Bulding rigid fiberglass panels. A few questions.

Posted: Mon Oct 13, 2008 2:05 pm

I'm about to build some acoustic panels for my studio. It is already treated fairly well with Auralex products as designed by them. But now that I'm going to track drums in this room, I want to have some ability to really deaden the room.

So I'm going to build some 2' x4' rigid fiberglass panels. I am an HVAC guy by trade so I can easily buy the ductboard (that's what we calll it) in 10' x 4' sheets and cut it down myself. I'm just wondering what the suggested thickness is. I was going to use about 6 of the panels to build an acoustic cloud over the area for the drums to kill the reflections from the ceiling. Then I'll also build a few that I plan on putting around the room vertically on stands so I have flexibility. I will be covering the panels in some sort of fabric but I havent decided on a pattern and color yet.

Another question is; Does it matter what side the foil back faces? One side of the sheets are covered in foil and the other side is just the rigid, itchy, fiberglass. If I can face the foil to the outsides on both sides of the panel, I figure there's a smaller chance of the fibers working through the fabric which I dont want. (That stuff is the worst itch ever)

So to recap:

How thick over all for good absorption?

and

Does it matter which way the foil faces?

and

Thanks

Posted: Mon Oct 13, 2008 10:37 pm

Foil to the wall from memory. Trust my memory, I don't.

Posted: Tue Oct 14, 2008 12:21 am

Fiberglass has pretty good absorption capabilities when it is present in greater thicknesses. It absorbs frequencies around 125 Hz pretty well at around 4 inches thick. It's actually somewhat reflective to higher frequencies, however. The cloth you were going to cover it with should help. If I were you I'd face the foil side to the back. Though I'm not sure how much of a difference it would make anyway. If you want more info about fiberglass and how it works with sound- look up it's absorption coefficient on google or something.

Posted: Tue Oct 14, 2008 5:35 am

Thanks guys. 4" is what I was thinking too.

Posted: Tue Oct 14, 2008 11:36 am

[quote=\"EricWatkins\"]
Does it matter which way the foil faces?

and

Thanks[/quote]

The difference is the foil will reflect and the insulation will absorb. So what you have will be reflective on one side and have ability to absorb on the other. What I cannot say is how good a job of absorbing the panels will actually do because it has the foil face.

Whatever cloth you use should pass the breath test(you should be able to breath air through it with no resistance) or this will create a reflective surface as well.

\"If I can face the foil to the outsides on both sides of the panel,\" What you really want is unfaced insulation so you don\'t even have these things to deal with.

Posted: Thu Oct 16, 2008 1:42 pm

EricWatkins wrote:

Another question is; Does it matter what side the foil back faces? One side of the sheets are covered in foil and the other side is just the rigid, itchy, fiberglass. If I can face the foil to the outsides on both sides of the panel, I figure there's a smaller chance of the fibers working through the fabric which I dont want. (That stuff is the worst itch ever)

Pfffft....

You don' know nuttin' bro... Try mineral wool and fire caulk... O M G...

Quote:

So to recap:

How thick over all for good absorption?

Absorbtion is mass and surface area.

If you are talking about panel absorbers... 4" spaced 4" off the wall is a good starting point.

If you are talking corner traps... take it 48" across the corner, if you got room.

Quote:

Does it matter which way the foil faces?

You want the foil to the wall/inside.

Quote:

Thanks

Just hope this helps....

Posted: Fri Oct 17, 2008 4:24 pm

the thicker the pannel the more it absorbs, is this a correct statment?

Posted: Sun Oct 19, 2008 3:32 pm

marshall92 wrote:

the thicker the panel the more it absorbs, is this a correct statment?

Maybe... maybe not... Confused

As a general rule, yes, but that's really relative to the placement of the absorber in the room.

Posted: Mon Oct 20, 2008 2:25 am

marshall92 wrote:

the thicker the pannel the more it absorbs, is this a correct statment?

All else being equal, the thicker the panel, the lower in frequency it absorbs to. A panel only half an inch thick will still absorb 100 percent above 1 or 2 KHz. As you go thicker, that 100 percent absorption is extended lower and lower.

--Ethan

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