My money is on the X being an LCD-2 with metal frame, LCD-3 pads, waveguide and a different dampening system. Which makes it quite a bit like the 650 compared to the 600. Wording is everything. Audeze says thinner than competitors not the Lotus driver.
Just to confirm, the LCD-X have brand newly developed drivers (called Fazor) and they sound really, really good! A very good step up from the LCD-2s and give the LCD-3s a decent run for their money.