Sennheiser HD 660S2 Review

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Sources / Amplification

For this section I have selected a set of popular tube amps, solid state amps and higher-end portable sources.

First up is the new EarMen ST-Amp, and it’s been used as a DAC/AMP combo. The HD 660S2 here sounds musically neutral. There’s a good amount of body but never too much. The S2 sounds controlled, powerful, and precise. The ST-Amp is a little to the warmer side but that’s perfectly ok for the pairing with the HD 660 S2. The vocals are a little more to the front in this combo, but it makes the whole engaging. The left-right balance and stereo imaging here is excellent, as well as the dynamics. It’s not the best technical performance (intimate and less spacious, less extension), but a very musical one.

Connected to the Ferrum OOR amplifier (with the Hypsos PSU) with the Musician Audio Aquarius as DAC, the HD 660S2 sounds very wide and spacious. You get a more neutral presentation with lighter body as with the ST-Amp (especially in the bass region), but you also get improved speed, better extension, and a higher clarity. The presentation here is more forward with some more aggression, but it’s al perfectly under control. It’s a technically strong combo with excellent positioning and a high level of musicality.

Switching to tube amps, the HD 660 S2 and the new Auris Audio HA2-SE+ combo (fed by the Aquarius DAC) sounds smoother and warmer. The tube presence is clearly noticeably here, but it never becomes an overly warm or dark type of sound. You get excellent dynamics, a good amount of body, nice extension and sparkliness up top. The dynamics and detail retrieval here are good, but it’s the combo doesn’t sound as fast, precise and extended as the OOR combo does. In exchange you get the tube flavour, smoothness, and softer vocals.

With the Feliks Audio Euforia evo we reviewed just 2 weeks ago, the HD 600S2 sounds even better. It reaches a higher technical level without losing anything of the OTL tube goodness the evo has to offer. The vocals here are softer than in the HA2-SE+ but the overall speed and technical level are better. Think improved extension, decay, precision, spaciousness, and width. If you like a high technical level but also desire tube smoothness, then this is a very good combo for you.

Switching to portable device, the latest addition to the DAP line-up is from Cayin Audio, and it’s their N7. I prefer the HD 660S2 on medium gain with the Class A amplification circuit. This way you get controlled body, excellent dynamics, and a high level of precision. The HD 660S2 is a little slower sounding from the N7, but it has more than enough power to drive it. For me personally I would love to have a cleaner presentation and tighter bass. The combo is engaging and musical, but it isn’t as precise, tight, fast, and refined as with a desktop amplifier.

With the Astell&Kern SP3000 DAP there is more energy and focus. The delivery is tighter and faster, and the vocals are more realistic, and positioned somewhat more to the front. The amount of body is good, and bass comes in with a tight punch. The mids are spacious and airy, the treble section lively and extended. This is one of the best portable sources I tried the HD 660S2 with. You get excellent precision, the warmth and smoothness of the HD 660S2 and the control and dynamics of the SP3000.

With the Chord Electronics MOJO 2 DAC/AMP, I used a 3.5mm convertor and fed it with my laptop & ROON. The clarity and speed are good here and the Mojo 2 is fully in control. You get a more neutral amount of body, but the delivery is tight. The energy levels are excellent with this combo, but it isn’t the most refined and extended even if the stereo imaging id spot on. I use the Mojo 2 when I am working at my day job and I use the HD 660S2 with it all the time, but I do have to admit it’s not the very best combo. The HD 660S2 can sound even better but don’t get me wring. This combo sounds more than just ok.

While the HD 660S2 plays more than just nice with solid state amps, I personally feel the HD 600S2 offers that something extra when connected to an OTL tube amp. That shouldn’t come as a surprise however, as this has been said many times already when Sennheiser’s (or other brand) high impedance headphones are discussed.

From portable devices the HD 660S2 doesn’t always perform up to level, and I really recommend a quality source and amplifier to hook the HD 660S2 up to. If you insist on using a portable player, my recommendation for the SP3000 is an easy one.

 Conclusion

In very short we can say the HD 660S2 is a great headphone with an excellent price/quality ratio.

Where the Sennheiser HD 660S was good, it to me never was the headphone that could make me completely forget about the HD 600 and HD 650. That’s exactly what’s different with this new S2 update. This time I do feel that people in 10 years’ time will still be talking about the HD 660S2, just like they did with the HD 650 and HD 600. The original HD 660S did not get our recommended buy award, but I feel the sound quality has improved in every possible way here. As such it is getting our Recommended Buy Award this time, and the HD 660S2 now is featured on our Best Headphone list.

Pro

–          Accessories

–          Comfort

–          Sound quality

–          Dynamics

–          Bass performance

–          Top end sparkle

–          Musicality

Con

–          Packaging

–          Desktop amplification recommended for best performance

Page 1: Sennheiser, HD 660 S2, Specifications, Box & Accessories

Page 2: Design, Build Quality, Comfort, Sound pt. 1

Page 3: Sound pt. 2, Comparisons

Page 4: Synergy, Conclusion