My home theater is well insulated and built using double drywall. It has never completely limited the bass from shaking the home, but the IB has a unique issue in that half the sound is not in the home theater.
The back side is going into an unfinished utility and power room in the basement, line array IB.
Would putting insulation in the rafters help much or do we just need to accept that earth quack feeling throughout the whole house.
Another reason the effect is so much greater is that the IB is so much clearer sounding then the box sub. I now enjoy the bass substantially louder, I just hated the boxy boom.
The front wave impact is the same as any other sub.
Only about 8" of solid wood or 4"-6" of concrete stops the migration of bass.
I'd seal the area containing the rear wave as much as possible. Then add as much Corning 703 semi-rigid insulating panels as can be packed into the room, to kill the rear wave. The thicker the layers of fiberglass the lower the frequencies absorbed. Also adding a semi-rigid membrane on the front of the panels and spacing them just off the wall will attenuate more bass.