Here’s a start..
Magico Ultimate
https://www.youtube.com/watch?v=afi4pyrSuRs
Classic Audio Reference https://www.youtube.com/watch?v=XZWu0OOdYbc
Volti Audio Vittora https://www.youtube.com/watch?v=Cz_Vkhgx4cs
JBL Everest Project
https://www.youtube.com/watch?v=h-Do6XOb4Uw&t=15s
Mark Levinson Daniel Hertz
https://www.youtube.com/watch?v=X6v7X3baUtg
I don't have any, but would be happy with any of the above... :-D
PureAudio Project OB speakers look interesting as well. Not horns, but pretty high efficiency. :)
https://www.youtube.com/watch?v=4E-XEIBnxy8