Sennheiser HD 660 S: Keeping It In The Family

22nd February 2018

The latest evolution in a highly successful line of headphone designs that began with the legendary HD 580, Paul Rigby reviews the new Sennhesier HD 660 S

According to Sennhesier, the open backed, dynamic HD 660 S headphones are made , “…for the demanding listener,” which certainly conjures pictures of furrowed brows and studious listening via serious audio applications. The end product actually promises to be rather fun, though. If the previous incarnation of this design, the HD 650 is anything to go by that is. Although the HD 650 design is one of the most successful and popular sets of headphones from the company, the 660 S should now be considered as the new cans on the block.

The HD 660 S features a lower 150 Ohm impedance and a new transducer design developed in-house. These changes promise to affect the control of the diaphragm movements which relates to specially manufactured precision stainless steel fabric, adapted to the contour of the diaphragm. Voice coils made from aluminium are featured too.

Packing elliptical ear cups, the 660 S package arrives with a choice of cables, made of OFC copper.

Presented with 6.35mm and 4.4 Pentaconn connectors with the 3.5mm adaptor and weighing 260g without the cable, the headphones take a firm yet comfortable grip of your head during use.


I began with Inbetweenies from Ian Dury’s album, Do It Yourself. I wanted to see how the headphones handled as a general purpose design, one that might be used for a range of niche uses. Some headphones only work at their best when faced with top quality support equipment. While the head amp fitted inside the Leema Quasar all-in-one is very good indeed, because the Leema was my first port of call, it is not a specialist external model. I wondered how the new 660 S headphones would handle this internal feature.

Firstly, I noticed that they were relatively easy to drive. Easier than the older 650 models, for example. Also, the general soundstage was open, airy and clean in nature with plenty of space to manoeuvre. This space allowed instruments to ‘stretch’ as it where. A bit like pulling a concertina outwards. That is, you could ‘see’ more of the middle bits of notes. There seemed to be more information coming from piano, secondary percussion (the cowbell was quite informative – too often it hides behind other instruments) and vocals while bass provided an organic foundation, giving bass a tonally more interesting and realistic aspect.

Also, this is a very well recorded yet still very busy soundstage with plenty going on and lots of opportunity for muddle, bass blooming and midrange smearing. I didn’t get any of these negative reactions here. Instead, the 660 S headphones offered admirable focus and precision and never threatened to lose control over the entire track.

I then moved to the Icon Audio HP8 MK.II to give the 660 S headphones freedom to show itself at its best. Listening to Barbra Streisand singing I Can See It from My Name is Barbra (1973).

Once more, the 660 S headphones showed the benefit of its broad soundstage. For many headphones, this track, in which Streisand fronts a large orchestra, has the orchestra sitting in a restricted position smack in the centre of the stereo image from whence it refuses to move, giving the impression that the song was recorded in mono. The 660 S opened up the entire soundstage and spread the orchestra instruments left and right with a sense of depth to add a further dimension. Because of this, the song was more of an occasion rather than a musical experiment in which Streisand appears to be peering at the orchestra from a far. The 660 S allowed the listener to be intimately involved with the music, pulling you into the soundstage itself, wrapping you up in the emotion of the performance.

I then turned to CD and Barclay James Harvest’s Child of the Universe from Everyone is Everybody Else (Polydor) in which I was impressed by the tight bass that hit with real impact. That’s not to say that it sounded plastic, generated or false in any way but there was a real precision in the lower frequencies that increased the apparent speed of the track as the bass was so fleet of foot.

On this firm foundation, the mids were detailed while never being bright or strident. In fact, there was an admirable insightful quality to the mids that prevented any sense of the bland or the dull. The 660 S always demanded the ear’s attention, alerting them to this and that detail highlight, whether that be the detail within a vocal harmony sequence or the fragility in the treble-soaked cymbals.


Anyone who has been brought up on the classic 650 headphones will be familiar with the basic approach of the 660 S models. The 660 S do move the sound quality up the ladder by a couple of rungs though in terms of detail and insight. The new 660 S phones can also successfully judge what detail to highlight and when. There’s a tremendous sense of midrange perception with this design. That is, you always feel that you’re getting a good, honest performance from the music your hearing. Some headphones can make you feel that the artist has turned up to fulfil a loathsome contract date. Not the 660 S, the performer always seems on top form. Mainly because the Sennheisers bring you into the action. Wholly involving, engaging and absorbing, the Sennheiser 660 S headphones will never let you down in a musical crisis. They are, in fact, the headphones version of Lassie. Dependable, responsive, speedy, full of enthusiasm and always able to tell you that Jimmy has fallen down the well (actually Sennheiser is still working on the last bit).


Price: £430



UK –




GOOD: midrange insight, bass impact, broad soundstage, easy to run, comfort 

BAD: nothing



Origin Live Sovereign turntable
Origin Live Enterprise 12″ arm
Transfiguration Proteus cartridge
Icon PS3 phono amplifier
Leema Quasar all-in-one system
Icon HP8 Mk.II headphone amplifier
Aesthetix Calypso pre-amp
Sennheiser HD 650 headphones
Vertex AQ & Tellurium Q cable
Blue Horizon Professional Rack System

Harmonic Resolution Systems Noise Reduction Components

All vinyl was cleaned using an Audio Desk’s Ultrasonic Pro Vinyl Cleaner