I've always liked Sonabs, and similarly Shahinians, particularly with classical music. Not the best if you're into pinpoint imaging, but they always sound believable, never harsh, or exaggerated in any way... easy to listen to, but not boring, or really missing much detail.
I've never heard of a single driver Sonab though, afaik they only made 2ways with at least one tweeters - osually many more! The OA-14 used 4 tweeters while the OA-12 used 2, & even the little cube shaped OA-11 used 1.
Aha, I just looked on Carlssonplanet, and they DID make a single diver speaker, the V-1. I stand corrected, those must be quite rare! Looks like their first production speaker.