Single driver vs traditional 3 way loudspeakers

@grinnell    Single driver crossover less design assuming no any  coil or capacitor involve, for 2 way like monitor DE Capo   the woofer may connect direct with no crossover network, but tweeter using capacitor that meaning first order crossover design involve  for tweeter only, They must using capacitor to avoid blow up tweeter .   Most of 2 way design using one High quality coil ( Inductor   ) for woofer also to  get off cone break 
frequency. If De Capo dont using any coil i dont know is good or no .
@auxinput   Agree for 100 % , in all my design i am simply remove whizzer cones 

@kenjit  agree, how whizzer cone , just piece of paper can be compare with High quality tweeters , This is Woo do. Basically whizzes cone   drivers was used  in all analog Tube amps and Pro acoustic in Cinema
How they widely used in High End is magic 

I’ve listened to several full range driver speakers and all have compromises. Either they are soft, or lack bass, or have whizzer cone artifacts. The Cube Audio Nenuphar look interesting with a 10" woofer and 3 whizzers.

PHY has introduced a 6" driver that has no whizzer cone and yet is extended and smooth at high frequencies. Its hard to get it to go below about 60-70 Hz, but at that point you can use a sub with it quite successfully. I recommend keeping the deep bass out of that driver- to make the highs right it has a very lightweight voice coil that simply does not handle a lot of power. But it is 96dB at 1 watt, so you don’t need a lot of power to make it work in most rooms.

A 6 inch or even 4 inch cone will never be better than a real 1 inch tweeter for high frequencies. The dispersion will be narrower and more distortion. 

I prefer keep it simple with as few drivers as possible, usually 2, but 3 can be good too.   One is OK but will always have limits.