[Folex]

This is probably hard to gauge because cable, cups etc influence how a headphone sound. And the term "best" means to you so there is going to be different answers. I'm just curious what people think the best pure driver is. 

 

[Head Injury]

  This is probably hard to gauge because cable, cups etc influence how a headphone sound. And the term "best" means to you so there is going to be different answers. I'm just curious what people think the best pure driver is. 

People have done some amazing things with the Fostex T50RP driver. It may not be the best, but it deserves special mention for that.
 
The best driver from a purely performance standpoint would probably belong to an electrostatic.