Single driver vs traditional 3 way loudspeakers

@grinnell  you wrong  , look stereophile specification 
   
Description: Two-way reflex-loaded loudspeaker for use with stands 26-28" high (not included). Drive-units: 1" impregnated fabric-dome tweeter, 7" woven carbon-fiber cone woofer. Impedance: 8 ohms. Sensitivity: 92dB/W/m. Frequency response: 44Hz-20kHz, ±3dB. Crossover frequency: 3kHz.    (  that mean you got crossover )

Not having a crossover network the De Capo instead uses Mundorf Supreme Silver Oil capacitors as a tweeter high-pass filter.

Full range single drivers do have their following.  That being said, it's incredibly difficult to engineer a single driver that will do a wide range (from low 50 Hz all the way up to high 20 kHz).  Some can do this, but with compromises.  I think the Mark Audio paper drivers are some of the most natural sounding full range, but they don't have good low bass response and the highs are soft and rolled off.

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.  I have not heard them directly, but youtube videos seem to reveal the typical whizzer cone effect.  It's a type of echo or resonance or shouty effect.  It's not perfect and is not going to be as transparent or clean as a traditional tweeter, but it provides a single driver full range scenario.

The Seas Exotic 8 is another possibly decent full range solution.

Single fullrange speakers suffer from bad distortion in the highs because the cones are not high quality enough to do high frequencies. You would never use a 4 inch dome as a tweeter in a 2 way speaker would you? Most tweeters are one inch. They need to be small and light to work well. Secondly small fullrange speakers cant do bass. Not just 50hz but even 150hz. 

What you need is at least two drivers. Each handles one half of the frequency range. A crossover device is then used to split the signal in half. 

Speaker design is not rocket science.  

@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