Single driver speakers. Are they worth considering ?

The main issue full range driver is suck out upper bass and lower mids so you listen much more thinner sound than good 3 way LS, that reason that majority audio guys hate SD . The Perfect Single Driver that can work alone with no issues unfortunately does not exist.

One thing that struck me is that most of the top level speakers, the priciest ones almost no one can afford,  that gets fantastic reviews in all the magazines are multi driver. It looks like that is the solution the designer goes to when money is no issue. Maybe it's expensive to create good crossovers and reduce the problems multiple drivers introduce but it can be done. It may be the best solution right now.

Lowther full range driver in a rear bass horn enclosure.  pure, simple, efficient. 

Does a trumpet have a crossover?  

I own Zu, Tannoy, and Fyne. I've owned a silly number of other conventional brands also. The minimalist approach sounds best to me. Actually: sounds most like real music. 

Designers brag about 'how well the drivers integrate' but think about that closely; what they're actually saying.