Left: SPL for 18WU/8741T00 on Jenzen mid baffle. This is the best response I've seen from this driver so far. I thought the 2.5 kHz dip was kind of intrinsic - and maybe it is, but on the Jenzen baffle we have a nice smooth response all the way to 6 kHz except for the usual 1 kHz rubber surround resonance.
Right: Same driver on 25 cm baffle. I think this clearly demonstrates the importance of spending time on cabinet design. A lot of trouble can be avoided in the initial stages, where most diy speakers starts with a dream design and all hell breaks loose when the problems have to be fixed in the crossover.