I received an ESP950 in the mail today and at first listen I was greeted with a high-pitched squeal even though the tranducers, pads, and amp are all brand-new from Koss . Regardless of the noise (which hurts my brain a bit, actually) I soldiered on to get a feel for the sound. First off, I was surprised by how close the soundstage is. I'm not usually a big stickler for soundstage, but this is like almost Grado-level soundstage. Bigger pads would have gone a long way here. Next I found the treble extension to be pretty lacking, more than I expected from an electrostatic. It doesn't do cymbals well, and the upper registers of piano feel a little strained, but the rolloff is pretty smooth and isn't that offensive. Bass extension is acceptable but nothing to speak of, midbass levels are decent but lacking impact. The midrange, though, this is where the sweet stuff is. Guitars and vocals are where this headphone shines. It's fast, has great body and decay characteristics, is good at picking detail out, and is aggressive, but not offensively so. I'd put it somewhere between Sextett and Grado levels of aggression. Definitely likeable if you're a midrange fan.
I think my views are a little skewed due to how I hyped up this headphone in my head. I expected a lot from it, being an electrostatic, and wanted it to perform way above its price bracket. I've been listening to a K501 and HD700s for the past week, so that doesn't help. Unfortunately, the lack of treble extension hurts a lot, as I listen to a lot of cymbal-heavy music (metal). Again, these are my rough thoughts, after AT MOST an hour of listening time with a small subset of genres. Time will tell if my opinion on them improves.
As an aside, I find that the ESP950 would actually do very well with poorly-recorded music, as it doesn't excel in extension on either end or in super-detail. Actually, it sounds kind of... vintage-y. Like from the 80s. Which I suppose makes sense, but Stax don't sound that way.
Edited by Ikarios - 1/31/13 at 4:17pm