I would say that the HD 800s are more natural and less analytical than some top ‘phones. This is good thing, especially when combined with the excellent treble performance on offer here, which exhibits only very small errors. The HD 800s seem to have a small dip in the upper midrange which makes them slightly soft dynamically. The treble is extended, and is smoother than on many headphones. I'd say the treble of the HD 800s is very slightly warmer than is perfectly neutral. Despite that, on occasion, vocals can sound slightly "sharp" rather than completely pure (this may be the HD 800 revealing decoding errors, but I believe something else is going on as well).
Each instrument seems more diffuse than it can with other headphones and many speakers, which I would guess is due to the spatial engineering of the HD 800. In any event, the slightly more diffuse sound on offer will be attractive to some listeners and may ameliorate some of the inevitable high frequency imperfections.
This brings us to the question of whether the HD 800’s spatial engineering helps with the sense of soundstaging that is often a problem with headphones (a Sennheiser claim). In a word, I’d say no. The performers don’t seem to be on stage in front of you much more than with traditional headphones or earbuds. And with a standard amplifier, you still lack the crossfeed of left sounds into your right ear (and vice versa) that is part of normal listening.
Don’t get me wrong, the HD 800s are no worse in these matters than other phones. In fact I think they offer significantly more of the sense that instruments are being played in real space than other headphones, and that is an important advantage. But with the HD 800s those instruments in real space are positioned left and right of your ears, so the soundstage isn't like live music (with its positioning of performers in front of you, spread left to right). Just like other headphones, the HD 800s don’t image like speakers or live performers.
All of this may seem like damning with faint praise, which isn’t really what I intend. The above remarks are there to explain the character of the HD800s and need to be viewed in the context of the general neutrality of these headphones. Most headphones are pretty obviously flawed, if we’re honest. With the HD 800, Sennheiser has gone a long way to reduce those flaws, which makes this a very special pair of headphones. This also means that a description of the character of headphones like the HD 800 is likely to make small flaws seem bigger than they really are.
Because the flaws in the HD 800 are in fact quite small, my colleague Alan Sircom was enthralled with the HD 800s when he reviewed them in our sister magazine from the UK, Hi-Fi Plus. He compared them with $25,000 loudspeakers to give you a sense of how much he loved them.
I’m more in the camp that likes, but doesn’t love, the HD 800. I believe that has less to do with outright flaws in the HD 800, and much to do with what I want a headphone to do. I want a headphone to provide an alternative listening experience. I want to hear things on recordings that I don’t hear as well via speakers. This partially comes from my sense that headphones just can’t do the virtual reality thing that traditional speaker-based audio can. At the same time, I need a certain vividness in my headphone listening that makes up for the things headphones inevitably take away.
From some perspectives this vividness is called coloration. Maybe. But the declaration of coloration refers to reasonable though arbitrary notions of “correct”. All I know is this: live music is vivid. The HD 800s, at least with the amps I used initially (primarily the Luxman P200 and PS Audio GCHA), are not vivid, which is what keeps me on the “like” side of the line. I have since tried the prototype Woo Audio WA 22 amp (which is tube rather than solid state and has variable output impedance). The WA 22 takes the sense of vividness up a notch, mostly by making the midrange contrast level higher, while introducing minimal if any deleterious side effects. The mostly subtractive errors noted above are still there, but they are diminished in the overall presentation. This gets me to the level of really, really liking the HD 800s. The HD 800s are so good that I could easily live with them over the long haul.