Construction pics of some acoustic absorption panels

ooheadsoo · « **on:** 11 Jul 2004, 02:08 am »

I'm posting this here just in case anyone is interested. These were constructed after reading many of Ethan Winer's posts and articles and a few tips taken from Jon Risch's diy panel trap.

I call it the "Ghetto Panel."

Fiberglass: 48 sq.ft. 3lb. pcf 2" Certainteed brand rigid fiberglass panels(6) - ~$71
Burlap: $3 a yard, ~$4.65 per panel, total x 4- ~$18.60
Frame materials: lumber - $1.09 a piece x 6, 4 packages of corner braces $2.74ea., upholstery nails x 2 $1ea. - ~$21

Total ~ $111
Please note though I purchased 6 panels of fiberglass, I only purchased enough other materials to assemble 3-4 traps. For 2 more panels, you would probably need another $22 or so.

Tools: drill, philips screwdriver, hammer

Here's what the raw panel looks like for those who don't know. (I didn't.)

Some tools, minus hammer.

The lumber cut up by a home depot employee. When choosing the lumber, I asked for the cheapest 1x2 they had. A good thing to do is to try to pick pieces that are actually flat. I wanted to get on to making my panels so I didn't pay attention to it. It's not bad, but for those perfectionists...you probably already knew that didn't you?

Here's that bracket I chose. You can probably save a buck or two by buying cheaper brackets without included screws and buying the screws separately...but I wanted to go build my panels, not hunt down screws

It also would probably be easier to use a flat bracket unlike the ones I chose.

Here's the assembled frame. I predrilled holes for the brackets and then screwed them in by hand.

Here I placed the fiberglass on top of the burlap and the frame on top of the fiberglass. Then I flipped it over and nailed in like so:

I used 2.5" nails I already had lying around the house.

After nailing the fiberglass to the frame, flip it over so that the fiberglass side is facing the burlap. Then, fold the edges of the burlap over and use those thumbtacks/whatever to secure them.

Flip it over when you're done and this is what you get: Genuine Ghetto Panel.

Takes me about an hour per panel. Use more thumbtacks if you can spare them. The burlap loosens up by itself over time and the creases diminish. You could consider ironing it I guess...

MaxCast · « **Reply #1 on:** 11 Jul 2004, 02:37 am »

Very cool. I was going to suggest ironing the burlap, but you already pointed that out. Maybe paint a sail boat on it or something

If I ever make some I'll but a nice U of M flag on that sucker.

Anyways, how does it work?
How low in the frequency range does it work for?

Rob Babcock · « **Reply #2 on:** 11 Jul 2004, 03:34 am »

I'm wondering too. Let us know what affects they have. Looks like they wouldn't absorb very low freqs, not being that thick. Maybe down around 200-300 hz?

ooheadsoo · « **Reply #3 on:** 11 Jul 2004, 05:46 am »

Technically, it's about twice as effective as foam at 125hz. If I could space it from my walls (which I can't, they would be semi decent at low levels.) At 250hz, it has a coefficient of 0.86, foam has a coefficient of 0.30. Ethan's site has the specs of fiberglass vs. foam lined up by each other. http://ethanwiner.com/acoustics.html#mhf%20absorbers My undocumented research showed that the numbers are from the manufacturers of each type of material, respectively. However, I thought I saw those foam specs on a 4" package. Anyway, according to the specs, fiberglass is just far better. I shoulda gotten the 6lb. pcf stuff but I think I'll wait til I get new digs before I do that.

I'm pretty sure paint will disturb the permeability of the burlap

As for how it works, the clap test is just astounding. My little listening corner of the room has a relatively crisp clap reverb. If I clap in the opposite corner of my room, it's very metallic and echoey.

Rob Babcock · « **Reply #4 on:** 11 Jul 2004, 05:48 am »

You could try needlepointing a pattern! Er, maybe not.

JLM · « **Reply #5 on:** 11 Jul 2004, 11:43 am »

Great post, do you training for a living? It looks like a 30 second DIY clip from television.

Besides ironing the burlap, I'd also recommend using the old window screen replacement trick to get the material tight:

1. Nail the burlap to the top of the frame;

2. Have a helper carefully compress the entire frame slightly length wise so that it bows towards the back;

3. Stretch the burlap and secure to the bottom of the frame and then release the frame. This extra tension on the material will keep it tight in both directions.

OTOH I work with guys that wear new shirts to work that look like that.

BTW, Ethan has mentioned before that painting the fabric shouldn't have any deletrious acoustical effect on the fiberglass.

ooheadsoo · « **Reply #6 on:** 11 Jul 2004, 04:40 pm »

Thanks. Train? Not sure what you mean by that

That window trick sounds great. This morning, I don't see any marks left over except for the center crease which runs up and down the long way. I think I'd have to stretch it the other way to get it to come out, which would be tough. If only the burlap came in wider swathes! It comes in 48" wide swathes which are not long enough to wrap the edges.

Russtafarian · « **Reply #7 on:** 11 Jul 2004, 07:15 pm »

Where did you get the fiberglas?

ooheadsoo · « **Reply #8 on:** 11 Jul 2004, 08:51 pm »

I got it from a warehouse right by my place (lucky me) in City of Industry. When I talked to the guys there, they said that there was a place in LA and a place near Irvine that carried the stuff and that was about it. I can give you more details about the place I went to if you need them.

Russtafarian · « **Reply #9 on:** 12 Jul 2004, 04:48 pm »

Yes, I'd like the Irvine location information. Thanks.