Sennheiser HD 660 S - HiRes Audiophile Open Back Headphone

Product Description

Sennheiser's new HD 660 S is an open back, dynamic headphone designed for the passionate audiophile. Meticulously crafted for the most demanding listeners, the HD 660 S builds on the legacy of the legendary HD 650, surpassing the exceptional performance of its predecessor incorporating a new and improved transducer that delivers lower harmonic distortion producing a more natural, lifelike audio experience. It is exceptionally accurate and transparent, with an expressiveness that immerses the listener in every emotion and nuance of the music. Employing a lower 150 ohm impedance, and supplied with cables using balanced (4.4 mm Pentaconn) and 6.35 mm connectors, the HD 660 S offers connectivity versatility to provide reference class fidelity with stationary and mobile audio players alike.

Top Reviews

Amazing headphones, the best I've ever used
by Sam (5 out of 5 stars)
August 20, 2018

I bought these as well as the Beyerdynamic DT 1990 Pro to compare the two. The latter lost, easily.

The HD 660 S is incredible. No frequencies pop out like the Beyerdynamics (too harsh in the high end), everything is very even. Excellent in the mid-range for sure, unlike many headphones that try to push the higher frequencies to come across as "super pro." It's natural for our brains to go "ooh" when we hear bass, or crisp highs, but you don't want these things when judging a mix!

Bass is quite good (but not ear-rumbling), about as good as my Shure SRH1540's. If you want a good pair to judge bass and sub-bass, definitely grab the Audio-Technica ATH-M50x in addition to the HD 660 S, and prepare to be amazed-I've never heard such good subs in a pro level headphone. Don't get the ATH-M50x as your sole pair of headphones, they're problematic in the mids and mid-highs.

Some things to keep in mind with the HD 660 S:
- These are pro level open-back headphones meant for studio use, so you must be in a quiet environment to use them properly. Also, don't wear them in public because external noise will ruin it for you, and you'll annoy people around you because they'll be able to hear everything.
- Headphones sound a little better after a brief burn-in period (48-72 hrs). Plug them in, put them on your ears, and fire up some heavy rock or electronica at a volume that's loud, but not painful. Then remove the headphones and let them sit for a few days. This loosens up the material around the drivers. Some people think this is a myth, but some of the best mix engineers in Hollywood disagree.

In short: get these headphones, they're incredible!
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The Return of the King
by JasonCManley (5 out of 5 stars)
February 18, 2019

The predecessor to the Sennheiser HD 660 S (the HD 650) gained something of a reputation for being "The King" of Hi-fi headphones. Leading some reviewers and headphone enthusiasts to even refer to the HD 650 with that moniker

Sennheiser is one of the main pioneers of the headphone market. Their now "legendary" HD 600 line began, ironically, with the HD 580 Precision in 1991, followed by the HD 580 Jubilee in 1995, then the HD 600 in 1997. The HD 600 was the gold standard until the 2003/04 release of the afore-mentioned HD 650.

That brings us to the 2017/18 release of HD 660 S. The headphone industry has grown exponentially since the release of the HD 650; largely driven by listener habits. Listening to a digital library of files or streaming audio (via computer or smart phone) is the norm. That development has ushered in a number of headphone designs from makers both old and new. With so many options today, why buy into the Sennheiser HD 600 Series? Even more specifically: why buy the Sennheiser HD 660 S?

My personal experience with the HD 600 Series began last year with the purchase of the HD 6XX Massdrop x Sennheiser release (which is actually an HD 650 with a different paint job). I have also auditioned the HD 58X Jubilee (another Massdrop x Sennheiser collaboration). What prompted me to buy the HD 660 S was curiosity.

As it stands, the HD 660 S is Sennheiser's flagship Hi-fi headphone, under $1000 USD. Their HD 800 Series captures a different market share (the $1000-plus cohort). So, that leaves the HD 660 S as the company's current offering for those seeking performance with cost in mind.

Upon opening the package from Amazon, I was greeted by the handsome HD 660 S box and the phrase "The Legend Continues" at the forefront of the product photo. The headphone keepcase contains the headphones, two detachable cables (4.4 mm Pentaconn 'balanced' & 6.35 mm standard plug) along with the manual. It also has rather clunky adapter for stepping-down the 6.35 to a 3.5 mm input. My preference, when using 3.5 mm, would simply be to use one of my cables from the 6XX or 58X.

Design wise, the headphone is nothing if not sexy. The overall aesthetic remains unchanged from its predecessors. You might have difficulty telling them apart from the others at some appreciable distance. The new styling cues are what give the 660 S its upscale look. The paint job is now a matte black finish, giving it a more 'modern' look. The ear cups have a darkened look with the driver being easily visible still. The outer driver "cover" bears some resemblance to the HD 800 series. This design choice is seemingly on purpose to tie the headphone into the pricier brethren upstream.

The 'on head' experience is familiar to anyone that has owned any of the HD 600 series. If you haven't, the word I would use to describe the fit is "cozy". The ear cups are a little firm at first but they soften up very quickly with a few successive listening sessions. The comfort is the same, with or without glasses on. You'll occasionally read about the "clamping force" of the HD 600 series of headphones with a number of suggestions about how to mitigate said 'clamp'. In my opinion, just simply *wearing* the headphone is the best course of action. Novel concept, right?

The sound can best be described as "balanced" and "resolving". With no frequency sticking out more than the other. An age-old discussion among headphone aficionados with the HD 600 and HD 650 is whether or not the sound was 'veiled'. Having heard the HD 6XX (650), I can definitely say that the 650 is a laid back (some call it veiled) headphone. The difference between the 650 and 660 S is not night and day but more early morning and afternoon. Whereas I view the 650 to have a laid back and relaxed presentation; the 660 S is more forward with daylight while retaining most of the smoothness of the 650's.

Some controversy has arisen online (*imagine that*) that the Massdrop x Sennheiser 58X Jubilee collaboration is a $150 USD version of the 660 S. My admitedly anecdotal experience is that I found the 58X Jubilee a very pleasurable headphone to listen to and certainly a bargain for its listed price. And while I do hear similarities between the two, I can confidently say the 660 S is a superior headphone. The 58X Jubilee is very much a member of the HD 600 family of headphones in its presentation. However, I find the bass slightly boosted and the overall sound signature more "colored". The 660 S is a more resolving, "complete" listening experience, to my ears, full stop.

This line of headphones, designed by Axel Grell, are all classics in their own right. The newest entry, the 660 S, aims to take the throne as the successor of this very important headphone lineage. Its success will largely depend on your expectations. If you are looking for a great sounding, "neutralish", non-fatiguing, yet still very resolving and crisp open-back headphone experience under $500 USD - you'd likely be hard pressed to find something better.
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Amazing product from Sennheiser
by Kuhaku (5 out of 5 stars)
February 20, 2018

Amazing product from Sennheiser. Please note that the drivers in this are 'based on' the HD 700, but not taken directly from the HD700 which one can see if one can read the frequency response graph. Anyways, there are certain people saying that HD650 are superior and there is no reason to replace it with this, well, those opinions are really biased. Don't get me wrong, HD650 is a great pair of headphone, but you can't really compare it to this because they have quite different signatures because the HD650 is somewhat a little more colored as in it is adjusted so it produces good sounds, but not staying 100% real to the original recording. On the other hand, the HD 660S is the definition of 'clarity', the sound is clean, crisp and stays true to the original recordings across the board. In terms of bass if you are concerned, no, they are not blow-your-head-off bassy, they are clean and punchy. In other words, it is just the right amount of bass for any music if you don't think it is enough, you can always turn the bass up in the EQ or use dac/amp with bass boost feature. To sum it up, the general idea of this headphone is a combination of the clarity of the HD700/800 (not that different) with no roll-off highs and clean sound across the board. This is a worth-it investment. (I can wear this for the entire day. Comfort wise, the clamping force that people complain about do exist, but it is pretty much gone after a week of use)
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Mids of the Godz
by Fastguitars (5 out of 5 stars)
April 15, 2018

Rich, sweet, detailed, thoroughly satisfying audiophile sound.

Incredible midrange.

Very comfy, tho slightly tight.

Sennheiser has created another (HD-Family) classic.

You'll keep this one.
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Yes they are spendy.. but WOW they are worth every penny!
by Erick Gruis (5 out of 5 stars)
January 22, 2019

These headphones do everything right. Highs are super detailed but without any hint of harshness. Mids are every so slightly laid back but still very present. Bass is very strong! The low end is super punchy and hits very low but isn't bloated or exaggerated.

The best thing I've noticed is the imaging! I don't know how they do this but it literally sounds like you are listening to a band in front of you and every instrument can be placed. These things have set a new standard for me and I doubt I will even attempt to look further for a very long time.

My other headphones are Sony MDR-1A's and I still love them. They have a wonderful sound and super strong bass! Plus, they can be driven with just about anything although, an amp certainly helps them a lot. But, they aren't even in the same league as the HD660S. They will be my go to for times when an open back setup isn't appropriate.

If you are on the fence with the HD660S, rest assured they are worth the cost.

A few notes.. the cables are 10ft long. Most of the time, a 6ft cable would suit my needs but honestly I would rather err on the long side than the short. I hate moving around at my desk and accidentally ripping my phones and amp all over the place.

Also, these are moderately easy to drive but a good, strong headphone amp is pretty much mandatory if you want any volume and the best sound. My Objective2-ODac from Mayflower Electronics works great and sounds amazing! It may be being pushed toward it's limit though at higher volumes but I haven't experienced any sound quality loss or distortion. I may upgrade my amp for these headphones but that has more to do with the audio addiction that anything else :-)
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Rich sound stage, comfortable, great value
by Mark (5 out of 5 stars)
August 7, 2018

This is the best headset I've ever owned, it is worth every penny.

I'm not an audiophile, and I'm not a professional person in the audio world, but I know what I like, and I know when I put on my $90 gaming headset vs this headset that the sound stage is bigger, the world feels open, and the sounds richer, deeper and not constrained. Music, games, and movies have never been more enjoyable when wearing this head set versus any I have ever previously owned or used.

I am also using a Schiit - I'm Fulla Schiit DAC, which may/may not contribute to my experience through an on-board sound card.

Won't hesitate to purchase another Sennheiser product in the future.
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Wonderful headphones!
by DKDC (5 out of 5 stars)
January 16, 2018

I love these headphones. I auditioned them with many others (including Focal Elear, the HD 650's etc.) and decided they are worth the price over getting the HD 650's (or the equivalent and yet only $200 Massdrop 6xx) for the extra bass. I read every review I could find and agree these are wonderful (and disagree with a review by an audiophile "authority" that they are "shouty" or harsh on the high end). The bass will not blow your socks off but the detail and clarity is outstanding and for an open-back headphone it is more than sufficient for my needs. I power them with a Dragonfly Red. I also find they are very comfortable and can be worn for hours at a time.
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... sound warrant the extra cost I find them very comfortable to wear for long listening sessions I
by gonzo213 (5 out of 5 stars)
April 6, 2018

I has many others chose this headphone over the lower number Sennheiser HD I also feel the detail and full accurate sound warrant the extra cost I find them very comfortable to wear for long listening sessions I just wish they did come with a pentacon to 2.5 mm adapter as my portable dap does not support the pentacon at this time.
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Strident at least to my ears...
by Jeff M (2 out of 5 stars)
January 20, 2019

I purchased Sony MDR-7506, which sound great especially for the price. However after use for several weeks, they were not very comfortable and got warm with extended digital piano playing due to closed back.

I ordered the HD660 headphones since the reviews indicated they are clearer without the "Sennheiser veil". I did find a review online that said they were not smooth and the reviewer was right according to my hearing! I wasn't expecting how strident the HD-660 was. Voices in the mid to high have a grating artifacts that do not sound natural. The same when playing on my digital piano in the mid keys. My piano was unplayable with them.

I returned the HD 660 S and exchanged for the HD-600, which are much smoother. They work great with my piano. I was surprised how much difference there is in the two headphones.

Of course picking a headphone is subjective. Everyone's hearing is going to be different.
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Magnificent deatil and balance
by Kim Sh (4 out of 5 stars)
February 8, 2019

These are moderately expensive headphone, but they live up to Sennheisers reputation and their price. The level of detail revealed by these is terrific. They display the Sennheiser balanced and transparent sound beautifully, not getting in the way of the music. They are comfortable for long listening sessions and that's lucky, as I felt like I wanted to listen to all my favorite albums all over again. I have used them played through a Musical Fidelity DAC and headphone amp and from a Pono player. The Pono player sound incredibly detailed, but when you go to the dedicated headphone amp you realize that portable players may not quite have the punch needed for things like massed choral works on these headphones. Its only by comparison that you get that though as they sound great.

For acoustic music they excel, detail is fabulous, including placement of the instruments. I have a recording of Britten's War Requiem that just sounds flat on other things after these.

They are not cheap, but they are worthy of their price. Recommended for listening to classical and small ensemble music. Also for things like Dave Mathews or Yes that have high complexity. Nice work again Sennheiser.

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