here's my bass-monster... I call it "the monolith"
(6 stacked bales of R-13 insulation draped in only the finest of white sheets!)
def. made a difference in bass clarity in my room
on my rear wall there's a 4" thick mattress mounted, as well as a sheet of plywood at an angle to break up the side walls... I think the mattress is good for doing vocals in front of more than trapping much bass in the front end of the room