Quick Help--Fiberglass tiles. . .

pjchappy · « **on:** 18 Jan 2005, 08:26 pm »

I went to Lowes today and saw some compressed fiberglass ceiling tiles. . .I am thinking of using these and place 4" wedge foam on top, then hanging them on the wall.

The 2 acoustic numbers on the box were 55 and 35. I don't remember what the letters were that corresponded to the numbers. What do these numbers represent, if you are able to tell w/ such little info. . .

The panel is 5/8" thick compressed fiberglass. I understand that the numbers represent the amount of sound absorbed, etc. However, what frequency range, etc.?

Thanks!

p

Ethan Winer · « **Reply #1 on:** 19 Jan 2005, 05:53 pm »

PJ,

> saw some compressed fiberglass ceiling tiles. . .I am thinking of using these and place 4" wedge foam on top, then hanging them on the wall. <

I don't see any advantage you'd get from using both fiberglass and foam. It will be easier if you pick one or the other. If you use fiberglass, you'll peel off the plastic facing, bundle enough of them together to be at least two inches thick, then wrap them in fabric and/or build a wood frame. If you use foam you can install it as is.

--Ethan

pjchappy · « **Reply #2 on:** 19 Jan 2005, 07:02 pm »

Using both won't offer lower frequency absorption?

The main reason I am going to use both is b/c I don't want to put the foam directly on the wall, as I previously had done in another room w/ spray adhesive. . .I have to do some repainting as a result.

I was just going to attach the foam onto the boards and then hang them. . .

p

davejcb · « **Reply #3 on:** 19 Jan 2005, 08:45 pm »

Quote from: pjchappy

The main reason I am going to use both is b/c I don't want to put the foam directly on the wall, as I previously had done in another room w/ spray adhesive. . .

Use thumbtacks, nice and easy!

Ethan Winer · « **Reply #4 on:** 20 Jan 2005, 02:09 pm »

PJ,

> Using both won't offer lower frequency absorption? <

Not really. What affects how low a panel absorbs to is the type of material and its thickness. For the best performance you'd use four inch thick 705 rigid fiberglass. Or a sandwich of 705 and 703 with the 703 side facing into the room. (703 absorbs highs a little better than 705.) Foam is okay too if it's thick enough.

--Ethan

ToddSTS · « **Reply #5 on:** 20 Jan 2005, 09:30 pm »

Ethan,

I just picked up a case (6 panels) of 2" 703- FSK from a local distributor. I plan on using it across the corners of the room to make simple bass traps. I have a few questions.

Would it be better to sandwich two panels to make a few 4" panels or use the 6 panels individually throughout the room? (it has five corners)

Do I need to peel off the foil for maximum bass trapping?

Thanks in advance. I hope this isn't considered thread hijacking since we're still talking about fiberglass. I can post a new topic if necessary.

Todd

MaxCast · « **Reply #6 on:** 20 Jan 2005, 09:38 pm »

Quote from: pjchappy

The main reason I am going to use both is b/c I don't want to put the foam directly on the wall, as I previously had done in another room w/ spray adhesive. . .I have to do some repainting as a result.

pj, if you use foam, glue the foam to 1/4 peg board. Lots of nice little holes to hang on a nail. They go up and down in a jiffy. Be sure to get the liquid nails for foam (purple tube).

Ethan Winer · « **Reply #7 on:** 21 Jan 2005, 05:18 pm »

Todd,

> Would it be better to sandwich two panels to make a few 4" panels or use the 6 panels individually throughout the room? <

For bass trapping the panels should be four inches thick, but you also want as many as possible. Can you buy more to make six panels, all four inches thick? That's really your best choice.

> Do I need to peel off the foil for maximum bass trapping? <

Peel it off only one of each pair, so the side facing the room has foil and there's no other foil inside or behind.

--Ethan

davejcb · « **Reply #8 on:** 21 Jan 2005, 06:34 pm »

Quote from: Ethan Winer

Peel it off only one of each pair, so the side facing the room has foil and there's no other foil inside or behind.

Really... Why do you say this? I have 2" 6lb/ft3 FSK doubled up to 4", you think I should remove the foil facing on the panel behind? Any measurements to back this up?

Thanks!

ToddSTS · « **Reply #9 on:** 21 Jan 2005, 07:32 pm »

Thanks Ethan. I actually went back to your acoustics FAQ and sort of answered my own question between that and your postings on another forum.

I found from my reading that if I am targeting the lower frequencies then thicker is better. If I am looking for more absorption across the spectrum then more exposed fiberglass (rather than thicker) is better.

Please correct me if I screwed that up.

Thanks again for the response. I think I will try my hand at constructing 3 4in. panels from my current supply and see how difficult that is. Then possibly get another box to make some more panels.

Would placing a thin 1/8" or 1/4" piece of pegboard in between the sandwich of 2" panels make a difference? I was thinking that it would help with rigidity. But I don't want to affect the absorption properties too much.

Todd

Ethan Winer · « **Reply #10 on:** 22 Jan 2005, 02:32 pm »

Dave,

> I have 2" 6lb/ft3 FSK doubled up to 4", you think I should remove the foil facing on the panel behind? Any measurements to back this up? <

Yes, I have measurements!

Without giving away too much, my partner and I tested a variety of such combinations at IBM's acoustics lab. We found that having more than one facing always had worse low frequency absorption than either one facing or no facings.

--Ethan

Ethan Winer · « **Reply #11 on:** 22 Jan 2005, 02:35 pm »

Todd,

> Please correct me if I screwed that up. <

You got it exactly right.

> Would placing a thin 1/8" or 1/4" piece of pegboard in between the sandwich of 2" panels make a difference? <

Yes, and that difference would not be for the better. Anything relatively massive and rigid, like plywood, placed in front of, behind, or inside, a rigid fiberglass panel will block the wave flow which is needed for absorption.

--Ethan

Xi-Trum · « **Reply #12 on:** 29 Jan 2005, 08:44 am »

Quote from: Ethan Winer

Without giving away too much, my partner and I tested a variety of such combinations at IBM's acoustics lab. We found that having more than one facing always had worse low frequency absorption than either one facing or no facings.

--Ethan

So that I understand this correctly, if I have multiple fiberglass panels sandwiched together, I need to remove all the foil backings on them except for one? And the one panel with the foil backing needs to be outside with the foil facing the room?

Thanks.

Ethan Winer · « **Reply #13 on:** 29 Jan 2005, 03:07 pm »

Xi-Trum,

> if I have multiple fiberglass panels sandwiched together, I need to remove all the foil backings on them except for one? <

Yes.

> And the one panel with the foil backing needs to be outside with the foil facing the room? <

Facing the room absorbs more bass but less mids and highs. Facing away from the room does the opposite. So for corner bass traps the foil should face the room. For mid/high absorption it should face away, or you can just remove the foil entirely.

--Ethan