Sennheiser HiRes Audiophile Headphone (HD 660 S)

Product Information

And where several of my more aggressively noisy test staples – Metz’s Strange Peace album, for one – become strident and wearing on the HD 580 Precision, the HD 660 S’ more forward mid-range and tighter bass make it possible to listen to the entire album from start to finish without reaching for a pair of earplugs. There’s enough clarity to separate the rolling waves of guitar distortion and clattering drums, and even the brash, overdriven drum and bass of Current Value’s Bigger Picture manages to bounce along excitedly without ever veering too far into harshness. The fit and comfort depends a little on how much time you give them. Out of the box, HD660S is quite tight and their fit is quite tight on the head, and while this might mean that they won't be fully comfortable for any head, it also means that they are pretty secured in place, you can bang your head quite a bit without them falling off your head, and you can do quite a bit of movement without fear that they'll fall. It is a known fact that HD6XX series headphones become quite a bit more comfortable with some wear, and we are able to confirm this, after wearing them for a few weeks they can get so comfortable that you may forget they are on your head. The earpad width is large enough for most ears, but it is quite a bit smaller than that of Amiron, for example, which is quite a bit larger. The earpad material, on the other hand, is really nice to the touch, pretty soft, but with a texture, allowing for an excellent overall comfort. In the long term this could induce listening fatigue, but even so, the timing is more correct and true to reality. The depth of the soundstage is pretty good. With my eyes closed, I can walk myself through the quality recordings. On well recorded material I could never hear the sound becoming too crowded.

Everybody shits on HD660S, I think its best sounding out of the box headphone I ever tried, I absolutely love that frequency response! The only problems with them is that the clamping force on the head is a little too strong, and they can sound a little "veiled" or distant in the lower presence region around 800Hz to 1500Hz—the HD 650 a bit more so than the HD600. Some will say the HD 650 has more mid-bass bloom, which it does, but it amounts to the same thing relatively speaking.The HD 660 S has been created to enjoy music in supreme quality and from many different audio sources. Thanks to its low impedance it also offers reference-class fidelity with hi-res mobile players. Naturally, the HD 660 S reveals its full potential when it is connected to the balanced outputs of a dedicated headphone amplifier such as the HDV 820 or to the balanced output of a mobile digital audio player. Accordingly, it comes with a choice of cables for just about any occasion. All cables are made of highly conductive OFC copper, featuring very low handling noise and sturdy para-aramid reinforcement. I begin to understand this new headphone. As before, compared to the HD600, the HD660S is the one that sounds with the most powerful frequency extremes, fuller and cleaner. There is a somehow attenuated mid-high frequency area compared to the 600, balanced by a rise slightly above it. This contributes to the feeling of a cleaner sound, but in direct comparison the voices seem timbrically a bit "muted". But if one get used to the 660S' sound, it seems that maybe the 660S is right, while the 600 emphasizes some harmonic components perhaps a little more than the necessary (but very pleasantly). Nevertheless, some chorus lines seem slightly better outlined with the 600, while on the other hand the 660S has better positioning of the orchestra and chorus sections. Overall the 600 seems timbrically more "phoney" sounding than the 660S. 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. The HD660S has the sound of an headphone of the 600 series. We are far from the 700 and 800 sound landscapes, and comparison with these two headphones can basically be reported to what was written about the 600/650. Instead I will stress the differences between 660S and 600.

The midrange of HD660S is quite clear, well expressed and natural. In fact, this has been something quite noticeable about Sennheiser headphones in general, and especially of this series, but they manage to get a really true-to-life tone for their midrange, thing which is quite lovely for any kind of music you'll be playing from them. Rich is a good way to talk about the midrange of HD660S, and even if you prefer a presentation that is slightly different, trying HD660S at least once might open your eyes to a new signature. The HD 650 and HD 600 have always been categorized as being more musical than the other models and this has been achieved through the good reproduction of the midrange. Listening to Infected Mushroom – Return to the Sauce I can sincerely attest that it’s an extraordinary experience!Maybe if you like a more lazy, relaxed and less dynamic sound with less detail, then yes, the HD 650 can bring exactly this to the table. So they didn’t improve the build quality of the HD660 S over that of its predecessor so how about its comfort? Ummm, depends on what you like really. Where as the HD650 felt like “sand conforming to your hand” as I said in my HD650 review, the HD660 S is like the bear hug a relative gives you after not seeing you in a really long time. It’s not that it hurts, but it’s quite tight, and as a personal opinion, it’s way too much so for my preference so I PERSONALLY (so do at YOUR OWN RISK) bent the metal band on each side of the ear pads just slightly and it made it, to me, considerably better. 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. In the treble range, the headphones deliver transparency and detail resolution that gives the sound a brilliant that can only really be found in the high-end price range. Percussive details or small echoes you’ve not heard before can be discovered with glee here. In addition, the HD 660 S certainly shows the limits of a production. Room, Dynamics, Levels Sennheiser has been around since like forever and they’re one of the most respected companies in audio. In the past, Sennheiser has impressed us with a lot of top-quality products like the HD800, the HD 800S and many 5XX and 6xx series headphones. Sennheiser has also upped their IEM game and they have successfully launched the IE 200, IE 300, IE 600 and IE 900 inear monitors.

Fresh out of the box, the clamping force of the headphones is a bit stronger, but most probably in time it will loosen at the level of the HD 600/HD 650. Anyway, what is really important is that sonically HD 660S is quite different from the HD 700, which for me is a good thing. Disclaimer: The Sennheiser HD 660S2 was sent to us by the local Sennheiser press agency in exchange for this review. Sennheiser is not related to Headfonia in any way. There’s little-to-no sound isolation here, so don't take these headphones with you on your commute. (Image credit: Future/TechRadar/Henry St Leger) Sennheiser HD-660S2 review: Price & release date 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.

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. Sennheiser would have you believe that you can just go and run the HD 660 S straight from a smartphone. While it’s twice as easy to power this headphone it’s a bit of a stretch to use a smartphone directly. I tried it and the sound did play out but I found myself pushing the volume all the way up and needed more. So do yourself a favor and always use an amplifier with the HD 660 S. Final Analysis 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.