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#1868961 - 01/08/08 01:14 PM

Which side for paper/foil backing on fiberboard?

Bob Singleton
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Registered: 01/08/08
Posts: 1
Loc: Texas

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I noticed on one of your pages discussing rigid fiberglass density tests <http://www.ethanwiner.com/density/density.html>, that you included photos of some raw 701/703/705 FRK used as corner traps. Some had the kraft paper toward the room, some towards the corner.

Does it matter, in your tests, if the kraft is facing the room, or facing the wall?

My application is that I will be using some 4" 703 FRK for wall and ceiling treatment. The panels for the ceiling will have about 6" of dead air between the 703 & the ceiling, and the walls will have about 2" of dead air between the 703 and the walls. They will be covered with acoustically transparent materials.

I may add corner trapping as needed after I test the room with the walls & ceiling in place. I'd like to know which side the kraft paper should be on for those, as well. Any thoughts?

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#1868999 - 01/08/08 01:39 PM

Re: Which side for paper/foil backing on fiberboard? [Re: Bob Singleton]

David011777
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Registered: 12/11/06
Posts: 17
Loc: Ithaca, NY

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Hi Bob,
The kraft paper serves to reflect higher frequencies back into the listening space but has not impact on low frequency absorption. Some would argue that if you were to blanket a room with 703 (no kraft paper) that the room would sound muffled and "dead" - therefore, alternating some panels so that high frequencies can reflect off these surfaces mitigates this problem significantly. That said, if you are covering most walls with insulation I'd recommend alternating the kraft facing - if there's lots of open wall space, you're probably okay with all kraft paper facing backwards.
If the insulation in the ceiling is laying on top of suspended panels (or drywall), it makes no difference which direction the kraftpaper is facing since these other structures will reflect higher frequencies anyhow.

Hope this helps, David

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#1869013 - 01/08/08 01:49 PM

Re: Which side for paper/foil backing on fiberboard? [Re: David011777]

gullfo
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Registered: 03/30/04
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Loc: Old Tappan, NJ, USA

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just be aware most building codes also need the insulation covered with a non-flammable surface.

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#1869434 - 01/09/08 08:13 AM

Re: Which side for paper/foil backing on fiberboard? [Re: David011777]

Ethan Winer
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Registered: 06/12/00
Posts: 5470
Loc: New Milford, CT, USA

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Originally Posted By: David011777

The kraft paper serves to reflect higher frequencies back into the listening space but has not impact on low frequency absorption.

Just to clarify, there is a difference in LF absorption. You get more with the FRK facing the room. I do agree with your idea to alternate direction around the room, as long as there's no FRK at direct reflection points.

--Ethan

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#1869543 - 01/09/08 11:30 AM

Re: Which side for paper/foil backing on fiberboard? [Re: Ethan Winer]

irthwirm
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Registered: 06/14/07
Posts: 8

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whats ideal for a recording room. And I'm talking about portable 2x4 at 4inch thick traps with 703. Mostly for the vocalist which i will surround him. Do i want some FRK or none. Muffled i don't want but i guess i could always eq. My main goal is to take out the open room sound. It's very subtle as is but when the music is cranked it is pretty obvious.

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#1870049 - 01/10/08 09:08 AM

Re: Which side for paper/foil backing on fiberboard? [Re: irthwirm]

Ethan Winer
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Registered: 06/12/00
Posts: 5470
Loc: New Milford, CT, USA

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FRK for corner bass traps, non-FRK for reflection control.

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