my 12" axis is in 2.5 in.cu. tuned to 33 hz. did a 143.7 @41hz sealed, car off, on a good usb powered meter.
1 battery, lack luster hifonics 2610D.
never got the coil stinky, but i can push it to its mechanical limits.
the box is too big, i can tell. output around 30-40hz is amazing but...