Sennheiser HiRes Audiophile Headphone (HD 660 S)

Product Information

We up the pace with Bruce Springsteen’s Dancing In The Dark and the Sennheisers continue with their smooth, refined delivery. There isn’t a hard or harsh edge in sight and the headphones show rhythm, flow and swagger. There is a good sense of space around the different elements which allows you to dip in and out, focusing on one or just listening to the sum of all the various parts. They really are an easy, uncomplicated listen.

How close is the guitar with the 660S! It's exciting but there's less sense of distance of the stage. Nevertheless, the timbre of the strings are exciting, albeit slightly resonant on the lower end, while the 600 has a more "acid" sound. The reverb of the recording venue is more evident in the 660s.The HD 660 S easily reproduces the entire audible frequency range, from true low bass levels to well above 20 kHz. It features impressive levels of detail resolution and balance, making it a go-to choice for hi-res sound sources of any genre. When it comes to sound density, all 3 models are effortless. The sensation of a meaty sound, full of substance and density is best present on the HD 650 and HD 660 S. 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. The DT880 initially comes across as the most detailed of the three because of its brightness and more aggressive presentation. Upon closer listening, it maintains a slight edge over either Senn in detail retrieval in the bass and the treble. The 6XX and the 660s are slightly more detailed in the midrange than the DT880. The 6XX probably is the one with more resolution in the mids, and the 660s is the one that’s smoother and more forgiving. Both of these qualities have advantages in certain situations.

Now, the sound signature I personally favor is a relaxing, warm and sensual sound that just drifts me away in the emotional experience of the music being performed. Yes, accuracy is still important but I will happily sacrifice some of that if I'm presented with a clean, warm sound that can wisp me away into an experience that makes me yearn for more.Now with enhanced bass depth, the fan-favourite Sennheiser HD 660S2 headphones have a more impressive all-round sound than ever. Renowned for their neutrality and musical delivery, Sennheiser’s HD 660 headphones have a cult following. Now in S2 form, the updated model features lighter voice coils and improved airflow, helping to enhance the bass response. Dropping from 110Hz to 70Hz, the bottom end now has noticeably more impact, without spoiling the headphone’s legendary sonic precision. Even though the majority of the HD 650 users might say that it excels in the bass department, I am of a different opinion.

As expected from an HD 600-series Sennheiser, the mids on the HD 660S are simply spectacular. In terms of frequency response, they are simply perfect to my taste. The upper midrange on the HD 6XX and HD 58X came across as a little forward or shouty, as they had a little extra energy at around 3k-3.5k, but this was not the case at all for me on the HD 660S; I found its upper midrange to be very smooth. The timbre on this headphone’s mids is–again, like the other headphones in the series–spot on and very natural sounding. For detail retrieval and resolution in the midrange, I thought that these performed great as well. From my listening, I personally found them to be an upgrade over its predecessors as well as a little more resolving than the LCD-1, Sundara and DT 1990 Pro in the mids.Many critical listeners demand a neutral sound from high-end cans, and the somewhat tame bass performance oftheHD 660 S2’s predecessors was a common gripe. As stated before, the 660s has a very mild and somewhat rolled-off-at-either-end v-signature. The 6XX has a neutral-warm signature that is also somewhat rolled-off with mediocre extension both high and low. The DT880 is neutral-bright with excellent bass and treble extension but also somewhat lean bass. The amount of treble in the 660s is between the 6XX and DT880, but closer to the 6XX than the 880. The 660s and DT880 are quite similar in midrange quantity. The 6XX and 660s have similar amounts of midbass, being slightly more than the DT880, but the DT880 has the extension advantage and more subbass presence overall, despite it being somewhat lean in the lows (at least compared to its treble). I think the DT880 also has more bass punch/slam. It’s more dynamic. I wouldn’t say it has great punch/slam because of the lean-ness of its bass, but it is overall more energetic and aggressive throughout the frequency range than either Senn. In my opinion, the HD 660 S is the true reference in the HD 6xx line, with the HD 600 coming second and the HD 650 coming last, with a more colored sound. The HD 660 S features a new transducer design developed by Sennheiser. This results in improved control of the diaphragm movements thanks to a specially manufactured precision stainless steel fabric, which is adapted to the contour of the diaphragm. Extremely light aluminum voice coils ensure the highest impulse fidelity. The transducers are carefully selected and paired by hand to ensure consistently narrow (±1 dB) tolerances.

Interestingly, despite the fact that I don’t feel the notes flying a few meters from me, I can clearly hear the angle at which they are emitted, a good sign that the holography is in effect. My interests/hobbies are fishing and relaxing to audio products and reviewing them to help other decide on what products would work for them. Few things make me as an audio enthusiast/reviewer feel more accomplished than when someone tells me that I helped them find the type of sound they've always been looking for.

Build Quality and Comfort

For now it's sufficient to state that the Sennheiser HD 600 and HD 650 are probably the most highly regarded enthusiast headphone in the world, and I highly recommend both. The HD 650 is a bit too warm sounding for me (just a bit), and the HD 600 is my favorite of the two. Hm. Well they sort of state that it's a new design, but I'm betting that's a bit of poetic license—the HD 700 is a relatively new design. Thing is, impedance and phase measurements are almost identical. This problem is no longer present on the HD 660S and this is probably one of the best improvements of the new model. The specs of the HD 660 S brag a SPL top-end of 104dB and a less than 0.04% distortion using 1kHz at 100dB. These controlled sound tests are certainly reasonable bench test but I like to just get down to the real deal and run the “Butch Vig SPL test” with some Nirvana. The HD 660 S performed quite well. Even at intense levels, this headphone remained tight and unflappable. It was only at the very top end that I could hear a little bit of distortion. Soundstage