high SPL w/o fold down seats

[LoudBimmer]

Idk if I should stick with plain ported boxes or try 4th order like Rusty mentioned, using 6" aero port firing straight into cabin.

Next on my list if really small ported box tuned to 35hz

As of right now, I'm using trunk as a box in a way. Creating 6th order bandpass.

Any kind of input is really appreciated, especially from people who did this kind of set up with great results