Room Treatment, On The Cheap

[meuge]

ACOUSTIC TREATMENT ON THE CHEAP

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Before I begin, let me emphasize that anyone is welcome to try this at home. Aside from shooting someone with a staple gun, this experimental procedure is not dangerous in any way to your health or your wallet.

Furthermore, for those of you who know far more about the subject than I do, I want to apologize before proceeding, since the mere sight of my creation will probably either offend you, or make you laugh, or possibly both. I dont doubt that Ive made mistakes along the way, and I am absolutely sure that this is far from being the most sound (heh) acoustic treatment youve seen. You have to realize, though, that these panels were also intended to improve the general appearance of my room and eliminate the sight of bare white walls, which almost succeeded in driving me insane during my first year here.

I hadnt originally envisioned that Id be building acoustic treatment for my room. But with a pair of RF-3IIs in a reinforced concrete room it was only a matter of time. While at the high end the frequency response of my speakers was fairly flat, the incredible reflective power of the walls was easily heard. During the more sibilant musical passages you could feel the treble build up, rather than sustain, to the point of being uncomfortable at volumes I do not consider particularly loud. Furthermore, the reflections muddied the sound. The loss of definition could be heard when a sustained high-pitched note was played. Not only did this impact negatively on classical recordings, but some vocal material, as well as some of the more powerful rock with its high solos. Only a couple of weeks in this new room convinced me that something should be done. Adding a rug helped eliminate raw echoes, but the majority of the problems persisted.

When I first considered acoustic treatment it was more with curiosity rather than any intention to purchase, due primarily to the price factor. However, after some interesting reading I began to wonder whether a cheaper alternative to the commercial products was possible. In the end I decided to give a shot, primarily because the cost was low enough to try it on one wall without potentially suffering a severe monetary loss. My only concern was how to mount these panels after theyve been made, since I am prohibited from making holes in the walls. In the end I decided to use some heavy-duty double-sided tape, but more on that later.

The materials I obtained to do this are as commonplace as they can be:

1. Acoustic Ceiling Tile Panels

- purchased from Home Depot, $2.28 for 2x4, 1.59 for 2x2.

2. Fabric

- local fabric store 5 roll at $4/yard

- cotton with a slight addition of synthetics

- slightly stretchable to avoid wrinkles

(I had to compromise on the thickness of the fabric, primarily because of mounting and weight constraints)

3. Staple Gun

- purchased from Home Depot for $10.

4. Double Sided Tape

- also from Home Depot, $3.50/roll

5. Scissors, Dremel (for cutting panels) and other assorted instruments for cutting and measuring that I had accumulated previously.

Making the panels turned out to be pretty simple. I used sheets of fabric 6 wider than the ceiling tiles on every side in order to fold them over to the other side. While pulling to put some tension on the fabric I stapled the fabric to the back of the panels, one side at a time.

It turned out that the neatest approach to the corners was to simply fold the fabric over very carefully and staple it in place. After the fabric was secured in place it turned out that the panels looked quite good in their coffee-colored glory.

To mount the panels I made corners, using the double-sided tape, and a strip in the center for the top side, so that each 2x4 panel got 5 4 strips at the top and 2 at the bottom. For the 2x2 panels 2 strips were by far, enough. I used much more tape on the first couple of panels and they are stuck to the wall so hard that theyll require force to come off later. For cosmetic as well as sound scattering purposes I placed the panels about 3 apart.

Initially I only completed a few panels on the wall opposite the speakers. The improvement in sound was immediately noticeable. Some of the forced squeal that I heard before was gone, and I knew I had to finish the job. So I went back to Home Depot and the fabric store the next day and got the entire room done. Then I invited a few friends over (some with very good ears) and got a lot of complements. A lot of the aggressiveness of the highs was completely gone. The room was finally passive for a clap test, and the music was far more defined. The difference is hard to describe in words, but it was absolutely unambiguous. But whats most impressive is the cost of this entire endeavor. The fabric turned out to be the most expensive component of the panels, at about $4/(2x4) panel. However, even including the price of the fabric, the tape and the staple gun, the price of a 2x4 panel came out to about $8. The entire room probably cost me on the order of $60-70 and it was worth every penny.

So here I am now, finally being able to enjoy Itzhak Perlmans violin at live volume without having to run out of the room. Waiting on a B&K ST-2020 stereo amp I wonder whether this has become another addiction. But alas, I have to get back to work, because science does not slow down its pace for a young audiophile.

I hope this made some sense and hope that youre not yet asleep, but just in case youre about to pass out, heres something that always brings a smile to my face the view from my window.

Enjoy!

[Andronicus Dragon]

Nice job. It goes to show you that where there is a will there is a way, money be damned. Actually any price would have been worth it not to hear Perlmans Violin shriek...The Horror!

[artto]

I dont mean to discourage you or anyone else from trying to tame a particularly challenging acoustical environment, but Id like to shed some light on what youve done.

First let me say that Ive gone the route you have many, many years ago. And I did so, (not to brag) much more cheaply. As many of you know, Im an architect. One large commercial office project I was fortunate enough to work on as a young architect had a lot of left over and scrap acoustical ceiling tile. At the time I was also in the process of building my dedicated listening room so naturally I acquired a lot of this stuff for free (not stolen). My intention was not to use it for ceiling tile, but simply as sound absorption panels in my room.

What I discovered, and Im sure you will too over time, is that for musical purposes, which involves a wide range of frequencies and dynamic range, common acoustical ceiling tile is not a very good product for the task at hand. Such tiles are reputable products for noise and reverberation control as long as they are used with the full knowledge of their limitations. If you look at the absorption coefficients of acoustical ceiling tile you will notice that they have a rather narrow absorption bandwidth. In other words, they do exactly what they were intended to do, absorb a reasonable amount of midrange frequency sounds that are typically encountered in office and commercial environments such as talking and printer noise. As you know, they are very narrow (very little depth) and consequently the absorption coefficient starts to roll-off very quickly with decreasing frequency, and even at higher frequencies above the center frequency. The result is basically a midrange suckout.

The tiles I used were camouflaged by hanging linen panel curtains in front of them but for the most part were completely exposed on the walls for absorption. Some tiles were placed inside of the large polycylindrical Masonite diffusers. Eventually I removed all ceiling tile from the room as it created a somewhat hooty sound along with excessive juke box bass.

There are many key aspects to achieving good acoustics such as control of interfering noise, reverberation time, reflection, diffusion, impulse responses, modal resonances, etc. Too often I see people concentrating far too much on absorption, or even worse (no offense), as in this example, using absorption products and/or techniques that affect a relatively narrow bandwidth. The Noise Coefficient Rating (NRC) is an AVERAGE of sound absorption at six frequencies, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, and 4KHz. So even though acoustical ceiling tile specifications may show a NRC of 0.65 or more, the predominant absorption is in the 500-2KHz bandwidth with maximum absorption centered at 1KHz (see attached acoustic_tile_NRC graph from Master Handbook of Acoustics, F. Alton Everest).

So as you can see, youve tackled only a very small part of the problem, and while for the moment you probably feel youve made an improvement by tackling something that was particularly annoying to you, I suspect with time, youll recognize that in doing so, youve also exposed and created other ones. Also, I can virtually guarantee that the double sided tape won't hold for too long. I've used that stuff before and it always, eventually, falls off.

[Olorin]

Would stacking them so as to increase the thickness do anything to improve the performance at lower frequencies?

[artto]

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On 7/22/2004 12:21:27 PM Olorin wrote:

Would stacking them so as to increase the thickness do anything to improve the performance at lower frequencies?

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Possibly. But look at the frequency absorption curve for these products. The low frequency absorption is very poor. Even the higher frequencies are not absorbed as well as the midrange. These types of panels are clearly not intended for anything near 'broadband' performance and are not really suitable for musical applications. Whether we are talking about, reverberation time, absorption, diffusion, or whatever, the keyword is "BROADBAND".

[Cal Blacksmith]

So what would be a good material on the cheep? AS for LF, if you raised each pannel about 1 inch, wouldn't that create a bass trap?

Just wondering

[artto]

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On 7/22/2004 1:12:12 PM cablacksmith wrote:

So what would be a good material on the cheep? AS for LF, if you raised each pannel about 1 inch, wouldn't that create a bass trap?

Just wondering

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No.

Look at it this way, if we used a 1/2" sheet of cement backerboard instead of the acoustic ceiling tile and raised the panel about one inch, would that create a bass trap? Same answer.

For instance, the Masonite diffusers in my listening room absorb more bass than treble (this is a fact, not my opinion). But you have to consider that most of these diffusers are at least 4'x4', and up to 4'x8', and they are bowed as much as 18" to the nearest interior wall surface (often another diffuser), and as much as 2' or more to the actual interior structural wall surface. When you consider the cross-sectional area and volume behind these diffusers its easy to see how they can be useful in absorbing, and even diffusing the longer wavelengths of lower frequencies. The diagonal dimension is a little more than 8'-9" which is roughly equivalent to 1/4 wavelength of a 31Hz tone which enough to start having some substantial impact. At the same time, not as much midrange and treble absorption is necessary because of their very efficient diffusion characteristics. This sort of diffusion provides a more natural logarithmic-like decay as we hear in a concert hall as well as getting rid of things like flutter echo. And even these devices are not considered "bass traps". As I said before, absorption is not the answer to good acoustics, especially if its not properly applied.

Masonite panels are also very inexpensive, but they do take up more interior space. Celotex, Roxul, Owens Corning 705 or Homosote are all forms of rigid insulation with higher density and better broadband sound absorption properties than acoustical ceiling tile. Model railroaders use Homosote and Celetex under the roadbed because of its sound absorbing qualities so it's not that expensive. Our Canadian friend Mike Hurd brought Roxul to my attention and from what I can tell, it has the best overall acoustical absorption properties for this type of material. However, I would still caution against considering this a "bass trap". The term 'bass trap' is actually a misnomer as most products specifically marketed as such are actually broadband absorption devices. It's how they are used that makes them bass traps, and what they do is actually INCREASE or improve bass response in the room, making it more uniform throughout the listening area.

[mikebse2a3]

Room Treatment on the Cheap!

One thing that I've done playing with room acoustics that is very cheap is to take boxes or large pieces of cardboard and fold them into Triangular shapes and locating them in the corners of a room. I make sure and seal the boxes with shipping tape or something similar and you can leave them empty or stuff some of them, a mixture would probably be best to spread the absorption character of the boxes. I suppose you could paint or put paper on the boxes to decorate them up some.

The advantage of these over some treatments is they will not deaden the room but they will clean up some room problems that fall in the midrange and lower. I could especially tell it cleaned up vocals in the room I tried this in.

I've never heard a room that couldn't be improved with some kind of corner bass traps and this cheap trick will let you learn something about your own room acoustics.It can add some balance to your room acoustics especially if you have carpeted floors.

As artto has basically said our rooms are our largest problems and cannot be ignored if you want the best sound you can achieve!

Have FUN!!!

mikeb

[artto]

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On 7/22/2004 7:04:37 PM mikebse2a3 wrote:

Room Treatment on the Cheap!

One thing that I've done playing with room acoustics that is very cheap is to take boxes or large pieces of cardboard and fold them into Triangular shapes and locating them in the corners of a room. I make sure and seal the boxes with shipping tape or something similar and you can leave them empty or stuff some of them, a mixture would probably be best to spread the absorption character of the boxes. I suppose you could paint or put paper on the boxes to decorate them up some.

The advantage of these over some treatments is they will not deaden the room but they will clean up some room problems that fall in the midrange and lower. I could especially tell it cleaned up vocals in the room I tried this in.

I've never heard a room that couldn't be improved with some kind of corner bass traps and this cheap trick will let you learn something about your own room acoustics.It can add some balance to your room acoustics especially if you have carpeted floors.

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Sorry to pop your bubble too, but this is another big misconception. And it indicates a nearly complete lack of understanding of acoustic principals and acoustic properties of materials. I don't have time to fully respond to it tonight, but I will get to it tomorrow. In the meantime I suggest you throw that stuff out with your egg cartons.

[DrWho]

nice pics meuge...very well thought out and displayed.

anyways, one thing in your defense that i wanted to bring up is the fact that your room has concrete walls...concrete (in my experience) seems to be very midrangy. Thus, your wall treatment does indeed address that issue.

I think artto is just trying to point out that over time, you're gonna start noticing the unnaturaleness of the treatments that you've just implemented. And there's nothing wrong with that...it's just a matter of training your ears and then moving on to the next mod. And then you're gonna hear new flaws in the next stage and move onto something else.

The other route you can take is to educate the crap out of yourself and try to do everything perfect the first time and then end up changing stuff anyway *cough* artto *cough*

Side note...is there a difference between "normal drop" cieling tiles and "acoustic" cieling tiles? Or is this just two names for the same thing? If not, how would one go about telling the difference between the two? I'm not planning on building these tiles or anything (working on some masonite ones similar to what artto has that are talked about in the dope from hope papers), but my curiousity is getting the better of me

[mikebse2a3]

"Sorry to pop your bubble too, but this is another big misconception. And it indicates a nearly complete lack of understanding of acoustic principals and acoustic properties of materials. I don't have time to fully respond to it tonight, but I will get to it tomorrow. In the meantime I suggest you throw that stuff out with your egg cartons."

Its OK artto no bubbles busted here. I now use ASC tube traps and RPG diffusers in my room and understand there are limitations to any cheap treatments like whats been suggested in this thread. Even good products can cause problems if not used properly.

On my way to using these products I've read about acoustics and tried many homemade devices learning along the way. I'm not claiming these will replace proper bass traps in the corners(these aren't bass traps) or will cure all the problems more properly designed products would do but in the spirit of the title of this thread I just wanted to suggest something cheap and in my case "when I couldn't afford much else but had more time" something that had a beneficial effect in my room at that time. By stacking these boxes from floor to ceiling in the rear corners of the room it cleaned up an audible problem in the vocal range of that room without any bad effect that I could detect for the cost of a roll of shipping tape and free cardboard.

mikeb

[artto]

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On 7/22/2004 10:45:35 PM DrWho wrote:

The other route you can take is to educate the crap out of yourself and try to do everything perfect the first time and then end up changing stuff anyway

*cough* artto *cough*

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That's exactly what happened to me, even with all the information I was armed with. LOL (although that was nearly 25 years ago and 4 major room revisions since)

[artto]

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On 7/22/2004 10:45:35 PM DrWho wrote:

Side note...is there a difference between "normal drop" cieling tiles and "acoustic" cieling tiles? Or is this just two names for the same thing? If not, how would one go about telling the difference between the two? I'm not planning on building these tiles or anything (working on some masonite ones similar to what artto has that are talked about in the dope from hope papers), but my curiousity is getting the better of me

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There are acoustical ceiling tiles, and there are acoustical ceiling tiles.

Most ceiling tiles that are made for suspended "T" bar systems are intended for simply absorbing sound in the frequency range the ear is most sensitive, which is centered around 1KHz. These are often used in schools, commercial areas/office buildings, areas where partitioned kiosks are used, basement recreation rooms, etc. These are most commonly available from major hardware/home improvement outlets/building materials suppliers.

The types used for broadband applications such as music in recording studios, sound control boths, auditoriums, stadiums, etc., and are substantially more expensive. They are also usually much thicker and have more complex surface topology and use a different materials. And they are available from professional sound contractors/distributors, directly from the manufacturers.

The manufacturers of both types usually publish some sort of architects and engineers specifications. You should look for specifications that give performance coefficients (NRC values) for at least all six of the standard ASTM test frequencies. Avoid using a consolidated "averaged" NRC as these can be very misleading.

[artto]

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On 7/22/2004 11:15:06 PM mikebse2a3 wrote:

Its OK artto no bubbles busted here. I now use ASC tube traps and RPG diffusers in my room and understand there are limitations to any cheap treatments like whats been suggested in this thread. Even good products can cause problems if not used properly.

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OK Mike. You had me scared for a while.

[artto]

But really folks, want good acoustical treatment on the cheap? Something to get started? The link WhooseYoDaddy provided on another post is a good place to start. http://www.audioadvisor.com/store/productdetail.asp?sku=SNXJRCHF&product_name=Juniors%20Acoustic%20Panels

As I mentioned in that same thread, there are "kits" available from Musician's Friend, Sam Ash or Parts Xpress starting at as little as $69, with more varied and substantial kits up to $400. http://www.musiciansfriend.com/srs7/sid=040723082527024015232212010398/g=home/search/d=tp?q=auralex

Any single one of these will make more difference in sound quality when properly applied than any single component, or group of components you can buy at any price, regardless of how well they are set up.

If you want to take things a step further in the DIY arena, panels that can be bowed into convex polycylindrical surfaces can be made from 1/8" to 1/4" tempered Masonite which costs less than $10 per 4'x8' sheet.

Roxul rigid insulation can be had in standard thickness of 1" to 4" and even thicker upon special order in 2'x4' (or was it 3'x5'?) sheets and simply covered with linen for a few bucks per sheet. Your biggest challange will be finding availablity in your area. http://www.roxul.com/sw34066.asp

Celotex and Homosote 1/2" and 1" rigid insulation panels can also be had for less than $10 per 4'x8' sheet from building materials suppliers. These can be laminated to produce thicker panels by simply screwing them together. These may also be cut into smaller tile size pieces for better distribution. Just be careful of the dust when cutting.

Avoid using materials such as products intended for a specific acoustical applications which are not "musical" such as most acoustical ceiling tile. Avoid things like cardboard and egg cartons, glass, and even plastics. Be careful with things like drapes, curtains and carpeting as these materials usually need to be on the heavy side to have any real effect and are still mostly biased towards the treble range as far as absorption goes.

Remember, its not about absorption. Its about (for starters) BROADBAND absorption AND diffusion.

The book "Master Handbook of Acoustics" by F. Alton Everest has Appendix of detailed NRC ratings for various materials and methods of using them. The book also covers separate chapters on the acoustics of listening rooms, small recording studios, control rooms, etc.

[mace]

Here is an interesting article, which I got off this board some time back (I can't remember original poster). It is an acoustical study of egg carton. Comparing this with the "acoustical ceiling panels" it seems egg carton's aren't quite as absorbtive, do absorb in the same mid-range but not the high range.

Artto: any measurements available on the stuff you linked to here (Juniors Acoustics Panels, Auralex Wedgie Box (i'm not sure if I want 24 wedgies...))?? I couldn't find anything at the links you kindly provided.

Kudos to the original poster for such a detailed report! I'm considering doing the same thing (curved panels aren't an option, neither is spending $75 on four 2'x2' pcs. of foam) in my familly room. I'd also like to do something like this in our entry way to kill sounds (voice) from carrying upstairs.

Has anyone heard of "Duct Board"? A recording studio owner I know uses this to line the recording room. When I walked into the studio I could feel the pressure change in my ears, it was quite dead (don't know frequency specific, though, I was just playing guitar, no listening). Anyway, Duct Board runs about $25 for 4'x10' sheet here in town. I was wondering if anyone else had tried it?

Regards,

mace

egg.pdf

[NOSValves]

oopshttp://forums.klipsch.com/idealbb/view.asp?topicID=52345' target=_blank>

[Parrot]

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On 7/26/2004 10:12:57 AM NOSValves wrote:

oops

http://forums.klipsch.com/idealbb/view.asp?topicID=52345"'

target=_blank>

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What did you do? Forget to take the eggs out of the egg carton first?

[mace]

What did you do? Forget to take the eggs out of the egg carton first?

Good one!

[artto]

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On 7/25/2004 11:19:14 PM mace wrote:

Here is an interesting article, which I got off this board some time back (I can't remember original poster). It is an acoustical study of egg carton. Comparing this with the "acoustical ceiling panels" it seems egg carton's aren't quite as absorbtive, do absorb in the same mid-range but not the high range.

Artto: any measurements available on the stuff you linked to here (Juniors Acoustics Panels, Auralex Wedgie Box (i'm not sure if I want 24 wedgies...))?? I couldn't find anything at the links you kindly provided.

Kudos to the original poster for such a detailed report! I'm considering doing the same thing (curved panels aren't an option, neither is spending $75 on four 2'x2' pcs. of foam) in my familly room. I'd also like to do something like this in our entry way to kill sounds (voice) from carrying upstairs.

Has anyone heard of "Duct Board"? A recording studio owner I know uses this to line the recording room. When I walked into the studio I could feel the pressure change in my ears, it was quite dead (don't know frequency specific, though, I was just playing guitar, no listening). Anyway, Duct Board runs about $25 for 4'x10' sheet here in town. I was wondering if anyone else had tried it?

Regards,

mace

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Yes, contrary to popular belief, egg cartons make terrible acoustic control devices.

I highly recommend that you do NOT use the acoustical ceiling tiles to 'kill sounds' for anything in music or home theater applications. As I said before, these products were not designed for broadband applications such as music and can actually make the sound worse instead of better.

Maybe I'm interpreting some of this wrong, but I must admit, I don't understand the reluctance to use acoustic foam panels. There are plenty of variations in pattern types and colors out there that can blend with many different decor. You could also cover these with fabric if you wish. They don't take up much space. They don't have to be permenantly secured. They can be secured to the wall with staples or long steel "T" pins like the ones used to tack a piece of paper on message boards or those office panel partions which makes them easy to move around and experiment. The 'T' pins leave only a very small pin hole in the wallboard which can easy be repaired if you feel it needs to. Fiberglass panels such as those made by RealTraps can also have different kinds of patterned 'design' fabric or wood frames to fit any decor. If your decor is more traditional, for pure diffusion you can also use fluted wood columns like those that are now premade and available at Home Depot. There are plenty of 'trim' options that can be placed around walls and ceilings etc. Use your imagination! There are tons of options out there! Consider how many concert halls have their interiors built. It doesn't matter how traditional or contemporary they are. In older halls diffusion was achieved by lots of columns, statuary, and various ornamentation. Even pictures on the wall can provide some diffusive qualities for middle and treble frequencies, book/record cases, furniture, etc can provide absorption and diffusion to one's acoustical advantage, when used properly. Consider how much you've spent on your recordings and equipment. Why skimp when it comes to the most important aspect of being able to achieve good sound? Spending extra money on cables or amplifiers pales in comparison to what good acoustics achieves. If you're not willing to do this, or simply are in a situation where you can't (we've all been there, including myself), then you must admit and resign yourself to the fact that you will never be able to get anything close to the most out of your recordings or equipment, regardless of how good they may be. On the other hand, don't spoil it by trying to do acoustical things "on the cheap" that may do more harm than good. Yes, it will sound different, but if you're like most people, it will probably take you some time to hear what it's destroying verses any improvements it made.

I'm not sure what your friend means by "duct board". At any rate, most recording studios have somewhat different acoustic requirements than a home theater or listening room has. You don't want your HT or listening room to be too dead (absorptive). And no offense to the recording studio owner you know, but most recording studios that I have seen or been in have terrible acoustics. They usually rely on close mic and sound isolation booth techiques, neither of which are used for true stereo recordings, and special "near field speakers" (or even headphones) for monitoring.

More in-depth information on the specific products I mentioned can be found on the manufactuer's websites. ie: www.auralex.com