There aren’t many headphones with as much heritage and history as the Sennheiser HD 600. The fact that you can still waltz over to the Sennheiser website and buy a pair, despite the model being over twenty years old, just goes to show that they’re still a respected icon and part of the furniture in the headphone market.
A number of new versions have been launched over the years, including the HD 650 and HD 660, not to mention the very latest version we’re testing here; the Sennheiser HD 660S2.
Price
The Sennheiser HD 660S2 costs £499 ($599 / AU$849), so this puts them in the premium wired headphone category. Their most natural rival would be the Beyerdynamic Amiron (£545), although prices are quite spread out at this level and you can pick up excellent options if you spend a little more, if not a little less. It really depends on your budget.
Design & build
Anyone familiar with this series of audiophile headphones knows the formula here. The Sennheiser HD 660S2 features an open-back over-ear design, with this model featuring a 38mm driver complete with an ultra-light aluminum voice coil.
Look through the perforated grille that covers the outer part of the headphones and you can see part of the inside behind the driver. The HD 660S2 uses a vented magnet system to minimize distortion – Sennheiser has put a lot of thought into the system used on these particular headphones to optimize the way air flows around the drive unit.
On the earbuds themselves, you’ll find plush, generous velor ear cushions that sit comfortably on your ears – it’s like slipping your feet into a pair of chic (and very comfortable) slippers. In testing, the Sennheisers don’t struggle to encase our ears and create a firm seal. Along the headband, the padding isn’t quite as generous, but it’s soft and springy so you don’t feel any unwanted pressure on the top of your head.
Sennheiser HD 660S2 technical specifications
Type Open back, wired
Director 38mm
Sensitivity 104dB
Impedance 300 ohms
Weight 260g
Cable length 1.8m (x2)
Cable type 6.3mm (with 3.5mm adapter), 4.4mm balanced
At just 260g, the HD 660S2 aren’t exactly heavy (Beyerdynamic’s Amiron headphones are 340g) and they didn’t weigh us down during testing. Out of the box it’s worth noting that the clamp weight is a little on the firm side, but there’s not too much pressure and over time we expect this to relax a bit.
To evenly position the earbuds you’ll need to manipulate the left and right sliders – they’re a little stiff, but once you’ve got them in the right place, you’re unlikely to fiddle with the positioning.
In the box you get a 6ft headphone cable with a 6.3mm connector, a 6ft cable with a 4.4mm jack and a 6.3mm to 3.5mm adapter.
As you can probably tell from the design, the HD 660S2 isn’t intended for on-the-go listening – the farthest you’re likely to walk is from your amp to the seat in your listening room. The impedance is 300 ohms, indicating that they will perform at their best when connected to something with a bit more grunt than a typical smartphone or laptop. We conduct most of our testing with a Chord Mojo 2 DAC – starting with amplification around this level will help get the best out of the HD 660S2.
Sound
Anyone who wants sound out of their headphones beforehand may want to shop elsewhere. The Sennheisers present the music in a wonderfully relaxed way and take on every song. They’re ridiculously easy to listen to. Pair them with any genre of music and you can just sit back and let it flow through your ears.
The way the HD 606S2 handles the mid-range and tuning is a real highlight. The vocals sound super smooth and exude sophistication. Play A-Has MTV disconnected version of Bring it on at 24-bit/94kHz and the Sennheisers paint a beautifully intimate picture. Morten Harket’s soft tone is both captivating and gentle. The accompanying instruments such as guitar and piano are additional ingredients that contribute to this soothing interpretation.
We pick up the pace with Bruce Springsteen’s Dancing in the dark and the Sennheisers continue their smooth, refined delivery. There is no hard or rough edge to be seen and the headphones exude rhythm, flow and swagger. There’s a good sense of space around the different elements that allows you to pop in and out, focus on one or just listen to the sum of all the different parts. They really are an easy, straight forward listening experience.
However, play a more bass-heavy track, with more demanding dynamics, and the Sennheiser HD 660S2 starts to struggle a bit. Billie Eilish’s Bad guy requires tight, controlled and dynamic bass. And while the HD 66S2 can produce more than enough bass weight, it sounds mellow by the standards of rivals like the Beyerdynamic Amiron. There’s a lack of tightness and punch, which also stifles the song’s approachable dynamics. The best wired headphones at this level make those bass kicks more impactful.
And it’s the same story with Massive Attack’s Angel. The sense of spaciousness and sophistication is to be applauded, but it’s the low frequencies that really make this track and while the Sennheisers show quantitatively enough, it’s the quality that’s lacking. The HD 660S2 doesn’t really communicate the build-up of drama in the song. The best pairs are able to add more detail and texture.
Pronunciation
The Sennheiser HD 660S2 is a really easy, straight forward listener. If you’re a fan of acoustic or vocal tracks, you’ll love these over-ear headphones. Many will find the mid-range price alone worth the price of admission. It’s just a shame they’re lacking when it comes to dynamics and punch in the bass department. If they could tighten up their act in the lower frequencies, you’d probably be looking at five-star performers.
TO SCORE
MORE:
Read our review of the Beyerdynamic Amiron
Also consider the Shure SRH1540
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