These are my absorber panels and corner deflectors.
The absorber panels consist of paper egg crates glued to plywood. I stretched foam rubber sheets over the front and staple gunned them on the backside. Then I found a couple of different thick yet stretchy materials to cover, again stapled on the back. The WAF with room treatments like this is choosing the right material. I think I did pretty well with the burgundy with black stripes and black with grey stripes. The accent my darkish blue walls with the lights on, and disappear with them off. Keep in mind my room triples as my office, listening room, and HT.
This construction is quite absorbant above the bass frequencies. I used a couple of thicknesses of plywood, so some are fairly heavy and the lighter ones have a cheap 1"x2" frame for support to keep them flat. I hang them just like a picture. The foam rapped around the back serves 2 purposes. 1. The units can't rattle against the wall. 2. A somewhat sealed airspace exists on the backside, because the weight holds them against the wall. This causes the entire unit to also serve as a panel absorber for the lower frequencies.
I built 6 of these in various sizes for less than $80. The one pictured is also the smallest at 2'x4'.
The triangular monolith standing in the corner in the other pic is my corner deflector. I have concrete corners, and I built 2 of these to go behind OB speakers, which can be very resonant near corners. These help the rear waves flow out of the corner instead of getting trapped and reflecting around back there. They also work great with the Frugel horns that I just built. They are a simple construction. Just a triangular box. The bottom half is filled with concrete, and the top is filled with concrete and a lot of styrofoam scraps to keep the weight down, the center of gravity lower, and recycle something going to a landfill otherwise. Total cost 2 sacks of concrete and a sheet and a half of plywood, so not much. At some point they'll get a black or navy blue material cover to make them disappear back in the corners.
