Good good, and they've improved the frequency response on this LCD-X now, so it's a better basis for EQ than it was before. I mean it's not the epitome of a smooth EQ'able frequency response, but it's a lot better than it was. I'm less wowed about the super low distortion than some people, I think it doesn't matter past a certain point, but it's obviously not a negative point.......just I don't really think the super low distortion makes it a better blank canvas than some other headphones that have higher distortion but a smoother & closer matching frequency response as a starting point. I think soundstage potential of a headphone is to some extent baked into the design of the headphone, but I'm not particularly convinced that this headphone is necessarily better on that front than quite a few other headphones. All-in-all I think this is a pretty expensive headphone to use as a blank canvas for EQ, but I could understand how it could give decent/good results when done so.....as to how good I don't think it would sit right at the pinnacle, so a little expensive then.
EDIT: as a bit more qualification, I'm not convinced the soundstage would be really that great in this headphone. I'm saying this mainly because I have a Hifiman HE4XX that is EQ'd to Harman and the soundstage is pretty good, but not as good as my HD560s and K702 for example, and the HE4XX is a planar headphone with large round earcups and angled pads (so similar to LCD-X)......is there any big difference in the structural/size of the earcups that differ largely between HE4XX and the LCD-X that might explain how the LCD-X might have better soundstage?
EDIT#2: I do like the accurate channel matching of the LCD-X in this review, it's an often underrated & not often mentioned variable....my EQ experiments with exact channel matching through the frequency range from 20-10000Hz have shown me that it improves overall clarity and makes a noticeable difference to an extent that I've been able to tell while blind if channel matching was activated or not when used with my K702. So that's a good plus point for this LCD-X.