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Types of fabric to cover rigid fiberglass?

post #1 of 17
8/23/08 at 11:54am
Thread Starter 
Is there any rule of thumb to knowing what fabrics will work well for absorbing rather than reflecting sound that can be used to cover fiberglass? Or is GOM or other 100% AT fabrics the only type that won't decrease the effectiveness of the fiberglass?

I've brought just over a thousand square feet of 2" OC703 and need to cover it, so we're talking about a large amount of fabric.

I also just started noticing comments about formaldehyde and am worried about health issues now considering the type of room my HT is in.

Are there any types of fabrics that I can completely wrap the fiberglass in that will trap some/any formaldehyde toxins but still not reflect sound? I've been looking at tricot nylon which is cheap and has a tight weave but stretches (think spandex) that I think would seal up fairly well but it's worthless if it reflects sound since I've just made a huge investment in this fiberglass. People also talk a lot about muslin but no one has said if muslin reflects too much and makes the fiberglass pointless. And of course there is GOM or celtic which is AT but then we're talking about a LOT of money for the fabric.

For my HT, all 4 walls, floor and ceiling are 8"+ thick cement (16'x22'x9') which is why I bought so much insulation. The plan is to put 1" fiberglass on the front wall (AT Screen/false wall), 6" on back wall, 4" on the ceiling (ceiling is coffered with 8" wide mdf/crown "beams" and 4'x4' areas of fiberglass), and 1" on the lower 4' of the side walls. I will also have 34" face super chunk bass traps for the front corners.

I'm not sure if in my environment I am fine with a more reflective fabric? My theory is bass is going to be an issue more than mids and highs, so what should I do?
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post #2 of 17
8/24/08 at 8:40am
Quote:
Originally Posted by distoga View Post

Is there any rule of thumb to knowing what fabrics will work well for absorbing rather than reflecting sound that can be used to cover fiberglass?

The quote below is from my Acoustics FAQ.

--Ethan


Quote:


Nearly any porous fabric is appropriate, and one popular brand is Guilford type FR701. Unfortunately, it's very expensive. One key feature of FR701 is that it's made of polyester so it won't shrink or loosen with changes in humidity when stretched on a frame. But polyester is a common material available in many styles and patterns at any local fabric store. Another feature of FR701 is that it's one of the few commercial fabrics rated to be acoustically transparent. But since you're not using it as speaker grill cloth to place in front of a tweeter, that feature too is not necessary.

Shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. The standard test for acoustic fabric is to hold it to your mouth and try to blow air through it. If you can blow through it easily, it will pass sound into the fiberglass. Burlap and Muslin are two inexpensive options, but nearly any soft fabric will work and also keep the glass fibers safely in place.
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post #3 of 17
8/25/08 at 5:30am
I ordered a zillion samples from GOM but I really didn't like anything. So I used the blow-through test and the wife and I went shopping at fabric stores from NYC to Boston. We finally found a fabric that we loved and passed the air test. We found it in a small place in the fashion district in Boston. Sorry don't remember the name off the top of my head.

Here is photo of the fabric in one of the arches. We just love the pattern and it was only $7 a yard!
LL
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post #4 of 17
8/25/08 at 7:01am
Thread Starter 
That is a really nice pattern. Does a hand rub across the fabric get any fiberglass splinters in your hand or irritate it?
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post #5 of 17
8/25/08 at 8:02am
No. It's very fiberglass friendly.
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post #6 of 17
8/25/08 at 8:12am
Quote:
Originally Posted by distoga View Post

Is there any rule of thumb to knowing what fabrics will work well for absorbing rather than reflecting sound that can be used to cover fiberglass? Or is GOM or other 100% AT fabrics the only type that won't decrease the effectiveness of the fiberglass?

I've brought just over a thousand square feet of 2" OC703 and need to cover it, so we're talking about a large amount of fabric.

I also just started noticing comments about formaldehyde and am worried about health issues now considering the type of room my HT is in.

I'm in the process of hanging OC703 what is the formaldehyde issue???
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post #7 of 17
8/25/08 at 8:48am
Thread Starter 
It's a known carcinogen and puts off an orderless invisible gas that can also cause breathing problems, asthma, and associated problems in low dose, major issues in high dose.

Edit: I also read an article talked about marine life that mentioned half life but I'm not sure if that's only a characteristic that it takes on when in water or all the time. If it's all the time I wonder if venting it for a long amount of time before installing is a smart thing to do since it becomes a gas at room temperature and if left long enough maybe would make the remaining amount nothing to worry about.

I've thought about wrapping and sealing in plastic but again wonder if that would ruin the acoustical properties that it's there for in the first place.
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post #8 of 17
8/25/08 at 9:42am
Quote:
Originally Posted by distoga View Post

I've thought about wrapping and sealing in plastic but again wonder if that would ruin the acoustical properties that it's there for in the first place.

The plastic will cause it to refect high and probably mid frequencies (depending on thickness). So if you are using it to get rid of first reflections (i.e. on the sides of your room) then it would defeat the purpose. For bass absorption though, it is fine (although at some thickness that might be an issue too).
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post #9 of 17
8/25/08 at 9:45am
There are other studies that seem to minimize the danger of exposure to rigid fiberglass fibers, so there's more than one opinion out there. At any rate, unless you're banging the panels around the amount of fiber released into the air would be insignificant. If you live in a major metro area you're exposed to more carcinogens on the way to your car than you are from exposure to properly wrapped acoustic panels.

Frank
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post #10 of 17
9/12/08 at 10:11am
Hello all... I'm building rockwool acoustic panels and happen to have access to a lot of fabric called Duck Cloth. It's pretty heavy and canvasy, doesn't really allow air through. Would this be out-of-the-question to use as covering? I guess I'm asking, how important is the blow test really? Any help appreciated.
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post #11 of 17
9/12/08 at 10:19am
Quote:
Originally Posted by wp910 View Post

Hello all... I'm building rockwool acoustic panels and happen to have access to a lot of fabric called Duck Cloth. It's pretty heavy and canvasy, doesn't really allow air through. Would this be out-of-the-question to use as covering? I guess I'm asking, how important is the blow test really? Any help appreciated.

Move on to something else. If it fails the pass-through test, it's not suitable. Sorry.

Frank
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post #12 of 17
9/12/08 at 2:14pm
Quote:
Originally Posted by distoga View Post


I've thought about wrapping and sealing in plastic but again wonder if that would ruin the acoustical properties that it's there for in the first place.

The plastic will reflect hf and mf. The good thing about this is that if you need just a bass trap and not a broad band absorber, bales of batt insulation still in the plastic wrapper work pretty well. The best part is, you can buy them at HD, see if they solve the problem, then return them (unopened) and build ones that are more visually pleasing.
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post #13 of 17
9/12/08 at 2:22pm
Quote:
Originally Posted by Sailn View Post

The plastic will reflect hf and mf. The good thing about this is that if you need just a bass trap and not a broad band absorber, bales of batt insulation still in the plastic wrapper work pretty well. The best part is, you can buy them at HD, see if they solve the problem, then return them (unopened) and build ones that are more visually pleasing.

You could actually leave a *thin* plastic layer on the front of a regular bass trap, though I wouldn't do that for a high frequency panel. I also wouldn't wrap the whole panel front and back in plastic.

Salin's right...the pink stuff in rolls does a credible job in the corners, even if you leave the plastic on. Looks like hell, but looks aren't everything.

Frank
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post #14 of 17
10/13/08 at 8:39pm
Hi, new DIY'er here. Hoping to tap your collective knowledge...

What about velvet? Any opinions on whether or not that would make a decent fabric for DIY panels? I'm sure it would fail the pass-through test, but it seems like it might be soft enough to have its own dampening qualities.
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post #15 of 17
10/14/08 at 6:52am
Quote:
Originally Posted by yadmonkey View Post

Hi, new DIY'er here. Hoping to tap your collective knowledge...

What about velvet? Any opinions on whether or not that would make a decent fabric for DIY panels? I'm sure it would fail the pass-through test, but it seems like it might be soft enough to have its own dampening qualities.

Velvet would only be useful if you were *trying* to make the panel more absorbent to high frequencies because some element of the design detracted from it somewhat. I wouldn't use it otherwise because a 4" panel made from mineral wool or rigid fiberglass is going to be absorbent enough in the highs...it's just not necessary, and there are a ton of better options.

Frank
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post #16 of 17
2/14/13 at 10:01am
My recent experience taught me that anything is good but burlap is particularly good
because it is nonreflective and coarse (in a rustic way), also extremely hardy.

3M 77 is da spray to use. If you will do a lot grab a spray can gun while at it, it will save
your wrist.

Last, avoid my mistake and stay away from cold weather, do not spray indoors, if no light
breeze turn a big fan, the fumes cause pulmonary fibrosis.
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post #17 of 17
2/15/13 at 8:23pm
Quote:
Originally Posted by bobpaule View Post

My recent experience taught me that anything is good but burlap is particularly good
because it is nonreflective and coarse (in a rustic way), also extremely hardy.

3M 77 is da spray to use. If you will do a lot grab a spray can gun while at it, it will save
your wrist.

Last, avoid my mistake and stay away from cold weather, do not spray indoors, if no light
breeze turn a big fan, the fumes cause pulmonary fibrosis.

Be cautious when using materials like these. Both burlap and 3M Super 77 Adhesive are EXTREMELY flammable and if you do a quick test with a small sample you'll see everything engulf in a quick flash. Spray adhesives should not be necessary if you're meticulous folding and stapling your fabric.

Most cheap burlap is a bit loose weave so I don't usually recommend it for use with mineral wool (as mineral wool is quite crumbly/dusty compared to fiberglass). It can still be used of course, but going with a tighter weave burlap usually looks a bit better. Get flame-retardant fabrics whenever possible, or ****** sprays to coat the fabrics before you use them.
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