My experience with audio tweaking has general been
basically of 2 camps. The first beening where you make an improvement that turns out ot be no improvemnt. The second is where you make your improvement and get a slight improvement, no order of magnitude stuff. Last night I was able to do a bit of experimenting with some 2421 diaphrams Giskard sent me. These diaphrams were installed into 2470 bodies and bolted to 2345 lens. The comparison was made to my 2 way 4Pi's, this combo uses the 2226H and a 2002 Eminence cd on a Eminence lens XOed at 1600 Hz. This is a very good sounding combo, however due the the high XO on the 2226 I always thought the midrange was a bit lacking. The JBL cd's were an attempt to cross lower and hopefully hand some of the midrange to the 2470/2421. Since these diaphrams were 16 ohm it presented some XO problems, the Pi Xo was designed for 8 ohm drivers and since the Pi XO uses top octave augmentation, it's not simply a matter of scaling components and I'm no XO guru. However luck intervened as I stopped into my local JBL dealer yesterday and Al (the dealer) asked if I wanted to take one his Urei 525 active crossovers and give it a try (with an eye to purchase).(gotta love try before you buy)
I must say I'm quite impressed with both the JBL cd's and active crossovers. The 2470/2421 didn't play as high as the Eminence cd, however since the Pi XO uses TOA in the XO and the JBL was unassisted that's not a surprise. The JBL is much clearer and detailed in comparison, plus the lower XO point (800Hz) improved the midrange significantly. The bass was also quite shocking. Having the amp directly coupled to the driver certainly gave the bottom end a kick in the drawers, I've now got a fresh batch of rattles and resonances to track down. My only complaint is that the horn combo can be kind of zingy at time, I'm hoping that's the metal lens is responsible and some padding will take care of it.
Kelly