The dual 18" PR's in my HT SW really only kick in at very low frequency i.e. sub 30 HZ. Off the top of my head they each have a mass of around 1500 to 1800 grams. This is about 3.5 pounds. At these low frequencies the 15 inch driver's main job is to drive the PR's, not to produce direct radiated sound.
My 18" music SW is a 7.5 cu foot sealed box which I augment with a BASSIS. This avoids any potential problem with ports or PR's.
My 18" music SW is a 7.5 cu foot sealed box which I augment with a BASSIS. This avoids any potential problem with ports or PR's.