DIY acoustic panels?

I did a little research and found a site that tells you how to build acoustic panels:

http://acousticsfreq.com/how-to-build-your-own-acoustic-panels/

Apparently, fiberglass board insulation at least two inches thick is needed. The sample construction uses 2″ Roxul RHT 80 at $0.78 per square foot.

As far as decorative fabric, anything that is acoustically transparent, where the sound can reach the fiberglass. The page suggests putting the fabric up to your mouth and blowing through it to see if air freely flows through it — so I guess the lighter the better.

Be aware that the denser fiberglass (such as the 8lb Roxul Rockboard 80) does not work effectively if you start layering them past 2" or so.  If you want a really thick bass trap (such as 6" - 8") it is best to use 3 lb panels, such as Owens 703.

@bobk3 That's exactly what I did for my dedicated HT room. I built 14 4x2 Ft panels using Roxul 80. Worked very well. I used an acoustically transparent black grill cloth from Fabricland. Check your local fabric shop, the may have something similar.