I've been listening to the X, and compared to the LCD-3, there is a lot less sub-bass presence but equal amounts of mid-bass. The bass also isn't as authoritative because of the much wider imaging that the X offers and the increase in treble which distracts from other parts of the frequency spectrum.
It is very interesting to see what Audeze did with this new line of headphones as they were certainly targeting the people that complained about the LCD-2/3 sound-stage and treble short-comings (I am part of that group of people).
So far the X has astounded me with the micro detail extraction and the much wider imaging. It also shifts emphasis from the mid-range to the treble when comparing to the LCD-2 and 3s, which in combination with the wider horizontal sound stage, it loses that old intimacy factor the older siblings offered.