Yep, Downunderwonder is right. Most soundproofing products only attenuate early reflections to make the room sound better acoustically. Nothing except big hulking mass will effectively stop bass from leaving the room. If your goal is to soundproof your room so that you won't piss off your neighbors, it's a lost cause. Bass control literally has to be built into the building itself: concrete, foot thick insulation, double pane windows, resonating chambers, stuff like that. Forget about trying to sound proof a bedroom or makeshift practice space. It's not going to happen. Either play at a lower volume, or find a space where noise isn't an issue.
Rickenbacker Club #506