Ethan's traps vs. Auralex

Sorry to resurrect sucn an old thread, but it's such a good one that I couldn't resist. I have made many 2" thick rockwool trays for my 15'x16' music room, including 6 of them hanging from the ceiling, the middle ones with floodlight cans pointing straight down. This has really improved the sound of my room, but I have a question: In my room, the "absorber" side is always facing the inside of the room, and the back is made of a plywood type substance that I can't spell, but is pronounced "loo-on". Have I mounted these things with the wrong side out? Or would I be a lot better served to remove the backs of these panels so that the sound is absorbed from both sides? If so, this makes so much sense that I can only laugh at myslf for not thinking of it myself. :rolleyes: If anyone knows about this, please respond...I'm trying to think of ways as we speak to remove the backs of the panels and support the frames so that the sound can be absorbed from both sides.
 
Chris,

> the back is made of a plywood type substance that I can't spell, but is pronounced "loo-on". <

Luan is simply the type of wood the plywood is made of. I believe it's an inexpensive form of Mahogany.

> Have I mounted these things with the wrong side out? <

No, you did it right. But they'd work even better if they were 4 inches thick and had no plywood backing at all.

--Ethan
 
Ethan Winer said:
> Have I mounted these things with the wrong side out? <

No, you did it right. But they'd work even better if they were 4 inches thick and had no plywood backing at all.

--Ethan
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Hi Ethan - thanks for the quick reply. I know the panels have helped tame the room, but I was afraid I'd built them backwards! At this point, there's no way to double the thickness of the panels, but since there's a frame around the outsides, it's possible I could remove the backs - or enough of them to let sound through but still hold the rockwool in place. Do you think that might make a noticeable difference?

Just in case it matters:

The room is 15'x16' with the ceiling about 10' 6". Three of the 4 corners have 2'x10' panels diagonally across, and the fourth has a doorway on one side, so I placed the last 2'x10' panel on the side where the door wasn't. From what I'm reading on your excellent site - thanks so much for putting that up, BTW! - it looks like the panels hanging from the ceiling would also benefit from having as much of the back removed as I can manage. Is this correct? The big 4'x4' panel with the lights is hanging about 18" from the ceiling, and the four smaller 2'x4' panels are hanging at about 45 degree angles with their outsides angled up. Any advice greatly appreciated. :)
 
Chris,

> it's possible I could remove the backs <

I'm sure that will help.

> it looks like the panels hanging from the ceiling would also benefit from having as much of the back removed as I can manage. Is this correct? <

Yes. When you add a rigid back you negate the benefit of an air gap.

--Ethan
 
Ethan - I'm an idiot! I knew you meant that removing the backs would help...what I meant to ask was if removing parts of the backs - like with a shallow jigsaw - would make enough difference to be worth the trouble. If so, I'm there, as this could be done quickly - and I'm guessing the answer is yes, so I'll remove as much as I can.

On the ceiling panels, I could add an extra 2'x4' layer of rockwool on the tops of the ones that size without cutting anything, so I guess I'll do that. One last question: as a person with sensitive skin who doesn't want to be exposed to floating fiberglass particles, is there a certain type of fabric that should be used to contain this stuff, or is any fine cloth probably okay? Sorry for all of the newbie questions, and thanks for the help!
 
Chris,

> I'll remove as much as I can <

Exactly.

> is there a certain type of fabric that should be used to contain this stuff <

The text below is from my Acoustics FAQ.

--Ethan

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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