When Steve Guttenberg reviewed the Sennheiser HD 650 headphones, he rightfully called them "fit for a king"--while noting that they retail for a correspondingly princely sum of $500. Thankfully, the HD 650s aren't the only model in Sennheiser's high-end audiophile line. The Sennheiser HD 600s can be bought at a 40 percent discount to their big brother. Yes, you'll be substituting a grey and black plastic finish for the 650s' fancy titanium metallic housing, but you'll still be getting a high-end pair of open-air headphones while saving enough money to buy a really nice bottle of vintage wine to sip as you listen to your music of choice. (For me, that would be the losslessly encoded FLAC version of Phish's live June 6, 1998, rendition of "Piper.")
If you're not familiar with the open-air design, they leave the outside of the ear cups open so that sound waves moving away from your ear can continue away unimpeded and cannot interfere in any way with the sound moving toward your ear. In the case of the Sennheiser HD 600s, there are pieces of black metal mesh on the outside of the ear cups to cover the drivers and protect them from accidental damage.
Speaking of those drivers, Sennheiser is happy to point out that the HD 600s use computer-optimized neodymium magnet systems, which is supposed to minimize distortion, to drive lightweight aluminum voice coils. A 9-foot Y-cable (one wire to each earcup) delivers your tunes to the drivers and is terminated in a gold-plated 1/8-inch (3.5mm) stereo minijack connection. (Sennheiser also includes a phono adapter for the larger headphone jacks that snap securely over the smaller headphone plug.) Both the earpads and cable are user-replaceable--though Sennheiser is, of course, your only choice when doing so. Replacement earpads will cost you about $41, while cables cost about $25.
Since the HD 600s aren't nearly as efficient as most earbuds, you won't get ear-splitting levels of volume out of them with a portable music player, such as an iPod. However, listening to music at such levels can damage your hearing. I typically got a comfortable volume out of my iPod with the HD 600s. However, with some recordings I did crave a little more volume from time to time. Also, given their open-air design, which lets in outside sounds, you might have trouble cranking your music to try to compete with sounds in a loud environment. I wouldn't want to use them on the New York subway or to try to drown out my dorm-mate while he practices his guitar.
If you really do plan on listening to Phish play that 20-minute-long version of "Piper," you'll definitely appreciate the soft cloth padding on the ear cups. During my listening tests, I was able to wear the HD 600s for hours at a time, in some cases nearly an entire workday, without the annoying sweat that you sometimes get from headphones with leather-padded ear cups. Another bonus to the cloth padding is that you won't have to worry about the leather flaking off as you would with some headphones, such as the Sony MDR-V6.
Given their open design, the HD 600s really shine on live recordings giving the impression that you're really in a big space rather than a small room with cans on your ears. They deliver a wide range of the audio spectrum and deliver it well, digging deep into the bass registers, and reaching way up into the higher frequencies. However, despite the fact that they faithfully recreate very low bass, it lacks the oomph some closed-ear-cup designs can deliver. Specifically, I was able to compare the HD 600 directly with the similarly priced Denon AH-D2000s and enjoyed the more powerful presentation they gave to bass when compared with these Sennheisers. Also, the HD 600s felt a little shy in the uppermost treble regions, where there was just a very slight bit less definition and clarity to the sound. For instance, while listening to "Rise Up" on the excellent album Tonic by Medeski, Martin, and Wood, Mr. Martin's precise ride cymbal work popped more on the Denons than on the Sennheisers. The Denons delivered a crisper snap when the stick hit the cymbal, while the Sennheisers were ever so barely less snappy, though admittedly some people will probably have a hard time hearing the difference and most likely won't notice much deficiency if they can't do a direct comparison. The relative lack of warmth to the Chris Wood's upright bass and slight lack of punch to John Medeski's ascending bass line on the piano on the Sennheisers compared with the Denons is more apparent, but again is mainly a side effect of the open design. So, if you're already a fan of open-air headphones, this will likely not be a big issue and indeed, you may prefer it to the Denons' closed design.
Even though I have outed myself as a fan of closed headphones, that hasn't stopped me from thoroughly enjoying the Sennheiser HD 600s for the last few weeks. They are exceptional headphones and, in my opinion definitely worth the money, especially if you use headphones often. If you're a particularly persnickety listener though, you may want to step up and shell out the extra cash for Sennheiser's HD 650s. Just remember that these are really intended for home listening--ideally when connected to a home stereo with a solid amplifier.