SOUND ON SOUND

[blinddrew]

Hmm. So you could gwt a dozen for roughly £300. With no additional covering needed that puts them in a similar price to homemade rockwool + cara options.
That's going to appeal to a lot of people. Wonder how it compares to a rockwool block of the same size?

[Sam Spoons]

Density is about 40kg/m3 or ⅔ rds of RW3...

[Jorge]

https://www.bobgolds.com/AbsorptionCoefficients.htm

Compared with 4" thick Roxul Safe 72 kg/m3 or Owens Corning 703 48 kg/m3, the 4" Caruso polyester block has much less absorption of sound below 125 Hz. Same for the 4" Autex polyester in the Bob Golds' table.

If bass trapping is not important in your space and you get the fireproof version, the polyester would seem have the advantage of being a lot less itchy to work with than the rockwool or fiberglass.

[blinddrew]

Thanks Jorge, useful info. :thumbup:

[dfira]

So my polyester boards arrived, and seem about on par with what is being commented here.

If i stack about 4 of them (measuring 36mm in depth) in front of my girlfriends face as she talks, you can hear a reasonable amount of bass extension less than 4 and honestly it sounds like it might do more harm than good.

Tbh i never tried the speaking test back when I had rockwool panels, but pushing the boundaries of my memory, and acceptable comparisons, I would say they're not quite as good as a panel of rockwool for the same size, but now I'm worried about catching lung cancer from rockwool!!

If i buy some rockwool, what is the best fabric specifically, to cover them in?

[Sam Spoons]

All the science points to the risk of catching lung cancer as a consequence of using Rockwool is vanishingly small, and who's to say polyester is any less dangerous?

If you are really worried doping the panels with a dilute PVA adhesive solution will help secure the fibres and I believe Camia acoustic fabrics are still able to contain any remaining fibres despite being fairly acoustically transparent.

Others have, I believe, covered the RW in clingfilm before covering in acoustic fabric with some success.

WRT your 'girlfriend speaking' experiment I'd expect a small reduction in HF but no affect on low frequencies from a 36mm thick low density panel. You need much more mass and 'acoustic impedance' (i.e. the slowing of air movement as it passes through the panel).

[DanDan]

On a quick look Autex Ultrafirm 50mm has an Alpha of 0.26 in the 125Hz Octave band. This is the same as some of the top performing Rock fibre products. Polyester is commonly used in clothing, bedding. I am sure there is plenty of evidence proving it's safety regarding health and fire behaviour.

[Sam Spoons]

Polyester is commonly used in clothing, bedding. I am sure there is plenty of evidence proving it's safety regarding health and fire behaviour.

A good point, having said that the evidence for the safety of RW is also well documented. :thumbup:

[vetko10071979]

An acquaintance of mine had these panels, he mixes and sometimes does vocals, and he says he has improved the sound, especially in the high and medium frequencies.

[Sam Spoons]

Good to hear some nearly first hand experience. :thumbup: TBH we've maybe been too analytical and forgotten that nearly anything vaguely similar will work, aren't we always suggesting a couple of cheap duvets (which are almost always filled with polyester)... Just that some things work better than others.

[DanDan]

Many of the books refer to Owen Corning 703 and 705 as a sort of Gold Standard, or at least a very safe well performing choice.
Autex Polyester is way better.

50mm Fibre 125Hz
OC 703 0.16
OC 705 0.17
Autex AVA 0.25

[Jorge]

I am curious why you would choose a 2" thick sound absorber mounted on the wall for bass frequencies. Wouldn't you want an absorber to be either much thicker or mounted a distance from the wall, or both? My non-professional understanding of the acoustics is that you want to set up a resistance to vibrating air movement close to the region where the air velocity is at peak amplitude, which would be around 1/4 wavelength out from the wall. The 1/4 wavelengths of bass in the 40-125 Hz range would be about 1/4*1130/125=2.3 feet to 1/4*1130/40=7 feet, so the first 2" out from the wall would only be a tiny fraction of 1/4 wavelength. Attenuation of air movement of the bass standing waves in that region would be minimal. So I don't see the relevance of the coefficients you have cited, which are for 2" thick slabs mounted directly on the wall. The BobGolds charts don't have coefficients for 4" or 8" out from the wall but at 125 Hz, a 4" slab of OC703 3pcf mounted on the wall is listed to have a coefficient of 0.84, much better than a 2" slab of the same 703, which has a coefficient of 0.17 as you listed. For comparison the 4" thick Autex Polyester Acoustic Blanket on the wall has a coefficient of 0.50, virtually the same for all densities and substantially less than the 0.84 for the 703.
I don't do this for a living, so maybe I am missing something or did something wrong, or maybe you can recommend a better reference than the BobGolds tables.

[DanDan]

I am curious why you would choose a 2" thick sound absorber mounted on the wall for bass frequencies.

Nobody suggested that.

So I don't see the relevance of the coefficients you have cited, which are for 2" thick slabs mounted directly on the wall.

There is quite a lot that you are misunderstanding.
I quoted comparative data that shows Autex AVA to be much better than OC703/5
I used 50 because that is the data available for all three. Across the board one can extrapolate to thicker.

[Jorge]

I am curious why you would choose a 2" thick sound absorber mounted on the wall for bass frequencies.

Nobody suggested that.

You yourself suggested that by quoting the coefficients of 0.16 and 0.17 for 2" on the wall 703 and 705 that appear in the BobGolds table. Why not quote the coefficients for 4" on the wall and/or with an air gap, either of which is more realistic? The trends by thickness are not always linear, monotonic and predictable from simplistic reasoning, so empirical data are probably better, if a reliable source is available.

So I don't see the relevance of the coefficients you have cited, which are for 2" thick slabs mounted directly on the wall.

There is quite a lot that you are misunderstanding.
I quoted comparative data that shows Autex AVA to be much better than OC703/5
I used 50 because that is the data available for all three. Across the board one can extrapolate to thicker.

Maybe I misunderstood because you made a claim quoting a source that I could not find to read and understand. What is the source are you quoting from? I could not find Autex AVA on the Autex Global website, and could not find a table of absorption coefficients for "Autex AVA". The BobGolds tables, which I used many years ago in treating my studio, show Autex AAB but not AVA.

fixed quotes for you - Andy :beamup:

[DanDan]

Are you suggesting I am not a reliable source Jorge? LOL! https://www.masacoustics.it/wp-content/ ... -Sheet.pdf