Butt kisser lol , but on a serious note, Teknique
, center up the port when you do it . Putting the port one side or another will make it louder on the opposite front seat. So if you want all listeners to have a equal amount of base make sure to center it up . You will have to figure in the port length and port diameter to get the proper port tuning .
Basically it comes down to this ... your rear deck is at a set height , as is your enclosure . the only option to adjust "tuning" is to adjust the ports diameter , more diameter higher tuning ,opposite with less . All while the ports length stays stationary
Any time an enclosure is vented into a cabin, you will have a audible gain in output . Seats up is a sealed box inside a sealed box ... muffles the majority of output . now when the seat is down , it acts as another vented chamber .
hope I didnt get to technical for everyone