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#2758088 - 02/22/16 11:20 AM Bass trap clarification...bandwidth increase?
MikePope Offline
Senior Member

Registered: 08/16/15
Posts: 36
Loc: Maryland
Hi Ethan. My intuition and my knowledge are having a dispute that I believe only you can settle.

While I understand, very clearly, that when one is placing 705-FRK ON a wall or ceiling, the facing MUST be toward the room because if it's against the wall, it might as well not be there.

That said (here's where I'm not understanding), if 705-FRK panels are straddling a corner so both sides are freely vibrating, if the facing were AWAY from the room wouldn't it act as a broader-band absorber? Highs and mids being absorbed first, and larger wavelengths that makes it through the 2 inches of fiberglass would cause the facing to vibrate in sympathy and the fiberglass it's attached to dissipate the sonic energy as heat?

This seems intuitive, to me, but it seems you've always said facing should be out, no matter what.
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#2758101 - 02/22/16 12:09 PM Re: Bass trap clarification...bandwidth increase? [Re: MikePope]
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
I tested FRK material in a lab with the FRK facing the room and not facing the room. I also tested the same rigid fiberglass with no FRK at all. I believe we tested 705, not 703. In all three cases the panels were spaced four inches away from the floor. With the FRK not facing the room LF absorption was better than non-FRK fiberglass. And of course it absorbed mids and highs as well as non-FRK fiberglass. But LF absorption was even better still when the FRK was facing toward the room. So in order of effectiveness, at low frequencies only, and with a 4-inch air gap:

705 plain
705-FRK with the FRK away from the room
705-FRK with the FRK toward from the room

I can't easily get you numbers (though I might still have the data somewhere) but as I recall each step was about 20 percent more effective at low frequencies.

--Ethan

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#2758106 - 02/22/16 12:13 PM Re: Bass trap clarification...bandwidth increase? [Re: Ethan Winer]
MikePope Offline
Senior Member

Registered: 08/16/15
Posts: 36
Loc: Maryland
Clear! Thanks.
_________________________
Worst case, I'm just wrong.

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Moderator:  Ethan Winer