I went to listen to the LCD 3F a couple of month ago from a Sennheiser HDV-D800 as amp/dac and I compared it with the LCD X. It was IMO clear that the LCD 3F have a warmer/creamer and more intimate sound then the LCD X in this setup. The LCD 3F have not as much base as the LCD X and LCD 3C. The LCD X on the other hand didn’t IMO have the mids, is not as dynamic, is not as reviling and is not as colorful as the LCD 3F, so they don’t sound the same. By colorful I don’t mean adding artificially coloration, more like present the instruments naturally tonality. To me the LCD 3F sound like the classic, just a little bit clearer and with a bit less pronounced base. I can’t say exactly how much less base it has because it was not in my home rig.
Anyway I liked LCD 3F better than the LCD X in this setup. If one will like the fazor one better than the LCD 3C will probably dependent on if one is willing to change the extra energy and clarity (mostly in the midrange and lower treble) with the slightly reduced base. And that will to some extend depend on witch other dac, cables and amp one have.
Btw the new driver seems to requisite more burn in time to sound good then the old classic. The new not fully burn in, is according to the personal in the shop, pretty harsh.
I wish that Audeze one day will make a headphone witch has the clear and open sound of the LCD 3F with the base of the classic and if possible a little lighter.