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Author Topic: raw cotton for bass traps  (Read 4674 times)

maxime

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raw cotton for bass traps
« on: October 12, 2008, 08:15:58 pm »

Hello,

a friend of mine has a huge patch of raw compressed cotton, and he would give me 1m3 for free. I am thinking of using this as basstrap bags material. the density is about 80kg/m3, maybe more.
The fibrous nature of cotton seems perfect for acoustics work and also the density of the material is ok to absorb at the lower frequencies. but maybe I am all wrong!
I googled a bit, but couldn't find any useable info!

any ideas on the subject?

thank you

maxime
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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #1 on: October 13, 2008, 05:56:53 am »

Hi Maxime,

Yes, you can indeed use that material for that purpose.

Though it's a pretty "new" material for that kind of use, so it's no surprise you can't find that many infos about it on the web yet.

I have yet to see measurements of acoustic treatment using that type of core material, but no reason why it wouldn't work. It will work, but to what extent?

For the past couple years, I've used recycled paper cellulose bats built by a german company specialized in environmentally friendly insulation with great success - their density varies between 65kg/m
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Thomas Jouanjean
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maxime

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Re: raw cotton for bass traps
« Reply #2 on: October 13, 2008, 11:56:57 am »

thanks thomas,

that's good news!
I 'll tell you the results when the traps are installed.
I have a bit of sewing work to do till then

best

maxime
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C.Cash

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Re: raw cotton for bass traps
« Reply #3 on: October 14, 2008, 09:04:36 am »

not exactly raw cotton but this is what I used, worked really well and no itching;

http://www.greenmakersupply.com/pages/insulation___weatheriz ation/160.php
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jimmyjazz

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Re: raw cotton for bass traps
« Reply #4 on: October 14, 2008, 02:09:35 pm »

I'd be wary of its flammability.  It may not matter so much in a personal studio, but if yours is a commercial facility, your insurance company would probably frown on the installation of something that doesn't meet UL or other flammability ratings.
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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #5 on: October 15, 2008, 02:38:53 am »

In my experience, at least in Europe, all those insulation products, including cotton based ones, are either M1 or M0 fire rated.

Though I've seen rockwool actually burn when my woodcrafter's place burned down a year ago (horrible day...) and it wasn't pretty whatsoever. It burned like paper.
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Thomas Jouanjean
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maxime

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Re: raw cotton for bass traps
« Reply #6 on: October 15, 2008, 06:15:49 am »

Thanks for all your info!
My studio is mainly personnal.I was thinking of fire hazard. but to impregnate the cotton with flame retardant products would alter the consistency of the fibers too much and reduce density.
Be reassured that I'll comment the results anyway..

best
Maxime
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AndreasN

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Re: raw cotton for bass traps
« Reply #7 on: October 20, 2008, 05:44:59 am »

Thomas@Northward wrote on Wed, 15 October 2008 08:38

Though I've seen rockwool actually burn when my woodcrafter's place burned down a year ago (horrible day...) and it wasn't pretty whatsoever. It burned like paper.


Ouch! Hope it didn't set you back for too long.

Was it that hot, or didn't it live up to its expected high heat resistance? How is the rockwool burning? Combusting, melting, deforming..?

According to the Norwegian rockwool page, the product does not contribute energy to a fire. It should have a melting point above 1000'C and should not combust in any case.

According to their paper.. How was reality?
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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #8 on: October 20, 2008, 11:53:40 am »

AndreasN wrote on Mon, 20 October 2008 04:44

Ouch! Hope it didn't set you back for too long.

Was it that hot, or didn't it live up to its expected high heat resistance? How is the rockwool burning? Combusting, melting, deforming..?

According to the Norwegian rockwool page, the product does not contribute energy to a fire. It should have a melting point above 1000'C and should not combust in any case.

According to their paper.. How was reality?


We did have to reschedule a few things, but luckily only about 4 dual membrane traps and a handful of diffusors were lost in the fire (on top of all their machines that were destroyed either by the flames or the water + the product the firebrigades add to the water which seems to be very aggressive and made a lot of the tools rust), but luckily the building's structure was still sound, so they could rebuild rather fast.

Now, when it comes to the rockwool, what I saw was a red glowing mass of rockwool in the fire, (I arrived after the ceiling went down and looked from the street) and a few days after, when they showed me the damages, they showed me what was left of the rockwool: mostly some black dust, but sometimes ebony dark crunchy bits.

I have also noticed many times on construction sites that it happens that they adjust metal studs close to rockwool bats in ceilings etc, and when they cut the metal with the electric saw, the parts of the rockwool that are touched by the hot metal projections start glowing VERY fast and consume fast as well. no flames though.
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Thomas Jouanjean
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franman

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Re: raw cotton for bass traps
« Reply #9 on: October 23, 2008, 06:40:21 pm »

This is a bit disconcerting.. I have done a few projects in Europe recenty and I was under the impression that Rockwool was a fire retardent material, much like the fiberglass batts we use more commonly over here.. It seems that your experience Thomas, contradicts this?? This is a bit scary!
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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #10 on: October 24, 2008, 12:27:27 pm »

I was under the same impression. But I now have some doubts about it's real efficiency...

Maybe it's the type I use that is more sensitive? Next time I talk to the local St Gobain rep, I will ask him what's up with that.

Edit: the type that was used was Rockwool 431 ADAPT
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Thomas Jouanjean
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maxime

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Re: raw cotton for bass traps
« Reply #11 on: November 01, 2008, 11:48:05 am »

hello,

I made traps with cotton and the results are very pleasing. I 'll post some pics soon. I used a MDF frame with kraft paper facing glued to the frame only. I achieved a good density of material by compressing it a bit. It looks like a membrane (but the back of the pannel is not closed). The back fabric I used is hemp(I recommend it, as it's tough elastic and very open acoustically). The thickness is 10cm (10 pannels) and 15cm (8 pannels). I made 18 pannels already.
The results were already there with 6 pannels installed.
What surprises me is the fact that the high frequency reverberation was almost left untouched!

best

Maxime
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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #12 on: November 01, 2008, 01:40:52 pm »

Good news! - Looking forward to seeing them Smile
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Thomas Jouanjean
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maxime

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Re: raw cotton for bass traps
« Reply #13 on: November 13, 2008, 02:37:13 pm »

here are some pics:



some finished traps:
you can see the room side kraft paper. It was glued to the mdf frame. it's tensioned by the material under compression. I used 4" and 6,5" thickness modules.
the other side is hemp fabric, very tough and very open (stapled)
http://i156.photobucket.com/albums/t8/maximebdsn/basstrapsq/IMG_0641.jpg
the raw material:
http://i156.photobucket.com/albums/t8/maximebdsn/basstrapsq/IMG_0642.jpg
inside the trap
http://i156.photobucket.com/albums/t8/maximebdsn/basstrapsq/IMG_0645.jpg
the results are very good till 70 hz aprox. my guess is that I'd need some tuned traps for the lower range.


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Thomas Jouanjean

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Re: raw cotton for bass traps
« Reply #14 on: November 15, 2008, 06:12:05 am »

Good work! hope to see pics of the final install!

PS: please activate either your PM or E-mails contacts, could not reach you with either...
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Thomas Jouanjean
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KAyo

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Re: raw cotton for bass traps
« Reply #15 on: November 20, 2008, 12:59:04 am »

I've used Acoustic cotton with my set-up. And it works well. Real good I tell ya..
Made 9 bass traps, which are now ready to be placed in their respective zones. Learn't a lot from Ethan's videos etc..

Just need to find a carpenter to help do it professionally.
They are pretty big, heavy and i want them angeled on the ceiling and corners etc...

Will post pics as and when completed..

Cheers..
Kayo
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C.Cash

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Re: raw cotton for bass traps
« Reply #16 on: November 20, 2008, 08:26:58 am »

What do you guys think about framing the panels with PVC pipe to save weight?

Thanks.
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