{Mid bass & subwoofer}
Displacement is name of game.
Multiple speakers or ` larger ` , surface area . . . Two 8" 10" 12" 15" ,etc..,
Install whatever, where ever you can !
Even @ low volume the entire frequency range will be there !
Go Big or c-o-m-p-l-a-i-n about what is "lacking" . . .