My new ceiling panels. They are homemade binary amplitude diffusion. They are painted to match the ceiling paint, and a layer of matching colored Guilford cloth between the holey board and the OC703 behind. The ceiling panels are 6" deep, with 4" of FG lying against the front board. There is a web of supporting members every 2 feet to hold it all up. These took a lot of time to build, plus about 3 years to figure out how what and where plus healthy dose of procrastination. They changed the sound of the room drastically for the better. Midrange echo is mostly gone, except the front to back axis which still has some hard walls on both ends. All in due time.
Big thanks to Carlman who came over last Thursday to hang these up in time for the G2G. They are fairly heavy, but are held on the ceiling securely with steel hooks holding screws in the frame. The hanging system was invented by Shane, and it worked great. Too bad I didn't take pictures of that. A few years ago Bryan suggested I float 4" of FG in this ceiling tray. It's not dropped down 12" like he suggested then, but the most I could get away with.
There is also a big one installed on the left wall, 4" thick stuffed solid with 703. The sound is very cozy and intimate, with no loss of sibilance. It just doesn't echo anymore, and there is probably some bass improvement. 112 sq ft of treatment added in this batch with lots more to come on front and rear wall, corners. Bass has always been OK, flimsy walls I guess. Flutes pianos and other stabbing peak midrange spikes are much better now.
I have some measurements of the room from long ago before any treatment was added. Not sure if I could find them, but I will look for them when I get around to measuring the room again.
Maybe you can see the hooks on the ceiling after 1st panel is hung.
Carl's artsy photo of the finished ceiling. Two 4x6' panels flanking a 4x8 panel in the middle.