Acoustic TReatments - What, How much, & Where?

Hello all you room treatmentfiles.

Being at the point where I probably should have begun, now, I want to 'treat' the room, acoustically. Economic reasons say I might have to go by way of ‘foam’ stick ups on the wall, but I’d really rather not. The desired alternative, however, is panels, and they are mighty pricey. OK.

Reading over the online info at various panel makers websites, (ASC, RPG, GIK, etc), some panels have different ranges of absorbtion, reflection, etc. according to the makers.

Q: How do you know just the amount of absorbtion, or diffusion to incorporate into the room via panels, traps, etc.?

Is there some Rosetta stone that will decrypt this for me… or is it all “trial & ear-ror”?

GIK panels seem the most feasible cost alternative, presently.

Any suggestions or related experiences in regard to sources for, or treatments of, will be more than a welcome thing.

Thank you
Glad to hear you are working on the room. Whether you go DIY (which may be a little trial and error) or hire a design group to engineer the room, you will be much happier.

I don't know if this is the Rosetta stone, but this resource page may help you on your quest. Be sure to click on the listening room on the left of the page--it's kind of a tutorial that will give some basic insight. The simulator is kind of fun too.

Rives Resource Page
Nice resource page (Rives).

Checked it out but am not happy with what I read:

"Speaker Placement
I don't want a hard wall on one side and a massive opening to a kitchen on the other. It will be virtually impossible to get a sound stage and imaging with this"

Well crickey - that describes my listening room.
Time to sell my rig and put in a big screen ???
Rives - thanks. I've read so many web pages lately about the Basics of Acoustics, products, DIY, modes, speaker placements, waveforms.. etc. I'm losing it. You're not connected with the website are you? Doesn't matter actually, but it came to mind.. as I had just read about a review of what I thought was a Rives analog EQ, though it was quite old. 3 or 4 years ago, I think... Stereophile. But I thought that a way to go eventually.... if I had too. Money will decide that issue all by itself. I will look over things at the site in any case. Again, thanks.

I'm not far from your situation... I've two openings in my room, one to either side... one larger by far than the other... and they are not quite inline with one another... almost. I can close off the openings. I will soon. Probably my Xmas present to me. Doors! A swell present, huh?
RE imaging
Perhaps they meant "without treatment" things would be tougher, though I'm not sure, not having read that section yet.
I would suggest that you pick up a used RTA. (real time analyzer) A Behringer DSP8024 with mic goes for a bit over $225 on Ebay. Its the best investment that I ever made. Using the RTA function, you can see whats going on in your room. Locate the listening position that has the flattest responce. It will show you what that 1/4 turn of the tube trap did. It may take a while to learn how to use it, but it will be time well spent! There are the standard 1st reflection, flutter echo and bass traps in the corners treatments, but how much? You may not need as much treatment as you might expect. When you're done with it, you can sell it.
I am in your same position. I have been researching acoustic treatments for almost 6 months now. My biggest problem is that most treatments are pretty unsightly. I am not lucky enought to have a dedicated listening room. Instead I converted my living room into a music parlor with our grand piano and various guitars. This means that appearances is a very important consideration. Only recently have I made up my mind about which treatments to use. I know the products I chose are probably not the best but i think they offer the best compromise between performance and looks. Anyway, here is what I am going to use:

Eighth Nerve tri-corner and corner treatments (these are VERY small and inobtrusive)
GIK corner bass trap (these fit very nicely into a corner and can be used as a platform for decorations)
Acoustics First Sonora panels in custom sizes for 1st reflection points and wall behind speakers (with custom sizes I can design something artsy on the walls).

I estimate I will spend < $1500 for all of this. I hope this helps.

Everyone else, please feel free to let me know if I am missing something or if I am smokin' crack!
Try calling the folks at Echobusters. Very helpful and insightful. If you fax them a schematic of your audio room they will recommend the proper acoustic treatments.
I wrote a post for the Rives forum this morning--and the server lost it--along w/ my stream of thought!!!

Rives, the Marantz Esotec Ma-5 class A monoblocks are keepers. The Ma-5's have the magic holographic, harmonic presentation & decay of tubes with the beef, bass control and neutrality of tone solid state is characteristic for. Since in this setup I'm so close to the speakers the SPL produced by the little 30W monoblocks is adequate. My Forté 4 is not getting modded. Will keep you posted.

Weimboy, an open space can be successfully handled by Helmholz resonators. Member Jahaira built three of them and uses them in his house, where his listening space is open to the dining room. The ideal locations might take a while to discover. He said he'll bring them to my new setup; I expect them to deal with lateral diffusion. You ought to check them out.

Tbooe, I find Eight Nerve stuff too expensive & ugly. Slap echo can be handled by Golden Sound Acoustic Discs, and that's what I use.

Weim_boy and Blindjim, You can overcome a lot of the effect of the hard wall on the side of one speaker by simply toeing in your speakers til the axis of the speaker crosses at your hear or in front of you. Removes most of the side wall reflection issues, increases center focus, and makes a much wider usable stereo spread. Looks odd but works for most box speakers. Try it.

In treating your room, don't forget that you can use wall hangings, book cases, drapes hung over walls as if they were covering a picture window,etc. It doesn't have to be expensive audio product to get the job done.

If your going to go with the audio stuff before you buy make sure its purpose fits your needs, otherwise you will be wasting your money.
Hey guys/gals, Rives,
thanks for your comments/input.

Last night I did a few things to my room which made a noteable improvement.

First I moved the speakers further into the room, further apart and toed them in a bit.

Then I covered my Billy bags 500 cd rack with a comforter (this sits on a record cabinet on the back wall - the rest of the back wall is the stereo rack & tall record cabinets)

Next I got rid of the kithen - I moved the VPU 16.5 record cleaner in and voila - a vinyl maintainance room

Next opened the windows doors on the wall opposing the vinyl maintainance room.

This week end I'm planning to float some shakti stones on maple platforms in the pacific ocean which is in sight ~ 2 miles away - I'm hoping that this will be the glue that binds the sound stage together.


Newbee, i am no expert but i thought toe in reduces the soundstage width? In my room, as I decreased toe in I found the soundstage to increase width wise tremendously. Am i missing something.
Tbooze, With box speakers used in a stereo configuration there are two types of sound you will hear when seated in the sweet spot (especially). The first will be the sound which is phase correct, the 'stereo' sound and that will appear exactly withing the confines of the space between your speakers on the same plane as your speakers (in phase stereo sounds can appear to come from outside your speakers but this sound will be behind your speakers, not on the same place, and if you drew a straigt line from your head thru the speaker to the wall behide it it would still be on the inside of the line.

Then there is out of phase information. That is sound which occurs outside of the inner boundies of your speakers. It is most often caused by reflections off walls, ceilings, floors, etc. These out of phase signals can sound pleasant and seem to give you a wider soundstage, but on close analysis they detract from the sharpness of the focus of the stereo sound between the speakers.

In an unbalanced set up, one speaker near a wall and one speaker near an open space the reflections off the wall can not only diffuse the 'stereo' image between the speakers, but it can also cause image shift where in the center image, say from a centered voice, will shift toward the side with the wall.

JFYI, recordings often contain both in phase and out of phase signals. These too will effect the sense of width of your sound stage - but thats a different issue, they should.

For set up purposes there are test disc's which can help you locate problems caused by room reflections. For example, using one I once discovered a set up where when they played an out of phase voice the voice in a very diffused sound appeared on the left wall immediately in front of the left speaker which was close to the wall. The voice should have been, optimally, heard as "coming from all about your room" but as a minimum having no focus. I was able to eliminate that out of phase sounds'location on that wall by using substantial toe in.

If not having sharp center focus (on a sharp center focused signal) which is IMHO essential to getting the best soundstage depth obtainable because you need absolute clarity in the signal to get this effect, then its no problem. Lots and lots of folks love the sense of width they get and are happy with the compromised depth of image, and are really not concerned with getting the best sharpest'stereo' soundstaging available.

FWIW, since some folks forget what 'stereo' sound is all about, in its simplist application you have two microphones placed in front of a group of performers. One on the left side and one on the right side. A performer on the left sides signal will be picked up by both mic's but for the one on the left side the signal will be much stronger and on the right side much weaker. In a well set up system you will be able to exactly locate the position of the performer. A performer standing in the middle will be heard equally by both mic's and as a result you'll get equal signals from your speakers which will cause them to be heard as one speaker exactly in the center. There are no provision in the 'stereo' concept for 'stereo' signals to be heard outside the boundries of the speakers - out of phase, yes, but not 'stereo'.

Hope that helps to answer your question.........
THANK YOU...very informative. May I ask what test cd you use? Are the ones offered by Chesky any good? If so, which one?
I use "The Sheffield/XLO" test and burn in disc. It provides some tracks useful in set up including some good out of phase tracks as well as a 'walkabout' and signals for burn in use.

I also use a Stereophile Test disc, which measures low frequencies, in conjunction with a Radio Shack Sound level meter. I also use a test disc put out by Rives which is already calibrated for the RS meter.

Lastly I use a disc which is really a compilation of very simply recorded music performances which is an outstanding way of charting your progress in setting up your system and room. Its Test Disc 1, "Depth of Image" by Opus 3. It has been suceeded but is still available in a similar disc put out by Opus 3 and I understand its available on the 'net. The only negative part of owning this disc is that its a standard thats hard to meet. The will tell you on each track what to expect but you may not hear it! All that means is you still have work to do.

Have fun!

P.S. I also have the Chesky disc but I don't use it.
XLO CD is good--also the Granite Audio bass CD.

As integral as test CD's are... Just how do you determine, for example, the coefficient of the absorbers/diffusers needed? Many of the ones I've looked at post their own measurements of NRC ratings at different Hz....

Also, what's best behind the speakers, absorption, or diffusion?
Re last question, see my comments to Tboooe's thread on Room treatments if you're interested in my opinion.

I'll defer to Rives on your first question - I'm sure he would know - thats why he get paid the big bucks. :-)
There is a common misconception being perpetrated here.

The reflected acoustics off the side walls are NOT out of phase and will not destroy stereo image provided the speakers are an equal distance from the side walls and the listener is sitting in the middle with ear level at the height of the mid range.

Although the reflected sound will not be in phase with the primary signal reaching your ears directly from the speakers, the reflected sound off each wall will be in phase with that from the opposite wall and therefore still present a stereo image that allows you to pinpoint the sound position source between the speakers.

The critical factor is to ensure that the reverberant field has enough delay relative to the direct sound so that your brain can distinguish it from the direct energy....i.e. do NOT place the speakers right up against the side walls as the reverberant field becomes completely mixed up with the primary field and the brain can't figure it all out resulting in a poor stereo image...

I find that placing the speakers three feet away from side walls is a safe distance.
Shadrone, In reference to your first sentence. I must say I'm at a loss as to the nature of the common 'misconception being purpetrated' here, unless of course you believe that setting up the speakers as you have described, or as you have in your systems photograph, is the definitive or only way of setting up speakers and there is only one possible end result.

In my experience there are many ways of setting up speakers which present a satisfactory stereo image to a particular group of listeners. I'm not talking multi channel, home theater systems, which is an entirely different issue/sound. Just simple two speaker stereo.

My personal choice is a sound which is pinpoint source specific which reproduces most accurately the sound of the recording. This requires exacting set up (as far away from all walls as possible, especially the rear wall, having a triangulated listening position, and the elimination of as much of the room's reflected sound as possible, including (most importantly) deadening as much as possible 1st reflection points. This set up, properly executed, gives you exactly what is on the recording, nothing more, and little less. I reemphasize that is my personal choice and when I discuss set up, that is my point of reference. I don't care much for a set up which presents a larger 'apparent' sound stage by utilizing room surfaces. Again, MY choice - MY preference.

Many folks prefer a different sound (whether they really even know that they do because they may have never actually heard a set up as I descrbibed) and that is a 'bigger apparent sound stage'. This will include a good sense of presence of the musicians between the speakers and as well, provide for a greater sense of ambiance created by the reflected sounds from room surfaces. In fact this sound is so preferred by so many that speaker manufacturers make speakers to specifically produce that result, such as panels, many electrostats, bipolar's using dynamic cones, as well as Omni's.

Now regarding the 'in-phase' and 'out of phase' issue. You have admitted that the information which comes from the outsides of the speakers is out of phase with the direct sound between the speakers (as I stated in my post), but you conclude that in a perfect set up it is in-phase with itself and does not effect the quality of the central stereo image. I have no problem with that statement in itself (other than I don't agree that it doesn't effect the quality of sound from the recording), however I fail to see how in any way it supports your statement about someone perpetuating (I think that is the word you meant to use, not perpetrating) a misconception.

As I said in my other post, folks have preferences, and I have mine as you yours. Interestingly, what I describe and what I personally prefer, only came after I was exposed to a system that was capable of that level of performance. Until then I really didn't understand what folks meant by 'specific' depth of image comments, I thought it was all about equipment hype by salesmen as I only heard a more 'generalized' sense of depth of image, much as I thought break in being a bunch of hype by salemen and manufacturers.

Now, since you have joined this thread why not share with us your views of how both Blindjim and Tbooose can set up their systems - you will note both have sidewall problems (one speaker near a wall and another near an open space) and at least Tbooose has a backwall issue as well.

BTW, I looked at your system and photos. What a great looking HT system. Looks like you put in a lot of effort. Congratulations...........
I use test CDs to give me an idea of what's going on. For the final details I use listening tests and intuition.

Nevermind - I don't think you grasped what I was trying to say. I mean how did you construe what I say to mean that there is "a definitive or only way of setting up speakers and there is only one possible end result"; frankly, I just can't see how my comments imply this. Anyway, I meant no offence....just my two cents thats all.
Hi guys,

I thought I might share my experience with my imbalanced room. Hope this might help give some ideas.

My listening room is the standard L-shaped room. Early on I experimented with several setups, playing across the long wall of the foot towards the top of L, playing diagonally across the foot of the L, and lastly playing from the toe of the L towards the heel. Both room aesthetics and best sound response led me to staying with the later arrangement. This left the problem of having the right speaker "see" a side wall and the left speaker "see" a large open space. The effect of this is much as Newbee described. The image was pulled to the right and the only way I could balance the sound level from each speaker was to pull the left speaker much closer toward the listening position.

I'll fast forward to keep this short. What I have found to work very well for me was to use absorbtion along the right hand wall in an attempt to make the right hand speaker "see" little or no reflective surface. As a result, I have not had to use excessive toe-in or different placement of one speaker to the other. That's not to say that I don't still have other room issues to deal with, but the imbalance does not seem to be a problem.

One piece of advice I can offer is to avoid overdamping the room. It is easier to do than most people think. IMO, eliminating all slap echo can be detrimental. I also think, as Newbee posted, that alot can be done just by getting furnishings in first. I'm coming to the realization of this last point because I've stumbled into doing this last. The more upholstered chairs and things I've brought in the more this point is driven home.

Rives is correct that the DIY approach is full of trial and error, but it can also be fun and rewarding if you don't piss of your significant other in the process. I've tried DIY bass traps, DIY absorption and DIY room lenses. All have made an impact on the sound in my room and I do all three of these still, though the lenses tend to come and go. They do make a difference but I'm still accessing their effect since I've changed much of my system.


Shadorne, I thought I pointed out in my first paragraph what I thought was offensive in your post - your statement that you were going to clear up a "common misconception being perpetrated here", when in fact there was no 'common misconception' being perpetrated and all you really did was to say that in a perfectly symetrical set up the out of phase information appearing to the outside of the speakers did, in essense, not damage or effect the in phase information appearing between the speakers.

I didn't take offense, however I did want to make sure that folks reading all of these threads did not become confused by your statements and to what kinds of systems, and individual sonic goals, they might apply.

I would suggest however, as this has come up in other posts you have made, it is very helpful, and you'll draw far fewer flies, if the content of your post really matches the subject line of your post which you use to draw peoples attention.

Thanks for all the advice. I see you speak for everyone or perhaps you took a poll ;-)
As the search continues for me, I ran across some items Ethan winer had drawn up about acoustics and DIY stuff. Probably as frankly put and simple as one could ask for... and some items from Sound on Sound magazine. Both point towards 'studio' applications, however I see much of the info applicable to residential use.

As freehand cutting, say with a skill saw, is just not a good idea for me, I'd like to ask if anyone has found or fabricated diffusers that work, without the need for slicing and dicing curved woods..... naturally, the more affordable the better.

And, has anyone found a resource that will allow one to buy the merchandise (room treatments), try them... and if not satisfied, return them... I'm having little luck there.... a couple have said they'll take back their 'standard' stuff.. Fine. As it should be. but there have been ony a couple. most say "it's your's."... no returns.

Thanks. A lot. I do appriciate the thoughts. though my issues are a bit different than what you may have gleaned from my posts... my room is rectangular. 13.5 x 19.75 with openings to either side, though not across from each other and the openings are several feet past the driver of the loudspeakers. I found some 'ratios' for room sizing using the height as the baseline... and given one of those ratios, (there are three), my room comes out as close to great as should be super for listening. the openings which are about to be closed off as sooon as I can decide on the doors to be used, will be of immense help. I'm sure. I have one other door in the room that needs reversing so as to lessen the 'pocket' it creates as is. it's at the first point of reflection of the right speaker. it'll still be there... but only an inch or so, two, at worst.

I did read your posts as you mentioned previously. Funny, I was unable to find the threads doing the search thing... I had to look through the posts for each member to find it. it corresponds to much of what Ethan W. had written. Thanks.

have you found any items other than bookcases that can be used as diffusers behind the speakers? A friend says use the "Skyline" from RPG... Know of a suitable replacement with a smaller price tag?
many thanks.
There is a thread somewhere here that describes the DIY version of the Sylines. It's simple but tedious.
Wander around the acoustics forum as they have some good designs that are easy to make.

Search "studiotips and "superchunk" on google & you'll pick up some useful hits.

This link is a mother load of info on the topic:

Also you might go to the auralex site and send in a request for a room treatment design (it's free). You can get an idea how they'd treat your'll be pretty much what one would expect after you read everything you've mentioned(ethan's white paper) & my links here. You'll treat the corners (all 4) for bass, then the first reflection points on the walls & ceiling...etc..
Blindjim, Re diffusing materiels for use behind your speakers.

Assuming we are talking about high frequencies, and assuming that your talking about diffusing sounds directly radiating from the speakers, plants (live or artificial) can work well. I've used big Boston Ferns, medium sized dense palms, and weeping figs quite effectively for electrostats and boxes. Personally, I don't care for the 'audio room' look so many prefer, and even without book cases I would (and do) place strategically located wall mounted shelves with typical domestic garbage, books, CD's, Lp's, lamps/tables etc.

As Psychicanimal suggests, if you're crafty at all, it would be fairly simple to replicate the Skylines. All you need is some 1 1/2" square pine boards, a small table saw (easier to do cuts) some wood glue and clamps, paint, and patience. A friend of mine has done this several times very effectively. Your really don't have to be very scientific about it to get excellent results but it helps if you have the dimensional variations used in the Skylines. You could also do it with foam of some type as that could act as an absorber for the higher frequencies and diffusor for the lower (not LOW) frequencies, but I think foam would be tough to work with.

If you talking about a whole, or major part, of a back wall, because of bouncing reflections from other wall surfaces, I wouldn't go the dispersion route.

I'm sure its occurred to you already, but, FWIW, the further you can bring your speakers out into the room the less you need to be concerned with the need to diffuse or deaden the sound radiating directly from the speakers, and unless it is a hard surface such as glass, in the typical room after you hit the 6ft mark its probably of little consequence because there is sufficient time differential between the inital signal and the reflected sound (doesn't necessarily apply to bipoles, panels, or electrostats). I've heard speakers set up in front of an untreated glass that sounded excellent, with only one caveat to bear in mind. The other three walls had differing wall surfaces and were not uniformly reflective which eliminated 2d and 3d relect points so there were no strong high frequencies bouncing about the room.

Interesting stuff. Have fun, but don't get too anal - it will be very frustrating if you do! :-)
I second Newbee's last comments - furniture, plants, bookshelves, absoption behind the listening position, diffusers on side walls and moving speakers far away from rear wall and keeping listening position around 40% from the wall behind your listening position are all good suggestions (don't sit bang in the middle of the room).

I built a log fire place as an LF sound absorber/bass trap on the rear wall ....of course this is hardly as effective as the real thing (large GIK, Realtraps or other forms of large surface area thick panels) but aesthetically it is so much more acceptable.

thanks again.... i do appreciate it. much. I ttend to agree with the non treated esthetics. though I don't mind adding something somewhere if indeed the end result is more than fair to middlin'. I've long since thought about the notion of using some ferns... trees... shrubs.. etc. though fake ones like the silk items are about the same money as the Echo busters & Skylines stuff. Whoa! I had no idea till recently. I will have a look about... the issue isn't the doing, it's the safety in doing it where details count. that's where I have a real challenge. it's been recommended more than once that I refrain from using power tools. i tend to ignore that portion much of the time.. especially if it's rough work. Fine stuff does cause me some problems. the 'eye's' do not, in fact, have it anymore.

Whoa! thanks a heap. I'll most certainly have a look about. thank you very much.

I couldn't do the graph thing, naturally, but I do have the area drawn up via a PC program I use a lot for all sorts of jobs (room arranger) super little gizmo... it's shareware.
So this weekend I'll fax it off to Auralexx. I spoke with them recently too. the idea of 'foaming' the room dosen't appeal to me terribly. Some however seems in order. Like the corners and ceilings.

I got the speakers about as far out into the room as I'd care to go right now. they can go more, but the drivers are off the wall, respectively, 47.5 and 32.5, from front and side walls. Roughly 7.5ft +/- apart. I have a "faux fireplace' directly in the middle of the speakers. had a big TV in there till last week. hung some heavy curtains over the gaping hole. Now it's a 40+ sq. ft. 'closet'. I do sit about right where you said to sit.. Not quite half ways back... equa distance from the speakers as they are apart. give or take a couple inches. Behind me is a wall of more drapes, a really long material covered couch... & that's it.

Picking out doors maybe this weekend.. to cover the three openings FP, LEFT HALL & RIGHT KITCHEN. So past the corners, most all of these 'treatments' will be on stands, unless i do the 'brick-a-brack' shelf here and there bit Newbee suggested. ...and nno, I'm gonna keep the false wall/frieplace for two reasons... I need the closet space, and it makes the room dimensions almsot spot on for a listening room. I may well add something to the back of the thin sheet rock of that wall to help things out a bit.
I wouldn't go with the auralex foam either, but the drawing you'll get from auralex will give you an idea of room treatment placement. From that point you can address the areas any way that suits you. I'll be building my room treatments this winter...looks like a no brainer. I'll be going with the super chunk approach with rockwool or owens corning 703 or 705. Some panels also.


Thanks much, I'll look into it some more... You have used or dealt with these folks previously?

Shame they don't trot out the shipping info prior to placing the order, huh?
yes, ive used them on 2 to custom make a panel to go over my door for soundproofing (apartment living, complaining neighbors)..they did a great job. most recently bought a pair of wallpanels and bass traps...going to get another pr of wall panels soon..shipping for 2 3'x4' panels and 2 4'tall bass traps was 50 bucks i think...also a HUGE selection of fabric colors/patters for panels..good luck
if your budget is an issue (it is for me) definitely go and buy the $200 RoomTunes kit from michael green audio. WAY better looking than panels and easier to figure out. Once all your corners are treated, look into a few bass traps, and you are done.... no affiliation. I just bought a set and am thrilled beyond belief. I no longer desire better gear, i had it all along. Acoustic treatments made much more of a benefit than any cabling decisions ever did... the 2 together however, are magic.


I do thank you for the info... I've been to that site several times without any succesful results... I jmust be missing some link somewhere but I can't seem to find either the appropriate products that interest me or pricing or details about them... I even tried dcalling and that too did nothing... all I got waws someone no longer afiliated with Mr. Green.

the coloring of the website too as I recall, is also quite difficult to get past. So I just gave up on Green's stuff.