.29
5500 155.7 0.29
5750 162.8 0.29
6000 169.9 0.30
6250 177.0 0.30
6500 184.1 0.31
6750 191.1 0.31
7000 198.2 0.31
7250 205.3 0.32
7500 212.4 0.32
7750 219.5 0.32
8000 226.5 0.33
8250 233.6 0.33
8500 240.7 0.34
8750 247.8 0.34
9000 254.9 0.34
9250 261.9 0.34
9500 269.0 0.35
9750 276.1 0.35
10000 283.2 0.35
11000 311.5 0.37
12000 339.8 0.38
13000 368.1 0.39
14000 396.4 0.40
15000 424.8 0.40
16000 453.1 0.41
17000 481.4 0.42
18000 509.7 0.43
19000 538.0 0.44
20000 566.3 0.45
22500 637.1 0.46
25000 707.9 0.48
27500 778.7 0.50
30000 849.5 0.51
32500 920.3 0.52
35000 991.1 0.54
37500 1061.9 0.55
40000 1132.7 0.56
50000 1415.8 0.60
60000 1699.0 0.64
70000 1982.2 0.68
80000 2265.3 0.71
90000 2548.5 0.74
100000 2831.7 0.76
125000 3539.6 0.82
150000 4247.5 0.87
175000 4955.4 0.92
200000 5663.4 0.96
225000 6371.3 1.00 (approximately 100' x 100' x 22')

THX recommends 300ms midband decayOn the above list, 0.3 seconds is at 6000 ft^3, or about a 24x24x10 room.

stanger89:

Thanks!

That paper didn't turn out to be quite as helpful as I thought. But I did find Ethan's writeup on ETF so I'll give some of those suggestions a try and see if I end up with anything more reasonable.

pepar:

http://www.bobgolds.com/Mode/RoomModes.htm
calculates all these things for you, as well as the IEC and ITU RT60 ranges for frequencies (a little different than the above graph).
Wow, that'll keep me occupied for a while! Thanks!

heres my situation guys...ive got two windows that i need to treat to prevent sound from getting out...i know its almost impossible to make them "sound proof" but i need something to hang over them that would help deaden the sound that blasts out of them and into the neighbors houses...hehe...any ideas?

heres my situation guys...ive got two windows that i need to treat to prevent sound from getting out...i know its almost impossible to make them "sound proof" but i need something to hang over them that would help deaden the sound that blasts out of them and into the neighbors houses...hehe...any ideas?

Simply hanging a heavy curtain will do a little to help the sound from getting out, but very little. Mostly, it will be good for keeping light out.

Best solution, close your windows. If that doesn't work, and you're sure the noise is leaking through your windows, you can cut a styrofoam or other hard foam piece to fit the window cavity.

Odds are though, all of these will have little effect if your HT is being heard from houses away. Move it to the basement, and build a soundproof room.

eugovector:

Styrofoam won't help either.

http://www.bobgolds.com/Window/WindowPlug_CustomAudioDesigns_home_win1.gif
http://www.bobgolds.com/Window/WindowPlug_SmallBudgetRecording_AltonEverestMikeShea_pg67.jp g

Good Morning,

I am trying to salvage some acoustical qualities for my basement theater/game room project. I do plan to finish the space with consideration for all practical acoustical treatments (absorption, reflection, diffusing sound, etc,etc...). I am not terribly worried about sound leaking out to the surronding areas - I just want to optimize the acoustics within the theater area of this open floor plan.

I am now at the point of framing my screen wall and have some basic layout questions that may be of acoustical benefit later on:

From the sketch and photos below:

http://i227.photobucket.com/albums/dd153/cuzed2/ScreenStageRough-InQuestion.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/161-6148_IMG.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/161-6146_IMG.jpg

In the upper RH corner, to the right of my screen, I will need to frame and box-in some plumbing, my water meter is in this space. This will result in a 22" wide x 6' deep bump-out to the RH side of my screen.

I'm thinking I might gain an acoustical advantage (at the cost of floor space) if I were to put a matching wall like structure to the LH side of the screen?

What does everyone think, well this help acoustically?

I was also thinking of filling a portion of this hollow space to end up with bass traps?

Open to all suggestions (and your questions) that will help me in optimizing this open floor plan?

Thanks
CuzEd2 - Craig

I'm looking to turn a 10'W x 11'L x 8'H bedroom into a cozy HT. I've been reading this thread, and I'm at the point of information overload. The room is located upstairs with solid Sheetrock on all sides and plush carpet.

I will be mounting my 50" plasma on one wall, and will be using a 5.1 speaker setup for purely movies/TV (no stereo music). Speakers are the Energy Veritas line with a HSU VTF-3 subwoofer.

I did the "clap" test in the room and yikes, there is a lot of ringing in the room. So I know it needs some serious acoustic help.

From my reading, it sounds like I should start with the front wall. Now I'm a bit confused on how much of the wall I should cover and with what. Floor to ceiling with 1" OC 703 wrapped in cloth? Or should I alternate different panel types for broader frequency coverage? Or just panels half way up the wall?

It also sounds like in this small of a room that ceiling treatments are not recommended. Can I start with just treating the front wall, then see how it sounds and add additional treatments? Or are the room dimensions such that I seriously need more to really accomplish much of an improvement?

Sorry for the noob questions.

Guys,

Start here:

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

Then follow up with any questions. Yes, left-right symmetry is important, as is reducing ringing and bass resonances.

--Ethan

Ethan,

Thanks for the link containing the tutorial. I skimmed it and am printing for more leisurly reading later.

I believe I will go ahead and build out both front corners for better symmetry (both acoustically and to be more visually balanced).

Thanks Again
Cuzed2 - Craig

I have some spare 1" CertainTeed 475 Ultra Duct Gold that I want to play around with. If I'm making panels for my front wall (where my projector screen is) should I remove the foil backing or just face it towards the wall?

EDIT: I assume the foil backing is similar to OC's "FRK" backing material.

TIA

As you can see I have taken your advice

I have since gone ahead and balanced the screen area by "boxing" in both sides.
This leaves cavities about 18" deep on both sides of the screen, floor to ceiling high, and about 6' from the front edge back to the screen wall.

Looking for suggestions on how best to treat (fill) these caivities - bass traps. etc ???

Thanks in advance!
CuzEd2 - Craig

http://i227.photobucket.com/albums/dd153/cuzed2/ScreenStageRough-InQuestion.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/DenAreaFramed.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/RSScreenRoughBoxed.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/LSPartialWall.jpg

http://i227.photobucket.com/albums/dd153/cuzed2/ScreenRoughBoxed.jpg

I have some spare 1" CertainTeed 475 Ultra Duct Gold that I want to play around with. If I'm making panels for my front wall (where my projector screen is) should I remove the foil backing or just face it towards the wall?

EDIT: I assume the foil backing is similar to OC's "FRK" backing material.

TIA
You can leave the foil if it faces the wall. Sound passing through the fiberglass won't "see" any difference between a layer of sheetrock and a layer of sheetrock with a thin layer of foil directly covering it.

- Terry

You can leave the foil if it faces the wall. Sound passing through the fiberglass won't "see" any difference between a layer of sheetrock and a layer of sheetrock with a thin layer of foil directly covering it.

- Terry

Thanks a bunch Terry. I'll just leave the foil on then. They'll be spaced off the wall roughly 1" as I plan on using a french cleat to mount them.

Thanks a bunch Terry. I'll just leave the foil on then. They'll be spaced off the wall roughly 1" as I plan on using a french cleat to mount them.

Uhhh...I'll wait for someone much more knowledgeable to answer this, but I believe if you are going to have a space between the wall and the treatment, then you would want to remove the foil. If it were right up against the wall, then foil or not wouldn't matter since sound would reflect off the wall regardless of whether it were the foil or drywall; however, with a 1" space behind the treatment, removing the foil will have an impact.

Uhhh...I'll wait for someone much more knowledgeable to answer this, but I believe if you are going to have a space between the wall and the treatment, then you would want to remove the foil. If it were right up against the wall, then foil or not wouldn't matter since sound would reflect off the wall regardless of whether it were the foil or drywall; however, with a 1" space behind the treatment, removing the foil will have an impact.
Yup, exactly. I guess what I said to mobius was not completely unambiguous: "a layer of sheetrock with a thin layer of foil directly covering it". This does not mean you can add an air space in between foil and sheetrock!

Regards,
Terry

with a 1" space behind the treatment, removing the foil will have an impact.

There's no real detriment to having foil in the rear of a panel, even if it's spaced off the wall. I've tested this in a lab, and it works fine. If anything, you'll get even more bass absorption, as well as no reduction in HF absorption.

--Ethan

There's no real detriment to having foil in the rear of a panel, even if it's spaced off the wall. I've tested this in a lab, and it works fine. If anything, you'll get even more bass absorption, as well as no reduction in HF absorption.

--Ethan
Would there not be more absorption at a certain band of bass frequencies due to diaphragmatic action, but less at others due to them not passing through the panel two times?

yngdiego-

Let me know how your room sounds with the energies, my ht room is 13x15 and was told the vientas would be to much for my room to accomadate.

Would there not be more absorption at a certain band of bass frequencies due to diaphragmatic action, but less at others due to them not passing through the panel two times?

Sure, but the main difference is the amount of absorption at high frequencies on the face exposed to the room.

--Ethan

I'm trying to work out the optimal acoustic treatments for the room below. Basically it's a small bedroom and not many placement options. Drawing is to scale, where one small block is 4 inches. The angled lines you see under the drawing are the Dolby 5.1 recommended angles for placement of speakers.

Equipment:

Onkyo 905 Receiver
Pioneer 1150HD 50" Plasma
Energy Veritas speakers (v2.4, 2.0C, 2.0R)
HSU VTF-3 subwoofer
DTV HR20-100

Room:
Upstairs bedroom, two outside walls, plush carpet, sheetrock walls, 8' ceilings. Approximately 105 degrees to the rear surrounds.

My design reflects a 6.5' equilateral triangle between speakers and primary listening position, plus 6.'5 to the center speaker. Viewing distance is 7.5'. TV and center speaker are on a stand, so their relative distances cannot change. Rear surrounds are as far back into the room as possible given the door placement.

Questions:
1. The bass traps in the front corners eat up a TON of space and thus the front speakers are very close to them. Is this a significant problem? I know 1' from the back wall is recommended but this room is tiny. Toeing the speakers makes it that much worse.

2. On the left and right sides of the window I would have about one foot where I could put acoustic panels. Is that worth it? I plan to have drapes over the window. Should they be 2" or 4" OC703?

3. Should I put an acoustic panel directly under the window behind the center channel? It would be about 22" high. 2" or 4" OC703?

4. (Not on diagram). On the left and right walls at the reflection points one web site recommended a horizontal 2'x'4 panel, but my speakers are 45" high. Should they be vertical instead? 2" or 4" OC703?

5. (Not on diagram) In addition the site recommended two 2'x4' ceiling panels directly over the L and R main speakers, PLUS two more centered towards the middle of the room between the loveseat and TV. I've read elsewhere that in a room as small as mine, ceiling treatments are usually not needed. Four panels seems like a lot to me. Ideas?

6. Should the back wall in the closet get any treatments such as bass traps?

7. Do I need any diffusion panels?

Any and all feedback is appreciated. The room has pretty bad slap echo, BTW. Thanks!

Questions:
1. The bass traps in the front corners eat up a TON of space and thus the front speakers are very close to them. Is this a significant problem? I know 1' from the back wall is recommended but this room is tiny. Toeing the speakers makes it that much worse.

2. On the left and right sides of the window I would have about one foot where I could put acoustic panels. Is that worth it? I plan to have drapes over the window. Should they be 2" or 4" OC703?

3. Should I put an acoustic panel directly under the window behind the center channel? It would be about 22" high. 2" or 4" OC703?

4. (Not on diagram). On the left and right walls at the reflection points one web site recommended a horizontal 2'x'4 panel, but my speakers are 45" high. Should they be vertical instead? 2" or 4" OC703?

5. (Not on diagram) In addition the site recommended two 2'x4' ceiling panels directly over the L and R main speakers, PLUS two more centered towards the middle of the room between the loveseat and TV. I've read elsewhere that in a room as small as mine, ceiling treatments are usually not needed. Four panels seems like a lot to me. Ideas?

6. Should the back wall in the closet get any treatments such as bass traps?

7. Do I need any diffusion panels?

Any and all feedback is appreciated. The room has pretty bad slap echo, BTW. Thanks!

1. You could give yourself a little breathing room by going superchunk style.

2. I think most folks would say that in a room that small, Yes, Every little bit on your front wall will help to keep reflect sound from bouncing back from your primary sound source. I'm no (insert title of one who excels at geometry), but it looks like the angles aren't quite right for a centered seating position, but those sitting on the sides will reap the benefits since that would be a first reflection point for you mains and center. 2" should be fine.

3. For the same reasons, I think so. Is you center channel free standing or tucked in an equipment stand? Center channels tend to sound better if they aren't living in a box, but are out in the open, free to breathe.

4. Use the mirror trick to find the First Reflection points for your tweeters and mids at all seating locations. If it takes 2 panels on each wall, make sure you cover them all.

5. I still haven't put up my ceiling panels, so I can't tell you from personal experience, but at the 2007 HES, Richard Bird of Rives Audio cited a study that found that the ceiling was the most important spot to treat. I'd at least hit the Front Reflection for you 3 front speakers and you main seating location.

6. Does the closet have a door? If so, you may actually want to treat the door.

7. I think the rule I was quoted by auralex (I should have written it down) was that you need 4' of space for a 4" skyline diffussor. IF you're going to do diffussion anywhere, it would be on that back wall, but I think most people will tell you that you're probably sitting a little too close. Am I remembering wrong guys?

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

Unless you're going to hire a professional, start with the basic treatments, fire up your system, takes some measurements with a program like REW, and see how it sounds. Then add more treatment, listen and measure some more, and so forth.

Small rooms are nice (I have to say that because I can't afford a big room), but they have more noticeable room modes. Ethan does a great job explaining it all on the real traps site, but it goes something like...in a smaller room, the first mode occurs at a higher frequency, and at less frequent intervals thereafter, making them more noticeable. You're room measurement ratios match almost perfectly one of the recommended ratios of 1:1.26:1.59, so the modes that you do have should be pretty evenly spaced. Still, I'd plan on supplementing your bass traps with an eq like the Behringer BFD.

My local SPI is offering a wrapped panel product. They can wrap most of their panels in GOM 701 for a modest fee. For example, 1 panel of 2x4x2" 703 FRK (foil) costs $8.25. The same panel wrapped with GOM 701 with mounting hardware costs $41.72. Discounts start at orders of 100 or more. The panels are wrapped at their Illinois factory, and then shipped to the local store. They need about 3-5 days lead time. If you interested in buying some inexpensive panels, call up your local SPI store and find out if they have a sample panel you can check out.

1. You could give yourself a little breathing room by going superchunk style.

2. I think most folks would say that in a room that small, Yes, Every little bit on your front wall will help to keep reflect sound from bouncing back from your primary sound source. I'm no (insert title of one who excels at geometry), but it looks like the angles aren't quite right for a centered seating position, but those sitting on the sides will reap the benefits since that would be a first reflection point for you mains and center. 2" should be fine.

3. For the same reasons, I think so. Is you center channel free standing or tucked in an equipment stand? Center channels tend to sound better if they aren't living in a box, but are out in the open, free to breathe.

4. Use the mirror trick to find the First Reflection points for your tweeters and mids at all seating locations. If it takes 2 panels on each wall, make sure you cover them all.

5. I still haven't put up my ceiling panels, so I can't tell you from personal experience, but at the 2007 HES, Richard Bird of Rives Audio cited a study that found that the ceiling was the most important spot to treat. I'd at least hit the Front Reflection for you 3 front speakers and you main seating location.

6. Does the closet have a door? If so, you may actually want to treat the door.

7. I think the rule I was quoted by auralex (I should have written it down) was that you need 4' of space for a 4" skyline diffussor. IF you're going to do diffussion anywhere, it would be on that back wall, but I think most people will tell you that you're probably sitting a little too close. Am I remembering wrong guys?

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

Unless you're going to hire a professional, start with the basic treatments, fire up your system, takes some measurements with a program like REW, and see how it sounds. Then add more treatment, listen and measure some more, and so forth.

Small rooms are nice (I have to say that because I can't afford a big room), but they have more noticeable room modes. Ethan does a great job explaining it all on the real traps site, but it goes something like...in a smaller room, the first mode occurs at a higher frequency, and at less frequent intervals thereafter, making them more noticeable. You're room measurement ratios match almost perfectly one of the recommended ratios of 1:1.26:1.59, so the modes that you do have should be pretty evenly spaced. Still, I'd plan on supplementing your bass traps with an eq like the Behringer BFD.

Thanks for your input.
1. Does the superchunk style have better/worse absorption properties than a typical "hollow" bass trap? I do agree the extra few inches gained might be very valuable.

2. Not sure what angle you are talking about. If you are referencing the front speaker toe-in, I just took a stab at that in the diagram. They might need more/less, and I'm certainly open to suggestions.

3. The center channel will be on a open suspended glass shelf just under the TV, so it will have lots of breathing room.

4. When using the mirror, should I cover any wall area that I see any part of the speaker, or just from the front grill forward?

6. Closet does currently have sliding doors, but I was thinking of taking them out and putting up a sheer curtain so there was more depth behind the listening positions.

7. If I left the closet doors off, there is significant surface area I could put diffusion and it's 4.5' feet from the listening position.

So sounds like 2" of 703 for everything except the bass traps?

My local SPI is offering a wrapped panel product. They can wrap most of their panels in GOM 701 for a modest fee. For example, 1 panel of 2x4x2" 703 FRK (foil) costs $8.25. The same panel wrapped with GOM 701 with mounting hardware costs $41.72. Discounts start at orders of 100 or more. The panels are wrapped at their Illinois factory, and then shipped to the local store. They need about 3-5 days lead time. If you interested in buying some inexpensive panels, call up your local SPI store and find out if they have a sample panel you can check out.

Pardon my ignorance, but who/what is SPI? Google didn't find much for me. Is there a site we can plug in a zip or city to find local dealers?

Pardon my ignorance, but who/what is SPI? Google didn't find much for me. Is there a site we can plug in a zip or city to find local dealers?

http://www.spi-co.com/servicecenterdirectory.cfm

http://www.spi-co.com/servicecenterdirectory.cfm

Anyone work with the one near San Francisco? They really didn't seem interested in my business.

I just called the SF office and talked to Rene. She was actually very helpful and even looked up shipping to San Diego. Her price was $1.50/sqf for Manville 814 and OC703.

http://www.bobgolds.com/InsulationContractors.htm

I was looking at doing OC703 "super chunk" triangles in four corners of my tiny 10x11 HT. I wasn't looking forward to all of the cutting and assembly. I came across the RPG ProCorner system, which is vastly easier to install. Now it's a lot more expensive than just stacking up OC703, but the sound absorption coefficients under 500 Hz are significantly better than what OC publishes for 703.

Are they really that much better, or will 'super chunking' the corners with 17x24" triangles be just as good or better bang for the buck?

I was looking at doing OC703 "super chunk" triangles in four corners of my tiny 10x11 HT. I wasn't looking forward to all of the cutting and assembly. I came across the RPG ProCorner system, which is vastly easier to install. Now it's a lot more expensive than just stacking up OC703, but the sound absorption coefficients under 500 Hz are significantly better than what OC publishes for 703.

Are they really that much better, or will 'super chunking' the corners with 17x24" triangles be just as good or better bang for the buck?
There are free spreadsheets around the internet that allow you to input your room dimensions and get a graph of the room nodes. If your room has a "big" problem in the range which the RPG is superior, then perhaps it is worth more. But the SSC traps are darned good for a darned good price.

Wait for the pros, though, to answer! :)

I was looking at doing OC703 "super chunk" triangles in four corners of my tiny 10x11 HT. I wasn't looking forward to all of the cutting and assembly. I came across the RPG ProCorner system, which is vastly easier to install. Now it's a lot more expensive than just stacking up OC703, but the sound absorption coefficients under 500 Hz are significantly better than what OC publishes for 703.

Are they really that much better, or will 'super chunking' the corners with 17x24" triangles be just as good or better bang for the buck?

One cannot compare the raw material spec (OC703) with a device spec. The size and configuration makes all the difference! Check the "SuperChunks" device measurements here:
http://forum.studiotips.com/viewtopic.php?t=536

Generally, an open-cell foam product will not outperform semirigid fiberglass of the same shape and dimensions.

Regards,
Terry

OK all you acoustic DIYers...a couple of panel questions... I want to make some panels out of 2'X4'X2" thick OC 703 or 705. If I simply wanted to wrap the panels in GOM and mount to my walls, would the 703 be rigid enough for that or should I go 705? Also how would I achieve a beveled edge look to the the panels. Not quite sure how to cut that or what tool(s) would be best? I would think that my table saw would just tear it up. Thanks in advance..

OK all you acoustic DIYers...a couple of panel questions... I want to make some panels out of 2'X4'X2" thick OC 703 or 705. If I simply wanted to wrap the panels in GOM and mount to my walls, would the 703 be rigid enough for that or should I go 705? Also how would I achieve a beveled edge look to the the panels. Not quite sure how to cut that or what tool(s) would be best? I would think that my table saw would just tear it up. Thanks in advance..
I doubt that either are rigid enough to do what you ask, especially the 703. Most of us make or buy frames, brackets, etc for our fiberglass panels. For cutting and/or sculpting, a cheap electric carving knife works quite well. But again, it is not rigid enough to bevel and have that bevel still be a bevel after stretching cloth over it. Commercial panel makers chemically harden (google it) the edges so that bevels and such are maintained after covering.

OK...than what type of rigid fiberglass is used in the panels you can get from bpape and Sensible Sound Solutions? Here is the link:

http://sensiblesoundsolutions.com/product_info.php?cPath=21&products_id=42

It appears to be some sort of figid fiberglass with GOM over it. That is what I am going for. Is this a different type of fiberglass panel?

OK...than what type of rigid fiberglass is used in the panels you can get from bpape and Sensible Sound Solutions? Here is the link:

http://sensiblesoundsolutions.com/product_info.php?cPath=21&products_id=42

It appears to be some sort of figid fiberglass with GOM over it. That is what I am going for. Is this a different type of fiberglass panel?
Without speaking for either of the companies you mention, I'll reiterate that any frame-less covered fiberglass panels of 703/705 with a (distinct and well-defined) beveled edge has been chemically hardened to maintain the shape. And it is to be expected that a vendor would not be too specific on how they make their products.

If you follow the link in my sig and go to the pages on building absorbers (starting at pg 16) you will see how to get an edge profile without messing with chemicals. I've applied an eased edge, but could have just as easily beveled it.

Thanks...I'll check it out for sure. I may end up just contacting bpape and having him set me up with some panels that look professionally done. They look great and mine as of now do not.

Thanks...I'll check it out for sure. I may end up just contacting bpape and having him set me up with some panels that look professionally done. They look great and mine as of now do not.
Reason #1 to buy commercial solutions. :)

BTW...I saw your panels. Very nicely done, but I just don't want to go to that much trouble.

BTW...I saw your panels. Very nicely done, but I just don't want to go to that much trouble.
Reason #2 why to buy commercial solutions. ;)

OK...plan B...

The custom panels are just a little too pricey for me. I was thinking of framing up basically a 4'X8' frame on the walls and than placing two layers of Linacoustic in them. Would that work? I am only looking to treat the walls as reflection points to deaden the room a little more. I am not looking to address bass with these. Would this be an effective solution for that? To finish it up I would stretch my left over speaker cloth from Parts Express over it and glue and staple that. Than cover the edge and staples with some finish grade molding.

OK...plan B...

The custom panels are just a little too pricey for me.
Reason #1 to DIY absorbers. :D

(And) why I was thinking of framing up basically a 4'X8' frame on the walls and than placing two layers of Linacoustic in them. Would that work? I am only looking to treat the walls as reflection points to deaden the room a little more. I am not looking to address bass with these. Would this be an effective solution for that? To finish it up I would stretch my left over speaker cloth from Parts Express over it and glue and staple that. Than cover the edge and staples with some finish grade molding.
At this point you should go to Bob Gold's wonderfully informative absorption coefficients (http://www.bobgolds.com/AbsorptionCoefficients.htm) and research the materials typically used for absorbers. I don't know a thing about your room, but unless it's huge, 4x8 absorbers on the walls seems really big. It's really easy to over dampen a room, and more absorption can be added later if needed. And, with that same thinking, if you are already absorbing highs and mids, you should go for as much LF absorption as is practical. As opposed to highs and mids, nearly all rooms (in homes) need bass trapping, so you might as well go low there, too, as separate traps added elsewhere later will also suck out highs and mids.

OK...plan B...

The custom panels are just a little too pricey for me.

The cheapest I've see is from SPI. My local one quoted me $41.72 for a GOM 701 wrapped 703 FRK 2'x4'x2".

The cheapest I've see is from SPI. My local one quoted me $41.72 for a GOM 701 wrapped 703 FRK 2'x4'x2".

SPI?? I Googled them and couldn't find anything. Do you have any more info.

Also pepar...I have addressed bass some already but I am not done. I have LOADS of 6lb Roxul mineral wool in the front corners behind the screen wall as well as several 2X4X4" Roxul batts on the floor behind the screen in the corner of the floor and back wall. See pic...
http://i45.photobucket.com/albums/f71/jandawil/btrap.jpg
I will also hang a few 4" thick pannels on the back wall spacing away from the wall some to help more with bass. The bass traps I have already added have helped a ton. My room is 16' by 21' so it's decently big. The 4X8 panel would cover maybe 1/4 of the two side walls so that would still leave a lot of wall. If you or others think that is too much I will certainly heed you warnings.

Also pepar...I have addressed bass some already but I am not done. I have LOADS of 6lb Roxul mineral wool in the front corners behind the screen wall as well as several 2X4X4" Roxul batts on the floor behind the screen in the corner of the floor and back wall. See pic...

I will also hang a few 4" thick pannels on the back wall spacing away from the wall some to help more with bass. The bass traps I have already added have helped a ton. My room is 16' by 21' so it's decently big. The 4X8 panel would cover maybe 1/4 of the two side walls so that would still leave a lot of wall. If you or others think that is too much I will certainly heed you warnings.
Again, I would size first reflection point absorbers as small as possible to get the job done. Do the mirror trick, or think of bank shots in pool. Just an observation - from your pic, your right speaker pretty much "sees" only the Roxul to it's left. As such, your first reflection point absorber on the left is already in place. And another observation is that I'd toe-in the speaker so that it aims at the geographical center of the audience.

The cheapest I've see is from SPI. My local one quoted me $41.72 for a GOM 701 wrapped 703 FRK 2'x4'x2".


$41.72??????? are you sure on that?? We offer GOM on our GIK242 panel ($54.99) for a $30.00 upcharge and that pretty much just covers the fabric. :confused:

Glenn

I will also hang a few 4" thick pannels on the back wall spacing away from the wall some to help more with bass. The bass traps I have already added have helped a ton. My room is 16' by 21' so it's decently big. The 4X8 panel would cover maybe 1/4 of the two side walls so that would still leave a lot of wall. If you or others think that is too much I will certainly heed you warnings.

That is a great idea but just make sure you build them so the backs do not have a solid piece of wood (or anything solid) covering the back. I saw pepar's build and did see a hard back, which would not work for spacing off the wall.



Glenn

That is a great idea but just make sure you build them so the backs do not have a solid piece of wood (or anything solid) covering the back. I saw pepar's build and did see a hard back, which would not work for spacing off the wall.
True, Glenn. I didn't want them encroaching into the room any more than necessary, so they are flat-mounted. Also, I was not looking for enhanced LF absorption preferring instead to install bass traps for that.

That is a great idea but just make sure you build them so the backs do not have a solid piece of wood (or anything solid) covering the back. I saw pepar's build and did see a hard back, which would not work for spacing off the wall.



Glenn

That was my plan..

pepar...why I was thinking 4X8 because some very good HT's here cover the entire lower half of their wall in Linacoustic and GOM. My coverage would be less than that. Not sure how much is "too dead".

$41.72??????? are you sure on that?? We offer GOM on our GIK242 panel ($54.99) for a $30.00 upcharge and that pretty much just covers the fabric. :confused:

Glenn

Hey myfipe....I just went to your website and saw your panels...what do you use rather than GOM. They look pretty good.

That was my plan..

pepar...why I was thinking 4X8 because some very good HT's here cover the entire lower half of their wall in Linacoustic and GOM. My coverage would be less than that. Not sure how much is "too dead".
I have the lower half of my room covered with "wall" carpet, the cavity behind my false wall lined with 2" Linacoustic and strategically sized/placed absorbers of 2" OC SelectSound Black and I think my room is too dead. If I were building it today, I'd skip the carpet around the perimeter and keep the carpet on the front right and left walls for light control. YMMV.

If you're going to DIY and want a beveled edge, a perimeter frame is almost mandatory. For frameless, it's OC705. The 703 simply will not hold up to getting the cloth stretched tight enough to look decent. As was stated earlier, to treat the edges with a detail, they are chemically resin hardened to hold that shape and around the perimeter to withstand the cloth stretching without crushing.

In all honesty, while a bit more work, I'd rather see you do 3 2'x4'x2" panels with a bit of space between them. It's not all about coverage, it's about getting a good distribution of the absorbtion also.

Bryan

If you're going to DIY and want a beveled edge, a perimeter frame is almost mandatory. For frameless, it's OC705. The 703 simply will not hold up to getting the cloth stretched tight enough to look decent. As was stated earlier, to treat the edges with a detail, they are chemically resin hardened to hold that shape and around the perimeter to withstand the cloth stretching without crushing.

In all honesty, while a bit more work, I'd rather see you do 3 2'x4'x2" panels with a bit of space between them. It's not all about coverage, it's about getting a good distribution of the absorbtion also.

Bryan

Would 1" linacoutic work for that. I was thinking of building 1" frames and using the linacousic inside. What would be the difference practically speaking between 2" 703 and linacoustic. Obviously there would be no bass or broadband absorbtion, but for early reflections would that work. I am just looking to deaden the room a bit more.

I'd need to know what else is in the room to know what's appropriate. The 2" will extend significantly lower - well into the male vocal range (low hundreds). The idea is to keep the room balanced. Just deadening highs more may not be preferable without some lower absorbtion also depending on what the balance is right now.

Bryan

I'd need to know what else is in the room to know what's appropriate. The 2" will extend significantly lower - well into the male vocal range (low hundreds). The idea is to keep the room balanced. Just deadening highs more may not be preferable without some lower absorbtion also depending on what the balance is right now.

Bryan
As someone who has installed a lot of wall carpet in my room and now has a dead, but boomy room, I can attest to this. Use the 2".

As someone who has installed a lot of wall carpet in my room and now has a dead, but boomy room, I can attest to this. Use the 2".

You have 7,142 posts here yet you put carpet on your walls anyway? :D

You have 7,142 posts here yet you put carpet on your walls anyway? :D
I know exactly what you mean, Ethan, . . . NOW. But that was 7000 posts ago. :o

I can at least serve as a bad example.

I see some walls of the theaters in here completely covered in GOM ( or equivalent ) with acoustic insulation underneath ... wont these rooms be referred to as " dead "

I am in the framing/rough-in stage of my theater now and am a bit unclear as to what direction to take


I can add corner traps at the front and was was considering linocoustic ( or equivalent ) on the walls/ceiling ... this would be my preference as I can then use fabric/trim only for the finishing of the room

Room is 23'5" X 14'5" X 8'6"

Thanks for any advice

I see some walls of the theaters in here completely covered in GOM ( or equivalent ) with acoustic insulation underneath ... wont these rooms be referred to as " dead "?
Are you certain that underneath all of the GOM is insulation? There are panelized systems of acoustical treatments that, when installed, give the appearance of entirely GOM'd walls. These panels are either absorbers, diffusors or reflectors, but all look the same. Could this be what you saw?

Are there any guidelines for adding soffits for bass absorption (dimensions, amount/type of aborption material, etc)?

My room is 26' x 19.5' x 9.2'. I would like to add soffits all around that come out 2' from the walls and drop about 10" from the ceiling. My plan is fill the space by stacking 703 or 705 panels with FRK facing on the outer surfaces to minimize high frequency absorption. Should I stack as many of the heavier panels as I can, or is there a point where the diminishing returns aren't worth the added cost?

Thanks,
Darrell

Are you certain that underneath all of the GOM is insulation? There are panelized systems of acoustical treatments that, when installed, give the appearance of entirely GOM'd walls. These panels are either absorbers, diffusors or reflectors, but all look the same. Could this be what you saw?


Well then lets not dispute whether ALL the walls have acoustic absorption and take a look at my future theater room using the first reflection program from this forum

The room will have a 7.1 surround system ... what would be the suggestion for acoustic absorption/diffusors/reflectors in this case ? ( also assuming all walls/ceilings covered with a GOM type fabric )

http://i42.photobucket.com/albums/e301/Buk_A_neer/HTROOM.jpg

When calculating the reflections, don't forget the 2nd row. Not only is this another set of reflections off the side walls in the length dimension, but if it's on a riser, it will also have that set up higher than the first set due to higher seated ear position in the rear.

Based on that drawing, the acoustic center of those speakers appears to be very low in comparison to the screen image.

Bryan

When calculating the reflections, don't forget the 2nd row. Not only is this another set of reflections off the side walls in the length dimension, but if it's on a riser, it will also have that set up higher than the first set due to higher seated ear position in the rear.

Based on that drawing, the acoustic center of those speakers appears to be very low in comparison to the screen image.

Bryan

It maybe a little difficult to see in that picture but there are 2 rows of seats illustrated there in green.

Also I was considering a stage which would raise the height of the main speakers

However ... assuming it all remained as is ... from what I have read using linocoustic under the GOM in those early reflection points

what would you suggest to use in the areas that are not highlighted as a first reflection point ? cotton batting ?

Well then lets not dispute whether ALL the walls have acoustic absorption and take a look at my future theater room using the first reflection program from this forum

The room will have a 7.1 surround system ... what would be the suggestion for acoustic absorption/diffusors/reflectors in this case ? ( also assuming all walls/ceilings covered with a GOM type fabric )
Missing from your way cool model is the reflections from the back wall. The biggest difference in my room occurred when I added the rear wall absorber. There's some disagreement about lateral reflections, but I'm still confident about recommending the rear wall and front ceiling with 2" 703 (or equivalent). And placing a heavy rug in the front floor area.

Actually I do have those reflections in the model ( just cant see from that angle;) ) they occur mostly below chair rail height

What you do in the areas not showing reflections depends on what else is done in the room, the room construction, number and type of seating, number of people, etc. All of those things act on the decay in the room. I'm personally not a big fan of batting. It looks nice but it offers only high frequency absorbtion and filling all the rest of the wall surface with that IMO skews the decay curve to being too dead up high.

Bryan

My plan is fill the space by stacking 703 or 705 panels with FRK facing on the outer surfaces to minimize high frequency absorption. Should I stack as many of the heavier panels as I can, or is there a point where the diminishing returns aren't worth the added cost?


In general, more is better.

What is FRK facing?

Finishing drywall in small home theater; intend to put 1" insul-shield on the front and on the bottom 44" of the sides, with batting above. I want to cover it all with fabric, probably a deep red or burgundy.

Any recommendations for fabric and a fabric source for this purpose?

Is GOM fabric appropriate and cost-effective for this purpose?

Thanks -

jchretien4

What you do in the areas not showing reflections depends on what else is done in the room, the room construction, number and type of seating, number of people, etc. All of those things act on the decay in the room. I'm personally not a big fan of batting. It looks nice but it offers only high frequency absorbtion and filling all the rest of the wall surface with that IMO skews the decay curve to being too dead up high.

Bryan


Although not shown in that diagram ... I want to build a enclosure for the sub and center channel up front and also enclose the side speakers with Roxul in the front corners ( behind the side speakers and also behind the sub/center channel )

There are 2 rows of 4 Coaster studio seats 12' and 18' from the screen and the room size is 23'5" X 14'5" X 8'6" ... resilient channel on walls and ceiling with double drywall , 136" Carada BW 237:1 Scope screen and a HD80

all the other walls/ceiling I would like covered in fabric

It will be a 7.1 Axiom speaker system ( 2 X M80 mains, 1 X VP150 center, 2 X QS8 surround, 2 X QS8 surround rears & EP600 sub )

so I assume using 1" linocoustic on those first reflections would work but if batting would deaden the sound too much then what could I use in lieu of batting to keep the areas without linocoustic the same 1" depth so it all looks smooth when covered in fabric ?

In general, more is better.

What is FRK facing?

FRK is a foil like covering on one side of the panel that reflects higher frequencies but still allows low frequencies to be absorbed. Compare the absorption coefficients for same density and thickness panels on this webpage:

http://www.bobgolds.com/AbsorptionCoefficients.htm

-Darrell

Interesting. I guess I can see why one would worry about too much high frequency absorption.

But I assume you will have to cover the FRK with something else? Fabric?

Interesting. I guess I can see why one would worry about too much high frequency absorption.

But I assume you will have to cover the FRK with something else? Fabric?
Well, yes, and it must be acoustically transparent so that the sound can get through it to be absorbed.

So is that what you guys are using in areas outside of first reflection points is a FRK faced insulation ?

Well, yes, and it must be acoustically transparent so that the sound can get through it to be absorbed.

Do you mean acoustically permeable? Transparent would be important covering a speaker, but covering a treatment it wouldn't matter so much whether it is absorbing some and transmitting some through to the insulation beneath, right?

Do you mean acoustically permeable? Transparent would be important covering a speaker, but covering a treatment it wouldn't matter so much whether it is absorbing some and transmitting some through to the insulation beneath, right?
This has come up before and perhaps it's semantical, but to be precise, whether the sound is absorbed by the covering itself or passed through for absorption by the 'glass underneath doesn't matter. So the cloth covering really only needs to not be reflective. Personally, though, the GOM FR701 Style 2100 I used to cover my false wall - with speakers behind it - is also covering my absorbers. It was just simpler that way.

FSK facing is NOT used on panels where you're trying to address first and early reflections. You want those to absorb all the way up.

The FSK is useful when you need to add some additional bass/low mid absorbtion without overdoing the highs. Rear corners, soffits, LOW lower portions of side walls, etc. are places where this can be effective.

Bryan

Here is a better shot of the first reflections using the first reflection program from jeffreylebowski

http://www.avsforum.com/avs-vb/showthread.php?t=822273&highlight=reflection+program

no suggestions as to what to cover the remaining walls ? ... it sounds from Bryan's response that a FSK facing may be used in the areas outside the first reflection points but possibly not ALL those surfaces ... is that correct ? ... should I wait till the room is complete to determine what to cover the remaining walls ?

http://i42.photobucket.com/albums/e301/Buk_A_neer/bsmt3.jpg

Here is a better shot of the first reflections using the first reflection program from jeffreylebowski

no suggestions as to what to cover the remaining walls ? ... it sounds from Bryan's response that a FSK facing may be used in the areas outside the first reflection points but possibly not ALL those surfaces ... is that correct ? ... should I wait till the room is complete to determine what to cover the remaining walls ?
Here is what I would do based on my own experience. (Visit my link.) First, I would cover, as precisely as possible, the first reflection points of the three front speakers. I would use 2" of OC 703 (or equiv.) Next I would install bass traps Studio Superchunks-style. The more two-surface junctions you can do, the better. Aesthetics will no doubt be a limiting factor, but all four corners would be good - floor to ceiling. And then I would listen to the room/system. If you have the know-how, use one of the freeware/shareware programs, like Room EQ Wizard, and a mic and do some testing. From this you can decide whether or not you need any further treatments.

If nothing else, my stepping up to post this may cause the real acoustical experts to chime in! :)

Here is what I would do based on my own experience. (Visit my link.) First, I would cover, as precisely as possible, the first reflection points of the three front speakers. I would use 2" of OC 703 (or equiv.) Next I would install bass traps Studio Superchunks-style. The more two-surface junctions you can do, the better. Aesthetics will no doubt be a limiting factor, but all four corners would be good - floor to ceiling. And then I would listen to the room/system. If you have the know-how, use one of the freeware/shareware programs, like Room EQ Wizard, and a mic and do some testing. From this you can decide whether or not you need any further treatments.

If nothing else, my stepping up to post this may cause the real acoustical experts to chime in! :)

All good advice ... thanks ... I did d/l the wizard proggy a little while back now that I think about it ;) ... I will plug away at finishing the room/basement and then revisit this topic once I can test the results

I did a search on Acoustiblok in this forum and I really didnt find the good or bad. Anyone ever use it? Worth the time and trouble? Their demo at CEDIA Denver was impressive.

We are considering being a dealer and installer for them. Of course, I like others opinions here first.

THanks!

Just a thought, Justletmein, that your chairs and listeners will block the sound getting directly to the rear wall . . .

All good advice ... thanks ... I did d/l the wizard proggy a little while back now that I think about it ;) ... I will plug away at finishing the room/basement and then revisit this topic once I can test the results
I think your take away here should be that it's very easy to over-dampen a small room, and care needs to be taken to absorb sound as evenly as possible at all frequencies.

Exactly. You're not going to get an exact answer without doing a full analysis of the space. For the basics:

Front corners - broadband bass control.

Front wall - dead broadband 100% coverage.

Side walls - reflection coverage.

Balance - depends on desired room finish and a ton of other options. You can use some online calculators to determine what your target decay curve SHOULD be for your usage and then use REW as a free tool to measure what you actually have.

The other option is to hire someone to do the design for you.

Bryan

Front wall - dead broadband 100% coverage.



I think this must have been discussed somewhere but I haven't come across it.

If a front wall is otherwise covered with all absorption panels other than the screen, how much difference is there between:

1) AT screen with absorption behind it
2) non AT screen with absorption behind it (I presume higher freqs would tend to reflect off the screen, but mid-lower freqs would be absorbed).
3) non AT screen mounted traditionally against the drywall

And assume an average HT front wall is 14 x 8 = 112 sq feet; and an average 106" screen @ 4.33 x 7.66 = 33.22 sq feet. So the screen makes up 30% of the front wall.

It seems than 1) would be ideal, but how much worse is 2) or 3)?

It all depends on your situation. I don't mean to sound like a broken record but every room and every situation is different.

Most non AT screens have a gap behind them that will allow maybe some 1" absorbtion even when mounted flush frame to wall. Yes - the highs will still reflect (nothing you can do about this) - but - the mids (vocal range) will still be absorbed and help to focus things to the screen even more.

Bryan

Interesting. I forgot that I had previously read another view which was:

"If the screen is not micro-perforated, then it's not worth putting fiberglass behind. The solid screen would reflect frequencies above a few hundred hertz. But below this frequency, the absorption ability of even 3 inches of fiberglass falls off significantly. So you'd end up with an absorber peaking at a few hundred hertz."

from this same thread at: http://www.avsforum.com/avs-vb/showthread.php?p=5359089#post5359089

Presumably creating a hole in the mid freqs that pass the screen and are absorbed behind it? But it's just 30% of the wall, and probably some high freqs would pass the screen and be absorbed?

Anyone have any direct experience with trying it both ways? Absorber behind a non AT screen and not? Or replacing a non AT screen with an AT screen?

Interesting. I forgot that I had previously read another view which was:

"If the screen is not micro-perforated, then it's not worth putting fiberglass behind. The solid screen would reflect frequencies above a few hundred hertz. But below this frequency, the absorption ability of even 3 inches of fiberglass falls off significantly. So you'd end up with an absorber peaking at a few hundred hertz."

from this same thread at: http://www.avsforum.com/avs-vb/showthread.php?p=5359089#post5359089

Presumably creating a hole in the mid freqs that pass the screen and are absorbed behind it? But it's just 30% of the wall, and probably some high freqs would pass the screen and be absorbed?

Anyone have any direct experience with trying it both ways? Absorber behind a non AT screen and not? Or replacing a non AT screen with an AT screen?
I think that there are two things going on here. First, that some recommend fully treating the front wall a la the Live End Dead End philosophy. And second, that the cavity behind a false wall and AT screen should be fully treated so as to reduce/eliminate comb filtering. I happen to follow both myself.

edit: I even have sculpted a 2" 'glass "mask" for the center speaker.

pepar:

I don't know if treating the front wall qualifies for "Live End Dead End".
a) what if one treats the back wall too? Is that DeadEndDeadEnd.
b) the reason for treating the front wall is that with 7.1 we can get a lot of artificial ambiance from multiple speakers, but for films we're more paranoid about imaging (I'm not suggesting anechoic chambers).
c) the front wall treatment usually tends to be a bit thin (HF absorption) for what I think of as "Dead End", at least from what I remember of Don and Carolyn Davis's LEDE invention. I think they really wanted to kill an end (more than a wall). As opposed to Non-Environment where they want to kill 3 walls and 1 ceiling -- which I believe is probably not a good idea for home theatre.

And second, that the cavity behind a false wall and AT screen should be fully treated so as to reduce/eliminate comb filtering. I did some measurements of that somewhere....
http://www.bobgolds.com/SmX720/20060708/home.htm

I even have sculpted a 2" 'glass "mask" for the center speakerDid you measure what that did to your speaker? I found that it turned my very nice speaker into a not so nice one. See "The rockwool baffel" on the same page.

Did you measure what . . (the 2" glass mask) . . did to your speaker? I found that it turned my very nice speaker into a not so nice one. See "The rockwool baffel" on the same page.
I really meant sculpted. The holes around the drivers were beveled at a 45 degree angle so the drivers could "see" a very wide angle. Test it? No, I didn't, but I took the precaution I just mentioned. I applied the mask at the recommendation of John Dahl.

pepar: sorry. link repaired.

BTW, when I put together my living room plasma setup, I elected not to have the edges of my speakers near anything. Seemed more idiot proof.
http://www.bobgolds.com/LivingRoomPlasma/Construction/home.htm
YMMV - especially with speakers behind an acoustically transparent screen.

pepar: sorry. link repaired.

BTW, when I put together my living room plasma setup, I elected not to have the edges of my speakers near anything. Seemed more idiot proof.
http://www.bobgolds.com/LivingRoomPlasma/Construction/home.htm
YMMV - especially with speakers behind an acoustically transparent screen.
Thanks, I'm there now . .

pepar: sorry. link repaired.

BTW, when I put together my living room plasma setup, I elected not to have the edges of my speakers near anything. Seemed more idiot proof.
http://www.bobgolds.com/LivingRoomPlasma/Construction/home.htm
YMMV - especially with speakers behind an acoustically transparent screen.
Was there a "conclusion" to your AT screen distance from speaker test? It looked like the greater the distance, the less there was an effect on response.

BTW, here's my sculpted 'glass mask.

http://peparsplace.com/assets/images/HT_221.jpg

pepar:

Was there a "conclusion" to your AT screen distance from speaker test? It looked like the greater the distance, the less there was an effect on response.

True, but there's a diminishing returns. I don't remember the officially accepted distance, but 6" to 8" rings a vague bell. (i.e. speaker distance behind AT screen)
The discussion, and conclusions, were over at Rubin's SMX forum.

Hi all

I am setting up a dedicated HT space in my basement, however it is a rental so I cannot do too much modification. My front wall has a window behind the screen, and also a heavy metal-framed exterior door to the left of the screen. I am looking for advice on proper acoustical treatment.

Kit and dimensions first:

I am using an Onkyo 705 receiver to power an Aperion 5.1 setup with the 10" Sub, 533-VAC center, two 533-T towers, and a pair of 422-LR sats for surround. For picture I am projecting a Sharp XVZ-12000 MKII onto a 106" Greywolf.

My screen wall is 17'W x 8'H. The seating position is about 15' from the wall, on a 10' wide couch.. The two side walls are blank. Behind the seating there is another 8' of open space then the basement narrows to a 20' long 6' wide corridor. There is no rear wall as such, because there are wooden slatted doors to one side of the corridor and a large metal spiral staircase on the other side

The front wall contains a 7'H x 3'W door that is set 18" in from the left wall, and a 5' W x 42" H window 1' in from the door and 1' down from the ceiling; the window is recessed 8".

Because of the door placement, my screen is 4" off-center on the front wall, and the towers will need to at least 3' in from the front wall in order to allow the door to be opened. The screen (not AT) will cover the window completely.

The center will be be mounted on a 18" stand about 1' away from the screen wall, and the sats will most likely be on stands.


THANKS TO ANYONE WHO HAS WADED THROUGH ALL THAT!!! NOW TO THE QUESTIONS!

I have read up on acoustical treatment, but have never worked with it. My questions are:

1) I hear it is important to treat the screen wall. I am concerned due to the door and window that it will be harder to treat, and cause weird sound artifacts. Will it be enough to put a fabric curtain on the window and the door's glass panel, or should I be treating the rest of the wall with foam? Do I not even need to worry about treating the window as it is behind the screen and I have no rear wall reflecting anything?

If I don't want to cover the whole wall with foam because of aesthetic issues (my wife's more than mine), does it make sense particularly to treat behind the speakers??

2) What is the minimum suggested treatment for the side walls? Floor to ear-height, 2 foot wide covering on the primary reflection points for each of the 3 speakers on each wall? Or is that total overkill and I should set up the system and see what the issues are before I order any foam?

3) Given that my towers will be a few feet in diagonally from the room corners, does having corner bass absorbers help?

(The foam I was looking at was the 2" wedge foam from foambymail)

Thanks for comments on these questions, and any pointers that could suggest a different way of looking at this... I am here to learn.

Thanks

Alex

In general, foam is an inferior product. The Foam By Mail is pretty worthless. They've been caught putting up cheap products for sale and then copying Auralex's specs to their site and touting them as their tested results. I'd stay way away from any company with those kinds of business ethics.

The front wall should be treated fully. Not sure what you mean about no rear wall reflecting.

Side walls need to be addressed minimally for early reflections and then again to finish bringing general decay times into line for the room volume and usage.

Bryan

Thanks bpape. Will steer clear of FBM... what should i use instead that works but is cheap? In terms of fully treating the front wall, with a big door and a recessed window does that mean treating the wall around those, or should i be concentrating on treating those spaces?

i said no rear wall reflecting bc there is to all intents and purposes no single rear wall to the space - a third of the wall is slatted wooden doors at 25' away that will diffuse sound, a third is 50' away at the end of a corridor and a third is an irregularly shaped large spiral staircase at 25' with no flat surface.

Thanks again

Alex

In general, foam is an inferior product. The Foam By Mail is pretty worthless. They've been caught putting up cheap products for sale and then copying Auralex's specs to their site and touting them as their tested results. I'd stay way away from any company with those kinds of business ethics.

The front wall should be treated fully. Not sure what you mean about no rear wall reflecting.

Side walls need to be addressed minimally for early reflections and then again to finish bringing general decay times into line for the room volume and usage.

Bryan

Just so I understand... would you say don't use even Auralex foam? Or just steer clear of FBM?

In general, foam is an inferior product. The Foam By Mail is pretty worthless. They've been caught putting up cheap products for sale and then copying Auralex's specs

Bryan

Auralex is good stuff, FBM is not, Fiberglass is better than both.

A picture is worth a thousand words, and as much as it will pain you, you should probably start at the beginning of this thread.

I have a rental, non-dedicated space, and for $300, was able to DIY 12 2x4 panels that hang to the wall with a french cleat system, 2 3/8" holes in the wall for each. A little spackle and paint when I move out, and voila.

1) I would be good to see a picture. You may opt to reverse your room by 180 degrees to have the window and door at your back. Curtain both with light blocking fabric.

2) You can accomplish a lot with 2x4 panels, you don't need to go all the way to the floor, assuming that you have other absorption in the room (carpet or rugs, soft furniture).

3) Ethan will tell you that you'll need bass traps. The rest of us would probably say that you'll want bass traps :)

Eugo hit it. IF you must do foam, use Auralex. However, for the same or less money, you can use OC703 or an equivalent or even cheaper is mineral wool (though a PITA to work with IMO) both of which inch for inch are a better solution.

Cover as much of that wall as you can. User THICK curtains over the window. A door is a door - not much you can do but put a panel on it.

Bryan

I was going to go with some Auralex bass traps in the corners of my room. I have done testing and thats where the problems seem to be. In the rear of the room I do not hear a breeze going by like I do standing in the front of the room. That may have something to do with the bass traps I added to the rear speakers area by adding holes to it lining it with some fiberglass insulation and covering it in the same outdoor carpet as the rest of the room. I have my sub pointing at my screen across the room and I plan on putting a 2nd sub under my center channel. I was thinking some framed fiberglass and then some cloth at the store would help tame the midrange and possibly address some of the standing waves I have as a result of the big woofers in my mains I think. I would also use those as diffusers and the same for the rear row in my room. I am supposed to do something to the front of the room but I have not figured out what exactly. I have been reading and testing the room as fast as I can. I think I may have around $1000.00 or so to spend. If anyplace took payments for their products over a time period that would also help. I had it picked out but it has been so long in my build I lost the kit I had picked out. There are more details in the theater build thread and specifically on this page. (http://www.avsforum.com/avs-vb/showthread.php?t=717629&page=13) I have some wood working experience not much though. I have a heated garage to work in and I could rent tools if I needed. Whatever works best without being a waste of money is what I am interested in. If anything is unclear or if I am going to fast just let me know.

For $1k budget and DIY skills, you can go a LONG way toward a total room treatment solution.

Bryan

For $1k budget and DIY skills, you can go a LONG way toward a total room treatment solution.
Indeed, DIY is a huge "force multiplier." :)

Indeed, DIY is a huge "force multiplier." :)

Yes, I bought 256sqft of 2" 3Lb Fibre glass insulation, plus a crapload of GOM fabric for about $700. That's enough for 4 super chunk corner bass traps, and several wall/ceiling panels.

Thrown in a turkey carving knife, Velcro, a little molding, Roto fasteners, and I'm set!

I can only fit 12" diagonal across the corners of the room. Do you recommend something on the top of the sides of the room also then? Is treating only a partial amount of the front wall ok? It is important to mention that my ceiling acts like diffusers on the sides and that the rest is also PVC ceiling tile but it is not as rigid.

Eidt: Or rather they are more rigid type of an abortion of lower frequencies I mean. Can I put carpet on the front wall to make it soft with some padding?

Yes, I bought 256sqft of 2" 3Lb Fibre glass insulation, plus a crapload of GOM fabric for about $700. That's enough for 4 super chunk corner bass traps, and several wall/ceiling panels.

Thrown in a turkey carving knife, Velcro, a little molding, Roto fasteners, and I'm set!

Velcro? Where?

I see... for the panels to the wall you are saying. I agree it looks safer that way. Alright thank you I think I got the list now.

Edit: There was some miscommunication on my end. I should have taken more time making the list. I'm not really interested in building one panel a week. Save $ up then build. I see a whole room treatment at one time being best so I will wait.

The 12" diagonal will still help - though I'd build them solid as opposed to straddling some 4". Just remember that not only are you losing surface area, but you're also losing depth of the absorber (ability to absorb deeper frequencies) so additional treatments elsewhere can make up for part but not the other.

Bryan

Do I still need to treat the front wall if my mains will be away from the wall?

The way I understand it, I don't need to?

Do I still need to treat the front wall if my mains will be away from the wall?

The way I understand it, I don't need to?

Nevermind I figured it out.

Thank you Bryan I will look at some columns today.

The 12" diagonal will still help - though I'd build them solid as opposed to straddling some 4". Just remember that not only are you losing surface area, but you're also losing depth of the absorber (ability to absorb deeper frequencies) so additional treatments elsewhere can make up for part but not the other.

Bryan

Could you specifically describe for us what material needs to be in the corners please?

Edit: Never mind we understand what you mean about solid. I argued with the crew to make them solid before but they would not go to get more insulation.

Could you specifically describe for us what material needs to be in the corners please?
Owens Corning 703, or equivalent.

Could you specifically describe for us what material needs to be in the corners please?

I'd bet money that this is mentioned a dozen times in this thread, but you need mineral wool or rigid fiberglass. OC703 is the most common choice.

Look for a material with high numbers in the 125HZ column here: http://www.bobgolds.com/AbsorptionCoefficients.htm

I'd bet money that this is mentioned a dozen times in this thread, but you need mineral wool or rigid fiberglass.
You'll not find anyone to give you odds on that. :)

Sorry. See the edit above. I think Bryan thought I meant to have my bass traps partially filled. :o

Could you specifically describe for us what material needs to be in the corners please?

Edit: Never mind we understand what you mean about solid. I argued with the crew to make them solid before but they would not go to get more insulation.
Did "the crew" not work for you? :confused: :) ;)

I am looking to use Roxul 60 for my bass traps. The guy I spoke to at the supplier said that some people are chopping the Roxul 60 into 2' right triangles and stacking them floor to ceiling rather than just fixing them across the corner in order to build the bass traps.

Three questions for the esteemed panelists ;-)

1) Cost and time aside, does it make sense to do this? Will a corner with essentially 14" deep of absorbing material be more effective as a trap than 4" deep with air behind? (This may seem like a silly question but this is not always intuitive, and I want someone here to confirm)

2) The Roxul is pretty cheap so if its worth it I don't mind the addnl cost - but I have heard it is a pain to cut - any tips or comments?

3) Finally, is the Roxul really a good alternative to the OC 705 for this purpose?


Thanks and have a nice day!

Alex

1) Cost and time aside, does it make sense to do this? Will a corner with essentially 14" deep of absorbing material be more effective as a trap than 4" deep with air behind? (This may seem like a silly question but this is not always intuitive, and I want someone here to confirm)
Alex

I'm no acoustical expert, but this last week I just got done installing two "super chunk" bass traps using OC703 material. Each triangle is 17" along the wall and a 24" room-facing side. I was told this was a better solution than 4" of 2'x8' material stacked in the corner with air behind.

To be clear - I have a sub-$2k system, with an Onkyo-705 powering an Aperion S10 subwoofer - enough to make a little noise, but not huge or high-end... so please comment with that in mind when answering the "is it worth it" question


I am looking to use Roxul 60 for my bass traps. The guy I spoke to at the supplier said that some people are chopping the Roxul 60 into 2' right triangles and stacking them floor to ceiling rather than just fixing them across the corner in order to build the bass traps.

Three questions for the esteemed panelists ;-)

1) Cost and time aside, does it make sense to do this? Will a corner with essentially 14" deep of absorbing material be more effective as a trap than 4" deep with air behind? (This may seem like a silly question but this is not always intuitive, and I want someone here to confirm)

2) The Roxul is pretty cheap so if its worth it I don't mind the addnl cost - but I have heard it is a pain to cut - any tips or comments?

3) Finally, is the Roxul really a good alternative to the OC 705 for this purpose?


Thanks and have a nice day!

Alex

I am looking to use Roxul 60 for my bass traps. The guy I spoke to at the supplier said that some people are chopping the Roxul 60 into 2' right triangles and stacking them floor to ceiling rather than just fixing them across the corner in order to build the bass traps.

Three questions for the esteemed panelists ;-)

1) Cost and time aside, does it make sense to do this? Will a corner with essentially 14" deep of absorbing material be more effective as a trap than 4" deep with air behind? (This may seem like a silly question but this is not always intuitive, and I want someone here to confirm)

2) The Roxul is pretty cheap so if its worth it I don't mind the addnl cost - but I have heard it is a pain to cut - any tips or comments?

3) Finally, is the Roxul really a good alternative to the OC 705 for this purpose?


Thanks and have a nice day!

Alex

I'm using also Roxul 60 for my panels, for bass trap I cut 17" right triangle and stack them from floor to ceiling. cover it with polyester batting and panel. I use hack saw blade to cut it.

I'm no acoustical expert, but this last week I just got done installing two "super chunk" bass traps using OC703 material. Each triangle is 17" along the wall and a 24" room-facing side. I was told this was a better solution than 4" of 2'x8' material stacked in the corner with air behind.
That is what the test data shows. What difference has it made in the sound?

To be clear - I have a sub-$2k system, with an Onkyo-705 powering an Aperion S10 subwoofer - enough to make a little noise, but not huge or high-end... so please comment with that in mind when answering the "is it worth it" question

Yes, it's worth it! I have two state of the art systems in my house, and both systems added together cost way less than many audiophiles drop on their turntable alone. What makes my system state of the art is extensive room treatment. Well, that and professional quality loudspeakers.

Bass traps and other acoustic treatment are not a silly audiophile tweak that can be appreciated only with $40k apiece loudspeakers. :eek:

--Ethan

A picture of my layout is attached.

http://www.realmsoftracon.com/wet/ht.bmp

General info: 5.1 (5.2 next year) HT only room, carpeted floors, smooth paint on sheetrock ceiling. The screen if about 3' off the front wall to allow for the television. (The screen is suspended from chains and is swung up to a 3rd hook when not in use) Unfortunately, there isn't enough room to have the speakers beside the screen, so they are under the screen.

So, next year I plan to do super chunks in the 3 corners. But for now, I want to reduce the RT60 of the room as it is pretty echoey.

Now, the simple answer is to just start building 703 absorbers. But is there a more quick n dirty way that will work about as well?

I ask because in an apartment I used to live in, I lined all the walls with black sheets in an effort to darken the room. But suprisingly, those thin Wal-Mart sheets also did a good job of deadening the room.

That's what I want for now, because the echo is the most obvious problem. So, here's my main idea for a quick, dirty, and cheap way to do it.

What if I got those $20 4x8 carpets, and mounted two behind the screen, two on the back wall, and two or three along the right wall? I'm thinking of simply screwing them onto the studs.

The advantages I see using carpets is if I get the darker red stuff, it would also help darken the room a bit, and would also look nicer than 2x4 absorbers all over the place.

And if I've been reading correctly, 2x4 4" absorbers won't do much for low frequencies anyway unless they are mounted 12-16" from the wall.

So, would this work well, or am I an idiot who would be better served with $180 worth of 703 or mineral wool?

And one other question on super chunks. The standard way is 703 stacked floor to ceiling. Has anybody tried stacking bags of fiber fill insulation floor to ceiling? It's basically pulverized newspaper squeezed into 25lb bags with dimensions of approx. 2'x1.5'x1'. And it's about $10/bag. Would that possibly work?

Thanks!

That is what the test data shows. What difference has it made in the sound?

Unknown. I haven't moved my equipment into the room yet. It will be a few weeks before all of that goes in. So I won't have a before and after impression of the space.

Thanks Ethan - but my question is whether it is worth the effort to *fill* the corners with Roxul, requiring 24 sheets and 72 cuts, or whether having 4" roxul in the corner with an air gap behind it (8 sheets, 8 angle cuts), would be sufficient for my needs... I certainly don't think the bass traps are a silly tweak, just don't know whether I would be able to tell the difference in the sound between one approach and the other.

Particularly interested in your opinion, since it was your FAQ i got the air gap bass trap design from :). Thank you SO much for putting that together, it was very informative

Alex







Yes, it's worth it! I have two state of the art systems in my house, and both systems added together cost way less than many audiophiles drop on their turntable alone. What makes my system state of the art is extensive room treatment. Well, that and professional quality loudspeakers.

Bass traps and other acoustic treatment are not a silly audiophile tweak that can be appreciated only with $40k apiece loudspeakers. :eek:

--Ethan

...but my question is whether it is worth the effort to *fill* the corners with Roxul, requiring 24 sheets and 72 cuts, or whether having 4" roxul in the corner with an air gap behind it (8 sheets, 8 angle cuts), would be sufficient for my needs...
Alex

If you get an electric turkey carving knife from walmart for $15, it makes cutting OC703 like slicing butter. I don't know how easy to cut the Roxul is though. It's really no effort, clean, and VERY quick. I was surprised how fast it went. I cut 96 'super chunks' in pretty short order.

Alex,

my question is whether it is worth the effort to *fill* the corners with Roxul, requiring 24 sheets and 72 cuts, or whether having 4" roxul in the corner with an air gap behind it (8 sheets, 8 angle cuts), would be sufficient for my needs.

Filling the corner is better, but not proportionately. So if the total cost of material is the limiting factor, you'll do better to spread the material around into other corners. But if "best" is the priority, and you don't mind three times more fiberglass and labor to get (approx) 25 percent better, then filling is great.

--Ethan

We're not at the liberty to consume the corners in the rear of our our room with angled bass traps... there will be 14" fiberglass columns with speakers on or in them (this will be a 9.1 setup)... Fortunately, we are at the liberty to consume the wall and behind the corners do to the coincidental "room in room" we're working with... I was wondering if this concept, the one on the right in the image, would be considered an acceptible solution for the rear corner bass traps... there will be an Earthquake SuperNova 15" in the front of the room, not sure how we will phase it but the mfg recommends pointing it at an angle towards the centeral listening point... the room dimensions are 22' long and 18' wide, w/ 8' ceilings and it will be a mostly sealed room, thick carpeted floors, sheetrock &/or fabric walls.

We also have the freedom to create recessed, fabric covered cavities in the wall almost whereever is necessary... but we're focusing only on the reflection point and the corners.

Also, R19 doesn't have to be used there, that was just entered to convey the concept and because we have lots of it...

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94001&stc=1&d=1194480171

I am about to build a 2x6 floor over a concrete garage floor and I was wondering if I should fill the spaces between the floor joists with insulation? Will this improve my acoustics?

I'm working on building out my cozy 10x12x8 HT. The 50" plasma TV will be placed in front of a window, with the center speaker directly under it. I want to get some heavy velvet blackout curtains for the window. I have a whole stack of OC703 I'm using for treatments around the room. The window is about 24" off the floor.

So my question is, should I order short curtains and cover the wall directly under the window with OC703, or order curtains that go to the floor and forget about the OC703? I'm thinking the OC703 would be the better acoustical solution. But I think the curtains going to the floor would look better.

Since the area in question is only 24" high and about 40" wide, does it really make much of a difference?

...
We also have the freedom to create recessed, fabric covered cavities in the wall almost whereever is necessary... but we're focusing only on the reflection point and the corners.

Also, R19 doesn't have to be used there, that was just entered to convey the concept and because we have lots of it...

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94001&stc=1&d=1194480171

Using a denser fiberglass such as 703, this may work. How much depth do you have for cavities? Does this depth exist behind all 4 walls?

Regards,
Terry

How much depth do you have for cavities? Does this depth exist behind all 4 walls?

Behind the rear wall of the room there is about 4 feet if we needed it, the front of the room will have a false wall made of fabric and there will be about 2' up there.

thanks!

Thanks Ethan, that's exactly the info I was looking for. Given that I am only going to be living here another 9 months, I will live with the air gap, and then fill when I build a permanent HT next time.


Alex,



Filling the corner is better, but not proportionately. So if the total cost of material is the limiting factor, you'll do better to spread the material around into other corners. But if "best" is the priority, and you don't mind three times more fiberglass and labor to get (approx) 25 percent better, then filling is great.

--Ethan

My post here was a serious one...

Sorry Dan, I guess everyone thought someone else would help you. :eek:

Now, the simple answer is to just start building 703 absorbers. But is there a more quick n dirty way that will work about as well?

Moving blankets?

The problem with thin treatments is they affect only the highest frequencies, and proper treatments absorbs over as wide a range as possible.

suprisingly, those thin Wal-Mart sheets also did a good job of deadening the room.

Maybe not as good as it might seem at first blush. Again, thin materials help a little, but they're not a good solution if you're at all serious about sound quality.

What if I got those $20 4x8 carpets

Same problem.

And if I've been reading correctly, 2x4 4" absorbers won't do much for low frequencies anyway unless they are mounted 12-16" from the wall.

Not so, assuming you mean rigid fiberglass. Further, if you put them across corners they'll do an even better job at bass frequencies.

Has anybody tried stacking bags of fiber fill insulation floor to ceiling?

Sure, and I mention using bagged insulation in my Acoustics FAQ (http://www.ethanwiner.com/acoustics.html), which will be a useful read for you generally.

--Ethan

Wow, a reply from the great one himself! (And that's meant in all sincerity)

Okay, so as I feared, while something as simple as sheets or carpet does help a little (and noticeably), it won't help near as well as even just 2" rigid fiberglass treatments. So I guess the sheet lined room was just a small taste of the improvement I can obtain from going "all the way".

I did read your FAQ several days ago, and it had lots of excellent info. I didn't remember reading about the bagged insulation...

[ checks]

I tried searching for bag, bags, bagged, and insulation and can't seem to find anything about bagged insulation. After a bit of searching, all I could find is a post on another forum where somebody said he asked you about the cellulose bag design, and you said it should work decently.

http://www.audiocircle.com/circles/index.php?topic=44090.0

I even tried registering at the musicplayer forums and searching, without much luck. (stupid 6 month search window).

So, whereas for stacking bagged insulation I'd probably end up spending $40-$50 per corner trap, whereas if I used 12 sheets of rigid fiberglass, I'd end up spending roughly twice as much. So, I guess my question is, do rigid fiberglass super chunks perform much better than cellulose super chunks, or is the advantage of fiberglass mainly the fact that it fits into the corner better and can be made to look nicer?

I think I may go ahead and do the carpet thing and add 4" absorbers down the road. While they won't do much for all but the higher frequencies (above 5KHz? 10?), they'll at least darken the room a bit. And they'd look much nicer than hanging the sheets like I did last time!

Thanks!

"Another great and inexpensive way to make a bass trap - if you have a lot of room - is to place bales of rolled up fluffy fiberglass in the room corners. These bales are not expensive, and they can be stacked to fill very large spaces. Better still, they are commonly available and you don't even have to unpack them! Just leave the bales rolled up in their original plastic wrappers, and stuff them in and near the room corners wherever they'll fit. Stack them all the way up to the ceiling for the most absorption." from http://www.ethanwiner.com/acoustics.html

Thanks Nathan, that's exactly the part of my FAQ I was referring to.

The thing is, the cellulose fiber is a little more compact, but still quite dense, at 25lb/bag. Definitely denser than fiberglass rolls.

I guess the only way to find out for sure is to get both and run LF sweeps with rolls, and again with bags.

One quick question. Which db meter is preferrable - the Radio Shack analog or digital meter? I thought I read somewhere that the analog meter was preferrable.

Which db meter is preferrable - the Radio Shack analog or digital meter?

I prefer the digital, but either is fine.

--Ethan

I'm working on building out my cozy 10x12x8 HT. The 50" plasma TV will be placed in front of a window, with the center speaker directly under it. I want to get some heavy velvet blackout curtains for the window. I have a whole stack of OC703 I'm using for treatments around the room. The window is about 24" off the floor.

So my question is, should I order short curtains and cover the wall directly under the window with OC703, or order curtains that go to the floor and forget about the OC703? I'm thinking the OC703 would be the better acoustical solution. But I think the curtains going to the floor would look better.

Since the area in question is only 24" high and about 40" wide, does it really make much of a difference?


Haven't seen any replies to my question. Thoughts?

Why don't you do both if they're in a place and of a size that you need that much surface area? You can easily do 703 behind the curtains.

Bryan

What are you using to cover 48x24x2 703, and are you putting it in a frame or just covering it with some kind of speaker cloth. And what are you using to hang it on the wall.

What are you using to cover 48x24x2 703, and are you putting it in a frame or just covering it with some kind of speaker cloth. And what are you using to hang it on the wall.
Start researching here (http://www.peparsplace.com/html/16.html). It's OC SelectSound Black, but it could have just as easily been OC 703.

Can I use some other/cheaper material to cover panel frames? I went to
fabric store and saw some good cotton material and was thinking if I could wrap my panels with that $8/yard material?
I read through forums and couldn't find a reason for using GOM - which is
polyester and it is see thru material versus higher thread cotton or something
else. Please suggest.:confused:

Can I use some other/cheaper material to cover panel frames? I went to
fabric store and saw some good cotton material and was thinking if I could wrap my panels with that $8/yard material?
I read through forums and couldn't find a reason for using GOM - which is
polyester and it is see thru material versus higher thread cotton or something
else. Please suggest.:confused:
No experimentation is needed, it works. First time and every time. No posting on AVS to find out is anyone else has successfully used <fill your "find" in here>. No spending my valuable time trying to "save a buck."

Can I use some other/cheaper material to cover panel frames? I went to
fabric store and saw some good cotton material and was thinking if I could wrap my panels with that $8/yard material?
I read through forums and couldn't find a reason for using GOM - which is
polyester and it is see thru material versus higher thread cotton or something
else. Please suggest.:confused:
I just purchased the burlap they sell at atsacoustics.com for $7 a yard. Don't know, but I'm sure it works.

What are you using to cover 48x24x2 703, and are you putting it in a frame or just covering it with some kind of speaker cloth. And what are you using to hang it on the wall.

I'm using a different and cheaper method. I went to my local Home Depot and got some fiberglass resin. I brushed some on all the edges, and it produces a nice firm edge.

Then I use some 3M spray adhesive to attach my GOM 701 black material. Finally, I'm using the rotofast hangers for wall mount.

Now I'm just part way through my project and at the resin stage. But later today I'll be gluing the fabric on two panels. I think they will look just fine, and I didn't need to take the time to build a wood frame.

People use GOM for the following reasons:

- It's fire rated.
- It comes in 48 colors
- It matches their false walls with speakers behind them where you NEED the acoustical transparency of the FR701-2100 GOM

Bryan

I wonder, does the glue keep any of the sound from being absorbed?


I'm using a different and cheaper method. I went to my local Home Depot and got some fiberglass resin. I brushed some on all the edges, and it produces a nice firm edge.

Then I use some 3M spray adhesive to attach my GOM 701 black material. Finally, I'm using the rotofast hangers for wall mount.

Now I'm just part way through my project and at the resin stage. But later today I'll be gluing the fabric on two panels. I think they will look just fine, and I didn't need to take the time to build a wood frame.

I wonder, does the glue keep any of the sound from being absorbed?
If used too much, yes. This can take the "porous" out of "porous absorber." :) It is best to confine spray adhesive to the back edges and corners of panels. Use the lightest amount to get the job done.

Regards,
Terry

If used too much, yes. This can take the "porous" out of "porous absorber." :) It is best to confine spray adhesive to the back edges and corners of panels. Use the lightest amount to get the job done.

Regards,
Terry

Oh that's good to know. I'm ready to cover a few 2x4 sheets with GOM today, and was planning on spraying the front and sides with the spray adhesive. I'll be sure to go extra light....very good input!

I did try and go very light on the sides with resin, so that much did cross my mind.

Anybody using these? They look very promising.

http://www.waveguideacousticsolutions.com/index.html

I've been talking with the proprietor, and will hopefully see some measurement data related to them.

Anybody using these? They look very promising.

http://www.waveguideacousticsolutions.com/index.html

I've been talking with the proprietor, and will hopefully see some measurement data related to them.

Would this be a product to use on the back wall behind the listening position?

Anybody using these? They look very promising.

http://www.waveguideacousticsolutions.com/index.html

I've been talking with the proprietor, and will hopefully see some measurement data related to them.

Great price if they work. Not factoring in time, There has to be, what, about $20 in Material cost to DIY one of these?

Would this be a product to use on the back wall behind the listening position?

That would be the most common position, but it all depends on the size, shape, and setup of your room.

I'm in the final stages of getting my small HT set up. The room has 8' ceilings, and is located on the second story. Walls are typical modern home construction dry-wall. The closet doors have been completely removed. Attached is to-scale drawing of the room and equipment.

Installed treatments are:

1) OC703 super chunk bass traps in all four corners, floor to ceiling.
2) 12" x 2" x 8' OC703 mounted on both sides of the window behind the main speakers.
3) Pending: Thick velvet blackout curtains in front of the window, behind the plasma.

Pending placement: Six 2'x4'x2" OC703 panels.

Now my questions are:

1) I plan on putting two panels at the FRPs on the left and right for the main speakers. The mains are floor standing Veritas v2.4 models. Should orient the OC703 panes in the vertical position or horizontal? The free FRP software I used showed a 4' long horizontal area on the side walls as the FRP, and one company that does freebie recommends for treatments also recommended horizontal. But given the speakers are tall floor standing models, I would think a vertical orientation would be better?

2) The same company that recommended the horizontal side panels, also recommended one panel _directly_ above each main speaker, butted up against the corner bass traps. These aren't FRPs, so do I really need to treat directly above the speaker?

3) For the ceiling FRP, the freebie software shows a 2' deep (top to bottom of the picture) by 6' wide (left to right). Could I do two 2'x4' panes pointing top to bottom in the picture, spaced apart say six inches? Or should I put them end-to-end left-to-right to form a 2' x 8' panel? I'm thinking the first option is preferable.

4) Along the back closet wall, should I have a diffusion panel inbetween the two bass traps?

5) Should I place an additional two panels along the side walls more towards the loveseat?


Thanks!

I'm in the final stages of getting my small HT set up. The room has 8' ceilings, and is located on the second story. Walls are typical modern home construction dry-wall. The closet doors have been completely removed. Attached is to-scale drawing of the room and equipment.

Installed treatments are:

1) OC703 super chunk bass traps in all four corners, floor to ceiling.
2) 12" x 2" x 8' OC703 mounted on both sides of the window behind the main speakers.
3) Pending: Thick velvet blackout curtains in front of the window, behind the plasma.

Pending placement: Six 2'x4'x2" OC703 panels.

It's very easy to over-deaden a small room. I'd do the bass traps, the walls behind the front speakers AND the FRP on the REAR wall. And then I would listen and take measurements before adding any more treatments. I might also do the ceiling before the "listen and measure" step.

It's very easy to over-deaden a small room. I'd do the bass traps, the walls behind the front speakers AND the FRP on the REAR wall. And then I would listen and take measurements before adding any more treatments. I might also do the ceiling before the "listen and measure" step.

I was considering a 30"x30" diffusion panel on the rear wall...but haven't bought it yet. Is diffusion needed in this small of a space? Or like you said, should the rear wall get an OC703 panel at the FRP?

I was considering a 30"x30" diffusion panel on the rear wall...but haven't bought it yet. Is diffusion needed in this small of a space? Or like you said, should the rear wall get an OC703 panel at the FRP?
Diffusion could work, and maybe even be better than absorption. I think it depends on the distance between the wall and your seats. In looking at your drawing, I see a closet and a door behind your listening position. Where would you place treatment back there?

I was considering a 30"x30" diffusion panel on the rear wall...but haven't bought it yet. Is diffusion needed in this small of a space? Or like you said, should the rear wall get an OC703 panel at the FRP?
FWIW, I am considering placing diffusors over some of my wall carpeting to breathe some "air" back into my room. If you want to see what I'm talking about, visit my site linked in my sig.

My room is 13' x 21' x 8'.

I'm in the final stages of getting my small HT set up. The room has 8' ceilings, and is located on the second story. Walls are typical modern home construction dry-wall. The closet doors have been completely removed. Attached is to-scale drawing of the room and equipment.
I'd move the side surrounds forward to just inches behind the ears of your audience.

Diffusion could work, and maybe even be better than absorption. I think it depends on the distance between the wall and your seats. In looking at your drawing, I see a closet and a door behind your listening position. Where would you place treatment back there?
...
I'd move the side surrounds forward to just inches behind the ears of your audience.

I would place the diffuser on the rear closet wall between the two super chunk bass traps. A 30"x30" would fit nicely in the space. The distance from the rear wall to listening position is 5 feet.

The rear surrounds are located very close to the Dolby recommended 110 degrees. How would moving them closer to the listener be beneficial?

I would place the diffuser on the rear closet wall between the two super chunk bass traps. A 30"x30" would fit nicely in the space. The distance from the rear wall to listening position is 5 feet.

The rear surrounds are located very close to the Dolby recommended 110 degrees. How would moving them closer to the listener be beneficial?
They are tight against the rear wall. Right now the rear lobes are crashing into the corners. I'll bet that they perform more like monopole than dipole mounted like this. And I subscribe to the THX recommendation that they by even with, or slightly behind listeners.

Just my $.02.

I would place the diffuser on the rear closet wall between the two super chunk bass traps. A 30"x30" would fit nicely in the space. The distance from the rear wall to listening position is 5 feet.

That would work fine, I imagine, if he left the closet doors open and had nothing hanging in the closet. :)

That would work fine, I imagine, if he left the closet doors open and had nothing hanging in the closet. :)
...
They are tight against the rear wall. Right now the rear lobes are crashing into the corners. I'll bet that they perform more like monopole than dipole mounted like this. And I subscribe to the THX recommendation that they by even with, or slightly behind listeners.



Closet doors have been removed, and nothing is in the closet except the bass traps. :)

How high does THX recommend the rear surrounds be placed? I've always heard at ear level when stand up, which puts them a couple of feet higher than the listening position.

Closet doors have been removed, and nothing is in the closet except the bass traps. :)
DOH! Well, if he's not going to use the closet as a closet, I'd consider removing it (or at least the small stub on the left rear). But whether he removes it or not, I'm not sure how much the trap in the door-side of the closet would do. If he hangs anything there, any mid- to upper-frequency treatments will not be effective.

How high does THX recommend the rear surrounds be placed? I've always heard at ear level when stand up, which puts them a couple of feet higher than the listening position.
Yep, height-wise a couple of feet above the ears.

I am building stage for my home theater, and was wandering if sand filled stage a must. What else can be used. I am new to theater building and
looking for suggestions.
I have been reading a lot during my theater construction phase and getting
all sorts of useful info from this forum.
What I have done is put carpet pad underneath theater stage to separate it
from floor, and have about 1/2" space to the walls.
I would appreciate your suggestions/advise.

Eugene.

I am building stage for my home theater, and was wandering if sand filled stage a must. What else can be used. I am new to theater building and
looking for suggestions.
I have been reading a lot during my theater construction phase and getting
all sorts of useful info from this forum.
What I have done is put carpet pad underneath theater stage to separate it
from floor, and have about 1/2" space to the walls.
I would appreciate your suggestions/advise.

Eugene.
FWIW, I wanted mine coupled to the floor and built the riser so that I could (some time in the future) add bass transducers. You can see my construction and comments here (http://peparsplace.com/html/10.html).

I am talking about stage in front, where front speakers and sub will be placed.
It seems like most of people fill it with sand, and try to decople from walls, not sure about floor though. By the way I have been to your page a few times, getting ideas, thank you. One thing I noticed you have hardwood on the floor, you don't have problems with that?

I am talking about stage in front, where front speakers and sub will be placed.
It seems like most of people fill it with sand, and try to decople from walls, not sure about floor though. By the way I have been to your page a few times, getting ideas, thank you. One thing I noticed you have hardwood on the floor, you don't have problems with that?
DOH! I'm sorry. Yes most are filling front stages with sand. I would, too, if I had one.

In the area between the first row and the screen, there is a throw rug with the heaviest, springiest rubber pad I could find. In other areas, the amount of hardwood exposed is dwarfed by the LaZBoys, the 2" fiberglass covering the cavity behind my false wall and first reflection points, as well as the wall carpet. IN fact, I am planning on lowering the LCR speakers allowing a reduction in the size of the front side absorbers and installing some diffusors to recover some "air" in the room.

If you get an electric turkey carving knife from walmart for $15, it makes cutting OC703 like slicing butter. I don't know how easy to cut the Roxul is though. It's really no effort, clean, and VERY quick. I was surprised how fast it went. I cut 96 'super chunks' in pretty short order.

Stanley Sharptooth Saw (can get on amazon) cuts Roxul (and thermal fiber brand rock wool) and rigid foam board like butter. It seems that it would cut OC703 well also.