Most subs have an 18db/octave low pass filter.
That’s news to me, I thought the THX standard was 24?
But generally, yes. Regardless of Q, having a main speaker that has a hump, and then having the sub take over below that hump can be challenging. It can also just be challenging for the room. So, this is, broadly speaking, a tone control.
However, I do think that many speakers, sealed or ported, have a bass hump. The ability to raise or lower the Q isn’t limited to ported speakers.
Raising the cut-off frequency AND sealing the box greatly reduces woofer distortion by controlling excursion, another benefit. Of course, at the end of the day what matters is whether the listener likes it or not.
@ncbassplayer