Originally Posted by Eggtuary
Looking through the stats on the 6 series, the thing that seems most weird to me is that the 690, a 2.5 way design, lists two crossovers: 600 Hz and 1.7 kHz. Shouldn't there only be one crossover listed, like the lone 1.5 kHz crossover listed for the 590 (also a 2.5 way)? Or does the listing of a second crossover tell us something about how they're going to use one of those low frequency drivers, in a sort of pseudo-midrange role?
All 2.5 way speakers have two crossover points. I have always wondered what the lower one on my 590's was, but was never able to find out.
On the 690, for example, the lower woofer operates from 36Hz to 600Hz. The upper woofer operates from 36Hz to 1.7kHz and the tweeter operates from 1.7kHz to 40kHz. This configuration allows ONLY the upper woofer, the one closest to the horn tweeter, to produce the lower midrange and makes for a smoother, more focused, blending of frequencies at the upper crossover point.
So the effect is only the one woofer is producing midrange and both are producing bass. This crossover technique has been used by JBL for decades in their larger, dual woofer, stage systems.
I hope that that this somewhat simplified explanation helps.
Edit: I do remember hearing somewhere that the lower XO point for the 590 was 500Hz @ 6db/oct. That seemed like a reasonable number, but I never read anything from JBL.