They are DIY Bass traps. I built them for my last theater room. 2 of the traps are made with the Roxul 60 Rockboard (6 lbs cubic foot) and 2 are Roxul 80 (8 lbs cubic foot) cut into triangles 24x24x33 (2x4 sheet cut into 4 triangles) They are covered with Guilford of Maine fabric. I could not find OC703 in my area so I used the Roxul stuff. I would use it again even if I had a source for OC703. It is significantly cheaper than the 703 - the only disadvantage is that it is not quite as rigid and twice as heavy.
The roxul 60 have very similar absorption as the OC703 panels everyone uses. I made the other 2 out of the 80 because it has a bit better low frequency performance. I found the specs here:
In my old theater I placed these in each corner of the room, so I only have 4. I also have some 4" thick and 2" thick wall treatments still in the storage room. The treatments made a huge difference in the room. In my current room one corner is occupied by a door so I'm going to try and get as much bass trapping as I can in the soffits.