usually i keep the back seat down but i dont really half to i took the stock 6x9 speakers out so the sound goes through there but the carpet shakes about 1 inch up and down with the bass. i put the air ports on both sides of that 10" sub so the sound could come through from the 2 10's in the back.that is what i use long with a component system, my other post called need help with my system shows what i have for bass, the 10" is bridged to that amp on full pass therefore its called mid's and the component system is also my mids and the 4 tweeters are my highs. im using a sub because i had no other need for it and i wanted to use it that sub does not sound good the way it is just for bass with my other 2 subs you wouldnt be able to hear that sub anyway but you can hear acoustics out of it.