Bonded Acoustical Cotton . Is it good?

michaelv · « **on:** 9 Jun 2005, 05:22 pm »

Hi,
I find this website:
http://www.acousticalsurfaces.com/echo_eliminator/wall_panel.htm?d=0

This is acoustical cotton. Is it better OC703 fiberglass or wedge foam? Based on description, acoustical cotton is easier to work with compared to fiberglass. It can be painted or wrapped with cloth.

Has anyone tried it or have experience with it.

thanks.

ScottMayo · « **Reply #1 on:** 9 Jun 2005, 05:59 pm »

Quote from: michaelv

Hi,
I find this website:
http://www.acousticalsurfaces.com/echo_eliminator/wall_panel.htm?d=0

This is acoustical cotton. Is it better OC703 fiberglass or wedge foam? Based on description, acoustical cotton is easier to work with compared to fiberglass. It can be painted or wrapped with cloth.

Has anyone tried it or have experience with it.

thanks.

Never used it, but at 3 lbs per cubic foot, it shouldn't be much worse than OC 703, and it would certainly hurt the fingers less.

I wouldn't paint it. You want the fibers to move against each other, generating friction. If paint sinks in, it's going to prevent that, and make the thing more reflective to boot.

If you get some, let us know how it works. I'm interested in how they keep it squeezed to the right density - uncompressed cotton should be lighter than that, I believe.

bpape · « **Reply #2 on:** 9 Jun 2005, 07:21 pm »

Don't paint it. Don't paint any porous absorber.

Overall, the BAC is wonderful stuff to work with. Also, it doesn't have as much problem with relfecting at high angles of incidence.

DTB300 · « **Reply #3 on:** 9 Jun 2005, 07:21 pm »

Contact the company as they are great to deal with.

Another site to visit is:

http://www.sensiblesoundsolutions.com/

"bpape" posts here on the acoustical forum and is also some great help to us newbies in the acoustical treatment area.

The absorption properties are listed on both site and could be compared to Fiberglass. They have 1", 2" and their 4" Bass Buster product.

Dan

michaelv · « **Reply #4 on:** 9 Jun 2005, 07:33 pm »

Thanks all for replying.

Another question.
Is fiberglass or acoustical cotton stiffer? I'm not very good at wood working, so i'm thinking of just wrapping fabric all around. However, the stiffness is my concern as i want the panel looks nice..

Or else i will try to build simple frame.

If the frame is needed , should i place backing board to cover full back or just a partial?

Saurav · « **Reply #5 on:** 9 Jun 2005, 07:35 pm »

Are prices for this stuff mentioned anywhere? I took a quick look but didn't see that info.

michaelv · « **Reply #6 on:** 9 Jun 2005, 08:12 pm »

If you go to http://sensiblesoundsolutions.com/index.php?manufacturers_id=11

you should see the price.

bubba966 · « **Reply #7 on:** 9 Jun 2005, 08:20 pm »

Quote from: michaelv

If you go to http://sensiblesoundsolutions.com/index.php?manufacturers_id=11

you should see the price.

Man that stuff's spendy!

Fiberglass is much cheaper. The 2" x 2' x 4' 703 I've been using as of late is about $10 a sheet.

Don't know how stiff the cotton is, but the fiberglass is stiff enough that you should be able to wrap it with fabric & have it still look good.

Saurav · « **Reply #8 on:** 9 Jun 2005, 08:38 pm »

Thanks.

bpape · « **Reply #9 on:** 14 Jun 2005, 08:56 pm »

The cotton is not as stiff as the fiberglass. However, it is much easier to work with, doesn't shed, doesn't absolutely need to be covered, and does a great job with steep angles. Yes, it's more expensive. For bass, I've found the cotton to be so much better that I don't even carry fiberglass over 2" any more.

As for the fiberglass... The 705 is dense enough and stiff enough that you can wrap directly. 703 with cloth stretched tight enough to look decent will crush at the edges - just not dense enough (and why it does a BETTER job for reflection points than 705)

michaelv · « **Reply #10 on:** 15 Jun 2005, 05:31 am »

for the bass trap, do you hang it half way between floor/ceiling/and wall to be effective or has to cover the whole corner from bottom to the ceiling?

thank.s

bpape · « **Reply #11 on:** 15 Jun 2005, 05:33 pm »

Depends on what you want and need. The tri-corners will get all frequencies. I'd either do the upper 4' to the ceiling or do the whole corner - not just the middle.

michaelv · « **Reply #12 on:** 15 Jun 2005, 06:02 pm »

bpape,
If budget concerned, which two corner would you cover? I mean two front corner or two back corner (behind the speakers)? I think covering from bottom to the ceiling is what i plan to do.

thanks.

bpape · « **Reply #13 on:** 15 Jun 2005, 06:48 pm »

For a listening room, I'd do the front corners since you want the front pretty dead anyway. Some people don't want the dead front wall and prefer it behind them. It's really personal preference. If you get 4 pcs, it's light enough that you can sit it in the corner and try it both ways to see what you prefer before actually mounting it more permanently.

klh · « **Reply #14 on:** 16 Jun 2005, 12:26 am »

The Acoustical Surfaces website shows the bass buster as being 4" thick but having a density of only 1.2 lbs/cf... not 3 lbs/cf.

klh · « **Reply #15 on:** 16 Jun 2005, 01:04 am »

has anyone found the BAC is 4" thick and 6 lbs/cf (or close to that)?

bpape · « **Reply #16 on:** 16 Jun 2005, 11:45 am »

Yes. The 4" is 1.2 lb/cu ft. For reference though, look at the numbers for OC 701, 703 and 705. The 701 is the best performer down low - not the higher density board. 701 is 1.5 lb/cu ft.

6lb is fine for pure bass absorption inside a resonant panel trap or behind a slotted or perforated Helmholz absorber. But, for a broadband absorber across a room corner, something lighter like this actually works better. I can't explain why but you can look at numbers from several different products and most of them show the same thing.

klh · « **Reply #17 on:** 16 Jun 2005, 03:40 pm »

I haven't heard that before. Not saying it's not true... just that this is the first time I've heard it. Can anyone else verify or repute bpape's statement?

bpape · « **Reply #18 on:** 16 Jun 2005, 06:18 pm »

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

Bob has made a hobby out of collecting data about the absorbtion coefficients of different materials. The OC numbers are from OC's own tests from what I understand.

For those who don't want to wade through....

OC701 - 4" A mount
1.29 1.22 1.06 1.00 0.97

OC703 - 4" A mount
1.24 1.24 1.08 1.00 0.97

OC705 - 4" A mount
1.19 1.17 1.05 0.97 0.98

4" Bonded Acoustical Cotton - (1.2 lb) A Mount
0.97 1.37 1.23 1.05 1.00 1.01

Note that the BAC performs much like some of the faced fiberglass with higher numbers at 250 and 500 but still close to 1 at 125 and still absorbing well up high. This can be terribly handy when you need the extra in those bands (as often happens in many rooms) but don't want to reflect the highs.

While I have not done any testing on the product in a controlled enviornment to yield comparable numbers, I will say that when it is used straddling a corner, it's bottom end performance is significantly better than the A mounting (as would be expected).

klh · « **Reply #19 on:** 16 Jun 2005, 06:34 pm »

Those results seem to indicate the best is OC703 against the wall (inch for inch).

I mean the results in the link.