One of the more interesting examples out there is the Sunfire Cinema Ribbon Monitor. Two side firing 4.5" drivers cross to a folded ribbon tweeter. I use these (with a sub, they only go down to app. 100 hz) as the outboard sound system for my digital piano. They're small, nicely finished, reasonably priced (though not cheap) and sound quite good.
An older example (vintage +/- 1998) of this tweeter type can be found in the Red Rose (Mark Levinson) ribbon monitor. The original (ribbon tweeter extends upward from the baffle) is very good - if not particularly neutral by high end standards - with unusual bass output for such a small box. I haven't heard the later version with the tweeter set into the box, but I've been warned that they're not in the same league. I still use a pair of the older version in my bedroom.
Good Luck
Marty
