These decidedly superior open-backed home headphones from the German canmeisters get the full and large hard case treatment, the all-encompassing blackness of the HD 660 S
design nestling into black foam in a presentation which says ‘Welcome to an audiophile headphone’. This elicited an immediate ‘ahh’ from a visiting headphone fan, who remarked that his mate from the pro sound industry had recommended Sennheiser as a brand that was always “a good bet at whatever price”.

And that’s exactly right — Sennheiser has all the advantages of scale, experience, accumulated research and technologies, to deliver value at every level. And when it does choose to put funds towards style or specialty application, there’s still a reassurance of what seems to be a top-down philosophy that sound comes first.

Sound is visibly first with the HD 660 S. Through the hex-grille of the headshells the rear of its newly developed driver is visible; this uses a specially manufactured precision stainless steel fabric adapted to the contour of the diaphragm, backed by “extremely light” aluminium voice coils.

It’s a great look, with the architecture moving outward from the driver frame to the elipses of the outer frame, the headshell and the surrounding support of a full-body yoke within which the headshells centrally pivot, allowing the velour cushions to find a soft but firm position around your ears. They are indeed light, just 260g not counting the cables, of which you have the choice from a full-size 6.35mm plug or a 4.4mm Pentaconn balanced stereo plug. A jack-to-minijack adaptor cable is also included.

If the headphones themselves are light, their sound is anything but, and they proved able to deliver tunes both old and new as if piped fresh from the studio. Archie Bell & the Drells recorded Here I Go Again in 1969, but a CD resissue of a ping-pong stereo mix had the Sennheisers driving an impactful and distortion-free drum kit into our head at reference levels, perfectly differentiated from the vocal treatment, strings, brass and soul guitar — this was an absolute resurrection of a performance. Remaining free of distortion at high levels is the great achievement of the HD 660 S, in addition to its dynamic and accurate delivery. It places everything in the right place with cleanliness and openness — this is a open headphone that really reminds you of the benefits brought by removing that reflective closed-back — music feels effortless and free, and entirely non-tiring.

While accurate and well-balanced, bass fans will love what these headphones can do with a big of meat downstairs. Black Harmony’s 1979 Don’t Let It Go To Your Head is well-laden with a dub reggae bassline that is strong but can muffle on ill-defined systems; the Sennheisers were just the thing to deliver pumping depths to the head while keeping the crisp vocal lead and harmonies clear above the throb — so revealing, indeed, that we could hear the stereo spread of the reverb acoustic, with the mids left and the highs right. There’s detail for you.

Yet follow this with a far lighter mix of Blondie’s Just Go Away and nothing sounds bereft — snappy snare, solos over jangling left-channel guitar, Ms Deborah central and strong. Everything sounded delightfully real — the gentle vocal style of Genesis’ In The Rapids, the complexities and effects and crisp harmonic-edged Clapton guitar on Roger Waters’ ‘The Pros & Cons of Hitchhiking’… so fine this latter sounded that despite review deadlines we drifted through the whole dream-scape of this first solo adventure.

Classical and jazz fans are fabulously served by this accuracy and detail. And all with longterm comfort. And when we played the soundtrack to ‘The Mission’ it was thrilling; the opening Ave Maria Guarani, although slightly peaky if too loud, was imaged so accurately every voice could be distinguished, while the orchestral The Falls and Gabriel’s Oboe were presented at the very peak of their magnificence. Again we had to listen to the entire album.

Because as often happens with the finest headphones, they encourage music listening through the ongoing delivery of their aural delights. From many a brand, these headphones would be over a thousand bucks. Once again, Sennheiser delivers value as well as quality in the
HD 660 S. Even with the review finished and other headphones in waiting, we held back from packing up the HD 660 S. Just one more album…

Sennheiser HD 660 S
Price: $799.95

Type: open, over-ear, dynamic
Impedance: 150 ohms
Sensitivity: 104dBSPL
Weight: 260g