One of the first lessons you learn after diving into the world of hi-fi audio is that no pair of speakers or headphones can ever be declared as the best. Even if you're rich (or mad) enough to spend hundreds of thousands of dollars on your audio setup, there's still a chance someone will listen to it with a straight face and remain utterly unimpressed. The main reason for this is that not everyone enjoys the same character of sound. What you could potentially find ideal, someone else may consider lacking in certain aspects. For example, I generally don't like when the bass is heavily emphasized, but there are plenty of users who wouldn't give a second thought to a pair of speakers or headphones that aren't exceptionally bass-heavy. That's okay, and don't let anyone tell you otherwise.
With that in mind, it's quite impressive what Sennheiser managed to pull off at around the turn of the century: they released two products that were met with universal acclaim by users and critics alike. In 1997, they released the now legendary HD 600, followed by the equally famous HD 650, launched some six years later. Both headphones share many characteristics—both were positioned as the company's flagship products, open-back, and almost universally liked, nay, loved by their owners. With a launch price of around $500, neither were exactly cheap, but for countless users, they represented the "endgame"; that last pair of headphones they'd ever need to buy. Over time, their price dropped significantly; nowadays, you can pick up the HD 600, as excellent as ever, for no more than $300, and the HD 650 for around $400. Let's not forget the Massdrop-exclusive HD 6XX, which is basically the HD 650 with a navy blue instead of a black color scheme—more than 40,000 users bought them (and continue buying them) for a measly $200, which is a bargain of a lifetime.
While the HD 600 and HD 650 remain among the most discussed and modded (in terms of aesthetics, comfort, and sound quality) headphones of all time, we're not here to talk about them. This review will focus on the recently launched Sennheiser HD 660 S, essentially a spiritual successor to the HD 600 and the literal successor to the HD 650. If you venture on to Sennheiser's official website, you'll find the HD 660 S in the "High-End Headphones" category. That might scare you into thinking that there's no chance you'll ever be able to afford it. However, things aren't as grim since the HD 660 S is priced at $499/€499. It's a hefty sum of money, but if the HD 660 S performs even better than its older siblings, then it too can be declared as "endgame-worthy", and I'll have no problem recommending it wholeheartedly. Heck, I'll even urge you to try to save up for it!
As you've most likely gathered by now, we have in the Sennheiser HD 660 S a pair of open-back hi-fi headphones devoid of extras, including gimmicks. It has no aspirations to be used outside of your home, nor would a pair of open-back headphones be suitable for outdoor use because of the sound leaking in both directions. Interesting, however, is that the impedance was lowered to 150 Ω (from 300 Ω), which should make the HD 660 S easier to drive with less powerful amplifiers and even some smartphones with higher-quality audio electronics. Its main purpose is music listening, although nothing is preventing you from using it for gaming as well since great hi-fi headphones will offer a terrific all-around experience. The color scheme Sennheiser went with this time around is matte black and anthracite, and the recognizable massive, perforated ear cups now look even more impressive than before. However, what's behind them is what is drawing most of my attention—that 38-mm dynamic driver, now with a brand-new transducer design and light aluminium voice coil. There's some speculation that this is the same speaker driver Sennheiser is using in their HD 700. A more accurate way to describe it would be that it's a variant of that driver; don't expect the HD 660 S and HD 700 to sound the same by any means.
- 38-mm dynamic speaker drivers (neodymium magnet)
- 10-41.000 Hz frequency response (specified by the manufacturer)
- 104 dB @ 1 V/1 kHz SPL
- Over-ear design
- Removable ear pads
- 4.4-mm balanced Pentaconn and 6.35-mm connectivity (3.5-mm adapter supplied)
- Detachable cable with a 6.35-mm connector (3 m)
- Detachable cable with a balanced Pentaconn connector (3 m)
- Weight: 260 g