Sennheiser HiRes Audiophile Headphone (HD 660 S)

Product Information

I would like to say that first and foremost I am NOT an “audiophile” but rather an audio enthusiast. I listen to music to enjoy it. Do I prefer a lossless source? Yes, of course. But I can still be very happy streaming from Pandora or even YouTube's “My Mix” playlist. I also prefer equipment that sounds the best to me personally regardless of what frequency response it has or rather or not it's “sonically accurate” and I always have and shall continue to encourage others to do the same. It should be noted that I have absolutely no affiliation with Sennheiser, I am not receiving any incentive for this review or to sweeten things out. This review is not sponsored nor has been paid for by Sennheiser or anyone else. I'd like to thank Sennheiser for providing the sample for this review. The sample was provided along with Sennheiser's request for an honest and unbiased review. This review will be as objective as it is humanly possible, and it reflects my personal experience with Sennheiser HD660S. Every opinion expressed is mine and I stand by it, the purpose of this review is to help those interested in Sennheiser HD660S find their next music companion. Comparing them directly to the AKG Q701 and the classic HiFiMAN HE-5 planar magnetic headphones, the HD 660 S display less soundstage width than the AKGs and less smooth mids than the planar HiFiMAN pair. However, the Sennheisers have more obvious energy and a less diffuse soundstage. Purists after the most balanced, neutral sound for their cash should perhaps look elsewhere. In this, and the following series of photos, the HD 600 is at left, the HD 650 at center, and the HD 660S is to the right.

The basic signature can be described as slightly dark compared to something fully neutral, but not overly so. It is warmer and more musical than something like HD600, it has more detail, more clarity, and it has better definition than HD650. It would be more of a headphone to satisfy both the users who love HD600 and those who love HD650, bringing forward the best of both worlds. During my time with them, post the slight bending, I had no issues with having them on my head and listening to them for several hours without any fatigue. They stayed firm in place regardless of my lying position and truthfully, I really enjoyed how they felt on my head (again post bending [which again I stress to do at your own risk]). Perhaps time will break these into the forming sand the HD650 is to me but even if it doesn’t, what’s so wrong with the loving brace of a relative who really misses you? The frequency range is expanded to 10Hz – 41kHz which is wider than the HD 650. One other notable feature promised by the HD 660 S is “crisp bass”. How’s The Build and Fit?I'm a 26 year old firefighter, for the City of Concord, North Carolina as well as the U.S. Army, North Carolina National Guard. The cliché of wanting to do this since I was born couldn't be more present with me. I've worked hard over the last several years to earn this position and now it's time for me to work even harder to keep it. The comfort while being worn for long periods of time is very good, and with HD660S, you can walk and even to some heavier exercise without damaging them, or without feeling any fatigue, and it surely is possible to wear them for prolonged periods of time without much issue, but you should mind the cable, which is quite long. There are no microphonics, and no other issues we were able to notice, but HD660S does not isolate from the outside noise (at all), and most music being played through them will also be heard outside, so they are quite open in this aspect. It’s easy to confuse clear and well defined highs with sibilant highs – one of the biggest mistakes that I see coming from some online publications. Some consider the HD 660 S to be sibilant but I tend to differ completely, I consider it having clean highs, without highlighted extremities. 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. Starting with the build quality, HD660S is quite sturdy. One thing that really feels different when switching from Audeze LCD-MX4 to HD660S is the weight, HD660S is incredibly light, and even in comparison to something lighter, like Ultrasone Signature DXP / Signature Studio, they still feel quite a bit lighter.

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. As before, the HD 660S2 headphones are designed for the critical listener. Hand selected speakers are carefully paired, giving these headphones the most consistent sound between channels. Precision, stainless steel fabric diaphragms deliver life-like realism for a true-to-life sound.The 660s is a fine-sounding headphone. I can listen to it and enjoy it for extended periods of time. Nonetheless, this sound section is a bit shorter than I often do because I think the big story with the 660s is found in the… I'll not wax poetic this time regarding the long and storied history and my experiences with the HD 6xx family of Sennheiser headphones. For that, simply go have a look at my " The Very Important Sennheiser HD 580, HD 600, and HD 650" review.