I'm doing a Christmas concert production (piano, mic'd orchestra, choir) on stage. The back wall is 71' from stage, brick, 30' high. The back wall is 80' across, and can go from the floor (up to some existing panels which start at 14' up and are 8' high above that. They do help some with overall room sound, but dont reduce the slapback)... One Big Wall, no bleachers. There are 2 speakers Front of house on either side of the stage, about 15 feet up. (above the basketball stands. They are pointed down towards the middle of audience, and it sounds pretty good from most places on the stage. HOWEVER, there is a nasty slapback echo noticable to anyone on stage because of the energy bouncing off the back wall. We pointed the speakers down as much as possible, even beyond the mounting brackets pre-drilled holes. I'm looking to add an acoustic treatment on the back wall to absorb/diffuse that. it will make a big difference to the conductor and performers on stage. Since the room is also used daily for backetball games and athletics, I'm looking for something that can fold down when needed, or more likely. some panels to set up for concert performances, of which there are only 3 main ones a year. I looked at curtains to match the stage, with 50% or 75% fold to match the stage curtain, cost was a bit high. I'm currently looking into making some wood frame panels with rigid fiberglass insulation inside, black fabric stapled over. 1) has anyone done that? got pics or plans I could see? I have Mitch Gallaghers book on home studio acoustics where he talks about making them. 2) 14' is big, so I'll probably need to make them fold verticallly to fit through a door to a storage room. I'll make them as thin as effectively possible to minimize storage bulk. 3) I'm considering angling them to provide most diffusion possible. would take more material, but making a big flat wall of panels will probably bounce back more to the stage than an angled (accordian) diffusion type approach. 4) rigging: will probably use wheels on bottom, and secure to a row of eye bolts into the brick where they touch the wall. just below existing sound panels where will be visually minimal. 5) size: if I make them 4 foot wide, and angle so they come out 3' from wall, that gets me a decent diffusion angle. A few hard surfaces at the hinges/connection point, but if frames are thin can live with that. 6) design: I'm guessing if the panels are angled, it wouldn't require using acoustically transparent fabric( $$$) in front of the rigid fiberglas mat) and go for something cheap and black. thoughts? budget is an issue. a stage curtain with carriers, track, and pull rope (matching the stage curtain) is in 15-20K range. I suppose we could rent pipe and drape, that would help - but it wouldn't be near as big (maybe 10' high?) If this would provide the accoustic solution we need, it would be worth building it and keep material costs under a few hundred $. Have you made or seen panels like this? Experience / suggestions welcomed. Thx!