single driver speakers

Voxativ used like with  Pure Audio Project use woofers  just formidbass,low bass the purity of the single driver can shine 
But No 1 driver can do it all.  I havd iwned,No names these 15 inch 
Full range drivers ,in s proper large ,cabinet, they too have peaks 
At certain midrange frequencies that can be stringent .
I now have a excellent monitor- monitor sudio New Studio coupled to their engineered stands.
Flanked by good Subwoofers. And sounds Excellent- don't let the price throw you off it is more accurate then any speaker under $10k
A Mega best buy,for under $2k buy at least 1 very good subwoofer
I have their Silver W12selling st 45% off ,older model.,there are several very good Brands of Subwoofers

As pointed out by some of the replies above, single drivers have wonderful midrange, speed, tone, timbre and clarity that is hard for mutiway drivers to match. For example, a piano covers a wide frequency range. The bass will be covered by a woofer, mids by either a smaller cone driver or a dome mid of different material, impedance, sensitivity, dispersion,  compared to the woofer. And the high frequencies of the piano will be covered by a tweeter, again of different size, structure, performance, measurements etc compated to the mid and woofer.
In a single driver, the entire piano’s frequency range is covered by the same driver acting as a point source, which is the ideal. Consistency, coherence, no phase changes, smmoth imoedance curve etc.
Another key point of single drivers is the high sensitivy. They don’t need a lot of power. You can use direct heated single ended power amps. And that's another argument between solid state snd tube amps.
Note that most owners of single drivers started with multiway systems.
Keep an open mind, go listen to a well made single driver, anything from a Zu, Rethm, Voxactiv etc.
Tell us your findings. You might end up joining the club.

If your in the NJ, NY, Eastern PA area or you want to fly to Newark Liberty make an appointment with Brian of Charney Audio. He builds full range single driver rear loaded horns based on the Tractrix theory.
I have had the pleasure of listening to Zu, Rethm, Beauhorn, Lamhorn, Horning, Cardersound, Cain&Cain, Voxativ and Carfrae. None of them can deliver the full spectrum of sound quality like the Charney Audio offerings! About a year ago I had the privilege of listening to the Charney Companion Lowther DX65 ($6500.00) next to the Voxativ Ampeggio Signature ($33,000.00) at a dealer. There was no compaison! Companion Lowther DX65 was superior to Ampeggio Signature in all areas! Imaging, soundstage, tonal balance, depth of field, and deep articulate bass. Yes I said deep articulate bass from a 5.5" driver, no sub needed! This from a speaker that is 1/5th the cost! Charney also offers the Companion with a Voxativ AR 2.6 driver ($8900.00) that slightly betters the DX65, but at a much higher cost.

Find out for yourself with a visit to Charney Audio.
http://charneyaudio.com/

Another vote for Charney if you want single driver. Of course all designs have there pluses and minuses so always something to keep in mind. You might gain in one area and give up in another. Lots of fun to try different designs though.

Single drivers must be the future, we just need the engineering to catch up. Overnight multiways will become obsolete.

In the meantime if you can live with their limitations then good for you. If you can't, then at least try to find a speaker where the entire midrange is covered by a single unit.

Unfortunately, in a lot of speakers the crossover point could not be placed in a worse point.