Sitting at the top end of Sennheiser's HD5x5 series of audiophile-grade cans, the HD595s have a luxurious, high-tech feel about them and a style that is instantly recognisable as Sennheiser. The construction is typically robust, with the grey plastic and black mesh earcups attaching via a swivelling mount to the adjustable, leather-clad headband, which has been thoughtfully padded on the underneath for comfort.
In fact, thoughtful is a word that comes up a lot with the HD595s, particularly when you look at details like the reinforcement around the points where plugs, cables and earpads meet, or the supplied headphone rest you can mount on a shelf, beside table or book case, or the included 3.5mm to 1/4in adaptor you'll need to plug the HD595s in to your PMP of choice. Most of all, a lot of thought seems to have gone into making the HD595s lightweight and very comfortable. They're not quite as easy on the ears, physically speaking, as the Audio-Technicas or AKGs, but they're very close.
Rated at 50Ωs, the Sennheisers aren't as easy to drive with an MP3 player or PMP as the Grado ‘phones, but they don't necessarily need amplification. They will, however, benefit from it. Overall, the HD595s exemplify positive qualities you might associate with Sennheiser: balance, clarity, and strong mid-range and high-end detail, but they also exemplify a couple of negative ones, namely what some see as a lack of bass and a slightly withdrawn, disengaged performance. You can argue a case that neither criticism is accurate, but with amplification the HD595s handling of bass improves and the Sennheisers grow in terms of presence.
Once you accept that these aren't bass monsters on the level of the Beyerdynamic 'phones, you come to appreciate how versatile and well-balanced the HD595 sound actually is. Listen to rock and there's enough 'oomph' to make heavy guitars sound good, but also enough mid-range clarity to bring the vocals where they should be - at the fore. Stereo imaging is another key strength, and the more open sound really helps tracks with layers of instrumentation, like Massive Attack's What Your Soul Sings or Talk Talk's Desire.
Acoustic tracks and stripped-back vocals sound fantastic, and when it comes to the small group jazz of Miles Davis's All Blues, there's a superb sense of space and intimacy, all the instruments sitting well together in one coherent mix. I'd prefer to listen to Wagner's Trauermusik on the AKGs or Audio-Technicas - you miss the thick, dark tones of the AKG K601s - but the HD595s still represent themselves well, partly thanks to the clarity and spaciousness of the soundstage.
Not everyone will love the HD595s and they can sound a bit too laid back and dry after the Grados, which give you a much more direct connection to the music. However, the Sennheisers are the more comfortable pair for long-term use. Overall, I'd say that the Audio-Technicas hit a sweet spot between the two in terms of sound, and are equally as comfortable as the HD595s, but it's a close call. Give both pairs a try if you can, and there's a chance that you might prefer the Sennheisers.
Great all-rounders and very comfortable as well, though the output may be too laid back for some. Like space and balance? You'll like these.