Indeed, single driver sound is highly subjective, and it's also extremely dependent on the actual build. Among my audio friends' circles we have several single driver speakers which are phenomenal speakers. Bruce Edgar's Lowther horn comes to my mind (RIP Bruce Edgar! He just passed away...), 100+dB/Wm efficiency, and had enough bass and high frequency extension to create the most memorable Cantata Domino experience I ever had. (It has full size chorus and church organ.) My Fostex Voigt pipe could reach down to 30s, and surprised me with the most lifelike timpani reproduction I ever heard, from any speaker. Although Bruce Edgars legendary designs are well known, but not sure whether you can buy any... my Voigt pipe is certainly one of a kind... the commercial Rethms comes to my mind, but that, in comparison completely lacks bass.
The most important consideration is that single driver speakers have NO CROSSOVER, and will give you the purest sound ever. That is, they will allow system weaknesses to pop up their heads that you had no idea there were. Generally, solid state amps are a terrible match for single driver speakers (although there are exceptions - Michael Yee amps sound great with them.) Also, they are EXTREMELY sensitive to you room acoustics and speakers placement, and it can easily take a year until you find their optimal position. However, if everything jives, you have an endgame situation. My Voigt pipe gave virtually identical experience with recorded jazz as a live jazz event - I listened to my friend's concert at the Dragon Upstairs (in critical listeners mode), and right afterwards put on the Jazz at the Pawnshop, and with closed eyes I did not get any hints which was the live, and which was playback... But that was after 15 years of playing around with them, and when I moved to my new place, I could never set them up so they image like that, and their midbass is not coming to life either. So, YMMV tremendously. They have almost infinite potential, but everything has to line up. If you want plug & play, look elsewhere, they are very long game speakers... provided you find the right one. If you can get an Edgar horn, go for it, although to my knowledge he designed that Lowther horn for my friend, and that might have been the only one he built. I have heard extremely disappointing reports from my friends when they ran into commercial single driver designs. Good luck!
The most important consideration is that single driver speakers have NO CROSSOVER, and will give you the purest sound ever. That is, they will allow system weaknesses to pop up their heads that you had no idea there were. Generally, solid state amps are a terrible match for single driver speakers (although there are exceptions - Michael Yee amps sound great with them.) Also, they are EXTREMELY sensitive to you room acoustics and speakers placement, and it can easily take a year until you find their optimal position. However, if everything jives, you have an endgame situation. My Voigt pipe gave virtually identical experience with recorded jazz as a live jazz event - I listened to my friend's concert at the Dragon Upstairs (in critical listeners mode), and right afterwards put on the Jazz at the Pawnshop, and with closed eyes I did not get any hints which was the live, and which was playback... But that was after 15 years of playing around with them, and when I moved to my new place, I could never set them up so they image like that, and their midbass is not coming to life either. So, YMMV tremendously. They have almost infinite potential, but everything has to line up. If you want plug & play, look elsewhere, they are very long game speakers... provided you find the right one. If you can get an Edgar horn, go for it, although to my knowledge he designed that Lowther horn for my friend, and that might have been the only one he built. I have heard extremely disappointing reports from my friends when they ran into commercial single driver designs. Good luck!