Also on my back wall, Im put up that 4" thick treatment suggested a long time ago but Im back wondering if I should leave an 1" air gap between it and the wall?

What does that improve again? Why 4" thick and a 1" air gap, why not 5" thick instead? No doubt, Im constantly confused.
I believe I remember a pro or two recommending that, but I only have 2" OC SelectSound Black panels on the back wall sized *exactly* as needed for first reflection point absorption. If that's what this is for - I apologize for not following your project closer - then the 4" with or without the gap will no doubt be better than my 2". The gap enhances the panel's LF absorption be adding a diaphramatic component to it. Personally, I like my bass absorption in the corners where all of the bass frequencies can be found.

I believe I remember a pro or two recommending that, but I only have 2" OC SelectSound Black panels on the back wall sized *exactly* as needed for first reflection point absorption. If that's what this is for - I apologize for not following your project closer - then the 4" with or without the gap will no doubt be better than my 2". The gap enhances the panel's LF absorption be adding a diaphramatic component to it. Personally, I like my bass absorption in the corners where all of the bass frequencies can be found.

Yeah, I total suck at keeping my build thread going. Been keeping my DIY sub thread up to speed just have so many pics to add to my HT build thread.

The reason for the 4" treatment on the back wall is because I sit 1' from the back wall in my HTRoom so it was recommended that I need some serious treatment behind my seating. Room design and seating is FIXED so no need to discuss why I shouldnt do that ;) I just want to try and handle the problems I created.

The real question is more of a generic one that I can seem to find in a search.

What is the difference acoustically between 4" acoustical treatment up against drywall vs 3" acoustical treatement, then a 1" air gap, then the drywall?

The real question is more of a generic one that I can seem to find in a search.

What is the difference acoustically between 4" acoustical treatment up against drywall vs 3" acoustical treatement, then a 1" air gap, then the drywall?
The difference is what I posted above. As for quantifying the difference, I haven't a clue on where to find tests. Maybe ask whoever made the recommendation?

The gap enhances the panel's LF absorption be adding a diaphramatic component to it. Personally, I like my bass absorption in the corners where all of the bass frequencies can be found.


Ah...cool. I missed that.

The 4" behind the seating was discussed in this thread a bit ago. One of the experts gave me that recommendation.

Has there ever been a definitive answer to how far you need to sit away from a diffuser for it to be effective?

The closest "test" I have is a short video that lets you hear the sound when very close to a diffusor. Bottom of this page:

RealTraps Videos (http://www.realtraps.com/videos.htm)

--Ethan

The closest "test" I have is a short video that lets you hear the sound when very close to a diffusor. Bottom of this page:

RealTraps Videos (http://www.realtraps.com/videos.htm)

--Ethan
Very nice. Great idea. :)

I have read through this thread and cannot find an answer to my questions.

1. How do you attach the Linacoustic to the drywall?

2. How do you attach the GoM to the Linacoustic?

~Josh

I have read through this thread and cannot find an answer to my questions.

1. How do you attach the Linacoustic to the drywall?

2. How do you attach the GoM to the Linacoustic?

~Josh

1) Short sheetrock screws. Don't screw them all the way in though (1/4 to 3/8 inch is more than sufficient). It only takes a couple, even for the largest pieces.

2) Place 1 inch furring strips at the ceiling, floor and corners. Fasten the GoM to the furring strips.

Here is a link about fiberglass health issues:

http://www.lungusa.org/site/c.dvLUK9O0E/b.35439/k.7DEB/Facts_About_Fiberglass.htm

Does not seem to be a major problem but more studies are likely on the way.

I went with the largest corner absorbers I could fit in, without encroaching on the placement of my front speakers. There was no testing or calcs behind my decision at all. Getting material isn't a problem as we use about 300,000 cubic feet of rockwool per annum at work. ;)

When I eventually move home and build a dedicted room my mad plan is to use 3 foot thick rockwool covering about 1/2 of the front wall and 2/3 of the rear wall. :eek:

I went with the largest corner absorbers I could fit in, without encroaching on the placement of my front speakers. There was no testing or calcs behind my decision at all. Getting material isn't a problem as we use about 300,000 cubic feet of rockwool per annum at work. ;)

When I eventually move home and build a dedicted room my mad plan is to use 3 foot thick rockwool covering about 1/2 of the front wall and 2/3 of the rear wall. :eek:
Beware, Peter. Rockwool is generally pretty dense, and has a very high flow resistivity at higher densities. This translates to ineffective absorption for a really thick (like 3 ft) layer.

What happens is that the waves don't penetrate all the way through the thickness, some fraction being reflected. So the whole depth isn't really used. You get better low frequency absorption with less dense material. This can be approximated/predicted through relatively simple mathematical methods.

Regards,
Terry

Terry,

We typically use 40kg/m3 rockwool. I believe at this density it should be OK ?

Terry,

I should have also added that as I move into the real design stage I intend to employ the services of a reputable acoustician, location unimportant. Know anyone you can recommend ? ;)

Anyone have a sugesstion?
Like this one for example:
http://wroclaw.gumtree.pl/c-Firmy-Us-ugi-piel-gnacja-i-uroda-TIPSY-STYLIZACJA-Szukasz-tego-co-JEST-w-tym-OG-OSZENIU-W0QQAdIdZ54992719
:confused:

Terry,

We typically use 40kg/m3 rockwool. I believe at this density it should be OK ?
Sorry, but substantially less density rockwool for a 3 foot thickness is much more effective at lowest frequencies. :( I do not recommend 40 kg/m^3 if you are after best low frequency performance.

I am of course available for detailed hourly consulting via email. And I work pretty cheap, especially considering the current dollar exchange rates. :D Just PM me.

Regards,
Terry

looking for low profile, reasonably attractive ceiling diffusion, preferably in black; anyone have any experience with:


GIK D1 Diffusor http://www.gikacoustics.com/gik_d1_diffusor.html

RPG Hemiffusors http://www.rpginc.com/products/hemiffusor/index.htm

or

Studio Outfitters Roundffusor http://www.studiooutfitters.com/roundffusor.html

or other suggestions?

anyone use these or other ceiling diffusors?

Or recommend someone who designs/builds aethetically appealing (i.e., no skylines) ceiling diffusion?

I've heard that ceiling diffusion is often preferable to absorption but it is difficult to find an acceptable way to implement this.

I'm considering just putting in coffers with some trim with absorption in the coffers at the first reflection, and get whatever diffusion the coffers can give for the rest of the ceiling.

Anyone have any pics of Hts with coffered ceilings?

thanks for any ideas.

I've heard that ceiling diffusion is often preferable to absorption but it is difficult to find an acceptable way to implement this.

I disagree with that advice. I much prefer absorption at reflection points.

--Ethan

I disagree with that advice. I much prefer absorption at reflection points.

--Ethan

Anyone have any info on comparisons between the two? (That is, specifically comparisons btw types of absorption vs types of diffusion -- not btw absorption vs no treatment.) especially for ceilings, but walls wld be interesting too. and not just reflection points but also general broader treatment? (my original query actually mentioned absorption at first reflection and diffusion elsewhere -- what I thought was a reasonable splitting of the difference).

Or info on whether varies types of diffusion is more or less broadband that various types of absorption? (some claim diffusion is more broadband)

Or have info on why Rives seems to get very good reviews when they seem to always specify diffusion for ceiling treatment? especially low ceilings?

Anyone have any info on comparisons between the two?

There's no way to measure if diffusion versus absorption is "better" other than subjective impression. I have absorption at all reflection point in my 16 foot wide living room, including the ceiling. When I put diffusors at the side-wall reflection points the degradation in imaging and overall quality compared to absorption was immediately obvious. Yes, this was subjective, but it was so obvious nobody could conclude otherwise.

Or info on whether varies types of diffusion is more or less broadband that various types of absorption? (some claim diffusion is more broadband)

Absorption will be more broadband, which is another argument in favor of absorption. Now, you could compare a 9-inch deep QRD diffusor versus 1-inch thick sculpted foam, and in that case the diffusor might work over a wider range. It will certainly work to a lower frequency. But a four inch absorber is much more broadband than any practical diffusor. Practical meaning not four feet deep etc.

--Ethan

In the sketch of my room below, the red area has a very pronounced increase in bass at about 40Hz. You walk over there, and its waaaaay louder than the rest of the room. The subs are in black. Both front and back walls have 2" OC703, front has superchunks in the corners, the back has half sized versions. The face of that bumpout has 2" OC703, and the walls have 1" OC703 at first reflection points. So my question is this---does it matter if there is a big peak over there since I don't sit there, and neither does anyone else? Or, should I try and soak it up with all my leftover OC703? Would it do me any good?

Thanks!

http://img.photobucket.com/albums/v613/Kevin_5/Home%20Theater/68b4e68a-1.jpg

Fatawan,

If it is not broken (in the listening area), don't fix it!

Low frequency room modes will sound really bad at the sides and corners of the room, where their pressures are always maximum. These are also good places to treate them, because if a specific room mode is partly absorbed anywhere, its effect will diminish to some degree everywhere else.

But if it is not an audible problem at the listening area, your effort will be wasted. And depending upon the type of bass absorber placed at that front area, it could adversely effect your sound stage.

Regards,
Terry

I have a difficult acoustical problem that I need help solving. The rough sketch below shows the general layout of my room. The yellow area is a wet bar that I want to keep and the blue area is the entrance. This makes for difficulty putting bass absorption in the corners. The general dimensions of the main room is about 18' x 17.5' the wetbar and entrance are about 3x3. I plan on having a riser with absorption underneath don't know how else. The screen wall is on the wall along the bar end of the room on the left side of the sketch.

Any help?


http://i291.photobucket.com/albums/ll301/mcneilms/sketch.jpg

Hi mcneilms,

Is this room already built? If so, the best thing is to listen to it from your seats, and measure the frequency and time/frequency response with a program like the free Room EQ Wizard. This can tell you whether you have significant offending room modes, which ones they are, and therefore where treatment can be effective.

If the room is not built, bass absorbers in the two available corners and/soffits running around the room can be an effective deterrent.

Regards,
Terry

I have a difficult acoustical problem that I need help solving. The rough sketch below shows the general layout of my room. The yellow area is a wet bar that I want to keep and the blue area is the entrance. This makes for difficulty putting bass absorption in the corners. The general dimensions of the main room is about 18' x 17.5' the wetbar and entrance are about 3x3. I plan on having a riser with absorption underneath don't know how else. The screen wall is on the wall along the bar end of the room on the left side of the sketch.

Any help?


If you do measure and decide you need bass traps, you may be able to get creative in where they go. If this room has attic above it, can you punch a hole in the ceiling above the wet bar or entrance and put a bass trap up there? If the bump-out between the wet-bar and the entrance is a closet in another room, can you turn part of that into a bass trap?

If this room has unused basement below it, another weird option would be bass trap built into the floor (think big metal grate). You could get double duty out of it by making the grate a trap-door and dropping guests you dislike through the floor as they are standing at the wet bar...

Hopefully you can get away without bass traps in those corners, but something to think about. Here is a shot of the bass trap over my entrance (2' x 4' by 2' deep):

http://i194.photobucket.com/albums/z196/pgmeyer/avspics/DSC_9749-1.jpg

.......You could get double duty out of it by making the grate a trap-door and dropping guests you dislike through the floor as they are standing at the wet bar...



lol, a grate for the grating! :D

If you do measure and decide you need bass traps, you may be able to get creative in where they go. If this room has attic above it, can you punch a hole in the ceiling above the wet bar or entrance and put a bass trap up there? If the bump-out between the wet-bar and the entrance is a closet in another room, can you turn part of that into a bass trap?

If this room has unused basement below it, another weird option would be bass trap built into the floor (think big metal grate). You could get double duty out of it by making the grate a trap-door and dropping guests you dislike through the floor as they are standing at the wet bar...

Hopefully you can get away without bass traps in those corners, but something to think about. Here is a shot of the bass trap over my entrance (2' x 4' by 2' deep):
Not that your entrance ceiling (or similarly located) trap won't do anything at all, but the idea is to put the traps where the bass "is." First, that is corners formed by three surfaces and second is corners formed by two surfaces. Cleverness and ingenuity are good, but effectiveness is king.

Just my $.02. :)

This makes for difficulty putting bass absorption in the corners.

Most rooms have 12 corners. Listen to Terry. Wall-ceiling corners are very effective, and even wall-floor corners are good if you have any available, such as the bottom of the screen wall.

--Ethan

Most rooms have 12 corners. Listen to Terry. Wall-ceiling corners are very effective, and even wall-floor corners are good if you have any available, such as the bottom of the screen wall.

--Ethan
Indeed, it's not like it requires thinking outside the box, but continuing the metaphor, it surely requires thinking about everywhere in the box.

Not that your entrance ceiling (or similarly located) trap won't do anything at all, but the idea is to put the traps where the bass "is." First, that is corners formed by three surfaces and second is corners formed by two surfaces. Cleverness and ingenuity are good, but effectiveness is king.

Just my $.02. :)

Agreed. Ideally the more room modes a bass trap will hit, the better.

A middle of a wall trap (not touching floor/ceiling) can work on the cross room modes (100 or 010, depending on the wall). A middle of ceiling trap can help with 001 modes. A trap suspended off the floor in a corner (not touching the top/bottom tricorners) will get cross-room modes (110).

A full height corner trap is often standard because it gets you some effectiveness on all of the above. It's got a bit on each wall to cover 100 010, it's in the horizontal plane corner, and therefore gets 110, and it's got the top/bottom tricorners covered, getting some coverage on the 111.

(and higher order modes, but I hate writing x00, etc.)

You can't see the rest of my room, by my entrance is actually in the back left corner. It's canted at 45 degrees to the room. mcneilms sketch seems to imply his entrance is in a corner as well. Because of that, traps in the ceiling or floor right up against the corner will actually have some effectiveness on the XXX eigenmodes (left-back-ceiling corner to right-front-floor). Tricorner traps out in the room, or traps on multiple walls in the corner would help even more.

I'll have two standard superchunks in the front, and a near-corner full upright trap in the back right. When working with Bryan, I suggested big side-wall traps to the left/right of the door (there is space there), but he preferred the ceiling trap. I've got a weird enough shaped room the only way I'll be able to tell what is working is to try it out and measure.

I've got a weird enough shaped room the only way I'll be able to tell what is working is to try it out and measure.
Yep, it will be interesting to see the test results. :)

If you do measure and decide you need bass traps, you may be able to get creative in where they go. If this room has attic above it, can you punch a hole in the ceiling above the wet bar or entrance and put a bass trap up there?
Great suggestion. These sorts of bass absorbers would occasionally be used in old recording studios that had free space above the ceiling. There may even be a name for them, though I don't remember what it was. You can use a larger space than the opening size, and just hide the opening with acoustically transparent fabric. Pre-calculating the net absorption is a bear, but in the old days, they just built it and fiddled with it until it sounded good. :)

Regards,
Terry

Hello all,

I have been reading here for a long time but have not located/found information about the optimum spacing of the corner SSC traps from the corner walls. Should they be tight to the walls or if one was to space them off the wall a certain distance....several inches maybe......would this help for the much deeper bass that is hard to tame....like below 30 Hz? If not...how can we address the very low bass? I will be installing my SSC traps in the next week or so. Thanks.

Wayne

Hello all,

I have been reading here for a long time but have not located/found information about the optimum spacing of the corner SSC traps from the corner walls. Should they be tight to the walls or if one was to space them off the wall a certain distance....several inches maybe......would this help for the much deeper bass that is hard to tame....like below 30 Hz? If not...how can we address the very low bass? I will be installing my SSC traps in the next week or so. Thanks.

Wayne
Tight in the corner. For lower absorption, more 'glass needs to be used. That means instead of the 24" face - 24" x 48" sheet cut into eight 17" x 17" x 24" triangles - you need to do the 34" face - each 24" x 48" sheet cut into FOUR 24" x 24" x 34" triangles.

Thank you for the response pepar. I will have only little 703 2" left after making the larger SSC corner traps for the four main corners front and back. I will, however, have quite a bit of linacoustic 1" left after treating the front wall with 2". To do a front wall....wall-ceiling trap...could I stack layers of 1" linacoustic to a height of maybe 8"...and put it in a frame...and straddle the wall ceiling corner? Would that work for additional bass trapping? Thanks.

Wayne

Thank you for the response pepar. I will have only little 703 2" left after making the larger SSC corner traps for the four main corners front and back. I will, however, have quite a bit of linacoustic 1" left after treating the front wall with 2". To do a front wall....wall-ceiling trap...could I stack layers of 1" linacoustic to a height of maybe 8"...and put it in a frame...and straddle the wall ceiling corner? Would that work for additional bass trapping? Thanks.

Wayne
Mmmm, I don't think so. Go here and compare the absorption of the two materials. The 703 goes a LOT lower than Linacoustic.

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.

from a few months back. . . anyone know what this "study" was?

Mmmm, I don't think so. Go here and compare the absorption of the two materials. The 703 goes a LOT lower than Linacoustic.
Beware of reading too much accuracy into reverberation room absorption coefficients, particularly at 125 Hz!

Regards,
Terry

Should they be tight to the walls or if one was to space them off the wall a certain distance....several inches maybe......would this help for the much deeper bass that is hard to tame....like below 30 Hz?
Unfortunately, bass this low is very hard to make a measurable dent in by adding just a few more inches of thickness. :(

Regards,
Terry

Mmmm, I don't think so. Go here and compare the absorption of the two materials. The 703 goes a LOT lower than Linacoustic.

Make sure you're comparing the same thing. The 703 is 2" while the Linacoustic is he is using is 1". If you take into consideration the same Linacoustic at 2" the coeffecients are very similar to the 703. They are listed on the coeffecients page.

Make sure you're comparing the same thing. The 703 is 2" while the Linacoustic is he is using is 1". If you take into consideration the same Linacoustic at 2" the coeffecients are very similar to the 703. They are listed on the coeffecients page.
Umm, yeah, so are the 1" specs . . . DOH!

703, plain 1" (25mm) on wall 0.11 0.28 0.68 0.90 0.93 0.96 0.70

Linacoustic RC 1" (25mm) 0.08 0.31 0.64 0.84 0.97 1.03 0.70

:o

Thanks for posting that, Pepar. So many use the 2" 703 I forgot that it also comes in 1".

I have to admit, when I made my traps, (I used the 1" Linacoustic RC because I had lots of extra) I wished I had purchased the 703. At 1" thick it was, at least, twice the work cutting enough wedges to fill the corners all the way to ceiling.

I have one back corner that has only a 12" length one side and unlimited on the other. So a conventional 17x17x24 is out. Are there other tested shapes that would give me depth enough to be effective?

Wayne

I have one back corner that has only a 12" length one side and unlimited on the other. So a conventional 17x17x24 is out. Are there other tested shapes that would give me depth enough to be effective?

Wayne
I don't recall seeing any tests of other shapes, but I'd probably build it as a 17x17x24 minus the volume of 'glass occupied by whatever limits the space to 12".

Thanks guys. Knew y'all could help.

Thank you for your input.

Does anyone know the Johns Mansville equivalent for OC 703? I think I can get it locally to do ceiling first reflection 2x4 panels but am not sure what they call it. Thanks.

Wayne

Does anyone know the Johns Mansville equivalent for OC 703? I think I can get it locally to do ceiling first reflection 2x4 panels but am not sure what they call it. Thanks.

Wayne

Linacoustic RC

It generally comes 1" thick in a 47.5" x 100 foot roll (others lengths are available). It also comes in 2" thickness.

Does anyone know the Johns Mansville equivalent for OC 703?

IS 300 (http://www.jm.com/insulation/building_insulation/products/hig1214dk_insul-shield.pdf). Linacoustic is 1.5lb/ft^3 while OC 703 and JM IS 300 are 3.0lb/ft^3 material.

Andre

Dan,

I have the Linacoustic RC....but I thought they made a rigid dense fiberglass in panels like the OC703 that had acoustic absorption properties that were very similar. I may be mistaken.......

Wayne

Wayne,

You're right, sorry about that. I see that Andre gave us a link to what you are looking for.

edit - I do know that the Linacoustic has very similar coefficients to the OC 703 though. http://www.bobgolds.com/AbsorptionCoefficients.htm

Dan,

I have the Linacoustic RC....but I thought they made a rigid dense fiberglass in panels like the OC703 that had acoustic absorption properties that were very similar. I may be mistaken.......

Wayne

JM 814 is what I used--same as OC703

thanks Fatawan.....I knew that my memory would be jogged....it was JM 814 I was thinking of.

Wayne.

I have one back corner that has only a 12" length one side and unlimited on the other. So a conventional 17x17x24 is out. Are there other tested shapes that would give me depth enough to be effective?

Wayne

You can build a 12x12" square absorber using the same amount of material as a 17x17x24 triangle. While not as thick right at the wall edges, it's thicker over a larger area and considerably thicker at 45 degrees to the corner. You also have the same amount of surface area exposed. I have people build these like this all the time.

Bryan

I just might try the square version. Thanks.

Wayne

Hey folks.

I'm struggling with the age old problem of trying to fit the biggest screen I can into the room, while also fitting in things like acoustic treatment etc. I'm wondering if there might be any solution to my dilemma I haven't thought of.

My screen wall is 160" wide. I'm trying to achieve a 124" wide screen, to be used with a side-masking system, using automated sliding panels. (They actually save me some room on the side over using curtains).

I'm attaching 2 google sketchups of the room. You can see my speakers will be in the corners and I'm going to need some corner acoustic treatment to tame the bass frequency lift. The problem is: how to fit the acoustic corner treatment in?

On the right side of the image near the room opening you can see I have very little side wall before it hits the room opening. Due to space a triangular corner trap is out. An acoustician suggested perhaps two panels for the corner: one narrow one to fit between the edge of the screen frame and the side wall, then another one on what is left of the side wall.

http://img365.imageshack.us/img365/6756/roomfullviewiv1.jpg



The side wall only extends 14" including trim for the doorway and only 10" to the doorway trim (so I can use an acoustic panel on the side wall that is either going to be 10" wide, or 14" wide if I'm willing to cover the doorway trim). You can see how tight for space I am on this side of the wall near the doorway:

http://img79.imageshack.us/img79/6130/closeupcornerjm1.jpg

The biggest problem I'm dealing with at the moment is the stacking of the side masking panels to the side of the screen. The panel stack will be almost 7" thick. But if I put an acoustic panel on the side wall that is 3" thick - one on each side of the screen - that will restrict the width at which the masking panels can retract to the side. Adding 3" of acoustic panelling on either side wall of the screen essentially reduces the viewable screen area from 124" wide screen to a 118" wide screen.

I could make the side acoustic panel (near the doorway) start AFTER the width of the masking panels - so the masking panels can go all the way to the side wall to preserve image size. But then that would mean a gap between that sidewall panel and the panel on the screen wall, and make for a sidewall acoustic panel only 3" wide, or 7" wide (if I extend it to cover the doorway trim).

Would this work?

Any other ways out of this dilemma. I'm really trying to maintain the image size I want.

Thanks.

Remove the rest of the sidewall and eliminate the corner. ;)

I'm in a similar situation.

Try these things, if you haven't already. They'll make a HUGE difference in both deadening the room and reducing bass boost...

1. Put as much padding around AND behind the screen as possible. Put up a layer of egg cartons, foam or whatever you can manage, followed by black carpet like Wonderwall. You'll have a black "feature wall", and it'll make your projected picture stick out more.

2. Experiment with plugging up the bass ports on your front speakers.

3. Get the front three speakers as far out from the wall as you can manage.

4. Toe in the left and right speakers.

5. If you have a subwoofer, experiment with placement, levels and crossover.

Good luck!

Remove the rest of the sidewall and eliminate the corner. ;)

Do you mean take out the drywall on the sidewall and inset the acoustic treatment so it doesn't stick out?

I'm in a similar situation.

Try these things, if you haven't already. They'll make a HUGE difference in both deadening the room and reducing bass boost...

1. Put as much padding around AND behind the screen as possible. Put up a layer of egg cartons, foam or whatever you can manage, followed by black carpet like Wonderwall. You'll have a black "feature wall", and it'll make your projected picture stick out more.

2. Experiment with plugging up the bass ports on your front speakers.

3. Get the front three speakers as far out from the wall as you can manage.

4. Toe in the left and right speakers.

5. If you have a subwoofer, experiment with placement, levels and crossover.

Good luck!

Thanks. I have planned to do acoustic treatment on the screen wall as well, but I figured I needed the treatment to wrap around the corner somewhat since my L/R speakers will be about 1 1/2 feet out from the room corners.

Would this work?

Any other ways out of this dilemma. I'm really trying to maintain the image size I want.

Thanks.

From personal experience I would say figure out a way to not have the speakers so close to the side wall on the left. The space on the right looks pretty ideal. The proximity of the left side wall can create imaging problems and bass problems that would otherwise be less severe.

"If I had it to do over again" I would sacrifice some screen size for more flexibility with speaker placement.

From personal experience I would say figure out a way to not have the speakers so close to the side wall on the left. The space on the right looks pretty ideal. The proximity of the left side wall can create imaging problems and bass problems that would otherwise be less severe.

"If I had it to do over again" I would sacrifice some screen size for more flexibility with speaker placement.
I was thinking the same thing. To maximize screen size and still have optimum speaker placement, I'd be looking at an acoustically transparent screen on a false wall - or a drop down AT screen - with the speakers behind the screen.

Just my $.02.

- Jeff

Drop your screen size to a 120"D 2.35 to 1 screen. Move the screen up higher on the wall. Place 3 identical center channel or 3 small identical bookshelf/monitor speakers horizontally beneath the screen as LCR.

bookshelf/monitor speakers horizontally beneath the screen as LCR
ONLY if the speakers are specifically designed to be used horizontally. Just because the say "LCR", doesn't mean you can install them anyway you want.

Yep, that didn't come out right.

I meant to say 3 center channels as LCR under the screen, mounted horizontally as designed, well away from the sidewalls, or 3 small bookshelf/monitors mounted vertically as designed, but spread out as LCR in a horizontal fashion, under the screen, well away from the sidewalls. Therefore, if you elect to use Bookshelf/monitors, they have to be short vertically speaking.

Do you mean take out the drywall on the sidewall and inset the acoustic treatment so it doesn't stick out?That's an idea but I meant that, if you remove the rest of that sidewall (with the big opening), you eliminate the corner as an acoustic issue.

Great feedback folks,

So you think it would actually sound better if I put the L/R speakers beneath the screen so they would get away from the side walls?

I have contemplated that before. I have little angled stands meant for a similar application. The speaker is held about 6" off the ground but angled up toward the listener...which is how my center channel is sitting at the moment. Acoustic treatment could go on the wall behind the speakers.

All the speakers (which I love and intend to use) are Hales Transcendence speakers - the T1 L/R monitors on stands and the (at one time very expensive) Transcendence Cinema Center Channel, which is quite big and provides a very hefty sound, while matching very well, timbrally, with the L/Rs. I actually do have a second pair of T1 monitors so if I wanted to I could have 3 perfectly matched speakers beneath the screen, but I'd like to try it first with the center channel since it sounds gorgeous.

For those who've tried that L/C/R under the screen, how does the sound match the picture vs the L/R higher and to the side of the screen?

(Kal, thanks, but that's a no-can-do in my room.)

Thanks,

I have personally discussed this concept with two different Cedia level whatever certified designers, a Revel rep, and had several positive reponses from AVS members on a couple different posts. All have stated this approach is much better than sticking the LR near the sidewalls. Your particular room looks like an acoustical nightmare from a timbre matching POV for the L/C/R, having the closed wall on the left and the open wall on the right. I would try to reduce the effects of those sidewalls as much as possible by getting the LR away from them and into the room if possible.

Great feedback folks,

So you think it would actually sound better if I put the L/R speakers beneath the screen so they would get away from the side walls?
Definitely get the speakers away from the sidewalls, but I think it would sound best with the speakers behind the on-screen image.

What's the difference between being near a side wall and being near the floor? Not much. Only highly directional speakers can work to help resolve that. None-the-less, even if you move the speakers in from the one side wall, you're going to have a timbre issue...and a big one if you don't have your crossovers at 80Hz and the speaker 3.5' (or better) from any boundary. You can treat the boundary to help; but, you cannot make up for a missing wall.

Getting the speakers higher, like behind the screen (or in front if you prefer), treating the boundary, and getting more directional speakers will all go to improve the situation.

As to your speaker choice. Ok choice; but, what criteria are you using to select those speakers? If you did not put them in YOUR room, positioned where you intend to, the speakers you heard are NOT the speakers you will hear. Just beware. What sounded good in one place may not sound good in another.

Thank you for weighing in Dennis...

What's the difference between being near a side wall and being near the floor? Not much. Only highly directional speakers can work to help resolve that. None-the-less, even if you move the speakers in from the one side wall, you're going to have a timbre issue...and a big one if you don't have your crossovers at 80Hz and the speaker 3.5' (or better) from any boundary. You can treat the boundary to help; but, you cannot make up for a missing wall.

I'm not sure I followed that. Wouldn't the scenario be somewhat evened out by having the 3 speakers beneath the screen, well away from the side walls (since I have a very uneven side-wall situation)? One other issue is that if you look at the sketches I posted you'll see that the speaker on the right is very close to the fireplace which is reflective metal and tile about 2 feet from the right of the tweeter. Not ideal :( so I think maybe getting it away from there could help (in putting the L/R beneath the screen...with the wall treated behind them). No?

FWIW I don't intend to use a subwoofer (various reasons).

Getting the speakers higher, like behind the screen (or in front if you prefer), ...

Sorry I'm a bit confused again. When you say "or in front if you prefer" do you mean following the suggestion of others in putting the speakers below the screen?

As to your speaker choice. Ok choice; but, what criteria are you using to select those speakers? If you did not put them in YOUR room, positioned where you intend to, the speakers you heard are NOT the speakers you will hear. Just beware. What sounded good in one place may not sound good in another.

Oh yeah...I'm all too aware of that. This used to be my high-end audio listening room. In order to make it into a Home Theater I've had to flip the location of the sofa and speakers 180 degrees. In doing so I went from having wonderful acoustics, and beautiful smooth response from practically any decent speaker I put in there...to...yuck! Suck-outs, peaks, crappier sound all around, even moving the speakers away from boundaries. I'm not happy.

Still, the Hales speakers are sounding "themselves" enough that I still like them and wish to salvage the enterprise somehow. The center channel were it is, beneath the screen actually sounds terrific (despite some bass bloat as I haven't treated anywhere).

To make all these matters worse, I'm STILL trying to use this as my 2 channel listening room too! My plan was to have the L/R speakers on stands and when I want to listen to 2 channel, pull the stands out into the room closer to the listening sofa for what I would hope would be better acoustics (or at least cutting out more of the room effects).

Thanks.

Rich,

I have been reading your posts now for over 3 years.

Quite frankly, I am very surprised at what you are trying to do with this room.

The Rich I have known from your previous posts would never consider using a front projection set up in this room for a multitude of reasons both on the audio side and the video side.

I I were you, an extremely picky videophile, I would either pick a different room for your HT, give up on the front projector and go with a big LCD or Plasma, or rip out the columns and close that room off with a new sidewall and door.

Wait for the new 70 inch Sony LCD with LED backlighting. Mount it high enough on the wall so that you have room to get the LCR's well off the floor and in from the sidewalls. Anyway you do it with this room, you are going to hate seeing the tops of those speakers lit up from the light coming from the screen.

Dang nabit. It's too early for this. :)

Exchanging one boundary condition for another isn't necessarily going to result in improvement (wall vs floor). Although floors tend to have moderate treatments (carpet & pad). What needs some investigation is the off axis response of the speakers. As well, a perfectly symmetrical placement simply means the SBIR from the left speaker is reinforced by the SBIR from the right. Here, however, the L/R differences are to the extreme.

The in front of the screen comment was tongue in cheek. Sorry.

Here's a telling comment, however. For two channel you're putting the speakers on stands and moving yourself closer to the near field. Why should speaker placement change? If the sound is better with the speakers pulled away from the walls and placed higher for two-channel, why would you degrade the sound just because you have your center channel running? In the end (in this case), to get a big picture, audio becomes the sacrificial lamb simply because the space doesn't lend itself well to boundary treatments.

What's the difference between being near a side wall and being near the floor?
Well, I can see that the big difference would be that the speaker designers "know" where the floor is and, if they are worth their salt, design for it. They have no idea where the side walls are. Some designers will include a SBE adjustment, but it needs to be engaged by the customer and then it is usually only a coarse correction. The simple solution is, as was recommended, keep speakers away from side walls.

Well, I can see that the big difference would be that the speaker designers "know" where the floor is and, if they are worth their salt, design for it.
I wish that were true. In a better world CE speaker manufacturers would give us polar plots like we have in the Pro side. Unfortunately, while only makers of floor standing speakers "know" where the floor is, measurements don't show any effort to minimize floor/ceiling interactions except for those few with directed wave guides (and similar mechanisms like horns (ala JBL for example). This is before we even get to the lobing effects. Typically horizontally aligned (or "center") speakers tend to be more forgiving of floors/ceilings and less forgiving of adjacent walls.

Again, because designers know that listeners tend to be on a very narrow vertical plane, above and below driver off axis response tends to be very poor while left to right off axis response is (in some cases) given some attention. These factors become very critical in room set up and design. With good off axis response, we want more reflection (and diffusion) and less absorption. With bad off axis response, we want absorption.

Rich,

I have been reading your posts now for over 3 years.

Quite frankly, I am very surprised at what you are trying to do with this room.

The Rich I have known from your previous posts would never consider using a front projection set up in this room for a multitude of reasons both on the audio side and the video side.
......

Wait for the new 70 inch Sony LCD with LED backlighting. Mount it high enough on the wall so that you have room to get the LCR's well off the floor and in from the sidewalls. Anyway you do it with this room, you are going to hate seeing the tops of those speakers lit up from the light coming from the screen.

If you'd been reading my posts you should know a 70 inch LCD is probably the last display I'd buy :);)

I've never really cared for LCDs, can't stand the off-axis performance among other things. I'd been planning the room around a 65" plasma but once I borrowed a friend's projector I was hooked on the cinematic experience. Plasmas are too small.

I won't see the tops of the speakers lit up: I've already experimented and will be covering the speakers with black material - they totally disappear when I do this.

Thanks twenty/twenty.

Dang nabit. It's too early for this. :)

Exchanging on boundary condition for another isn't necessarily going to result in improvement (wall vs floor). Although floors tend to have moderate treatments (carpet & pad). What needs some investigation is the off axis response of the speakers. As well, a perfectly symmetrical placement simply means the SBIR from the left speaker is reinforced by the SBIR from the right. Here, however, the L/R differences are to the extreme.

Thanks for the info.

What I have to do, I think, is get an AV receiver into the room so I can experiment to see what the speakers sound like in the corners vs aligned below where my screen would go.

The Hales speakers were known for good off-axis performance - one of the design goals. Previous to switching the room design, I'd had the Hales L/R monitors on the small stands that angle them from the floor. They sounded quite good, aside from a bit too much bass, which I hope I can tame somewhat with treatment. Anyway, I guess we can speculate only so long so it's time for me to try this out. I certainly appreciate your input.



Here's a telling comment, however. For two channel you're putting the speakers on stands and moving yourself closer to the near field. Why should speaker placement change? If the sound is better with the speakers pulled away from the walls and placed higher for two-channel, why would you degrade the sound just because you have your center channel running? In the end (in this case), to get a big picture, audio becomes the sacrificial lamb simply because the space doesn't lend itself well to boundary treatments.

Audio is essentially the sacrificial lamb here, in terms of maximising picture over sound.

Unfortunately in this room orientation (and it's the only one that will work with a projection set up), the speakers simply can not be left in an optimal position for 2 channel listening, as they would be too far into the room and especially with respect to the doorway, be in people's way, might be knocked over and just destroy any possible traffic flow in the room. Not only that, optimally setting up for 2 channel in this room would mean a very small projection screen to fit between the L/R speaker positions, at which point it would be "why bother?"

So the best solution I can figure is I could have the speakers on stands put more toward the corners and with treatment get good, if not optimal sound for movies from them. And when I'm going to listen "critically" to 2 channel music, I'd just pull the L/R speakers out to my standard position, more nearfield - not that much of a physical hassle. That's the best I can come up with since this is the only room I have for such things and have to deal with the challenges of trying to satisfy my desire for both Home Theater projection and my two channel listening.

Thanks.

you are going to hate seeing the tops of those speakers lit up from the light coming from the screen.

i can say that i definitely do hate it in my ht.

i was wondering, if i put velvet on top of my speakers to absorb the light, will that hurt the sound? i'm trying to make these suckers disappear when they movie is on. my room is a bat cave: everything is painted black, black seats, and charcoal gray carpet. but those gosh darn speakers (even tho black) are annoying under the screen. i don't have room to put them behind the screen

I'm in the same position in wanting the speakers to dissapear, so I've tried black velvet
on the speakers. It certainly made them disappear when on the sides of the screen. And I do remember it seeming to work with my center channel as well.

Even if you have black speakers they are still going to reflect light, hence if you really want to make them disappear it seems covering the reflective surface with some material is the way to go. The other thing I've done to minimize reflection is to angle the speakers upward toward the listening position, such that I can't see the tops of the speaker - the only thing facing me is the black grills so I don't see the speaker with the lights off.

actually, maybe velvet would be bad (high frequencies). i dunno.

btw, do any of you sound gurus know if this is bad for the sound: to black out light from windows, i cut these and thumbtacked them to interior of the windows, but material is not cushy or foamy, it's like plastic.

http://www.lnt.com/product/index.jsp?productId=1351360&cp=2167013.1331964.2476954&view=all&parentPage=family


53% polyvinyl chloride, 35% polyester, 12% polyurethane


my room: two windows on the side wall (about 1 foot above LCR and begin at 1 foot from the front of the speakers). one 70 inch window behind the screen. one 70 inch window on the back wall.

if i should put acoustical treatments in the windows (for example, the auralex foam i have blocks light), do you reommend any certain thickness/material types?

i will try to take some pics if that's easier

never mind the previous posts. the two side windows are not at the first reflection points. front and back windows i'll figure out at some point. i guess i'll try to create a bass trap that fits.

O.K. sorry to do this but ive just started the process of finishing the garage and need a little help....here is the basics:

ROOM..A standard two car garage. almost square dimensions.

equiptment... paradigm studio 60s the larger studio center from paradigm and the seismic 12 sub.

can you guys recomend a source for me to refer to regarding acoustical treatments. this thread is HUGE and Im sure its all here but i just don have the time to read it all. Thanks in advance!!

can you guys recomend a source for me to refer to regarding acoustical treatments. this thread is HUGE and Im sure its all here but i just don have the time to read it all.

No kidding. Some of the posts in this thread discuss how useless this thread has become because of the size and so much conflicting advice. :D

Room treatment is a deep subject, so here's the short version which will get you 99 percent of the way there. All rooms need:

* Broadband (not tuned) bass traps straddling as many corners as you can manage, including the wall-ceiling corners. More bass traps on the rear wall behind helps even further. You simply cannot have too much bass trapping. Real bass trapping, that is - thin foam and thin fiberglass don't work to a low enough frequency.

* Mid/high frequency absorption at the first reflection points on the side walls and ceiling.

* Some additional amount of mid/high absorption and/or diffusion on any large areas of bare parallel surfaces, such as opposing walls or the ceiling if the floor is reflective. Diffusion on the rear wall behind you is also useful in larger rooms.

For the complete story see my Acoustics FAQ. (http://www.ethanwiner.com/acoustics.html)

There's a lot of additional non-sales technical information on my company's web site (http://www.realtraps.com) - articles, videos, test tones and other downloads, and much more.

--Ethan

thanks Ethan.. ill check it out now!!!

Randy

I was wondering if anyone could help me out with an acoustics question-

When I first designed my theater, I was going to use inwalls (Triad Classic Gold Inwall LCR's) in the front wall and purchased the speakers on that assumption. I later decided, for sound isolation purposes, that it would be better to sheetrock that wall and build a false wall in front of it for the screen and the LCR's.

Would I be better off putting up sheetrock on the false wall since the inwall speakers were designed to mount against a reflective surface, just mount them to the studs and leave the screen wall open, or put the sheet rock most of the way up, but leave the top open so that I can put bass trapping behind the false wall? I would assume the last option, but wanted to check before proceeding.

Here is my build thread with a drawing:
http://www.avsforum.com/avs-vb/showthread.php?t=1043747

Thanks,
CJ

I was wondering if anyone could help me out with an acoustics question-

When I first designed my theater, I was going to use inwalls (Triad Classic Gold Inwall LCR's) in the front wall and purchased the speakers on that assumption. I later decided, for sound isolation purposes, that it would be better to sheetrock that wall and build a false wall in front of it for the screen and the LCR's.

Would I be better off putting up sheetrock on the false wall since the inwall speakers were designed to mount against a reflective surface, just mount them to the studs and leave the screen wall open, or put the sheet rock most of the way up, but leave the top open so that I can put bass trapping behind the false wall? I would assume the last option, but wanted to check before proceeding.

Here is my build thread with a drawing:
http://www.avsforum.com/avs-vb/showthread.php?t=1043747

Thanks,
CJ
For bass traps to work behind a false wall, the false wall needs to be acoustically transparent - at least at the lower frequencies. Will your speakers be behind an AT screen?

For bass traps to work behind a false wall, the false wall needs to be acoustically transparent - at least at the lower frequencies. Will your speakers be behind an AT screen?

The speakers will be behind an AT screen. However, I don't think I described very well what I thought the best option would be. That would be to mount the speakers in a false wall that is sheetrocked up to about 2 feet below the ceiling. I'm covering the wall in fidelio velvet, so the bass should be able to pass right through that opening.

Here's a diagram:
http://i242.photobucket.com/albums/ff256/coneilliv/ScreenWall.jpg

Thanks,
CJ

The speakers will be behind an AT screen. However, I don't think I described very well what I thought the best option would be. That would be to mount the speakers in a false wall that is sheetrocked up to about 2 feet below the ceiling. I'm covering the wall in fidelio velvet, so the bass should be able to pass right through that opening.

Thanks,
CJ
Sorry to seem like I want to spend your money, but with your design change (solid drywalling instead of in-wall spkrs there), have you considered non-inwall speakers? The inwalls' reason for being is no longer. And "regular" speakers don't have the compromises that inwalls have. They might be getting better, but they are still compromised.

A wall closely spaced behind an AT screen would cause comb filtering.

Just my $.02.

- Jeff

Sorry to seem like I want to spend your money, but with your design change (solid drywalling instead of in-wall spkrs there), have you considered non-inwall speakers? The inwalls' reason for being is no longer. And "regular" speakers don't have the compromises that inwalls have. They might be getting better, but they are still compromised.

A wall closely spaced behind an AT screen would cause comb filtering.

Just my $.02.

- Jeff

Don't worry- it's a good balance. You try to convince me to spend my money and my wife tries to convince me not to! I'm guessing that I'll be using the inwalls for the next year or two.

I thought that the screen being too close to the speakers cause the comb filtering.. I plan to have the screen offset about 6 inches from the false wall. Also, I forgot to mention that I will put 2" of OC 703 or similar on the drywall (but obviously not in front of the speakers).

Thanks,
CJ

Don't worry- it's a good balance. You try to convince me to spend my money and my wife tries to convince me not to! I'm guessing that I'll be using the inwalls for the next year or two.

I thought that the screen being too close to the speakers cause the comb filtering.. I plan to have the screen offset about 6 inches from the false wall. Also, I forgot to mention that I will put 2" of OC 703 or similar on the drywall (but obviously not in front of the speakers).

Thanks,
CJ
You also have the recommended distance between speaker baffle and screen. I've always thought it to be at least 9" with +12" being better. I guess my point is that you may make the effort to use the inwalls only to find that the performance is unacceptable. And then have to expend even more effort to correct it - with wall mounted speakers instead of inwalls. And 12" plus speaker depth between wall and false/screen wall.

Check the website linked in my sig - the neverending home theater upgrade. I've passed this way already.

You also have the recommended distance between speaker baffle and screen. I've always thought it to be at least 9" with +12" being better. I guess my point is that you may make the effort to use the inwalls only to find that the performance is unacceptable. And then have to expend even more effort to correct it - with wall mounted speakers instead of inwalls. And 12" plus speaker depth between wall and false/screen wall.

Check the website linked in my sig - the neverending home theater upgrade. I've passed this way already.

Boy- not what I wanted to hear! Aren't onwall speakers designed with the same near-wall boundary considerations as inwall speakers? At least I have a few months before I'm far enough along to where I really have to make a decision.

Thanks for the information and advice,
CJ

Boy- not what I wanted to hear! Aren't onwall speakers designed with the same near-wall boundary considerations as inwall speakers? At least I have a few months before I'm far enough along to where I really have to make a decision.

Thanks for the information and advice,
CJ
I'm pretty sure that inwall speakers are designed specifically to be flush with a wall. As for "non-inwall" speakers, they are not designed with any boundaries in mind. Some users will put them on stands, some wall-mounted and others perhaps in home entertainment furniture.

But my caution is re the distance between speaker face and screen and your wall and screen for reasons of comb-filtering. If you haven't, check my website.

You have time, so seek the opinions of others before deciding.

I'm pretty sure that inwall speakers are designed specifically to be flush with a wall.

They are.

As for "non-inwall" speakers, they are not designed with any boundaries in mind. Some users will put them on stands, some wall-mounted and others perhaps in home entertainment furniture.

Sorry- I didn't pay close enough attention. I thought that you were using onwall speakers rather than free standing speakers. Good onwall speakers also take into account the boundary effects of the wall on which they are mounted.

But my caution is re the distance between speaker face and screen and your wall and screen for reasons of comb-filtering. If you haven't, check my website.

You have time, so seek the opinions of others before deciding.

You are now using an SmX screen, which is what I'm going to be using. According to Ruben and based on measurements that he has taken, you can mount their screen within a couple of inches of the speaker without any noticeable comb filtering. I'm not sure that I buy that, which is why I was extending that to 6 inches...

Thanks again,
CJ

Sorry- I didn't pay close enough attention. I thought that you were using onwall speakers rather than free standing speakers. Good onwall speakers also take into account the boundary effects of the wall on which they are mounted.
That was my thinking until Mr. Erskine posted this (http://www.avsforum.com/avs-vb/showthread.php?p=14178415#post14178415).

You are now using an SmX screen, which is what I'm going to be using. According to Ruben and based on measurements that he has taken, you can mount their screen within a couple of inches of the speaker without any noticeable comb filtering. I'm not sure that I buy that, which is why I was extending that to 6 inches...
Me neither, but Ruben knows his product and I am not able to reconcile it. Anyway, I'll remeasure tonight as I might have misremembered the distance between the screen and the speaker baffle.

- Jeff

ugh this is becoming a pain trying to get tweeters to be ear level without being in the way of the screen. speakers have to be lower than screen's bottom edge obviously.

if speakers are low (say, 16 inches off the floor), should i add another plush rug under them to reduce the reflections?

ugh this is becoming a pain trying to get tweeters to be ear level without being in the way of the screen. speakers have to be lower than screen's bottom edge obviously.
a c o u s t i c a l l y t r a n s p a r e n t s c r e e n.

if speakers are low (say, 16 inches off the floor), should i add another plush rug under them to reduce the reflections?
The thickest carpet pad you can find would be good.

I'm sure I already know the answer to this but here goes. Would there be a huge issue of using Knauff? board to patch an area in a theater that has Lin RC 1" everywhere else. I only need a 4'x12' piece of Lin but of course I have to buy a roll of 50' to get it. Knauff comes in 4x10' and several places stock it.

I'm probably going to go with a roll of Lin RC but just wondered if there was a big enough difference between the two to cause issues.

No, Knauf won't work!!

Just kidding. :)

Knauf 2.25 pcf fiberglass is fully equivalent to JM Linacoustic RC.

Regards,
Terry

Knauf, Knauf, who's there?

What Terry said (the second time).

On GIK website it says that GIK’s design of the 244 (and The GIK Monster Trap) is to allow it to be used in quantity, to absorb as much bass as possible without over absorbing the high end, which leaves life inside of the room.

What is designed into GIK Panels to prevent over absorbtion at the mid and high ends?

How does this compare to the membrane on the Realtraps panels?

On GIK website it says that GIK’s design of the 244 (and The GIK Monster Trap) is to allow it to be used in quantity, to absorb as much bass as possible without over absorbing the high end, which leaves life inside of the room.

What is designed into GIK Panels to prevent over absorbtion at the mid and high ends?

Not GIK, nor do I play GIK on television, but the highs are absorbed at the surface and total absorption depends entirely upon surface area. Absorbing mids requires more depth (thickness), but no additional surface area, i.e. no more highs are absorbed. And lows require even more depth in the absorber - the more depth, the more absorption. Again, this is all accomplished with no additional (high frequency absorbing) surface area.

Usually, the amount of deep bass traps needed does not contain enough surface area to over deaden the room. It's not that anybody's traps are designed to prevent over absorption, it's just that the amount required to do the job doesn't deaden the room. It is a happy coincidence of physics. :)

Absorbing mids requires more depth (thickness), but no additional surface area, i.e. no more highs are absorbed. And lows require even more depth in the absorber - the more depth, the more absorption. Again, this is all accomplished with no additional (high frequency absorbing) surface area.

Have to disagree with you here, pepar. The Sabin is the fundamental unit of sound absorption at any frequency. Metric Sabins have the dimensions of square meters, and Imperial Sabins the dimensions of square feet. Surface area is implicitly involved in computing and using sound absorption materials.

At low frequencies (wavelengths comparable or large with respect to the dimensions of the surface), diffraction effects come into play, and there is not a simple linear relationship with area. But surface area still plays a significant role. I have built very low frequency bass traps which were many feet across, and extending floor to ceiling. Yes, these were also very deep (about 3 feet). As you correctly point out, absorption frequency is related to depth of absorber. but this does not allow one to skimp on surface area!

Regards,
Terry

Have to disagree with you here, pepar.
Thanks, Terry. From LDD1's post, a quote he says is from GIK's site, how would you answer his query:

"GIK’s design of the 244 (and The GIK Monster Trap) is to allow it to be used in quantity, to absorb as much bass as possible without over absorbing the high end, which leaves life inside of the room.

What is designed into GIK Panels to prevent over absorbtion at the mid and high ends?"

I have built very low frequency bass traps which were many feet across, and extending floor to ceiling. Yes, these were also very deep (about 3 feet). As you correctly point out, absorption frequency is related to depth of absorber. but this does not allow one to skimp on surface area!

Terry,

So what effect did this kind of enormous "very low FR" bass trap have on mid/high frequencies?

What frequencies are absorbed exactly with such a huge bass trap?

Thanks for the help!

Phil

What is designed into GIK Panels to prevent over absorbtion at the mid and high ends?"
I don't know what they use. But one typically uses a thin membrane on the surface, such as paper or foil, which will reflect high and mid (depending on the membrane weight, cavity depth, etc.) frequencies.

What frequencies are absorbed exactly with such a huge bass trap?

I have designed some to absorb with a peak frequency below 30 Hz. I have also designed wideband absorbers that absorb very efficiently from 50 Hz all the way up to 20,000 Hz.

The important thing is that a bass absorber does not generally have neatly separable components, each with their own independent characteristics -- membrane, porous absorption layer, etc. All of these interact to form a system with certain composite properties.

The interactions are, for the most part, relatively simple. This is physics, guys! You can't say that you have a mass that resonates at 100 Hz, or a spring that resonates at 100 Hz. You may have a mass on top of a spring (on top of the earth), which together resonate at 100 Hz. :)

Regards,
Terry

I am not sure this is the right place to put this question, so please let me know if this question should be in a different forum.
I am currently in the process of looking for a house to rent and one of the good candidates has a room with walls made of wood logs (on the inside). The outside of the house is brick, and I am not sure how much insulation there is between the logs and the bricks. One of the walls is drywall, and I plan of putting a screen/tv there. There is only one level in the house. This is the biggest living area in the house and there is not much outside light, so I'm thinking it may make for a good theater/game room. The log room is carpeted. The ceiling is constructed with wood as well. There is another smaller living area with drywall, but there are hardwood floors and much more light coming in. Which room would sound best, untreated? Which room is easiest to treat - financially and labor-wise ? I plan on putting a 5.1 system in that room. Any help would be greatly appreciated.

http://img365.imageshack.us/img365/6756/roomfullviewiv1.jpg


http://img79.imageshack.us/img79/6130/closeupcornerjm1.jpg



Just reporting back in for a moment. I had the dilemma of where to put my speakers for the best sound, especially as the very wide screen puts the speakers into the corners. I finally got hold of an AV receiver to get an idea of what kind of sound I'm getting with the speakers configured as above. I tried a couple things:

1. I tried the Hales dedicated Center channel with the Hales monitors on the sides. They are timbrally quite close and the center channel is a killer speaker in of itself. However I was fairly aware of the "center-channel" insofar as voices coming from the speaker. I'm really trying to free the sound up to get "out" of the speakers and "on to" the screen.

As I have two pairs of the Hales L/R monitors, I tried replacing the centre channel with another monitor, hence 3 of the exact same speakers for L/C/R, all arranged vertically (the center monitor below the screen on a stand angled up to the listener). Not surprisingly, this really did result in a greater cohesiveness to the sound, making it more like a continuous soundfield across the image. The monitor isn't quite as direct or clear as the center channel it replaced, but I think the coherency makes up for it and the sound does seem to stick more to the screen (you lucky folks who can do behind-the-screen speakers!).

At this point I'm wondering how much of this coherent quality I might get if I put the center speaker back in and use the Audyssee room eq from this amp. (One of the next things to try).

2. As per some other suggestions (and I was going to try it anyway), I also tried taking the speakers off the stands and aligning them under the screen, to get them away from the side walls. I figured this would actually work better but it actually did not. The sound was more congested when placing the speakers under the screen. I lost that open, expansive spaciousness and the sound did seem to come from "under" the image. The L/R speakers, when on their stands to the side of the screen, actually sounded better and seemed to "lift" the soundfield up more to screen height.

So I think I know where my speakers will be placed. I have to say I was actually surprised given the speaker placement how darned good movies sounded! Pretty smooth and spacious. More serious 2 channel listening with only the L/Rs shows I have acoustic work to do, though. It still sounds somewhat crude.

All this...and I am actually also doing an experiment trying some other speakers which could be amazing or a disaster. :)

Anyway, that's it for my update. I appreciate very much the input of folks on the thread. I'll no doubt be getting to some more questions as things progress (and my acoustician is doing up a design at the moment that I wouldn't mind passing by the people here as well).

Thanks,

Hello everyone,

First of all, i am extremely green on sound treatments and principles. All that i know is from reading these forums.

I am in the final stages of remodeling my basement room into a home theater. I have read most of this thread but there is so much to process. I am looking for some simple directions on how to treat my room.

Some information:
Since the room was already finished, i was limited with what i could do with regards to placement of speakers.
My room is 14.5 x 25 x 8.5. I am using half the room for the HT, so that is approx 14.5 x 13 x 8.5.
I really only have 1 90 degree corner in the room, that is in the back by the riser. The other "corners are angles, or doorways, or a wet bar.

The front wall is a floor to ceiling wall unit made from Oak, with speaker boxes for LCR. all the cavities are filled with insulation.
The sub is in a small half height cabinet on the right side of the room
In the back of the room i have a 12" riser, and there are 2 in ceiling speakers. The riser is also filled with insulation
The back wall and 1 side wall have windows

All the equipment is brand new. I haven't even powered it up yet, so i don't know what anything sounds like. i was waiting until the "construction" phase was complete before i unpacked the equipment due to dust, etc.

All the speakers are B&W, and the Sub is Velodyne DD-10
The receiver is the Sony STRDA5300ES Receiver.

Both the receiver and the sub have microphones and software for eq'ing the room.

In all the speaker boxes, i treated the inside with 1" OC705. I have more left over and could build panels with the extra.

So would like to treat the room, but not really sure where to start.

Should i start with the utilities with the receiver and sub? Not sure what type of information/output that would provide me to understand what to do next though.

I have read a little bit on REW, would that be better?

- Should i treat first reflections with the 705? Something else?
- In my 1 90 corner, i imagine i should put a base trap there? Make it out of the 705 or something else?

I am not an audiophile by any means, i would just like to provide the best HT environment within the limits that i have. I cant afford a professional to come test/treat my room. besides i like the DIY aspect of it anyway.

I am open to suggestions. Please ask me more more information as needed.

Thanks for any help.

I am looking for some simple directions on how to treat my room.

Yeah, there's too much information in this thread, and much of it is conflicting and confusing. Start here:

How to set up a room (http://www.realtraps.com/art_room-setup.htm)
Bass traps article (http://www.positive-feedback.com/Issue13/rives.htm)

--Ethan

Thanks Ethan.
I read over the information. Good stuff.

My challenge is that since i have no flexibility as to where to place the speakers, i need to maximize what i can with what i have.

What would be a good way to do that?
Should i get REW and start running tests?

Will the EQ software included with my equipment be sufficient? - i suspect not.

Also, should i build some panels out of the OC705? or would it be better to use it for a base trap and get something else for panels?

Thanks for the help.

Thanks Ethan.
I read over the information. Good stuff.

My challenge is that since i have no flexibility as to where to place the speakers, i need to maximize what i can with what i have.

What would be a good way to do that?
Should i get REW and start running tests?

Will the EQ software included with my equipment be sufficient? - i suspect not.

Also, should i build some panels out of the OC705? or would it be better to use it for a base trap and get something else for panels?

Thanks for the help.
There are quite a few knowledgeable acousticians on this thread. I recommend that you get a few opinions before taking any particular course of action.

Thanks pepar,
Nice build BTW.

Feel free to lob in your recommendations as well :-)

Thanks pepar,
Nice build BTW.

Feel free to lob in your recommendations as well :-)
I am not an acoustician and could only tell you that what I've done in my room has made a huge improvement and has resulted in a room/system that is quite impressive.

BTW, the "conflicting" information on this thread is mostly with regard to which of it is "too much." ;)

Should i get REW and start running tests?

You could measure your room, but it won't tell you much. Mostly it will show you how bad things really are. :D Regardless of what you measure the solution is more or less the same: As many corner bass traps as is practical, and absorption at the reflection points on the side walls and ceiling.

Will the EQ software included with my equipment be sufficient?

EQ is never a substitute for bass traps and other room treatment.

--Ethan

Thanks Ethan.

That will get me going.
A few more questions:

I have a box of OC705, so that is the basis for some of these questions.

- is OC705 good for first reflections? Or better for a base trap?
- for side walls, how high/long should i add OC70x? is a 2x4 panel sufficient dimension? My speakers are 39" tall, and are close to the side wall.
- does a corner trap need to be 100% filled with material (ie corner wedges) or can it be a series of progressively smaller vertical panels behind each other.
- for a corner that is greater than 90, would a trap be needed?
- my sub is in a cabinet, my intent was to fill the cabinet space around the sub with OC70x, hoping it would alleviate any potential issues. Worthwhile?

Thanks Ethan!

also, for those interested. Here is a rough markup of my room. Maybe it will help make recommendations.

There is/will be furniture in the room.
4 recliners on the platform. Table and chairs on the left side of the room.
sofa in front of the platform.

I am concerned with the windows on the right side of the room, as well as the back wall. Any suggestions there will be appreciated.

Thanks,
Roby

also, for those interested. Here is a rough markup of my room. Maybe it will help make recommendations.

There is/will be furniture in the room.
4 recliners on the platform. Table and chairs on the left side of the room.
sofa in front of the platform.

I am concerned with the windows on the right side of the room, as well as the back wall. Any suggestions there will be appreciated.

Thanks,
Roby
I'd be concerned about the right wall, too. But my concern would be about the speaker so close to it. As laid out, the left and right speakers will sound dramatically different. Any way to rotate your theater 90° clockwise putting the screen over the window and having L&R speakers well off - and equidistant from - the walls?

- is OC705 good for first reflections? Or better for a base trap?

Sure, 705 is good for both.

for side walls, how high/long should i add OC70x? is a 2x4 panel sufficient dimension?

It depends on how deep your room is and other factors. For a home theater I'd think you want at least two panels on each side wall. And more on the ceiling.

- does a corner trap need to be 100% filled with material (ie corner wedges) or can it be a series of progressively smaller vertical panels behind each other.

Panels four inches thick are fine, and filled is better. But only a little better. Not proportionally better for the amount of extra material needed.

for a corner that is greater than 90, would a trap be needed?

Yes.

my sub is in a cabinet, my intent was to fill the cabinet space around the sub with OC70x, hoping it would alleviate any potential issues. Worthwhile?

I don't know what you mean. But generally, you want bass traps in as many corners as you can, including those where the walls meet the ceiling (and floor if possible).

Here is a rough markup of my room.

Is the screen at the top and your seating at the bottom? If so, you'll do a lot better rotating the setup 90 degrees clockwise so the screen is on the right side.

--Ethan

Any way to rotate your theater 90° clockwise putting the screen over the window and having L&R speakers well off - and equidistant from - the walls?

Hi pepar,
Unfortunately no. everything is fixed. So i am trying to improve the areas that I can, realizing there will be some challenges that i may not be able to overcome.

Can you suggest anything to help to alleviate the fact the speakers are not equidistant from the walls?

- I don't know what you mean. But generally, you want bass traps in as many corners as you can, including those where the walls meet the ceiling (and floor if possible).

- Is the screen at the top and your seating at the bottom? If so, you'll do a lot better rotating the setup 90 degrees clockwise so the screen is on the right side.

--Ethan

Thanks Ethan,
Let me see if i can offer a better description. My sub is in a cabinet in the right side of the room. the cabinet opening is larger than the sub itself, so i was going to fill the remainder of the open space with OC705. Is this reasonable? Waste of time?

Regarding the layout of the room, its fixed (completed). i cant move anything. Can you offer any suggestions to improve the situation, given that I cant move anything?

Thanks for the help!

Hi pepar,
Unfortunately no. everything is fixed. So i am trying to improve the areas that I can, realizing there will be some challenges that i may not be able to overcome.

Can you suggest anything to help to alleviate the fact the speakers are not equidistant from the walls?
You can reduce the side boundary effect (SBE) with heavy duty absorption and make it better, but it still may sound different. An AVR/pre-pro with Audyssey would help.

You can reduce the side boundary effect (SBE) with heavy duty absorption and make it better, but it still may sound different. An AVR/pre-pro with Audyssey would help.

Hi pepar,
Can you help me understand what is heavy duty?
I have treated the "inside" of the speaker column with OC705. I can put absorption panel(s) on the side wall as well.

What would you recommend?

Also, my AVR (Sony) has eq software, but i dont believe its Audyssey.

Thanks for the help!

i was going to fill the remainder of the open space with OC705.

Okay, sure, that's fine and probably a good idea..

--Ethan

I just bought 114 sf of 2" 6 lb rockboard and 96 sf of 4" 8 lb rockboard for $184.27 including tax and shipping. :)

I bought it in Birmingham Alabama from Shook and Fletcher (http://www.shookandfletcher.com/), but they have several other locations in the Southeast. They are also a dealer for Certainteed, J-M, Knauf and Owens Corning, so I bet they can get your Certainteed Commercial Board 300, J-M I/S 300, Knauf Insulation Board and O-C 703 fiberglass board too. I'd guess they'd probably also have great deals on those fiberglass board products, but I really didn't check.

A week ago I talked to the folks at the Shook and Fletcher central phone number - they were just as disinterested in our small projects as all the other commercial suppliers seem to be. :mad: Today I just walked into one of their offices and met Randy Durbin. He is happy as heck to handle the kinds of little sales we need - so I told him I'd post his name and number out on the forums we frequent. Contact him directly at (205) 595-8441 or rdurbin@ShookAndFletcher.com.

DISCLAIMER: I'm not affiliated with Shook and Fletcher, nor related to, nor otherwise acquainted with Randy - I'm just a happy customer.

BTW, I spent a whole week exchanging emails and phone calls with manufacturers and dealers all over the country. Originally I was very ignorant about their own perspective regarding the purpose for their products, but by the time I finally got to Randy I knew exactly what manufacturers and model names I was actually interested in. More importantly, I knew exactly what applications the dealer thought those models were used in (even though we would all be using them in soundrooms and theaters).

You'll find that the above list is a pretty good list of products you should be asking for in your first conversations. The dealers think that all the rockboard and the fiberglass board products referred to above are used for insulating commercial buildings.

As documented on Bobs Gold (http://www.bobgolds.com/AbsorptionCoefficients.htm), there are a bunch of other products, like duct board for example, that work just fine for us. But my experience is, if you bring up these alternative products AND the commercial building insulation products in the same conversation, you'll just confuse the dealer and make him more resistive to helping you. I'd suggest if you need to explore these alternative products, do so in DIFFERENT conversations with the dealer.

Enjoy!

Kirk

My dedicted HT is 16x27 with 9ft ceilings. I'm about ready to paint and wanted to install some basic accoustical treatments before I start. In the attached picture, a false wall will be constructed about 2 ft in front of the front wall and my speakers will all go behind an 11ft wide AT screen. From what I have read, I should put 2" OC703 panels on the front wall from floor to ceiling and maybe 4 ft down the side walls. Not sure what else I should do at this time. When the room is completed and furnished I will have a pro come in, take some measurements, and tell me what else needs to be done. Just trying to save a little money and mess at this time. Any recommendations would be appreciated.

Thanks Randy

From what I have read, I should put 2" OC703 panels on the front wall from floor to ceiling and maybe 4 ft down the side walls. Not sure what else I should do at this time.

If you have two feet of empty space in front, I'd put foot-thick fiberglass on the front wall. Two feet thick is even better. You also need absorption on the rear wall, the side-wall and ceiling reflections points, and very thick fiberglass in every corner including where the walls and ceiling meet. If you do that, you won't need to hire a pro later. :D

Much more here:

Acoustics FAQ (http://www.ethanwiner.com/acoustics.html)

--Ethan

If you have two feet of empty space in front, I'd put foot-thick fiberglass on the front wall. Two feet thick is even better. You also need absorption on the rear wall, the side-wall and ceiling reflections points, and very thick fiberglass in every corner including where the walls and ceiling meet. If you do that, you won't need to hire a pro later. :D

Much more here:

Acoustics FAQ (http://www.ethanwiner.com/acoustics.html)

--Ethan
Thanks for the response Ethan. I may not really have that much empty space behind my false wall as that is where my speakers will go. Might only be a foot because I don't know at this time what kind of speakers I'll get. Or are you saying to put fiberglass everywhere except where the speakers go? If so, what kind of fiberglass?

Thanks Randy

I'm in the same situation. I've got a false wall approximately 1 foot from the actual front wall. I was going to cover it with 1" Linacoustic or similar. Would it be better to fill the whole area (1 foot thickness) with regular fiberglass? If I do Linacoustic is it better to attach it to the actual wall or to the front or back of the false wall (creating an air gap between the fiberglass and the actual wall)?

Also, is there any value at all in treating the area behind the screen (non acoustically transparent)?

In my situation (and this was arrived at by testing):

4" of rockwool covered by another 1" linacoustic across front wall behind screen.
4" panels of rockwool on back wall (2'x7'x4"x2 panels toward the corners)

1" linacoustic up to 44" on sidewalls- several panels with about 1' between each
1" linacoutic 3x5 panel on ceiling at first reflection point.

Guys, if you have a cavity a foot thick or more, fluffy R38 fiberglass is very good. And it costs less than rigid fiberglass and is easier to find.

--Ethan

The front and side wall treatment of the alcove (I have an alcove 9' wide and 3.5' deep within which the screen is inset) made the largest single audible and measureable difference in the room. Recall I used 4" of mineral wool (Roxul) covered by 1" linacoustic (easier than covering with black fabric).

I am nearing the completion of my d-i-y home theater and have a quick question concerning bass traps that hopefully all of you out there can help me with.
I currently have clothed covered, wood framed panels that straddle the two front corners of my home theater and go from floor to ceiling. They have an 1 1/2" of Linacoustic backing the cloth, not much help acoustically, but every little bit helps. I was originally going to build superchunk bass traps with OC 703 but I am running out money/time/patience for the bass trap portion of this build.
I can get my hands on as much Linacoustic as I need for the bass traps. I was thinking that maybe I could create a triangular box out of cardboard and then fill it with Linacoustic in odd shapes and pack as much in as I can while still being able to put a top on the triangular box. Would this setup work in a bass trap application?

Guys, if you have a cavity a foot thick or more, fluffy R38 fiberglass is very good. And it costs less than rigid fiberglass and is easier to find.

--Ethan

That's good news. I have a little over a foot behind my screen wall as well as an 18" deep by 23" wide soffit running around the room. The bottom of the soffit will be GOM. It sounds like filling these with fiberglass insulation should do a good job at bass trapping?

CJ

I'm asking a question here myself, but one suggestion for CJ: Use recycled denim instead of fiberglass. It performs similarly, and you avoid using fiberglass which has tiny particles which tend to get airborne and get into your lungs and is an irritant at best. It can be sealed up, but during construction you should take precautions. Recycled denim is 100% safe and a pleasure to install in this regard.
OK, my question: I am looking to find ideas on a source of pre-made bass traps--the box type with a front membrane that is tuned to a specific frequency. Something competitively priced but still works well. Something modular, like 2' x 2', for ease of installation in a variety of room sizes. Would be a special order. If anyone knows of reliable suppliers or manufacturers of these, please let me know.
Also, if anyone knows an better way to absorb low-end bass in a tight space (i.e., can only fit something on the wall a few inches thick, not much more), please let me know. E.g., I heard of building the tiers under the seats as bass traps, but don't know how well they perform.

Using the seating platform as a bass trap can work well; however, I would suggest you engage either Terry or myself to get this right. Best results can be obtained when the seating platform extends the full width of the room and runs to the back wall.

Thanks Glenn for the recommendation for the recycled denim. A lot of people here have used it with excellent results but I had forgotten about it. Recycled denim makes a lot more sense than fiberglass for these areas as I may want to access them in the future, without bothering with the itchiness and hazards of fiberglass.

CJ

I was thinking that maybe I could create a triangular box out of cardboard and then fill it with Linacoustic in odd shapes and pack as much in as I can

Yes, that's a good idea.

--Ethan

It sounds like filling these with fiberglass insulation should do a good job at bass trapping?

Yes.

Thanks Dennis. Is there any tests done on these sort of things (bass trap tiers) that gives the figures on how much per sq ft of tier it absorbs at what frequency? I just don't know if it will be enough or not, and whether I'll still need other bass trapping of the low bass frequencies.

I have been looking for OC 703 to make some traps and just ordered some from Readyacoustics.com on sale for $69 a case, $10 off. Best price I have found so far.

I have been looking for OC 703 to make some traps and just ordered some from Readyacoustics.com on sale for $69 a case, $10 off. Best price I have found so far.
What is in a "case?" And how much was shipping?

What is in a "case?" And how much was shipping?

I took a look at the website and a case is 6 sheets, each 48"x24"x2" (i.e., 48 SF). I'm not sure about shipping.

CJ

I took a look at the website and a case is 6 sheets, each 48"x24"x2" (i.e., 48 SF). I'm not sure about shipping.

CJ
That's half of the "bale" that comes from Corning. What I bought had 12 sheets and was 24" x 24" x 48". The price seems reasonable and that quantity is great for making flat panel absorbers. For 17" x 17" x 24" SSC bass traps it would make 8 lineal feet. For the bigger version, 24" x 24" x 34", it would make only 4 lineal feet.

Shipping costs are probably "not insignificant" as a former Sec of Defense liked to say, for the quantity needed for the amount of SSC traps most rooms require.

Just my $.02.

- Jeff

i finished my panel traps last night
oc 703 4" thick covered in muslin stradeling 4 corners
i was very impressed with the difference in sound, bass quality
have not treated first reflection points yet, but so far huge difference
i need to spend some more listening time and also rerun audussy
thanks to all for a very informative thread,
mike

What is in a "case?" And how much was shipping?
Shipping was about $20 for a case of 6 sheets. I have contacted everyone that I know of that might sell this stuff and they don't even return the call or e-mail. I should have the 703 in a week.

Randy

Shipping was about $20 for a case of 6 sheets. I have contacted everyone that I know of that might sell this stuff and they don't even return the call or e-mail. I should have the 703 in a week.

Randy
Congratulations!

i have a question i hope someone could answer for me.
my first reflection point for my mains are leather couch one side, leather loveseat other.
what should i do about this?

Did this thread loss about a week of posts after the first of this month?? :confused:

Did this thread loss about a week of posts after the first of this month?? :confused:All the threads did.

All the threads did.
Well, that's a relief!

Egbert Sousé: Was I in here last night and did I spend a twenty dollar bill?
Bartender: Yeah.
Egbert Sousé: Oh boy, what a load that is off my mind! I thought I'd lost it.

From "The Bank Dick," W.C. Fields, 1940

i have another question
i have a window 2 ft. behind the screen. i would like to cover it up, then put 703 panels.
my question is, will the space between window, and board used to cover it up resonate, or cause me any sound issues?
after covered it will be basiclly a hollow box.
what would any of you do?
thanks for your help,
mike

i have a question i hope someone could answer for me.
my first reflection point for my mains are leather couch one side, leather loveseat other.
what should i do about this?

anyone?

will the space between window, and board used to cover it up resonate, or cause me any sound issues?

Yes, it could. If you pack some fluffy fiberglass inside that will avoid any such problems.

--Ethan

I'm looking for a low-cost option for acoustic panels. My theater has a polished concrete floor, so I've got plenty of echo :(

Will these do the trick?

http://www.acoustimac.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=16&category_id=15&manufacturer_id=0&option=com_virtuemart&Itemid=19

Remember, I'm not looking to spend a lot here. I already spent too much on the rest of the basement remodel project.

Thanks for your help.

I'm looking for a low-cost option for acoustic panels. My theater has a polished concrete floor, so I've got plenty of echo :(

Will these do the trick?

http://www.acoustimac.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=16&category_id=15&manufacturer_id=0&option=com_virtuemart&Itemid=19

Remember, I'm not looking to spend a lot here. I already spent too much on the rest of the basement remodel project.

Thanks for your help.

Make your own for about half the price out of 703.

cramer_a:
panels are very easy to make just wrap 703 in speaker cloth, and glue with 3m 77.
i did mine like this then stuffed them in stained frames that i made. they look very nice.
u can get everything local.
i am in kent if you want pm me and maybe i can help

Ive just finished painting my 16' x 20, room and the carpet is due in in a few days so I need to get on with the acoustic panels. I will be making these with OC 703 and 705 pannels 4" off the wall... Here is my plan:


- Screen wall - 8 pcs of 1" thick 2'x4' OC 703 covered with polly batting and
burlap for complete coverage of screen wall. mounted flush

- side walls - two 4' x4' pannels of OC 703 2" thick on each wall (first reflection points) mounted 4" off the wall

- back wall - one 4' x4' pannel of 2" 703 centered 4"of the wall

- corners - "triangle" traps made with 4" thick OC 705 floor to cieling.....BUT i can only do the two front corners and the LEFT rear corner (there is a door right smack in the RIGHT rear corner.

- ceiling - two 2' x4' 1" 703 pannels just in front of seating positions


A couple questions.....


Any thoughts on this plan....Im all ears

Is three corners going to be a problem ( off balance ect) would I be better off just doing the fronts??

would doubling the thickness of the side and rear wall pannels make any improvements? Is it really worth the extra $

ANY help or suggestions would be MUCHO apreciated!!

snookfisher:
are your corner traps ssc style?
if so save your money and just use the 703,it is said the 703 better performance for these anyway

Warlord...

Im not sure what ssc style is...

"studiotips" superchunk. Stacked triangles of fiberglass floor to ceiling.

http://forum.studiotips.com/viewtopic.php?t=535

They are very common around here for front corners, especially for folks with false screen walls that can hide them.

No ...Iwas going to basicly make a panel and wedge it in the corner to make a space behind the panel in the corner. I guess it would be a triangle but not "filled"...just 4" thick 705 on the "face" .

"studiotips" superchunk. Stacked triangles of fiberglass floor to ceiling.

http://forum.studiotips.com/viewtopic.php?t=535

They are very common around here for front corners, especially for folks with false screen walls that can hide them.
Check the link in my sig.

HMMMMMMM...looks like i may reconsider my corner plan...thanks!!

OH yea...

Any thoughts on doing the left rear corne or would it be better to keep it "balanced" and just do the fronts?

OH yea...

Any thoughts on doing the left rear corne or would it be better to keep it "balanced" and just do the fronts?
A corner is a corner. Use all you got.

I read on another forum thread that while the mixing engineer for movies sits within the critical distance (nearfield) when mixing, the critical distance extending to one's primary listening position means that the room is over-deadened. The member went on to mention a spec for the correct decay. Now, I've heard the 300ms midband decay spec somewhere, but I thought having one's seats in nearfield is even better. Nirvana even. Can someone please comment on this before I start ripping out treatments! :D

I read on another forum thread that while the mixing engineer for movies sits within the critical distance (nearfield) when mixing, the critical distance extending to one's primary listening position means that the room is over-deadened. The member went on to mention a spec for the correct decay. Now, I've heard the 300ms midband decay spec somewhere, but I thought having one's seats in nearfield is even better. Nirvana even. Can someone please comment on this before I start ripping out treatments! :D

Links would be helpful to know what you read and are referring to. The nominal for small, as in home theaters, is 250 ms for a 3,500 ft^3 room. The smaller the room, the lower. Using an 18x12x8 room as an example, the critical distance is 13.1' if treated per the EBU spec. How large is your room and what is your current treatment. Better yet, what is reverb time also?

Andre

Hey, just getting ready to do my room and have a 10' wide area just behind my seating on the back wall that I will be covering with GOM.

What kind of DIY diffusion can I put behind the GOM? I have only got about 1" of depth to play with.

FYI, the rest of the room (upper 1/2 of the wall) will be Linacoustic covered with GOM & I'm planning on running 2" of linacoustic (or 3" of JM 3lb. spinglass) behind my AT screen...

Really appreciate the help!

I know these questions have already been answered somewhere in this thread already - but this thread is huge, I will apoligize in advance and ask again anyway:

1) I am closing in on my trimwork and theater details. It is time to order GOM fabric samples and select colors to cover my screen wall, bass traps and speaker grills. Would prefer to do business with someone who is active on these forums . Reccomendations?

2) Also; I will be going with two fabric colors; a red/burgundy, and a black for the screen wall and front corner traps. As for the black fabric - which GOM product is everyone using.

Thanks !

Not really much "support" required for buying bolts of fabric. I purchase mine from Silent Source (http://www.silentsource.com/acousticore-colorchart1.html).

I'll go even further and say you should never cover any large surface area with material that absorbs the mids and highs. It makes the room too dead sounding, and does nothing to solve the inevitable low frequency problems.
You want none of the back reflections to overlay the surround field or the bring the reverberent field forward (your reverberent field and surround field is created by the multi-channel processor or mix, not so much the room as is mandatory for 2-channel).

My absorbers are 2" Owens Corning SelectSound Black.

Hey pepar (and anyone else who would be kind enough to help!),

Two questions:

1. Is Linacoustic fairly equivalent to the OC SSB you used? If not, is there something "better" at the 1" depth that I could/should use on my back wall instead of Linacoustic?

2. Seems like you have begun to feel like you over-dampened your room. I'm planning on 1" Linacoustic all around the upper half of my room (GOM covered) and using a MinWool (6lb RT 80) behind my AT screen. Is that more or less than what you've done (excluding your corner studiotips traps)?

Thanks for the insight!

Phil

Hey pepar (and anyone else who would be kind enough to help!),

Two questions:

1. Is Linacoustic fairly equivalent to the OC SSB you used? If not, is there something "better" at the 1" depth that I could/should use on my back wall instead of Linacoustic?

2. Seems like you have begun to feel like you over-dampened your room. I'm planning on 1" Linacoustic all around the upper half of my room (GOM covered) and using a MinWool (6lb RT 80) behind my AT screen. Is that more or less than what you've done (excluding your corner studiotips traps)?

Thanks for the insight!

Phil
Linacoustic RC comes in rolls making it easier to cover expanses of walls easier than sheets. My room has wall carpeting from floor to ear level of seated persons. It was recommended to me that the wall above ear level be untreated. Any surrounds other than monopoles need reflective walls to create envelopment. Since upgrading to the OP 885 and Audyssey my room/system sounds fabulous. While I have removed the rug w/heavy padding in the theater front, I probably will not make any other changes.

Thanks for that reply--though I'm concerned about the upper/lower treatment question.

I'm sure I read earlier on this thread that the it is the ratio of wall treatment to wall area that is the key stat for general absorption, not the upper/lower placement. I'm not talking about 1st reflection points, just general surface treatment.

As per the surrounds, I have in-ceiling units just above and to the side of my seating positions. They have a ribbon and a dome tweeter. So I'm curious how they'll do with this setup!

Anyone able to comment on the question of upper vs. lower absorption wall-placement?

Big thanks,
Phil

Ok, seeing how there are thirty-six hundred posts in this thread I am not going to read through them all.. ;)

I have a quick question. If I want to stop sounds from crossing through a wall between two bedrooms (roommate likes late night Star Trek marathons) would it be more effective to double drywall/green glue the side of the wall in the room that is producing the sound or on the side of the wall in the room that I want to stop the sound from entering? (my room).

Thanks!

Better to have the treatment in the room producing the sound.

Ok, seeing how there are thirty-six hundred posts in this thread I am not going to read through them all.. ;)

I have a quick question. If I want to stop sounds from crossing through a wall between two bedrooms (roommate likes late night Star Trek marathons) would it be more effective to double drywall/green glue the side of the wall in the room that is producing the sound or on the side of the wall in the room that I want to stop the sound from entering? (my room).

Thanks!
There are also some wall construction measures that can be taken to reduce transmission.

Thanks guys, that's what I was wanting to hear.. he has so many electronics and computers and stuff on shelves on his wall that I am sure he doesn't want to move anything so I can soundproof.. Seeing that it is better to DD/GG his side of the wall, it might be inscentive to simply turn down the volume :D

It's a condo, and while I own it, I would rather not tear down the wall to build an isolation chamber :p

Another quick question (I hope!):

As per the pic, I have a 36" wide (floor to fir-down) opening that will now be behind my AT screen on my front wall.

Should I just rock it closed and then apply my 6" of absorption evenly across the entire area (sans Center speaker) behind the AT screen? Or, can/should I go deeper with the absorption in that 36" wide area, since there is more room behind it?

If the absorption isn't "even" would that introduce comb-filtering?

BTW, other than the bottom shelving and my Center speaker, I won't be using the shelves/opening at all. I do want to have some access to the closet behind, but there's a crawl-way to it from another room.

Big thanks on the help!

I'm really excited about getting this done--finally. :)

Linacoustic RC comes in rolls making it easier to cover expanses of walls easier than sheets. My room has wall carpeting from floor to ear level of seated persons. It was recommended to me that the wall above ear level be untreated. Any surrounds other than monopoles need reflective walls to create envelopment. Since upgrading to the OP 885 and Audyssey my room/system sounds fabulous. While I have removed the rug w/heavy padding in the theater front, I probably will not make any other changes.

Great info Pepar!

Even though I have mono-poles, I'll probably go for just a "band" of Linacoustic all around the room at ear height and a few inches above.

Would there be a problem if I filled the rest of the height on the upper panels with some quilting batting? I heard that doesn't absorb much of anything. It would have the aesthetic ability to keep my GOM uniformly tight across the whole panel.

Here's some pics of the construction of the wall panels so far.

This thread rocks--I really appreciate everyone's help!

Great info Pepar!

Even though I have mono-poles, I'll probably go for just a "band" of Linacoustic all around the room at ear height and a few inches above.

Would there be a problem if I filled the rest of the height on the upper panels with some quilting batting? I heard that doesn't absorb much of anything. It would have the aesthetic ability to keep my GOM uniformly tight across the whole panel.

Here's some pics of the construction of the wall panels so far.

This thread rocks--I really appreciate everyone's help!
Quilted batting not absorbing much? Well, it'll absorb the highs.

Quilted batting not absorbing much? Well, it'll absorb the highs.

Yikes--I didn't realize that! :confused:

So, what should you do if only part of your panel is being filled with Linacoustic?

Would you use a faced foam board, or would that also do some absorbing?!

The trick I have is getting my fairly large spans of GOM to look uniformly "tight" or "pillowed" inside my upper panels if I only fill a part of them with absorption.

BTW, pepar, I appreciate your point about preserving the ambient field above for proper surround.

Any ideas?

Another quick question (I hope!):

As per the pic, I have a 36" wide (floor to fir-down) opening that will now be behind my AT screen on my front wall.

Should I just rock it closed and then apply my 6" of absorption evenly across the entire area (sans Center speaker) behind the AT screen? Or, can/should I go deeper with the absorption in that 36" wide area, since there is more room behind it?

If the absorption isn't "even" would that introduce comb-filtering?

BTW, other than the bottom shelving and my Center speaker, I won't be using the shelves/opening at all. I do want to have some access to the closet behind, but there's a crawl-way to it from another room.

Big thanks on the help!

Bump?

Yikes--I didn't realize that! :confused:

So, what should you do if only part of your panel is being filled with Linacoustic?

Would you use a faced foam board, or would that also do some absorbing?!

The trick I have is getting my fairly large spans of GOM to look uniformly "tight" or "pillowed" inside my upper panels if I only fill a part of them with absorption.

BTW, pepar, I appreciate your point about preserving the ambient field above for proper surround.

Any ideas?
Which of your pics shows the panels you are referring to?

Sorry about the dead links--these should work now...

The following pics are of the upper panels (without any treatment yet, nor GOM), and the Front Wall.

I'm also wondering about whether to sheetrock over that 36" wide opening on my Front Wall (where the TV/equipment/shelves are) in order to get uniform absorption behind my screen. Or, should I take advantage of the depth to create a deeper absorption layer in that 36" area? But, would that introduce some comb filtering?

I'm upgrading to a projector and an AT fixed screen that will be part of a large proscenium I'm building. You can see the width of my screen (roughly) by the blue tape in the pic...

Thanks for the help!

Sorry about that.

It is this one--my front wall. I'm upgrading to a projector and an AT fixed screen that will be part of a large proscenium I'm building.

Thanks for the help!
Right, but do you have a picture/drawing of the panels you are constructing completely covered with GOM? BTW, no pic at this link, but I went back to your prior post to the image with the same name.

Right, but do you have a picture/drawing of the panels you are constructing completely covered with GOM? BTW, no pic at this link, but I went back to your prior post to the image with the same name.

I've fixed my original post above--the links should work now.

Thanks for the help!

Regarding the latest quick and dirty method by Jon Risch's, he said that any thickness will do when you just stack 3 rolls of insulation in the corners and tape some fabric to them. Does he mean any thickness of OC705 or any thickness of fiberglass period? I assume that there is no thickness variation in OC705 so he must be saying that ANY type of insulation would work. Am I wrong?

I haven't seen the article, but from everything I've read, any unfaced insulation should work.

CJ

Yikes--I didn't realize that! :confused:

So, what should you do if only part of your panel is being filled with Linacoustic?

Would you use a faced foam board, or would that also do some absorbing?!

The trick I have is getting my fairly large spans of GOM to look uniformly "tight" or "pillowed" inside my upper panels if I only fill a part of them with absorption.

BTW, pepar, I appreciate your point about preserving the ambient field above for proper surround.

Any ideas?
Can you build your panels with an uncovered and hard surface on top?

Can you build your panels with an uncovered and hard surface on top?

I sure could--though that would mean I have no room treatment other than my front wall 6" absorption behind my AT screen. And the 4" of treatment in the 2 rear-wall columns (18" wide by 6.5' high).

My side-walls are pretty wide though--8' & 10' away from my Mains--is it possible that I won't have FRP problems at that distance?

Also, what should I do with my front wall opening? Should I close it off with sheetrock and then apply the 6" of Roxul (RHT80-6lb 3" thick x 2) or yellow spin-glass (JM 1000-3lb 3" thick x 2)?

Or leave it open and use the extra depth for more absorption?

Big thanks on the help!

I sure could--though that would mean I have no room treatment other than my front wall 6" absorption behind my AT screen. And the 4" of treatment in the 2 rear-wall columns (18" wide by 6.5' high).
I was only asking if you could leave the tops of the panels reflective while still using absorption on the lower half (up to ear level?).

My side-walls are pretty wide though--8' & 10' away from my Mains--is it possible that I won't have FRP problems at that distance?
There will be reflections. You would need to look at your speakers' off-axis response/output to get an idea of how loud it would be. Sound travels about one foot per millisecond. Subtract the direct path time from the reflected path time and you would know how much of a delay there is.

Also, what should I do with my front wall opening? Should I close it off with sheetrock and then apply the 6" of Roxul (RHT80-6lb 3" thick x 2) or yellow spin-glass (JM 1000-3lb 3" thick x 2)?

Or leave it open and use the extra depth for more absorption?
I've seen others suggest stuffing it with fiberglass for a down and dirty trap. If I had a hole like that, that's what I would do.

Guys, if you have a cavity a foot thick or more, fluffy R38 fiberglass is very good. And it costs less than rigid fiberglass and is easier to find.

--Ethan

Cool, so if I build a cylinder bass trap for my corners, I can just use R38 as long as the diameter of the cylinder is over a foot?

I was only asking if you could leave the tops of the panels reflective while still using absorption on the lower half (up to ear level?).
I get it--yes, I certainly could put some hard reflective board, etc. up there above whatever height of my Linacoustic at 1" depth and cover it all with GOM. Would that work?


There will be reflections. You would need to look at your speakers' off-axis response/output to get an idea of how loud it would be. Sound travels about one foot per millisecond. Subtract the direct path time from the reflected path time and you would know how much of a delay there is.
Cool. I have an equilateral triangle between my LP and my Mains (11' between each speaker and LP). My Center is also going to be between 11-11.5' - so, using the RP - DP I come up with 14ms for my L-side L speaker, and 18.5ms for my L-side Center & I have 10.5ms for my R-side R speaker, and 15.5ms for my R-side Center. I used the mirror-method. How do those look?

I've seen others suggest stuffing it with fiberglass for a down and dirty trap. If I had a hole like that, that's what I would do.
Wow, that could be a very large bass trap! Do I not need to worry about comb-filtering across the front with that 36" opening being much deeper/more absorption than the other 2.5' on either side that will only have 6" deep?

If I did stuff the back closet, would I do the 6" across the whole wall behind the AT screen (opening and all) and then take the further "fluffy" absorption behind that, or would I begin the "fluffy" stuff flush with the stiff board-type absorption?

Thanks.

I get it--yes, I certainly could put some hard reflective board, etc. up there above whatever height of my Linacoustic at 1" depth and cover it all with GOM. Would that work?
Covering it all with GOM is an aesthetic thing? Even though GOM is billed as acoustically transparent, nothing is 100% acoustically transparent. And the sound will be going through it two times. I have seen commercial panel systems that are 100% covered though.

Cool. I have an equilateral triangle between my LP and my Mains (11' between each speaker and LP). My Center is also going to be between 11-11.5' - so, using the RP - DP I come up with 14ms for my L-side L speaker, and 18.5ms for my L-side Center & I have 10.5ms for my R-side R speaker, and 15.5ms for my R-side Center. I used the mirror-method. How do those look?
That will depend on the level of the delayed sound. the conventional wisdom that I have always bought into is treat all of the first reflections, install bass traps and then listen and measure.

Wow, that could be a very large bass trap! Do I not need to worry about comb-filtering across the front with that 36" opening being much deeper/more absorption than the other 2.5' on either side that will only have 6" deep?

If I did stuff the back closet, would I do the 6" across the whole wall behind the AT screen (opening and all) and then take the further "fluffy" absorption behind that, or would I begin the "fluffy" stuff flush with the stiff board-type absorption?
IIRC, you got that 6" recommendation from one of the acousticians here on the thread. That is three times the thickness that I have been told. My understanding is that 2' will do and that the extra 4" spread over the entire wall will not reach low enough to to provide bass trapping, which is best done in corners where all of the nodes "end."

Pepar, I appreciate the help.

So, I'm clear, how would I treat only a part of any of those upper panels without using GOM or something similar to cover/make flush the rest of the untreated panel? Just for clarity, the bottom panels are all bead-board and not available for treatment as per WAF.

Man this stuff is complicated, eh?! So, just 2" on the front wall behind the screen would do fine?

How effective will the "down and dirty" closet trap (which is mid-wall behind my screen) be? I can make that about 36" deep and down about 25" from the floor. That may be impossible to say exactly, I know, but is it worth doing?

Pepar, I appreciate the help.

So, I'm clear, how would I treat only a part of any of those upper panels without using GOM or something similar to cover/make flush the rest of the untreated panel? Just for clarity, the bottom panels are all bead-board and not available for treatment as per WAF.
Dunno, make sure she stands on her head then when in the room?

If you shouldn't place absorption on the top half and you are not allowed to place absorption on the bottom half, I don't know where it can go. :confused:

Man this stuff is complicated, eh?! So, just 2" on the front wall behind the screen would do fine?
It works just fine in my theater.

How effective will the "down and dirty" closet trap (which is mid-wall behind my screen) be? I can make that about 36" deep and down about 25" from the floor. That may be impossible to say exactly, I know, but is it worth doing?
Three feet of 'glass can't hurt and won't absorb any additional highs and mids over the 2". Plus, it won't be seen and subject to the WAF.

I better not quit my day job and become a technical manual writer! Sorry to be confusing--I'm not trying to be.

The bottom panels are decorative, so I'm out of luck there; however, the upper panels are wide-open for full, none, or some treatment.

So, I've been wondering about the viability of creating at least some FPR absorption in those upper panels with smaller-than-the-panel sized pieces of Linacoustic. If I only treated the FPR up to a 52" or so and left the rest of the upper panel untreated, but filled with a hard, non-absorbant board, then I figured I could cover the whole panel with its mixed Linacoustic and reflective with GOM and get something out of it. What do you think?

I could also perhaps fill the entire upper panels on the front wall (the ones outside the screen area) as well, unless that would hurt the surround field. Would I do something similar on the back wall upper panels also?

Great points about the bass trap, etc.

Thanks a lot.

I better not quit my day job and become a technical manual writer! Sorry to be confusing--I'm not trying to be.

The bottom panels are decorative, so I'm out of luck there; however, the upper panels are wide-open for full, none, or some treatment.

So, I've been wondering about the viability of creating at least some FPR absorption in those upper panels with smaller-than-the-panel sized pieces of Linacoustic. If I only treated the FPR up to a 52" or so and left the rest of the upper panel untreated, but filled with a hard, non-absorbant board, then I figured I could cover the whole panel with its mixed Linacoustic and reflective with GOM and get something out of it. What do you think?

I could also perhaps fill the entire upper panels on the front wall (the ones outside the screen area) as well, unless that would hurt the surround field. Would I do something similar on the back wall upper panels also?

Great points about the bass trap, etc.

Thanks a lot.
Your design criteria have put you well beyond my skills. I strongly suggest that you engage a professional who can model your room, work with your decor goals and recommend the correct acoustical treatments for your room. I am afraid that if I "help" you any further, I will screw it up. :)

Your design criteria have put you well beyond my skills. I strongly suggest that you engage a professional who can model your room, work with your decor goals and recommend the correct acoustical treatments for your room. I am afraid that if I "help" you any further, I will screw it up. :)

I appreciate your insight--sorry my room/decor criteria are so complicated.

That's a smart suggestion about a professional. I just happen to be in a lightly-populated part of Idaho, so retaining an acustician locally is impossible!

Still, I'm enjoying the pursuit at any rate and hope to have a great looking and and great sounding room soon.

:)

I have an acoustical product that is not tested by third party. The product is made by Empire West Inc. and they are known for the Ceilume ceiling tiles. I have the Metro style Ceilume tiles installed and above these are a steel reinforcement ceiling to support the concrete garage above which is a little over a foot higher. The tiles are attached using ceiling link that is ran along the joist using furring strips. The item I have a question about is the back panels which are designed to be added above the existing tiles to add more absorption. They sit like "meat tray" on top of the existing tiles between the runners. These add a significant weight to my tiles for which I may need to reinforce by adding support screws, caulk, or any sollution that would work.

In the past while measuring the effect of adding these panels I made note of absorption in the 40Hz area and bellow that. I am now experimenting with adding two layers of each back panel to observe the effect and they seem to add absorption to the area for which I am targeting. Pictured bellow is the effect of adding two layers to three tiles on the left side center of the front of the room (just above where my four subwoofers are located), and then adding another pair of three back panels to more tiles located directly next to the others so that they are centered in the room.

http://farm4.static.flickr.com/3087/2804850686_ed367a0946_o.jpg

None

http://farm4.static.flickr.com/3135/2804005109_3b3d9b24dd_o.jpg

Three pairs of two at the left center front of the room.

http://farm4.static.flickr.com/3145/2804852940_907a4bb0dd_o.jpg

Six pairs of two at the front center of the room.

My question is do I continue to add these or is there a more better approach that I could be taking to treat the area above my tiles? I already have enough of these to at least complete half the room.

I took the pair of back panels and put them on 30 tiles in the front of my room. I added a half layer of R19 between the back panel and tiles then duct tape them together so that it would not show when installed. I also duct taped the tile to the top of each horizontal runner as I went. Here is the result. My subwoofers measure 80dB but for testing purposes I choose to measure 75dB.

http://farm4.static.flickr.com/3133/2805191057_600defab7f_o.jpg

SteveMo,

Thanks for sharing this info - it is helpful as I have just received some of the ceiling-lume Stratford samples, and am still trying to decide if I want to go this route. Love the "look", but am concerned about the acoustic properties, they are so thin and light...

Your ceiling structure seems to make for an even bigger challenge - Seems this is why you are adding the "sandwich insulation absorption" layers to the top-side of the tiles?

I will also be using the Celing Max grid system for mounting. However; I will be mounting directly to the bottom of 2x10 wood joists, that have been packed nearly full with fibergalss insulation. I'm hoping > I will have enough absorptin directly above my tiles that I can skip the ceiling lume backer panels - your experienced opinion?

Thanks,
Craig

Yes the pressure of off the air off the steel above makes it espicially a challenge. I found that the back panels only made things worse. They make them heavy and difficult to install, then there is the matter that they themselves begin to trap noise but the noise they trap is then reflected back because there is no damping whatsoever. For the higher frequencies the tiles themselves are plenty for absorbing the highs and I have always had no complaints there.

I had tried with the ceiling link, the tiles, and with a layer of R14 laying above the joist. This I found to do more harm than good my particular situation. I would recommend playing a sine wave on a cd or program such as REW and sweep around until you can get them to start shaking. If they are lightly installed they should move very fast, gentle, and make no audible noise. If they are bouncing or causing the grid to slip up then somethings wrong and you may want to try a different type of absorption. The area the insulation above will help treat is your floot ceiling axial node which is when the sound is reflected from both the floor and ceiling. If these waves meet at the level you are sitting at the same instance you have cancellation. This is what we want to avoid. As you can see from the measurements above I have one at around 60Hz that I have been watching for a very long time with other treatments as well.

SteveMo,

Thanks for the quick response. Seems you have begun characterizing these tiles very well.

What I amtaking away from this is the following:

- The celinglume backer panels are probably not beneficial for our applications, (or at least not worth the added effort/costs)?

- As for noise with them vibrating or moving around in the Ceiling Link system - should not be a problem?

- I get the impression that when compared to conventional commercial/acoustical suspended tiles - that they are NOT detrimental? Perhaps it comes down to just the big question >> the degree of absorption one is expecting?

- The celinglume backer panels are probably not beneficial for our applications, (or at least not worth the added effort/costs)?

I don't see them as worth the cost. The effective difference is quite obvious but these exhibit strange characteristics in absoprtion effeciency when dealing with room boundries and they do not effectively treat an effective area with benificial absorption. They add an interesting reverberation effect. I think this is probobly targeted towards people with taller ceilings.


- As for noise with them vibrating or moving around in the Ceiling Link system - should not be a problem?


That depends. As I was suggesting with the playing of a sine wave, notice if they are laying directly in a peak or not. If they are, I'm afraid there may be some problems. One very easy way I could find peaks in my room was to simply observe where a tile would rattle. If you have some absorption in your corners your probobly alright. The largest concern here is that a support holding the tile is not firmly in place. I have to resize a few by my door that were cut to short with my extra ceiling link now. I can play Transformers through the whole movie (105dB peaks etc) with no rattles right up until the last explosion shot out of bumblebees cannon. Then the short ceiling link rattles. I will fix that for now but probobly I will be putting some more absorption, perhaps the same in the rear of my room once I get new surround speakers.

I measured the effective rattling limits of these tiles before treatments using one subwoofer in my build thread somewhere. As I recall it had been the entire room was buzzing around 80dB at 63Hz-65Hz and some around other frequencies. In other words other treatments are really going to decrease your chances of having any issues with a rattle here or there. You would have to be listening pretty loud to get that happening I would think. I have seen some suggesting to use weather stripping. Also having an object such as a speaker or other resonant cavity within near proximity will increase the likelyhood there will be an issue. When adding a back panel this becomes the most plausable cause of a rattle. If you run into real serious problems you may try placing the subwoofer in the back of the room which I found to help.[/quote]

- I get the impression that when compared to conventional commercial/acoustical suspended tiles - that they are NOT detrimental? Perhaps it comes down to just the big question >> the degree of absorption one is expecting?

No much has to do with the installation. How well they are installed will make all the difference. These are really good if you don't like tiny holes because you feel like your at school and want to though pencils at them. Yes, certainly the effective absorption is somewhat a mystery. There is actually an official spokesperson for Ceilume here that showed up right after I changed my title to read Ceilume Expert. You can search/read that thread if you want the official take on the absorption. My room is somewhat very similar to a testing facilty. Concrete square room with a steel ceiling. Placed tiles up there and measured with a HT in it. ;)

Can someone clarify reccomended treatment for my front wall...

I thought I had a room treatment plan until I stumbled upon this thread. I read the first dozen pages and I'm more confused than ever. :-) I'm pretty much a complete amatuer at this and I would appreciate any help that folks can offer...

I'm using my room for 50% surround music, 25% two-chanel music, and 25% home theater.

I'm pretty sure that I understand that I need some treatments on the side walls to deal with first reflections. I'm figuring some 2" panels from either GIK or ATS and using the "mirror test" to determing where the treatments should go.

I'm also thinking something like GIK Tri-Traps to treat the corners, but I'm not sure I could afford any more than two of them right now (although I intend to add more in the future)

I'm not clear on reccomended front wall treatment though. Can anyone offer me some advice here? Am I treating for bass or broadband frequency on the front wall? How do I know where to place treatments on the front wall?

Anything else I am missings? Other treatments that should be in the plans for the future?

Some photos of my room here. (http://www.avsforum.com/avs-vb/showthread.php?t=1052860&highlight=elee532)

Note that the first photo shows the end of the room that I will be using as the front. I'll have a 50" plasma mounted on the front wall. Also, you can't tell, but the left wall has a ledge about 4' from the floot with a window above is about 3' tall and 4.5' wide.

Thanks for any help!

Can someone clarify reccomended treatment for my front wall...

I thought I had a room treatment plan until I stumbled upon this thread. I read the first dozen pages and I'm more confused than ever. :-) I'm pretty much a complete amatuer at this and I would appreciate any help that folks can offer...

I'm using my room for 50% surround music, 25% two-chanel music, and 25% home theater.

I'm pretty sure that I understand that I need some treatments on the side walls to deal with first reflections. I'm figuring some 2" panels from either GIK or ATS and using the "mirror test" to determing where the treatments should go.

I'm also thinking something like GIK Tri-Traps to treat the corners, but I'm not sure I could afford any more than two of them right now (although I intend to add more in the future)

I'm not clear on reccomended front wall treatment though. Can anyone offer me some advice here? Am I treating for bass or broadband frequency on the front wall? How do I know where to place treatments on the front wall?

Anything else I am missings? Other treatments that should be in the plans for the future?

Some photos of my room here. (http://www.avsforum.com/avs-vb/showthread.php?t=1052860&highlight=elee532)

Note that the first photo shows the end of the room that I will be using as the front. I'll have a 50" plasma mounted on the front wall. Also, you can't tell, but the left wall has a ledge about 4' from the floot with a window above is about 3' tall and 4.5' wide.

Thanks for any help!
Minimum is to treat the first reflection points and corners for bass. Think in all three dimensions - all room surfaces have first reflection points. The biggest difference in my room was from the rear wall absorber. Check the site linked in my thread. Start at the first page.

Minimum is to treat the first reflection points and corners for bass. Think in all three dimensions - all room surfaces have first reflection points.

Are first reflection points on the side wall next to the front speakers?

So, given limited starting budget, would it make the most sense to put some 2" panels on the side wall and some bass traps in the corner and treat front and rear walls later?

Thanks.

Are first reflection points on theside wall next to the front speakers?

So, given limited starting budget, would it make the most sense to put some 2" panels on the side wall and some bass traps in the corner and treat front and rear walls later.
Do you have a diagram of the space with all of the important items drawn in?

Are first reflection points on the side wall next to the front speakers?



Side walls, back wall, front wall, ceiling, and floor. Search this thread for "mirror trick" for more info.

Do you have a diagram of the space with all of the important items drawn in?

Link #1 and #7...

http://www.avsforum.com/avs-vb/showthread.php?t=1052860&highlight=elee532

Link #1 and #7...

http://www.avsforum.com/avs-vb/showthread.php?t=1052860&highlight=elee532
Speakers . . screen/display . . seats?

lords of the acoustics, what say ye about my lair? does it need thine traps?


http://i11.photobucket.com/albums/a162/vinnyanddaisy/wfnoaud.jpg

I just built a 6" riser out of 2x6s and a 4'x8' piece of plywood. The bottom is hollow. Should I pack it with some R30 insulation to keep it from affecting the bass? It is sitting on carpet with pad on a concrete floor.

lords of the acoustics, what say ye about my lair? does it need thine traps?

All rooms need and benefit from bass traps.

--Ethan

Speakers . . screen/display . . seats?

Is the image below any more helpful? Unfortunatley, it's not drawn to scale or anything. Also, I have't exactly figured out where my surround speakers or sub are going to be placed.

So, I think I understand that I need some absorption panels on the side walls. What's not clear to me is whether I need some on the front wall as well.

I'm also thinking some bass traps in some corners. How do I determing the optimum place for bass traps? The corner created where the ceiling drops down toward the back part of the room would make a nice out of the way place to put some bass traps. However, I'm not sure if this would be an effective location.

Also, I'm on a limited budget, so I'll probably be doing this in phases. As a starting point, I'm thinking I can afford about six 2' x 4' x 2" panels and two or three corner bass absorption traps.

Two other questions while I'm at it...

Is it ok to put absorption panels behind drapes?

I had always heard that carpeted floors are better than wood floors. However, in reading through the first dozen pages of this thread, I see suggestions that a hard surfaced floor is better that carpeting. Can anyone clarify?

Thanks for any help!!

http://www.ulgm.org/PublishingImages/Room-Layout.gif

These photos were taken before I started remodeling the room...

http://www.ulgm.org/PublishingImages/IMG_0506.jpg

http://www.ulgm.org/PublishingImages/Left-Corner.jpg

Hey folks,

I'm at the point where I have to decide how much money I have to throw at my HT project and have just received one design for acoustic treatments, from the acoustician I've been working with. I'm just looking for second opinions because this stuff is darned expensive!

Here is an overview of my room, with screen and speakers indicated:

http://img179.imageshack.us/img179/1261/roommodeltopviewoe5.jpg

Here is a view from the couch:

http://img151.imageshack.us/img151/9485/roommodelfrontviewrp3.jpg

The acoustician's design suggests re-building the whole screen wall behind the speakers, with acoustic paneling behind the screen, screen wall, and some low bass traps spread along the floor and over top the screen.

There is an additional suggestion of acoustic panels on the ceiling, filling in the area within the ceiling bulk-head. The general areas of the acoustic treatment are represented in blue:

http://img299.imageshack.us/img299/1908/roommodelacoustictreatmrd2.jpg

Here's an image from the screen wall, facing the back of my room:

http://img149.imageshack.us/img149/8276/roommodelbackofroomsz7.jpg

As the room stands now, the general issues I'm having are a bass lift from the speakers being near the screen wall/room corners and a bit of lumpiness (dips) in the mid-range.

Any opinions on this design for acoustic treatment? It's quite expensive and I'm wondering how much I need to do to get some decent level of benefit. Could I forgo having the whole wall re-done and use traps in the corners or whatever?

Thanks mightily.

Rich H

Is the image below any more helpful? Unfortunatley, it's not drawn to scale or anything. Also, I have't exactly figured out where my surround speakers or sub are going to be placed.

So, I think I understand that I need some absorption panels on the side walls. What's not clear to me is whether I need some on the front wall as well.

I'm also thinking some bass traps in some corners. How do I determing the optimum place for bass traps? The corner created where the ceiling drops down toward the back part of the room would make a nice out of the way place to put some bass traps. However, I'm not sure if this would be an effective location.

Also, I'm on a limited budget, so I'll probably be doing this in phases. As a starting point, I'm thinking I can afford about six 2' x 4' x 2" panels and two or three corner bass absorption traps.

Two other questions while I'm at it...

Is it ok to put absorption panels behind drapes?

I had always heard that carpeted floors are better than wood floors. However, in reading through the first dozen pages of this thread, I see suggestions that a hard surfaced floor is better that carpeting. Can anyone clarify?


Maybe it's the not drawn to scale thing, but I'd move the front speakers away from the side walls as much as possible. Will the center speaker be under/above the display? If so, it will be very close to the front wall. If it is essentially the same as the L & R fronts, it's proximity to the front wall will probably make it sound very different and no longer timbre-matched.

I would definitely treat the front wall as well as the side walls at the first reflection points.

- Jeff

Hey folks,

I'm at the point where I have to decide how much money I have to throw at my HT project and have just received one design for acoustic treatments, from the acoustician I've been working with. I'm just looking for second opinions because this stuff is darned expensive!

As the room stands now, the general issues I'm having are a bass lift from the speakers being near the screen wall/room corners and a bit of lumpiness (dips) in the mid-range.

Any opinions on this design for acoustic treatment? It's quite expensive and I'm wondering how much I need to do to get some decent level of benefit. Could I forgo having the whole wall re-done and use traps in the corners or whatever?
Did your acoustician say anything about the glass window?

Yeah, it's not great having it there but he doesn't think it's too big a deal. I can't use curtains over the windows (for various reasons) so I'm sort of stuck with them.

Yeah, it's not great having it there but he doesn't think it's too big a deal. I can't use curtains over the windows (for various reasons) so I'm sort of stuck with them.
No curtains at all will impact your display selection process and maybe even your viewing hours/pleasure.

I just built a 6" riser out of 2x6s and a 4'x8' piece of plywood. The bottom is hollow. Should I pack it with some R30 insulation to keep it from affecting the bass? It is sitting on carpet with pad on a concrete floor.

Could anyone comment on this? Haven't got the sub yet but I was wanting to finish this riser up this week.

Could anyone comment on this? Haven't got the sub yet but I was wanting to finish this riser up this week.
I made mine specifically so that it would resonate. Fortuitously, it does and in the Hertz range of the mid-20's. Explosions, stomping olyphants, whatever, produce a real kick in the pants!

Check the site linked in my sig. Navigate to the "building the riser" section.

No curtains at all will impact your display selection process and maybe even your viewing hours/pleasure.

I've got that covered: Electric black out shades will be used for the windows.
Besides, I only watch films at night (and any stray light from streetlamps should be blocked by the black-out shades).

Anyway, I hope some of the experts here can have a look at what I posted to give an opinion.

Thanks.

I made mine specifically so that it would resonate. Fortuitously, it does and in the Hertz range of the mid-20's. Explosions, stomping olyphants, whatever, produce a real kick in the pants!

Check the site linked in my sig. Navigate to the "building the riser" section.

Nice. Question for you. Didn't you want to mount your absorbers about 4" away from the wall?

Nice. Question for you. Didn't you want to mount your absorbers about 4" away from the wall?
Ummm, no. Why?

Ummm, no. Why?

Everything I have read suggests that the more space between your wall and your absorber, the more effective they are. I figured you would know that or am I crazy? If that's incorrect, it sure would make it easier to mount to a wall without having to find a way to space it.

Maybe it's the not drawn to scale thing, but I'd move the front speakers away from the side walls as much as possible. Will the center speaker be under/above the display? If so, it will be very close to the front wall. If it is essentially the same as the L & R fronts, it's proximity to the front wall will probably make it sound very different and no longer timbre-matched.

I would definitely treat the front wall as well as the side walls at the first reflection points.

- Jeff

How do I determine where to place treatments on the front wall? Above the TV? Below the TV? Right/left of the TV?

Thanks. FYI, I don't have a center channel. I can probably move my speakers another 12 inches or so from the side wall.

Thanks!

1. I had always heard that carpeted floors are better than wood floors. However, in reading through the first dozen pages of this thread, I see suggestions that a hard surfaced floor is better that carpeting. Can anyone clarify?

2. My funds are limited, but I would like to add at least a few corner bass traps to my room. How do I determine where I should place them?

3. Is it ok to put absorption panels behind drapes?

Everything I have read suggests that the more space between your wall and your absorber, the more effective they are. I figured you would know that or am I crazy? If that's incorrect, it sure would make it easier to mount to a wall without having to find a way to space it.
Not crazy. I've heard that. The idea is to add some diaphramatic absorption to it. At what frequency it absorbs, i.e. vibrates, is calculable, but not by me or anyone I know. I have bass traps, so I don't need it for bass. And I didn't want the darn things encroaching into my room any further.

How do I determine where to place treatments on the front wall? Above the TV? Below the TV? Right/left of the TV?

Thanks. FYI, I don't have a center channel. I can probably move my speakers another 12 inches or so from the side wall.

Thanks!
Do the mirror thing. Your L&R front speakers have first reflection points on the front wall.

1. I had always heard that carpeted floors are better than wood floors. However, in reading through the first dozen pages of this thread, I see suggestions that a hard surfaced floor is better that carpeting. Can anyone clarify?
It's not that wood is better than carpet, or vice versa. It depends on the rest of the room and how it is treated. In a room with plaster walls and ceiling, carpet or area rug on the floor might be a good thing. Something else to ponder is the thinking that one should not have two parallel reflective surfaces - anywhere - as that will cause slap echo. Hard ceiling? Absorbant floor. Plaster back wall? Treat the entire front wall. Real home theater designers will use a mix of reflective, absorptive and dispersive treatments distributed throughout the room.

2. My funds are limited, but I would like to add at least a few corner bass traps to my room. How do I determine where I should place them?
Corners. ;) (Do as many as you can; it doesn't matter acoustically where you start.)

3. Is it ok to put absorption panels behind drapes?
Sure, the drapes are already absorbing the higher frequencies. Might as well get mid absorption there, too.

It's not that wood is better than carpet, or vice versa. It depends on the rest of the room and how it is treated. In a room with plaster walls and ceiling, carpet or area rug on the floor might be a good thing. Something else to ponder is the thinking that one should not have two parallel reflective surfaces - anywhere - as that will cause slap echo. Hard ceiling? Absorbant floor. Plaster back wall? Treat the entire front wall. Real home theater designers will use a mix of reflective, absorptive and dispersive treatments distributed throughout the room.

Is drywall a hard or absorbant surface? My walls are drywall, ceiling is drywall, and floor is carpeted. I need to make a decision about whether to have the carpet restretched or replace with laminate flooring. Any reccomendation?

Sure, the drapes are already absorbing the higher frequencies. Might as well get mid absorption there, too.

So, are you saying that drapes won't impede the panels?

Thanks!

Not crazy. I've heard that. The idea is to add some diaphramatic absorption to it. At what frequency it absorbs, i.e. vibrates, is calculable, but not by me or anyone I know. I have bass traps, so I don't need it for bass. And I didn't want the darn things encroaching into my room any further.

A fiberglass panel will have very little absorption due to panel vibrations ("diaphramatic"). I'll try to explain the primary reason airspace behind a panel improves low freq absorption.

Fiberglass and other soft absorbers work by transferring the motion of air particles (sound) into heat. The fibers are pushed back and forth by the air molecules, but lacking a restoring force, the motion of the fibers is highly damped, dissipating the energy into friction/heat.

At a boundary (wall), the sound waves are forced to maximum pressure, which means the air molecules are changing direction (effectively they have no velocity and are not moving). Since the air molecules aren't moving at the wall, the wall is a terrible place for "soft" absorbers. Fortunately, the air molecules are moving with maximum speed at a distance of (wavelength/4) from the wall. For high and mid frequencies, this is close enough to the wall for a 1" or 2" panel to encounter moving air particles. For lower frequencies, you need a thicker absorber or to move the panel out towards the "velocity zone".

I hope that is more helpful than it is confusing.

Is drywall a hard or absorbant surface? My walls are drywall, ceiling is drywall, and floor is carpeted. I need to make a decision about whether to have the carpet restretched or replace with laminate flooring. Any reccomendation?

Yes, it is both. Gypsum will reflect mid and high frequencies, but absorb a fair amount of low freq due to panel vibration. I'd go with carpet since all your other surfaces are hard.


So, are you saying that drapes won't impede the panels?
Thanks!

I'll step in and say that the drapes will allow low frequencies to pass through with minimal absorption, then hopefully those lower frequencies will get absorbed by the panel (given sufficient thickness and density). You'll get more Abs/$ if you seperate the drapes and panels, but you'll get more balanced absorption across the frequency spectrum if you stack them.

Is drywall a hard or absorbant surface? My walls are drywall, ceiling is drywall, and floor is carpeted. I need to make a decision about whether to have the carpet restretched or replace with laminate flooring. Any reccomendation?
The simple answer is that drywall is reflective. A more complete answer, and probably one that you can safely ignore for the purposes of acoustical treatments, is that it is reflective at mids and highs, but has a resonant frequency "somewhere" below those frequencies where it absorbs and then a range of frequencies that it passes. (Think about hearing a booming bass coming through a wall from another room.)

So, are you saying that drapes won't impede the panels?
Yes. Unless they are vinyl :) or metal :eek:, what the curtains do not absorb, they will pass through to the panels.

Fiberglass and other soft absorbers work by transferring the motion of air particles (sound) into heat. The fibers are pushed back and forth by the air molecules, but lacking a restoring force, the motion of the fibers is highly damped, dissipating the energy into friction/heat.

At a boundary (wall), the sound waves are forced to maximum pressure, which means the air molecules are changing direction (effectively they have no velocity and are not moving). Since the air molecules aren't moving at the wall, the wall is a terrible place for "soft" absorbers. Fortunately, the air molecules are moving with maximum speed at a distance of (wavelength/4) from the wall. For high and mid frequencies, this is close enough to the wall for a 1" or 2" panel to encounter moving air particles. For lower frequencies, you need a thicker absorber or to move the panel out towards the "velocity zone".
I was under the impression that the best place to absorb bass was where the molecules are moving their slowest - right at the wall and where all of the frequencies are present - in corners.

I think it's time for some real acousticians to speak up! ;)

I think it's time for some real acousticians to speak up! ;)

Define "real acoustician" ;)

i have a question i hope someone could answer for me.
my first reflection point for my mains are leather couch one side, leather loveseat other.
what should i do about this?

would it help to hang panels on the wall over the couches to absorb relections that might bounch off them. they are both right in the line of fire for my first refection points of my mains.
also would it be benificial to put cloth coverings over them, the couches.
in a perfect world i would move them, and hang panels where they are.
anybody know a solutions to this?

pepar

you might want to wash that **** of your foot before you stick it in your mouth...

check knight427 profile and do a google search (hint -football). He has a masters degree in architectural acoustics and a BA in physics and worked at very respected firms.

http://www.knightacoustics.com/CorporateProfile/KnightAcoustics.pdf

Look closely at GreenGlue test reports - yep it is same guy that was at the test lab.

http://www.soundproofingcompany.com/media/green_glue_testing/OL05-0414_Report.pdf

Note to knight427 - usually pros are allowed to indicate such in their .sig to avoid such confusion - the forum just does not like .sig links from those looking to improve their google page rank. As long as you are giving back as much as you get by helping people that would never hire you.


And I would only improve your answer by saying the quarter wavelength is the maximum velocity point - you still have some velocity even at tenth wavelength. Only at half and begin/end of the wave is the velocity zero and pressure max. That is why performance of absorbers "roll-off" in the bass - they don't immediately switch to non-absorbing at some magic frequency. Corners are at maximum pressure - which means pressure traps rather than velocity traps are most effective - but that does not mean a velocity trap cannot have some effect - or that traps are all one type or the other.

Define "real acoustician" ;)
Edited my post . . .

. . before reading krazmuzik's.

pepar

you might want to wash that **** of your foot before you stick it in your mouth...
In the spirit of being self-effacing, I'll leave my "real acoustician" comment up. And apply a generous amount of salsa habanero to my foot.

check knight427 profile and do a google search (hint -football). He has a masters degree in architectural acoustics and a BA in physics and worked at very respected firms.
Honestly, it's not real practical to google every member before participating in a thread discussion.

Isn't the best place for bass traps in corners, and aren't solid superchunk-style traps more effective than a 2" sheet straddling a corner?

In the spirit of being self-effacing, I'll leave my "real acoustician" comment up. And apply a generous amount of salsa habanero to my foot.


Honestly, it's not real practical to google every member before participating in a thread discussion.

Isn't the best place for bass traps in corners, and aren't solid superchunk-style traps more effective than a 2" sheet straddling a corner?

Corners are not always the only best. For example, I could significantly treat 80Hz - 150Hz by placing panels at the rear side walls. It would work very well. Yes the superchunks are superior.

- Steven

THX Tech I

@krasmuzik: You spoiled my fun! Also, I sort of glossed over the (1/4) wavelength thing in the interest of brevity, but I did hint at it.

@pepar: No worries, I am actually looking for a good reference to support my explanation, there are none easily found on the internet as everyone seems content to just blindly accept conventional wisdom w/o a rigorous explanation. I have something from a book, but I'll have to type it out when I have a chance.

Corners are not always the only best. For example, I could significantly treat 80Hz - 150Hz by placing panels at the rear side walls. It would work very well. Yes the superchunks are superior.

- Steven

THX Tech I
Some - many - of us are using rooms that are already small-ish and standing panels off the wall 4" - 6" (or whatever) not only encroaches upon valuable space, but can be an obstacle that people using the theater must avoid hitting. Is it not easier to achieve any given level of bass absorption in a corner than mid-wall? If one is already using panels at the first reflection points, how much additional LF absorption can be gained by "optimizing the air gap" between the panels and the wall?

Yes, it is both. Gypsum will reflect mid and high frequencies, but absorb a fair amount of low freq due to panel vibration.
Indeed.... leaving one to wonder what to do with sound isolation in presence of such an effect. Double drywall is surely going to make the panel more stiff, making it less of an absorber for low frequencies.

Advice I have gotten is to put double-drywall on the outside wall (and don't use one at all in front of concrete foundation wall). It doesn't work as well that way since it is not against the source of the noise but seems like an interesting compromise.

What do you think?

Yes that is why I don't have panels there. Although they would work good, it is just not practical to have some GIK 244 traps hanging on the walls with one right next to a door. Not sure about the air gap improvement. I moved my speakers already so to re-measure after spacing them might not show a very good example with my measurement. I could show you anyway but you would have to keep in mind that there is no system, just a computer,mic, amp and a speaker... Did you want to see a before/after? I can tell you that I can hear an immediate difference.

Here is how I spaced them with Velcro, furring strips, and the supplied clips. They stick right to the carpet walls up front. They would fall off the walls or become loose and hang crooked otherwise. The velco only method (on texture drywall) quit working after I stuffed insulation around the corners of my ceiling. I was amazed when one fell.

This is working fine so far and has survived plenty of abuse. I will be redoing the riser soon I think (raising some seats) so that a ceiling node improves with all my subwoofers located in the corners. It's the best I have heard yet. I will have to see if they still stay on the walls but something tells me they will be fine with less ringing around 20Hz - 30Hz. The lowest I have seen my 2" first reflection panels effecting was 40Hz, but I have not tested with the newer install. I'm still stuck enjoying the subwoofers and testing those.

And I would only improve your answer by saying the quarter wavelength is the maximum velocity point - you still have some velocity even at tenth wavelength.

So, for a 20 Hz sound wave, you'd want to try have your absorber approximatly 14' from the boundary? I'm glad it is still somewhat effective at 5'!

CJ

Indeed.... leaving one to wonder what to do with sound isolation in presence of such an effect. Double drywall is surely going to make the panel more stiff, making it less of an absorber for low frequencies.

Advice I have gotten is to put double-drywall on the outside wall (and don't use one at all in front of concrete foundation wall). It doesn't work as well that way since it is not against the source of the noise but seems like an interesting compromise.

What do you think?

Hi Amir, :)

Do you know about building two walls that don't touch, or touch only minimally? Plus, there is material that can be included in the wall construction that can help isolate. An example is here (http://www.kineticsnoise.com/arch/walls.aspx).

Hi Amir, :)
Hello pepar :). Good to see you in another context.

Do you know about building two walls that don't touch, or touch only minimally? Plus, there is material that can be included in the wall construction that can help isolate. An example is here (http://www.kineticsnoise.com/arch/walls.aspx).
Yes I do although I had not seen the above product (so thanks for that!).

The issue is that this and other similar techniques are about decoupling and mechanical transmission of sound. It doesn't stop the drywall from flexing and with it, transmit the sound to the other side. Hence the usual suggestion of using double drywall and green glue between them in addition to such isolation.

My point was that the very act of attempting to stop the noise from going into adjacent cavity by using twice as much mass, is going to make it less of an absorber (with or without green glue between them). The two goals appear in conflict here.