Previously the flagship model of Sennheiser's headphone range (excluding the infamous HE90, which can cost upwards of $15,000 in the Orpheus combination), the HD600s now play second fiddle to the HD650s. Despite no longer being top dog however, these headphones manage to produce a stunning symphony of sound that makes them great all round headphones.
The sound can be summed up quite well by the phrase laid back. The HD600s don't force the sound on you, they present it and you can listen as you please. This makes them good headphones for background use, but also means you've really got to listen to get the most of them.
There is a very defined dark characteristic to the HD600s, with prominent bass that lingers towards being slow (the sound hangs around, rather than vanishing quickly). This doesn't mean that songs are dominated by their bass lines, but rather that the music as a whole is given a heavier characteristic. Some people will like this warmer sound, others will find it unnatural. It depends whether you are in interested in a sonically pure representation of your music or would prefer a specific sound.
The mid range was where the HD600s really excelled, with a strong emphasis on vocal elements. Female voices in particular were exquisitely sweet, although both genders were given a lot of prominence in the recordings we tested with. Acoustic guitar strings had a wonderful plucking feeling, and the separation and detail in these sections of the music was spectacular.
Music in the higher registered had the same wonderful, smooth sound, but tended to suffer from a rolling off effect. This has been a hotly contested issue with this particular model, with various audiophiles arguing for or against the "roll off". In our testing the HD600 definitely exhibited some tendency towards dropping off the tips of higher notes. It was really noticeable in tracks with high range piano, which sounded extremely gentle, pushing it towards the back of the song. When combined with the other sonic characteristics of this model, it further enhances the slightly warm, dark sound, which isn't a bad thing, it depends on what you are looking for. In general we found the HD600's sonic signature to be suitable for a wide range of music, without excelling particularly in a specific genre (as the Alessandro MS-1's do in rock music for example). Electric guitars were probably the weakest sound in this model's range, and thus perhaps there are better options available elsewhere for that.
The soundstage was extremely impressive, giving great distance from the music with strong instrumental placement. Solid sound stage is important for ensuring adequate immersion within the music. With a really good pair of headphones you can just close your eyes and forget you're wearing them at all. The HD600s achieve this sort of effect, creating a brilliant virtual stage.
When we first pulled them out of the box, we were impressed with the design. Whilst the marbled blue pattern may put some people off, it felt really solid. Never underestimate the necessity for good build quality, because the downfall of many a pair of expensive headphones has been simple wear and tear. The one point we felt was a little weak was the extenders that allow you to move the cups up and down; they moved in two separate directions and we were constantly stepping cautiously around them for fear of doing damage.
Sennheiser models sport a standard, long-and-thin cup design, which the HD600s adhere to. They look quite misshapen at first, but they fit surprisingly well. For the first few minutes they were a dream to wear, but before long we began to notice a pressure being exhibited on our head. This "clamping effect" is well documented, and is a problem with many higher end Sennheisers. In our time with this model it didn't loosen up, and made them uncomfortable to use for long periods, however many say after a good period of wear-in they righted themselves. If you have a fairly small head then this shouldn't prove to be a problem.
The one problem this model has is the price tag. With an RRP of $799 or more, the HD600s aren't cheap by anyone's standards. Factoring in that you do need an amplifier to use them properly, and the cost skyrockets even further. Compared to the Beyer DT-880s or the even cheaper Audio Technica A900s, and it becomes a question of price versus performance. If the sound seems like it might suit you then you'll have a gem on your hands, but there may be cheaper alternatives.
