Just a question. Why are you using foil faced insulation?

I think you want fabric that approximates "acoustically transparent" or it will defeat the purpose of using the fiberglass.

Ethan told me to.

Just kiddin. The link Randy posted above to Ethan's page discusses the merits of foil backed pannels.

Some acoustic companies use burlap - ATS Acoustics Burlap

Thanks!

Is that something that's found in a fabric store?

I can't say that I know that answer. A phone call to your local fabric store may help though.

After an hour wandering around a fabric store, the only material I found that wasn’t $30 a yard or more, and didn’t look like something you’d find on a prom queen’s dress or down comforter, I walked out with some material similar to Carhats. Of cource they didn’t have it in black though. Next time I need fabric, I’m sending the women. What an awkward experience that was….. A very nice elderly lady took pity on me as I was walking around like a zombie and helped me find the stuff I ended up buying.

I’m going to start building these boxes today. I never gave any thought to what material I should use on the back side. I was planning to just staple some ¼ plywood to the backs to enclose the fiberglass, but also give them some strength. Now I’m wondering if that’s such a good idea. It shouldn’t matter, will it??? Anyone??

That will probably change the performance a little, but I can't remember exactly how.

For the two traps I built, I just split the plastic bag the acoutic sheets came in in half and used that as a backing to keep the glass in.

By the way, now that you have gone through your fabric adventure, muslin is very acoustically transparent and inexpensive. I don't know if you can find it in black though.

If you want to know how the plywood backing will affect your trap, check out the Home Audio Acoustics forum at hometheatershack.com. The guy who moderates it and answers most of the questions does room treatments for a living and is very knowledgeable.

For the frames, a biscuit joint works great and lets you leave the back open. Then just staple the fiber to the inside edges. If you don't have a biscuit joiner, you can still just cut a slice in the corner and put a biscuit (cheap at HomeD) in and glue it up. Saves time and, more importantly, weight, without adding a reflective back. Just and idea, worked for me.

The custom Art option is a huge improvement over the burlap otherwise available. To date, I have seen nothing that makes it worth buying these pre-made. But the ability to actually cover it with OK art might be worth the huge markup on the actual trap. Thanks for the site.