Good DIY Accoustic Treatment Materials

[wilyam]

Hi all,

I'm wondering what inexpensive materials would be good for dampening a room?

I'm wanting to treat a room that is roughly 4x3x2.5 (in meters LxWxH) with a carpeted floor, a double bed in it. The walls and ceiling are plaster rendered brick with one large window (roughly 2.5x2 (HxW) ) with heavy block out curtains covering it.

I was thinking something like dooners/quilts and maybe a box and/or skyline diffuser. What other recommendations in terms of material/types of treatment would you guys recommend?

Thanks in advance

[Guest Willow]

I'd start with Bass Traps first , wilyam , with the dimensions you quote it is probably a given they would be required.

Maybe PM Paul Spencer or Elill for some advice or wait till they find you , both have experience in the field.

[b.d]

Bradfords Supertel (like the American Owens-Corning 703 you might read about) a few feet thick in the corners is always recommended if you got the space. Lots of diffusion is good to, cant have too much really. Go easy on things like dooners though as they only absorb quite a narrow part of the spectrum and its easy to make the sound lifeless. Basically I'd basstrap the hell out of the room, add diffusers at first reflection points, then see how it sounds tonally before proceeding. Eq and toe in/out can also help at this stage, but isnt a substitute for bass traps and diffusers.

Edited February 26, 2011 by b.d

[andyr]

Hi all,

I'm wondering what inexpensive materials would be good for dampening a room?

I'm wanting to treat a room that is roughly 4x3x2.5 (in meters LxWxH) with a carpeted floor, a double bed in it. The walls and ceiling are plaster rendered brick with one large window (roughly 2.5x2 (HxW) ) with heavy block out curtains covering it.

I was thinking something like dooners/quilts and maybe a box and/or skyline diffuser. What other recommendations in terms of material/types of treatment would you guys recommend?

Thanks in advance

Why do you feel your room needs "damping"? It's carpeted, which is excellent, and the window has a heavy curtain ... however, the room's small size probably means it has bass problems.

BTW, I assume you meant your walls are plaster-rendered brick ... but your ceiling is plasterboard?

Regards,

Andy

[wilyam]

Thanks for all the replies

I agree, bass is a bit off a problem but the main thing that I notice is flutter echo within the room. All the walls (including ceiling) are brick and/or concrete. I was thinking some broad spectrum panel absorbers (made using Tontine Acoustisorb 3, potentially) will help a lot with reducing flutter echo with in the room also bass traps, and am looking into different designs that would work with my room (in terms of size of the traps etc).

I was thinking something along the lines of:

4x panel absorbers (to help reduce flutter echo),

2x bass traps (to help tighten up the bass end of things) and

1/2x quadratic residue diffuser (to help reduce hard reflections). All DIY of course.

What do you guys think? Any suggestions?

All advice is much appreciated

[b.d]

You can use diffusion to treat slap echo too, if you are not wanting to damp down the overall tonal balance. Easier than a quadriatic if you're feeling lazy is gently bent board of ply. As you might know it's just higher freq sounds ping ponging between parallel surfaces. Try the clap test at the listening possition to evaluate, it doesnt matter if you hear slap echo when you clap anywhere else in the room, you're dealing with directional frequencies so its specific to place.

[Craigandkim]

Have you read any of the other posts in here dealing with room acoustics?

Reference your ideas you seem to be on the right track- your first reflection points (all of them) will need to be treated by either absorption or dispersion.

[DanTheMan]

This is my generic advice: http://dtmblabber.blogspot.com/2010/12/room-treatment-advice-quick-and-dirty.html

Dan

[Guest Peter the Greek]

will need to be treated by either absorption or dispersion.

Ideally both.....products like RPG BAD or Quest AI Perfsorber - if off axis response is good.....if not absorb them

Supertel is only 32kg^m3 whereas ultratel is 48kg

Acoustica white batts are my preference as they're polyester and come in a variety of high densities

Also John Menville make a black poly product

[Paul Spencer]

The thing to watch is not to make the room dead, especially when it is small. The smaller the room, the higher the surface to volume ratio, the quicker it becomes dead.

Here's what I'd probably do. Start with the speakers against the short wall if you can. Put in some bass traps floor to ceiling in the front wall corners. Use rigid fibreglass 48kg/m3, it comes in big sheets 1.2 x 2.4 x 50mm thick. If you have the budget for it, get 6 of those for those two corners, so they will be 150mm thick. Then put the speakers just in front a little. They cost about $80 per sheet. If that's a bit painful on the hip pocket you might just use one or two layers with some foam as well. You can scrounge foam from old couches. In fact, one way to start experimenting with bass traps and treatment is simply with old couch cushions.

BTW, it pays to spread bass traps around the room. Check this out

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

Don't forget you can put them in ceiling corners as well.

The challenge in a small room is to sit far enough away to get a sound stage. Put the speakers too close to a wall and it gets ugly. Bring them into the room and you are sitting too close. Treatment lets you bring them closer to the front wall, the bass trap will do that for you. Focus the absorption on the front wall to tame ill effects there. Rigid fibreglass is good stuff because it works over a broad range unlike carpet and doonas that only tame high frequencies, killing the room before the job is done. You might try diffusors on the ceiling and side walls, QRDs seem like a good mix of performance and ease of construction. Not too hard to make with some MDF.

One thing to keep in mind is SBIR

http://redspade-audio.blogspot.com/2011/02/sbir-speaker-boundary-interference.html

Check out the Real Traps website, their video section in particular "hearing is believing." They show a small room highly treated, mostly with diffusors to make it sound bigger and they also double as bass traps.

One of the best things you can do is experiment, and in this area you can do it cheaply (or even for free).

I have an experiment of my own I want to do when I get the chance. I'll be comparing foam of various densities to rigid fibreglass. I have a couple of panels of rigid fibreglass that are waiting to become treatment. For now they sit in the room as both traps and front wall absorbers.

[Craigandkim]

Supertel is only 32kg^m3 whereas ultratel is 48kg

Acoustica white batts are my preference as they're polyester and come in a variety of high densities

Hello Elill,

there ya go again- pushing the 48kg/m3 again (just kiddin)

BTW I never heard back from the distributor of Acoustica white batts reference the NRC coefficients regarding their 100mm stuff.

Do you have this info anywhere?

[Guest Peter the Greek]

no....but it "should" be very similar to fibreglass. Its a strand based product....it should work.

Acoustica probably doesn't have the info....best get yourself some and do some tests.

Did they have it at lesser thickness? eg 25mm? if that was the same as the glass at the same thickness surely the properties are the same?

[Craigandkim]

The "50mm" Acoustica High Density White Batts 44-48 kg/m³ ....ratio @ 125hz = 0.40

Ultratel "50mm" unfaced..... ratio @ 125hz = 0.34

Ultratel dont make 100mm so it would be hard to ascertain the properties of Acoustica with any degree of accuracy.

Not sure if you remember but some time ago I inquired about obtaining 100mm stuff....they would not supply amounts under 4m³ (there abouts)

[Guest Peter the Greek]

just get a bunch of the 25mm stuff and layer it?

[aechmea]

The Fletcher Insulation fact sheet for their 32Kg semi rigid fibreglass sheets shows that 75mm thick has a greater absorption factor at 125Hz than the 100mm. Odd?

So maybe once the thickness gets to say 75mm there isn't much more to be gained.

On the other hand, 'The Master Acoustics Handbook' has a graph showing that density has little or no effect, but thickness does. They show a great difference between 25mm and 50mm but much less difference between 75mm and 100mm. The Handbook sends a strong message on getting the absorption sheets well out from the walls where the air particle velocity is greatest and SPL is least (quarter wavelength).

I seem to recall that Winer says that more surface area is better.

So ... putting these together

it seems to me that if you get stuff about 32 or 48Kg and about 75 - 100 mm thick and cover a good proportion of the corners (out from the wall surface) then it will be about right - well - at least better.

[aechmea]

The OP's room is concrete with plaster render. I looked up the table of absorption coefficients and that concrete+plaster situation is about as reflective as it gets - some 20 times more reflective than gyprock. Therefore there is no question that wilyam could do with a goodly quantity of damping treatment. Go for it.

Edited March 2, 2011 by aechmea

[Guest Peter the Greek]

If thats the case I'd bang up a 90mm stud framework over the entire room. Fill it with a reasonably dense insulation (I'd use 48kg ) and cover that in pegboard....wallah one massive bass trap, then go about treating reflections as desired. Concrete rooms are aweful things

[Paul Spencer]

The Fletcher Insulation fact sheet for their 32Kg semi rigid fibreglass sheets shows that 75mm thick has a greater absorption factor at 125Hz than the 100mm. Odd?

So maybe once the thickness gets to say 75mm there isn't much more to be gained.

On the other hand, 'The Master Acoustics Handbook' has a graph showing that density has little or no effect, but thickness does. They show a great difference between 25mm and 50mm but much less difference between 75mm and 100mm. The Handbook sends a strong message on getting the absorption sheets well out from the walls where the air particle velocity is greatest and SPL is least (quarter wavelength).

I seem to recall that Winer says that more surface area is better.

So ... putting these together

it seems to me that if you get stuff about 32 or 48Kg and about 75 - 100 mm thick and cover a good proportion of the corners (out from the wall surface) then it will be about right - well - at least better.

It's much easier to do too little than too much with bass traps. As the thickness goes up, the density becomes less important, but you should aim for more like 150mm. I've used more than a foot, but most of it is foam. Placing traps around the room is important because you are trying to damp the bass at multiple points.

Check out the link I showed earlier:

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

This is two densities shown compared to a bare room:

[DanTheMan]

I actually wouldn't worry about killing a small room too much. This is with 6" of sound damping foam(giant mattress sized) with a gap or 12" of R19 fiberglass isulation covering over 60% of the surface. These RT60s go from naked room to mostly clothed.

It still doesn't sound dead (to me). I've also got 25% of the room covered in 5.5" deep diffusors. I'd say it's about right, but could still use a little more diffusion. The room is primarily LEDE. The last wall, AKA the ceiling is untreated and will likely get diffusion. In pro audio forums, smaller rooms are generally preferred slightly dead of IEC. It seems counterintuitive to me while at the same time I like it. Perhaps too close of reflections just stink. My RT60 is pretty level at 0.3s in the HT. This little bedroom is more to my liking believe it or not.

Dan

[Craigandkim]

It's much easier to do too little than too much with bass traps. As the thickness goes up, the density becomes less important, but you should aim for more like 150mm.

Exactly Paul,

implementing "broadband bass traps" inherently implies you're positioning to absorb as much of the sub 300hz area as possible. In the first instance this should undoubtedly encompass bass traps in the front and rear corners (floor to ceiling).

It continually amuses me to see people expressing concerns of instantly turning their room into an anechoic chamber by the use of a couple bass traps.

These traps need size and mass to attenuate effectively at the lower levels. I am inquiring about 100mm thickness purely for maximum known absorption coefficients and ease of use constructing 300-500mm thick absorbers.

Aechmea you are spot on- size does matter and he's going to need some serious traps.

[Valavien.]

I have a whole lot of 100mm Tontine Acoustisorb 3 ready to be made into panels. It's specs seem good:

Acoustisorb 3

[Craigandkim]

Val,

how much did the stuff cost you up in Brissie? Who was the distributor?

[Valavien.]

I got it from Plastamasta Southside and I paid about $350 for the 100mm. It's very dense and quite stiff compared to regular insulation. It would want to for the price! I believe the 50mm is about $170 and the 75mm $190. I actually thought that each sheet was 1200mm wide but they are only 600mm so I got more pieces than I thought which will be useful.

They also sell green glue as well.

I recommend speaking to Dean Price, he is very helpful and friendly.

[Ken]

I used Acoustisorb 3, it does a great job in my application.

Bonus is that it is not Fibre Glass derived, therefore it is safe to handle.

However, if you are putting it at first reflection points, I would prefer something that diffracts the sound rather than trying to absorb, I have Acoustisorb covered in the studio polyester urethane type tiles.

Ken

[ngquan]

Hi , i am doing some panels for my room- using rockwool density 80kg/m3 -50mm thick.

Would that be ok at first reflection points?