Without taking anything from the Everest, I would really want confirmation about the super tweeter coming in at 20 kHz. That seems supremely wasteful.
Otherwise, this is almost what the DIY community calls a Woofer-Assisted Wide Band (WAWB) which has quite a following. The idea is to use a wide-band driver and/or horn to keep any crossover issues out of the human voice range, but adding a woofer to cover the lowest octaves. It’s a neat idea with many positives and also a lot of negatives but definitely an approach worth considering. I think of a WAWB as a variation on the full-range, single driver designs and a way of overcoming the limitations in bass output in a tidier manner than folded bass horns.
The DD67000 seems to take this to the extreme by adding a second woofer and a super tweeter, but I’d consider it more or less in the same faimly. Check out all the articles over at DIYaudio on the pros and cons of a WAWB.
Also worth noting, this is an ideal speaker for Sanders amps. The impedance is worse in the high frequencies than in the bass, a situation which is the opposite of what most normal amps are expecting, which have higher damping factor below than above. Do you need it to play from 20kHz to 40 kHz though??? That's another story.
