vented
big ol' slot vent with a thick mdf box...
and when I mean big, I mean big, the 15's sound best with giant vented boxes..
I used to run 4 L7 12's in two huge vented boxes, seriously power hungry speakers.
also a note on these L7's... do not skimp on the amp!
ended up dropping the kickers, went to powerbass 15's
cheaper, louder and surprisingly durable