Great thread!
It got me inspired to build some asborbers for my small room. The room measures 4400x3130x2055 mm and here's a sketch I came up with. There's a bed and a closet in the way atm, so I have the panels from the 4th cornerabsorber standing on the bed for now..
I'm going to fill the absorbers with 150 mm thick, 100kg/m^3, rock wool (isover cleantec G8379
Ljuddiagram).
The stands put the non-corner absorbers at a minimum of 90 mm from the wall.
Any suggestions on the material or design before I start?