Just wanted to throw in my two cents on this controversial headphone that gives different people such differing impressions. After more than a year and a half of being tempted to try it out, (and examining this thread on and off for about as long) I finally grabbed a pair. I don't have golden ears, and don't know all the lingo, but will do my best to give some early impressions and comparisons. I was anxious to see how these compared with some of my other high-end closed pairs. I was pleasantly surprised.
They are certainly darker than some cans. The contrast between light and dark becomes extreme when comparing the Z7 to the TH900. As much as I enjoy strong bass and don't always mind a darker signature for some kinds of music, I also love small details and a brighter headphone can help bring those out. The TH900 is the sun to the Z7's moon, in this area, especially when neither is amplified.
While having amazing bass, the TH900 really brings out the little details in fun electronic tracks at the same time as well in a style that has always blown me away. The Fostex can really hit synthesizer notes and such with a pointed authority that brings out the fun in many tracks with ease. But this involves a V shaped sound and what some call recessed mids, which some people don't enjoy for all kinds of music.
The Z7s are darker and have more forward mids. At first, when comparing these two, I felt like the TH900 won out over the Z7 in the vast majority of cases, when used directly from the source without added amplification. The Z7 was having a lot of trouble reaching the notes that the TH900 seemed to hit effortlessly, revealing details and presence for parts of the music that the Z7 seemed to be lacking. Even so, the Z7s brought a nice rumble and soundscape to things, along with immediacy to the vocals. But while that was interesting and enjoyable, it wasn't nearly enough to make up for what was lacking relative to the TH900. I know the TH900 has a lower impedance, but even when doing volume changes to compensate, the Z7 still lagged behind too much in some areas, to my ears.
Then I tried attaching the Z7s to a WA7 Woo Audio amp. The transformation was immediately obvious, and very pleasant to the ears. Given all that I had heard about how these cans don't really need amplification, this was not at all what I was expecting, but it was very clear. Now, the headphone's strong points of sub bass, power and and enveloping soundscape shined even more, but without sacrificing being able to hit some of the instrument notes with enough authority to be fun in a way that didn't lag behind the TH900s so much. In fact, the Z7s now had something that the TH900s lacked, in the overall presentation, thanks to those combined qualities, even when directly comparing the two sets of cans from the same amp. Very interesting, and quite enjoyable.
I had been skeptical, but it seems that HiFiGuy was right - these cans really do "sing" when well amplified, and lack something when they are not. I am also starting to see why Jude so confidently stated that the Z7 belong in the same league as some other high-end closed cans, despite costing less than many of them. Their approach may not be for everyone, but it brings something special to the table.
Since I'm having a fun time with these so far, as a musical and enveloping alternative to my micro-detail emphasizing cans, I decided to get the Kimber cable to see if these continue to scale up well. I look forward to seeing if they have any more nice surprises in store.