hmmm... for sq it's advisable you go sealed. some systems go ported but it would depend on the sub. Though IMHO sealed is the typical enclosure for SQ systems. Ported is typically for SPL systems. oh yeah, if ur going to use a 15" sub masasayangan ka. because in an sq system there is minimal play of the sub. people lessen the sub gain so that you can hear more of the kalansing ikanga ng mga tweeters and the mild thump of ur mid bass.