Single driver speakers. Are they worth considering ?

@jayctoy Here's what I was told (by Jon at Refined Audio) about building a small sealed box for a pair of Cube Audio Drivers:  "I have a <slight> preference for the presentation of the 8” Neo over the 10” Neo.. Not sure where/how you would crossover, but it may be necessary to put in a baffle step correction if you are crossing over at a low frequency....The 8” Neo in a sealed box about .7 to 1 cubic feet is amazing, I used that for a long time... The open baffle has a big, open soundstage. The sealed box will have a smaller, but better defined soundstage. So it is a matter of taste. I prefer the sealed box with the Cube speakers…"

With sub units augmenting < 100Hz, hence the discussion of crossing over...

yes
wideband drivers are great but
subs are needed
a highpass to protect them as well
and many like to add a supertweeter for even dispersion

so its a 3 way, with xo points around 60hz and 10khz. quite ideal actually. probably the best mid ive ever heard came from 1 way.
Ive heard extensively the WE 755a: best mids ive ever heard, spooky good

ps: if you want "fullrange" wideband= high end Headphones

I used 15 Ohm Lowther DX2 in home-made Fidelio boxes for almost a decade, finally just wanted a change.
Still, I am keeping them, as they do some things right; there is even some [illusion of] bass (with a SET amp).
However, they only sound right with that 300B SET amp, anything solid state was poor match (including Pass Aleph 4).