It is most likely the receiver sub level output, the amp settings, the enclosure isn't sealed properly, or perhaps the room is just too big? The mfw-15 models at 112db from 50-150Hz in 3cu.ft. with 250w, you'll gain 6db with the second sub. -3db point begins at ~35hz or so. This is all before room gain, of course. You've got plenty of mid-bass, so it's either the room or settings etc. I'm running two of these sealed subs (2.5cu.ft.) and my clothes vibrate with bass heavy music, 24ftx18ftx8ft room.
Run the inNuke in dual mono, and put a LR filter on there at 24db and set the frequency to 20Hz. Otherwise you could damage the driver.
Edited by robotbunny - 4/12/13 at 7:38am