Disc after disc, the first impressive aspect of the Edition 8’s is their ability to render instruments and ensembles without obviously emphasized (or de-emphasized) frequencies. This strikes me as one of the most basic design requirements of any transducer, but with headphones as with speakers, it seems that truly neutral tonal balance is something very hard to achieve.

Most headphones have some range of treble emphasis, however narrow. The Ultrasones mostly avoid this problem, though I did occasionally feel that the upper treble was slightly stronger than is purely neutral. This is a masterful achievement.
Bass is a potential strong point of headphones (because unlike speakers, headphones face a mostly known acoustic environment). But you still hear rolled off bass and bumps or dips from many headphones. Again, the Edition 8s are almost as neutrally balanced as I think a headphone should be. They might be slightly mid-bass heavy, but as I’ve argued in the past, this is a musically grounded choice.
The Ultrasone’s bass is not perfect, however. Drums and bass can be slightly indistinct. In addition, I didn’t get the impression that the bottom octave was as powerful as on, say, the Sennheiser HD 800s. These are small problems, however, and overall the Edition 8s have very good bass.
Beyond frequency balance, it is important to think of headphone performance in terms of some broad overall parameters. The first of these can be called naturalness, which is the ability of a headphone to avoid distortions that call attention to the fact that music is reproduced rather than live. In this, I rate the Ultrasones very highly, and a bit higher than the Sennheiser HD 800s (which also excel in this parameter).
I also like to consider the vividness of a headphone, which is ability of the headphone to make music sound intense and realistically alive. Again, the Ultrasones are quite good in this area, though they don’t quite reach the highest rank because they simply don’t seem as purely transparent or dynamic as live music does. The Denon AH-D5000s, of the headphones we had for direct comparison, were a bit more vivid (though there is a price for this—namely, somewhat more colored tonal response).
Finally, the Edition 8s make instruments sound quite natural, but they don’t sound completely open. Instrumental separation is very good. But instruments sound more like they are being played in a studio than in a live space. Since this is often the case, the Ultrasones may mostly be rendering what is on the recording, but you also sense that overtones aren’t as well rendered as the main body of an instrument. Another way of saying this is that the Ultrasones can sound slightly over damped, which I think is preferable to having obvious ringing distortion. Still, the Sennheisers have the Ultrasones bested in the part of virtual reality that comes from openness.

On Alison Krauss and Union Station’s song “Forget About It” [Alison Krauss & Union Station – Forget About It, Rounder], there is a solo violin playing during the introduction. The violin has gorgeous tone and as the dynamic trails off you can hear it down to a very low level, which is very good performance. But you’d like to hear more overtones from the violin (which is even lower level material) and that isn’t clear. On that same disc, the song “Maybe” has a drum thwack during the opening and the Edition 8s deliver it with startling power. Only the slightly clouded definition of the drum skin’s vibrations keeps one from perfection.
On Mary Black’s song “Leadboys Lassie”, from By the Time It Gets Dark [Gift Horse], Mary’s voice is very clear, as are the surrounding instruments. The accompanying acoustic guitar sounds like a complete guitar—strings and body. If anything, the body might be over-represented, but this natural warmth seems just right because it doesn’t call attention to itself. “Trying to Get the Balance Right”, also from that disc, has a piano accompaniment in which the piano sounds almost real, with left and right hand tonal accuracy plus a pleasing lack of dynamic brittleness.