From what I've read and personal experience stopping bass requires either a lot of mass (lead?) or decoupling. Otherwise the energy from the bass frequencies will just follow the materials to the next room.

I'm trying to do that for my new HT where I can. I'm definitely making some sacrifices as I just can't justify the cost in making the room completely isolated. I'm just hoping for a reduction, thou the more the better obviously.

-Ben
HT v2.0
HT v1.0