HomeTechnologySennheiser HD 660S2 evaluate: I’m an open-back believer

Sennheiser HD 660S2 evaluate: I’m an open-back believer

Man wearing Sennheiser HD 660S2.

Sennheiser HD 660S2 evaluate: I’m an open-back believer

MSRP $600.00

“The Sennheiser HD 660S2 present wealthy and detailed audiophile sound for vital listening classes.”


  • Detailed and dynamic sound
  • Glorious bass response
  • Balanced and unbalanced cables
  • Comfortable sufficient for lengthy classes


  • No case for defense
  • Clamping power might really feel too robust

Open-back, wired headphones are, for lots of audiophiles, the one sort of headphones price utilizing. They’ll wax poetic in regards to the superior audio high quality that comes from letting sound (which is to say, air vibrations) transfer freely in two instructions — towards your ears, in addition to away from them.

For the longest time, I used to be having none of it. Having spent many of the final 20 years listening to nothing however closed-back headphones and deep-seated wired and wi-fi earbuds, I simply didn’t suppose open-back cans may supply me something I wasn’t already getting.

I used to be flawed, and the Sennheiser HD 660S2 proved it.

Sennheiser HD 660S2.
Simon Cohen / Digital Developments

At $600, the Sennheiser HD 660S2 are expensive if you happen to’re evaluating them to the high-tech marvel that’s Sony’s $400 WH-1000XM5. In any case, the Sonys can function wirelessly, they characteristic excellent lively noise cancellation (ANC), they usually’re loaded with sensible add-ons like the power to routinely have interaction transparency mode once they sense you’re speaking. And yeah, they sound wonderful.

Nevertheless, vital listening — a time period I exploit to explain these uncommon moments when you may ease your self into the comfiest seat in your house and provides your self over to the act of getting misplaced in your favourite music — is an exercise that must be mediated by as little tech as potential. The HD 660S2 are very well-suited to the duty.

Earcup pivot close-up of Sennheiser HD 660S2.
Simon Cohen / Digital Developments

Design and luxury

A deeply plush set of ear cushions line the earcups, and a strip of reminiscence foam gives the scarf with wonderful stress distribution. Clamping power is a bit on the assertive aspect — although comfy total, I discovered myself conscious of the stress close to my temples. It’s not a deal breaker — I’ve been via numerous cans the place this was true proper out of the field, however regularly lessened over time.

Curiously, Sennheiser has opted for a reasonably slim headband. It’s simply 30 millimeters at its widest level as in comparison with the extra inexpensive $200 Sennheiser HD 560S, which has a 45mm width. Will the 660S2’s narrower band stay as comfy as soon as that clamping power relaxes just a little? It’s too quickly to say.

The metallic sliders have a fiercely notchy size adjustment, so there’s completely no concern that they’ll change as soon as you discover your measurement.

Top view of Sennheiser HD 660S2.
Simon Cohen / Digital Developments

The remainder of the design follows the model Sennheiser makes use of for its complete 600-series of headphones, with a minimalist strategy that stops simply in need of being utilitarian due to the shiny metallic mesh that protects the internals. It’s not solely practical — letting air transfer freely — however it’s additionally aesthetically pleasing, letting us glimpse the latticework that helps the 42mm dynamic drivers. My greatest critique is that Sennheiser’s solely nod to safety to your $600 funding is a nylon pouch. I do know that these headphones haven’t been designed with touring in thoughts, however the one factor that pouch will shield them from is mud.

Cables close-up of Sennheiser HD 660S2.
Simon Cohen / Digital Developments

Balanced or unbalanced?

One other characteristic the 660S2 share with their siblings is the removable, impartial left/proper cable system. Within the field is an unbalanced cable — the sort you’d use to plug into commonplace dwelling hi-fi tools (or a laptop computer/transportable participant with the included 3.5mm adapter). However in case you are a real fanatic, you’ll possible go for the second, “balanced” cable.

Balanced cables are solely appropriate with devoted headphone amps, or combo digital-to-analog (DAC)/amps that even have a balanced output.

Why “balanced?” The speculation is that indicators despatched alongside balanced cables are inherently much less vulnerable to interference we would be capable to detect as audible noise. I gained’t get into all the technical particulars, however suffice it to say that there’s a good quantity of debate as as to if balanced cables — on the very quick, 6-foot lengths Sennheiser has offered — make any distinction in any respect. I’ve two DAC/amps which might be outfitted with each 4.4mm balanced and three.5mm unbalanced outputs (an Ifi GoBar and a Questyle M15), and I’d be mendacity if I mentioned I may hear a distinction between the 2 outputs.

It’s price noting, particularly if you happen to’re new to the world of audiophile-grade gear, that these headphones have a 300-ohm impedance, which implies that despite the fact that you can plug them into a traditional headphone jack in your pc, you shouldn’t do this. You’ll nonetheless hear sound, however you’ll possible conclude that I’m loopy and that these cans aren’t something particular. As a way to carry out at their greatest, high-impedance drivers require extra amplification energy than common wired cans or earbuds. Belief me, even a budget-friendly DAC/amp goes to go a good distance towards making these cans hum.

Side view of Sennheiser HD 660S2.
Simon Cohen / Digital Developments

Easy sound

Nonetheless, what I did hear blew me away. I’ve loved the sound of the Sennheiser HD 560S, with their spectacular precision, readability, and ever-so-slightly heat EQ, however as I mentioned within the introduction, they nonetheless felt much less immersive than the closed-back cans I’d been utilizing. However going from the HD 560S to the HD 660S2 is like opening a door that you just didn’t even know was between you and your music.

In a phrase, the sound is easy. It simply springs forth and gently bathes you in its element, as an alternative of pummeling you, which I now acknowledge as a potential aspect impact of closed-back headphones.

I’ve lately developed a passion for blues guitar, which has prompted an exploration of artists like B.B. King and Stevie Ray Vaughan. Listening to a monitor like Vaughn’s Tin Pan Alley on the HD 660S2 is wonderful. The entire devices, from the deep thrumming bass to the lilting, shimmering highs produced by Vaughan’s guitar work to all the percussive hits — every is superbly rendered.

I used to be thrilled to find that deep, resonant bass — the a part of the listening expertise that I’ve at all times discovered missing with open-backs — is each bit as current on these cans as I had hoped for. Sure, audiophiles, go forward and say it. You advised me so.

Man wearing Sennheiser HD 660S2.
Simon Cohen / Digital Developments

Open-back cans, with their inherently open and ethereal high quality, ought to aid you hear nuances within the soundstage, and this undoubtedly proved true with the HD 660S2. The tracks from the Cowboy Junkies Trinity Periods recordings possess a novel sound due to the place they have been recorded. Faint echoes could be heard as one dies away earlier than the subsequent one hits, lending the songs a barely ethereal high quality, whereas on the similar time serving to to position you in the identical house because the band. I’ve heard it many instances, however the 660S2 made it sound much more pure.

Better of all, for me not less than, nothing felt prefer it was lacking. Fairly the alternative, in reality. I’ve been having fun with many moments the place a favourite track reveals a element that had been laying dormant for years and even many years.

Clearly, I used to be flawed about open-back headphones. However in my protection, I’ve by no means listened to a set just like the Sennheiser HD 660S2 earlier than. Now that I’ve, there’s no going (closed) again.

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