Best Cheap acoustic wall treatments?

Owens corning makes a 703 ridged yellow board that comes in 2'x4'x2" up to four 4 inches.This can be covered with a roma wool found at any fabric store.Careful what you wrap the acoustic panel with,if it is not acousticly transparent it will reflect the sound.Acoustic panels being four inches thick will absorb down to 250-500hz.Great for first reflections.Next is tubetraps.I made Jon Risches(he has a web site) and they turned out great and work wonders on exess bass.Then for the back wall you can make RPG skyline diffusers.
My room is based on live end, dead end, where the front is dead and the back is live but diffused.This is what worked for me you can play around with what ever works for you.All these can be made at home for pennies(well...dollars)Good luck!

It is a compressed yellow fiberglass.Do a web search at Google in your area.The lumber yards usually won't carry it.Try "insulation" in your yellow pages.I think I made (16) for about 250.00.Fabric incuded.I also user a thin plywood as a backing to staple the fabric to.The plywood also makes it easier to hang on the wall.