Im in the process of rebuilding. I had my first try didnt do so well a 148 at 56hz. Im going for it again. I have a pair of dd 3515sa and im going to try a 4th148 order with about 2.2k rms to the pair.
After talking with dd im going to try a 1:3 ratio
6 cubes sealed and between 15 to 18ft7 the ported tuned around 55hz about equal to sd. Ill plug it to 45hz with about 1.5sd and start playing from there.
It looks good from about 30-65hz
Ill post pics tomorow