Wayne, besides the woofers you use in Pi's, I have been looking at other similar high efficiency woofer. It seems that most have a hump or peak in the 2000 hz range, then fall off. Examples are Eminence Gamma 12, Some the hump is quite mild, Eminence Delta 15LF, Delta 12LF, Gamma 15.
What causes this peak? Is there any way to tame this in the crossover?