Using Devialet's active cross-over

[Jwg1749]

I agree with no crossover would be the best (just built such speakers this year) but I have not heard full range drivers which have enough bass energy for large rooms and good high frequency performance (except very large Sound Lab).
Also there is doppler distortion to consider. Bending Wave driver have a very wide frequency range and no inertia problem (no acceleration of a mass) but they have problems with reaching low frequencies. So a woofer with excellent time response is necessary and thus a cross-over.

Good points. It's hard to generate realistic bass with anything but a conventional electrodynamic driver, so a crossover somewhere is unavoidable if you want full range. The trick is to put the crossover where it's less noticeable, i.e. below about 500Hz. This is what hybrid ESL speakers do, e.g. Martin Logan and Sanders.