well according to the alpine rep i just got off the phone with he told me they were built just like the type Xs and have a higher xmax than the 1541d. He couldnt pull the spec sheet up on it for me since they havent even got them in yet but he sounded excited about them lol. was calling to get the dimensions of a ported box for the 15 and they only need 2 cu. ft minimum each for ported and slotted. Im getting excited