If you were to ask a random group of hi-fi buffs to name a brand of headphones, my money would be on most of them saying “Sennheiser” first. The venerable German company has been going strong since the Wirtschaftswunder of Germany’s post-war recovery. These days the company has restructured slightly and now licenses its consumer products to Sonova AG, one of the world’s biggest producers of hearing aids.
Sennheiser has kept its professional range of audio products in-house. However, even the brand’s premium wired headphones, like the HD660S2, now come under the Sonova AG umbrella. These are the first HD660 to be produced under the new licensing arrangement, so it will be interesting to see if the quality is as good as when Sennheiser was at the helm.
The HD660S2 headphones are the latest iteration of Sennheiser’s premium wired model designed for audiophiles. The headphones are an open-back design and cover the listener’s ears completely. The ear cushions are velour and comfortable as the soft material doesn’t make the ears sweat. Overall, the HD660S2 have a comfortable feel, although the clamping pressure is a little firm for my tastes, which will probably slacken off with wear.
The drivers used in the HD660S2 are Sennheiser’s own 38mm design that has a super-light aluminum voice coil. With an impedance of 300Ω, these headphones are best suited to a grown-up hi-fi system rather than an iPhone. The 38mm drivers have an exceptionally wide frequency response, ranging from 8Hz to 41kHz and are well-vented to allow air to flow freely. The downside of open-back headphones is you can hear every sound in the room you’re using them in.
By design, open-back headphones also leak like a sieve and the sound wafting from them is sure to annoy anyone in the room with you, unlike closed-back headphones. Also, these are not headphones for use out of doors; they are for listening to your favorite music playing on your primary audio system while you relax in the armchair.
Weighing in at a relatively light 260g, the HD660S2 are comfortable enough to wear for long periods; although the headband is slightly sparse and could do with a little more padding, the downward pressure on the head isn’t excessive. All in all, these headphones score a healthy 4 out of 5 for comfort.
Adjusting the headphones is fiddly as the thin metal expanding bands feel quite stiff. The adjustment could be a little more elegant for such a premium pair of headphones, but I checked the first-generation HD660S and they are very similar, so there haven’t been any corners cut. If the HD660S2 were a car, they’d be more BMW than Rolls-Royce.
Supplied in the box with the headphones are two sets of 1.8m detachable cables. One has the usual 6.35mm TRS jack plug, while the other offers a Pentaconn 4.4mm connector. The plugs that clip into each of the driver housings are a bit stiff, but presumably, most people won’t be changing them too often, if at all. Also included in the box is a 6.35mm to 3.5mm adapter and the fact Sennheiser has opted to go with 6.35mm is a clue to the type of kit the company expects you to use when listening to these headphones.
Listening to the HD660S2 is a joyful experience. These aren’t the most exciting or dynamic headphones but are consistently smooth, musical and pleasurable. These headphones can draw you into the music, making you concentrate on the music rather than doing what so many hi-fi enthusiasts do, which is to listen to the equipment. I selected Paul Simon’s new album Seven Psalms for my listening test using TIDAL Masters. Rhymin’ Simon may be an octogenarian, but this latest outing is a real tour de force for the master and a real departure.
The sound of the recording is stunning and perfectly matches the laid-back and unhurried presentation of the HD660S2. Look elsewhere if you’re looking for a pair of “in yer face” headphones. However, if you want headphones that can cover the broadest range of musical genres and serve sound that soothes and caresses the ears, then the Sennheiser HD660S2 are the ones for you. While listening, I could almost feel my blood pressure and stress levels dropping as the music enveloped me.
The bass levels of the HD660S2 are spot on; not too heavy but articulated with a surefootedness that sounded so good. I was using a trusty little Onkyo CR-555 to test the headphones. It’s not an expensive kit, but it has an old-school Class AB amplifier and sounds far better than its price would suggest. The midrange on the HD660S2 is just perfect and brings out every nuance in the vocals. The treble is focused but never harsh or overbearing and must be due to the low distortion levels.
If you want to get up close and personal with the music, this is how to do it. If you want headphones more suited to techno or metal, then maybe the HD660S2 will sound a bit tame. These headphones are like a car with an automatic transmission and a walnut dashboard. They are pure class act but no sports car.
Verdict: The new Sennheiser HD660S2 are a fabulous pair of open-back headphones. They suit most genres of music and have a laid-back presentation that swaddles the listener with beautiful and silky sounds. Sennheiser is still the best at what it does and I don’t think I have ever been disappointed by a pair of Sennheiser headphones since I bought my first pair of HD400s in Germany in 1982. If you want a pair of headphones for solitary listening using proper hi-fi, these are the ones for you. If you want more energy and aggression from your headphones, look elsewhere. I’ll stick with the HD660S2. Highly recommended.
Pricing & Availability: The Sennheiser HD660S2 headphones are available now and cost $599 / £499 / €558.
More info: sennheiser-hearing.com
- Style: Open-back circumaural.
- Drivers: 38mm.
- Voice coil: Aluminum.
- Frequency response: 8Hz – 41.500Hz.
- Impedance: 300Ω.
- SPL: 104dB (1 V).
- THD: <0.04% (1kHz,100dB).
- Connectors: 6.3mm & 4.4mm.
- Weight: 260g.
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