thanks for your interest in the subject. I do have something cooking and hopefully will show it soon. I do have a way of measuring impedance (software and a pro card), but my jig is not ready yet. I guess it's time to actually solder it up.
Yes, I want to make a passive circuit and need the exact impedance for the sim.
"phase distortions are easier to deal with"
phase is phase regardless of the nature of crossover (active or passive). The same frequency response will result in the same phase response (in a minimum phase system, which individual active and passive filters are- just ask mr. Hilbert)
"parts are cheaper (umm, price a GOOD cap for a 20 hz high pass passive vs the components for a similarly sounding active x-over)"
I was thinking more in terms of shaping the top end. But even the low end is not all that bad once you consider the load. It takes some big caps and coils at 4-8 ohms, 120 ohm is much more doable.
"and lastly, drivers that vairy TREMENDOUSLY with frequency dont effect the x-over points or slopes."
Yes, that's why I asked if anyone measured the impedance. If it varies wildly, a simple circuit I was considering might not work. But if it it indeed is fairly flat as you indicated in your first post, then I would like to give it a shot.