That's interesting Curtis.
I was wondering if the smaller subs such as the 20-39 or especially the 25-31 would reduce the effect. I would love to hear the Ultra series but with the EQ turned off for a more apples to apples comparison. The change in driver certainly could make a difference (aluminum vs. kevlar impregnated pulp otherwise referred to as darn strong paper).
"Those who preach the myths of audio are ignorant of truth."