Sennheiser HD 660 S: A classic headphone, reimagined

Going by Hollywood’s release schedule, remaking old films is big business; forget novelty, it’s about reinventing and reimagining the classics for a new generation. It’s an approach that doesn’t seem out of place with classic hi-fi, either, as that’s exactly what Sennheiser has done with its latest headphones, the HD 660 S.

Sennheiser HD 660 S review: What you need to know

Taking the design DNA of its classic, open-backed trio of headphones – the legendary HD 580 Precision, HD 600 and HD 650 – Sennheiser is reanimating the old generation by using the latest driver technology.

While it looks similar to the older model, the HD 660 S is a completely different beast. The HD 660 S adds meat to the midrange and low frequencies while attempting to retain the beautifully detailed, natural-sounding balance of its predecessors.

Sennheiser has also made the HD 660 S a mite less demanding of partnering amplification, so you can feasibly connect and listen from a phone or laptop – as long as the people around you don’t mind the music floating freely through the open-backed earcups. Venture outside, and the HD 660 S is a decidedly anti-social choice.

As ever, though, this is the calibre of headphones that deserve the best partnering equipment you can lay your hands on – if you have a good-quality DAC and headphone amp, your ears will thank you for it.

Sennheiser HD 660 S review: Price and competition

The Sennheiser HD 660 S costs around £430 and at that price, there’s plenty of competition. Audeze’s recently released LCD-2C (£599) provide the kind of brutal bass slam and detailed midrange that only planar magnetic drivers can provide but they’re a little less delicate in the treble frequencies than the HD660S.

If you’re feeling particularly flush but prefer a closed-back headphone for use outside your home, then the B&W P9 Signature (£699) provide a more bombastic presentation that lies somewhere between the two.

If the idea of being tethered to your playback device doesn’t appeal, and you’d prefer a closed back design that you can use out and about, then there’s only one logical choice. The closed-back £499 Audio Technica DSR9BT. These might not have active noise cancellation, but they’re the best-sounding Bluetooth headphones money can buy.

Sennheiser HD660S review: Features and design

Sennheiser has eschewed the design flourishes of previous models in favour of an understated all-black design. The plastic headband and earcups are held together with a wide metal band, the velour-effect earpads are twinned with a pair of soft pads in the headband, and the earpieces are covered with a plain black metal mesh. The only visual accents are the subtle silver Sennheiser logos on the headband and ear cups.

Delve into the box and you’ll find two cables. Both are 3 metres long but one has a standard stereo 6.3mm stereo TRS jack and the other a 4.4mm balanced Pentaconn connector. There’s also a small 6.3mm to 3.5mm adapter cable, so you can connect to laptops, phones or more pocket-sized DACs.

The 4.4mm cable is likely to spend most of its time in the box: apart from Sennheiser’s own HDV 820 headphone amp/DAC and a vanishingly small number of other devices, this connection standard has yet to hit the mainstream.

The HD 660 S are a comfy headphone. The soft velour earpieces sit easily around even relatively large ears, and there’s enough padding to stop things getting uncomfortable over longer listening sessions. The metal headband does perhaps clamp the earpieces a little too firmly around the head, but we found that eased off over the month or so we spent with them. And if it does feel too tight, there is an easy fix: you can tease it a little wider by clamping it over a pile of books overnight.

Sennheiser HD 660 S review: Sound quality

I spent weeks feeding the HD 660 S with a hugely varied playlist stretching from Bjork to Wagner, and Ed Rush to Fleetwood Mac, and across everything from vinyl to CD to hi-def audio via Tidal’s excellent streaming service. I also used them in tandem with a range of kit including a Chord Mojo, TC Electronics BMC-2 and a Naim Uniti Atom.

I’ve had a pair of HD 580 Precisions for around 25 years now, which are widely considered to be a very slightly inferior cousin to the HD 600 and HD 650. If, like me, you were expecting a subtle change in sound between these original models and the HD 660 S, then you’re in for a surprise – the difference is dramatic.

Where my two-decade old HD 580 Precisions sound lean and detailed, if slightly distant, the HD 660 S bring the music far closer. The bass still rolls off steeply below 40hz, but there’s now enough control and depth to do justice to bassy dance and electronica without resorting to bumping up the bass with EQ, and the mid-range has dramatically more meat on its bones. The treble remains smooth and delicate, even if it does seem more recessed as a result, and the overall sound signature is remarkably likeable across a wide range of musical genres.

One huge area of improvement is the sense of soundstaging. Where the HD580 Precision tend to lump instruments left or right, the HD 660 S do a much better job of spreading vocals and instruments across the stereo image. Fire up a good recording, and the difference is night and day between the two headphones.

And where several of my more aggressively noisy test staples – Metz’s Strange Peace album, for one – become strident and wearing on the HD 580 Precision, the HD 660 S’ more forward mid-range and tighter bass make it possible to listen to the entire album from start to finish without reaching for a pair of earplugs. There’s enough clarity to separate the rolling waves of guitar distortion and clattering drums, and even the brash, overdriven drum and bass of Current Value’s Bigger Picture manages to bounce along excitedly without ever veering too far into harshness.

There is room for improvement, however. While the HD 660 S warmer, more meaty sound works wonders with a lot of material, I couldn’t help shake a feeling that something wasn’t quite right in the treble department.

Whether it was Fritz Reiner and the Chicago Symphony’s rendition of Stravinsky’s Scheherezade, or Solti’s masterful take on Wagner’s Der Ring des Nibelungen, the HD 660 S’ restrained upper registers tend to dull the sense or air and space around instruments and voices. Where the HD 580 Precision give a wonderful sense of the air moving across the concert hall, and reveal the details of musicians breathing, turning score pages, or the audience shuffling in their seats, the HD 660 S’s smoothness pushes those details a little too far into the background.

Turn to musical genres which are propelled by bass and rhythm, such as techno, funk or jazz, however, and the HD 660 S’ talents are impossible to ignore. It’s here that the extra meat down low and the warmer midrange do a far better job of driving the music without feeling overly lightweight or clinical. Cue up Maurizio’s M4, or Appleblim and Peverelist’s Circling, for instance, and where the driving sub-bass retreats to the background on the HD580 Precision, the HD 660 S whip up a head-nodding barrage with zero effort.

Sennheiser HD 660 S review: Verdict

If you view the Sennheiser HD 660 S in isolation, then there’s much to recommend them. They sound great with a wide range of music, and with the right tracks, utterly fantastic. If you’re looking for an open-backed headphone which can turn its hand to the most eclectic of musical tastes, and which doesn’t resolutely demand the best DACs or headphone amps that money can buy, then this is a headphone which should certainly be on your wishlist.

What the HD 660 S is not, however, is a turbo-charged HD600 – it’s just far, far too different in my opinion. I found myself regularly flitting between my HD 580 Precision and the HD 660 S, and ended up preferring each for different recordings – my HD 580 for classical, well-recorded 70s rock and acoustic material, and the HD 660 S for noise rock, electronica, jazz or techno.

Just like one of the great Hollywood remakes, the HD 660 S has tried to improve on near perfection, and to its credit it has almost succeeded – but as ever, some people will just always prefer the original.