hehe not that much of experience, i always learn something new everyday, BUT, i´ve tested DD subs a few times already, and, the 512 loves something around 2 cubic feet, the 1512 loves something around 2.3 cubic feet, and from there, big ass boxes FTW lol , my 2512´s had 2.8 cubic feet per sub and man that was LOUD, i´ve seen people using 3.5 cubic feet for a 9512 on a daily box, that´s awesome lol