Isolation of the rooms surfaces with dense, heavy material is the key here.

A room within a room. Walls ceiling and floor need to be isolated from the original. Isolation prevents the transfer of bass vibrations thru to the rest of the house.

Lay a new floor structure (2x4's and 3/4 inch plywood) on a series of rubber shims or blocks.

The same principal is used for the walls, build the new wall structure (2x4's and 3/4 thick plywood or 3/4 thick drywall) and support it on some kind of shock absorbing material. Don't fasten the new wall structure directly to the old, again use shock absorbing material between and do not fasten too tightly , the tighter it is connected, the more bass will transfer to the outer structure.

Ceilings, isolation of a drop ceiling, isolate the hanging wires on springs and allow the edges of the grid system to "float" against the wall to prevent vibration transfer, use the heaviest tile inserts available or cut your own from 3/4 plywood or drywall.