Is there a monitor speakers with just one driver?

Lowther drivers are full range -- but they need specially designed cabinets to work well.

http://www.kef.com/qpoint2grp.htm

My favorite full ranger is the Fostex. Either 108Sigma or the 168 Sigma. They make sweet music but like most full rangers suffer on the bottom. Good thing is they are cheap (compared to some of the Lowthers) and there are plenty of good designs available in the public domain.

The Tannoy Dual Concentric Driver is actually 2 seperate speakers. The tweeter in the center has its own magnet and wiring, completely seperate from the bass driver surrounding it. Thus the Bi-Wire hookups on the back of any Saturn (S6, S8, etc), Definition (D50, D70, etc. Saturn replaced this model because it was identical to the High Definition, but half the price) or High Definition (D500, D700, etc), and on up the price list. The point of the driver was imaging. The Point Source idea, where all the sound comes from one point, makes for a VERY real sound. So if you use the Tannoy driver for midrange only, you'll be running through a crossover in the speaker, which doesn't sound nearly as good as biwiring (atleast with my D70's), so I think it would be, well, kind of a waste of a great sounding "Full Range" speaker. Their midrange is excellent though....