Wayne Parham Messages: 18790 Registered: January 2001
Illuminati (33rd Degree)
The way to do it is to use panel absorbers surrounded by a thick, solid set of walls. The panel absorbers form inner walls which absorb energy. This both attenuates sound going out and damps standing waves, smoothing room modes. The outer walls block what's left and help keep it contained.
That's a lot more than a little rework though. It's a complete, ground-up, room rebuild. Short of that, you just have to go with the panel dampers. They'll help, especially taming room modes, but a lot of bass energy will still pass through.