Best speakers out there for Midrange and HighsAlways ESL's, then Planer then Cone drivers, to cover mids and highs.
It's all about the mass to get the best in mids/highs.
The very best in just the highs are Plasma, but they are HF only, they have no mass as they ionize the air around the Plasma flame and that becomes the diaphragm.
Cheers George