Eminent Technology LFT 7 !!

Actually, I should have said "to minimize the degree of comb filtering created" rather than "to prevent comb filtering." And then place the second panel with the midrange driver up against the side of the first pair on which is located its tweeter. That will create a sort of coaxial driver, in the horizontal plane at least.

There may be a development on the LFT7 quest.  Keep you posted.  

Owned the ET LFT-8b for 15 year, upgraded the base driver then the tweeters to get to a level b.  Bruce made it easy and economical for Eminent Technology owners to upgrade.  Super nice guy, always gracious with his phone time.  Never got to the C version, not my cup of tea but if he were to return to an updated 6, I might be interested.  But in the end give me a fully restored LFT-3 and call me golden. 

The 8c isn't for me either @daytrader; no digital, thank you very much!

But there's a better alternative anyway: a pair of the OB/Dipole Servo-Feedback woofer system that Rythmik Audio and GR Research developed and market together. While the new ET "c" woofer is a dipole, that is all it has in common with the Rythmik/GRR woofer. It contains 2 or 3 (your choice) 12" woofers mounted in an open baffle frame. Unlike "normal" subs, it plays up to 300Hz. That enables one to use it in place of the stock LFT-8b woofer! Just leave the stock woofer disconnected (easy as it was it's own binding post). The plate amp that comes with the kit (yes, you have to build it, or have one of Danny Richie's cabinet makes do it for you. For a price, of course) has the most extensive range of controls on the market, including the option of a 180Hz 1st-order low pass filter, to exactly duplicate the filter used with the stock woofer.

And it's 100% analogue!