HD 660S2 - Audiophile Open-Back Over Ear Headphones with Deep Bass Extension and Refined Acoustic Performance, Over-Ear Headphones for PC, Music, Gaming, Podcasts, Premium Black

HD660S2 Review. Comfort: 9 Build Quality/Feel 7:10 When I first opened the box, I was initially underwhelmed by the build quality. To be fair I was coming from a pair of daily driver beyerdynamic DT 1990 MK1s and those are build solid metal and are very rigid. These are definitely lighter and a lot more plastic and therefore they feel cheaper in the hands. However, the lightness of these headphones is fantastic, they feel great to wear especially on long sessions. I still find the velour on my DT 1990s to be much softer, but that could be due to normal pad break in and it’s not really a fair comparison because there hasn’t been enough time yet. But on the beyerdynamics my ears did touch the drivers for a little bit and the inside of the ear pads and on these my ears are untouched and it feels fantastic Sound: 9.5/10 I bought these headphones with the idea that I was buying a different flavor of sound from my beyers. Initially I landed on the conclusion that these don’t sound as good but my the 1990s, but after several hours of listening and analyzing, I’ve come to learn that these sound more musical, and sound truly fantastic. They sound better than the DTs in many genres due to them not being so revealing of a song’s potential production mistakes, but there are certain genres like hard rock and metal that don’t excel as much on these, the vocals and bass sound great but the electric guitars and the drums (depending on the song) don’t have enough bite or dynamics. Value: 5/10 (at normal price) At normal retail price of 679.95 I could not recommend these. If you were looking for something cheaper somewhat similar in sound signature, I would go with the HD650 or 6xx depending on your price point. Luckily I was able to snag these on sale for 395 so I feel the value for the price that I paid is very good. My Final thoughts: If you were looking for a warm, musical set of all rounder headphones this is a great option to consider. I don’t think I could recommend them at a price of over $500 though, definitely wait for a sale to snag these. Also, when looking at these consider the type of music you listen to, I would say for about 80% of people these could be someone’s endgame headphone. The other 20% either have a different flavor preference for sound or looking to spend thousands on headphones to get the utmost quality which has diminishing returns. I would happily recommend this to someone looking to buy their first studio headphone or expand their collection.

Update on August 9, 2024: The iFi DAC combined with the iFi Zen Can produced clear sound and proper dynamics, but human voice sounded feeble and harmonics were missing (that is, a concert piano sounded like an electronic one). I figured it was the amplifier, not the headphones, so I gave a try to an XDUOO TA-10R, which is a hybrid headphone amp, using a balanced tube and Class A amplification (USB, optical, RCA, and coax inputs, a pseudo-balanced output that still sounds better than the 6.3mm unbalanced one). Once I swapped out the factory tube for a Gold Lion, the sound stage opened up, human voice became full, and the harshness around the high C vanished. Even poor recordings (uncompressed) sound good, providing a lot more presence than I experienced from the iFi combo. The fullest sound that goes deepest uses a Tungsram tube. I must admit that a $40 Koss would probably meet most people's need. Also, as my old friend said about 50 years ago, no headphone can compete with a good room setup (which can be hilariously expensive, but not necessarily. Compiling it from used items, you can get one for around $10k, which is still a lot less than the top-of-the-line headphones that still can't compete with it. Original review from May 24, 2024: Every time I put them on, I feel mesmerized. Have never had this experience with any other headphones; it's like the music comes to life around my head, as if I was present at the performance. Granted, that applies mostly to classical music, and the sound can easily bring tears into my eyes. Still, these babies produce excellent sound for everything I've put on them. I'm not a gamer, so I can't comment on the gaming performance, but there is at least one 5-star review on that subject. Anyway, beyond the subjective, sources and recordings are also essential to consider as well as the connections, so let me submerge into those details. Good headphones are no good for compressed sound, but plenty of headphones are made for such a clientele. The s2 with its refined sound is targeting an audience that cares for the original sound. Please, notice that when people "burn in" new equipment, during much of that (except for diaphragms in speakers), what happens is that the components adjust to each other, especially on the analogue side. The outcome ultimately determines if their combination is feasible or not. My current setup has been serving me well in the last five years or so, so I haven't made any changes. I used an iFi Zen DAC v1 (from the USB port on computer) and an iFi Zen Can v1 (on the RCA input from a relatively high-end LG Blu Ray player from the optical port through a digital-to-analogue converter). Connected the DAC with the amp through their balanced ports with a short decent balanced cable. Both amps were hooked up to the sources with SVS interconnect cables. Didn't use the "Trubass" feature on either one, because for my taste, it upsets the sound balance (the DAC also amps the bass at a higher frequency than the amp). My sources were the usual high-resolution recordings (both pop and classical) and Blu Ray movies I use for testing new components. The most prominent strengths of the s2 is extended bass and an adherence to the original sound signature. While the OEM cables are fine, out of the two supplied, I favor balanced one. I have found a purchase for a previous Sennheiser that didn't work out at the time giving me better resolution. Amazon is still selling it: KK Cable II-SO. (Added on 6/28/24: for movies, the original balanced cable works better; the KK produces less bass in return for better instrument positioning, and dialogues suffer from human voice being elevated around 500Hz, which makes conversations harsh and unpleasant to listen to. The original cable goes deeper, although perhaps a bit muddied in the lowest end, but conversations are clear). The only problem with the extended bass is that the housing loses a little control over it beyond a certain (obviously VERY high) volume, so I can sort of feel the ear cups moving, which breaks the illusion of being present. This is probably the main reason why the pressure around the ears is relatively high (and loosening it might not be the best idea). The s2 might not be the best for someone with a large head (it might feel uncomfortably tight) or unusually large ears that the ear cups cannot cover, and it took me a few days to get used to it, because I am on the high end of average head and ear sizes. The included bag is a plastic dust collector; I am using an anti-static bag instead. Hard cases are available for transportation, but the original box works for that, if only on occasion. As opposed to the planars I've heard (Moondrop Para and Hifiman HE400se, but others report the same problems with lot costlier planars), the s2 retains the familiar sound on the recordings I usually use for testing new equipment, and it extends the listening experience in gentle, but important ways. The bass reverberates in the concert hall, and is not victim to extensive channel separation. Even harmonics play the same or better than on anything else I've heard in this price range or below, although this is a feature that can warrant higher investments. No problem with high-pitched human voice being harsh and sibilants don't suppress other frequencies; the performance is actually toned down a bit in order to retain the sound that recordings must have been meant to sound like. In my understanding "warm sound" is often used for describing the feature, perhaps because no highs and mids dominate at the expense of the bass or each other. Despite the somewhat reserved (but not veiled) presentation, the dynamics don't suffer. I believe, the secret is ingenious engineering that uses physics: the proper driver and built-in sound paths in the earphones. Many other headphones have built-in electronics in the sound path, allegedly, to protect the user's hearing, but to me, it seems more like protecting the drivers from overload. Consequently, the s2 doesn't clip at low bass (emit a clicking sound, while cutting out the sound), while most the sound is there in that region, too. The headroom is like sitting in the concert hall, albeit a bit further in the back that the eight row, but the sound image remains steady at various volume levels. To me, the harmony and the unity of the sound, along with the original sound signature, is worth the price. Added on 04/03/25: The best cable I've found for these is https://www.amazon.com/gp/product/B0BZMS68RV, although it lasted only for six months. The best amplifier in this price range is a hybrid tube (the tube is only for buffering a Class A headphone amp) is the XDUOO TA-10R. Added on 12/22/25 The best affordable tube headphone amp for these turned out to be a Fosi GR70, available on Amazon, where I also bought it for under $180.

Sennheiser HD 660S2 - Audiophile Open-Back Over Ear Headphones with Deep Bass Extension and Refined Acoustic Performance, Over-Ear Headphones for PC, Music, Gaming, Podcasts, Premium Black I’ve actually bought these headphones three separate times now. There seems to be an ongoing price war between Amazon and Best Buy to see who can drop the price the lowest, and I kept chasing the deal. If you can snag these for under $420, they are absolutely worth it. If the price jumps back up toward $600, keep an eye out for the refurbished models that pop up around $350—they are what the product should be priced at. I’m currently running these through a Fosi Audio DS2 (the 2024 version) for both my PC and my portable gear. I use the 4.4mm balanced connection, which provides plenty of power to really let these breathe. If you’re using a standard headphone jack, your results might be a little different, but with a decent little DAC like the Fosi, they shine. The standout feature for me is how intimate and lifelike the vocals sound. Because the DS2 has a very neutral, "clean" profile, it balances out the natural warmth of the 660S2 perfectly. It creates a really relaxing, rich listening experience that doesn’t get tiring after a few hours. I bought these specifically for critical music listening, and they nailed exactly what I was looking for. In terms of the actual sound, the "stage" feels a bit narrow and close to your ears—it’s not a wide, airy stadium sound—but the bass is warm and has a nice punch to it. It feels impactful without being overwhelming. I also own the HD 490 Pro and the Fiio FT1, and they all serve different moods. While the 490 Pro is wider and better for picking out every tiny detail in a mix plus I also use them for gaming using custom audio cables from Hart Audio, and the FT1 is a "disruptor" with deeper bass because it’s a closed-back design and under $170, the 660S2 is the one I reach for when I just want to get lost in the music. It’s a premium piece of gear that feels like a long-term investment for anyone who loves high-quality audio.

There are plenty of opinions on this headphone all over the internet. None are bad, but some are pretty negative. Mainly because from what I am seeing, the reviewers are reviewing the price, not the product. They are saying, you get almost as good performance from model/Brand A or B for less money, focus on the ALMOST. While yes it is true, at $600 is expensive, but make no mistake about it is does out perform other headsets in many areas. This headphone is on sale for $100 more than the HD650, which is $100 more than the HD600, so this falls right in line with Sennheiser pricing structure now, and rightfully so. I don't think it is double or triple the other two 600 series headphones, but it is IMHO is a much better headphone, and worth $100 more. Literally, if you are looking at the 600 or 650's and aren't sure which sound signature is for you, get this one if you have the budget, or wait a little while and save for it... It is worth it. It has the best characteristics of both, which you can see some reviewers stating this. I believe it was Josh Valour who said it, but I do disagree with something he said, it was something along the lines that is in between both models, and a jack of all traits, but master of none. Well, it is a more well rounded performing headphone than both of those and I believe it Masters an overall warm, smooth, well defined, spacious sound with impeccable imaging. For me and my taste it is the PERFECTING SOUNDING HEADPHONE, and exactly what I was looking for. No headphone is the everything to everyone. So be honest with yourself on what you like, based on your ears, and not popular opinions, even if it is from experts, which they are, I am not disputing that at all. I am pretty new to the whole audiophile thing. One thing. But, I have learned that you really need to spend some time with the equipment to let it sink in and let your hearing mature to the product at hand. I realized this, when I purchased the Harmnicdyne athena, reviewers raved about them. It sounded like the overall characteristic I like so I decided to give it a try. I received them, put them on and listened, I was horrified. What I hadn't realized was that my hearing was skewed by listening to the hd560s so much (I really enjoy that headphone). Doing A/b comparisons only made it worse for me. So, I decided to force myself to listen to them. So, I did, I listened exclusively for 2 days, and when I would take breaks and come back and listen to the Athena I was truly amazed at how much I LOVED THEM!!! It is really hard to compare headphones; they all have their own characteristics, just as we all have our own opinions and tastes. So, I believe headphone reviewers have a very difficult job. As some of us expect them to tell us what is "BETTER" headphone A or Headphone B, it just isn't that simple. Headphone A might be better for you, but headphone B is better for me. That is the beauty of this hobby. There is no right, or wrong, better or worse. Just learn to appreciate what your ears tell you and take all other opinions with a huge "GRAIN" of salt. Josh Valour, DMS, The Headphone Show, The Source Audio Video Group, and some others, does a great job of describing the products and giving a sense of how the product is. I watch way too many reviews. LOL. I Hope this helps someone else on the audiophile journey. Here is my current stuff incase anyone care to see. I literally started with headphones and amps a little less than a month ago. The gaming headsets, I have had for about 6months to a year, that is what started it all. I have the HD560s, HD 660s2, Hifiman he400se, Harmonicdyne athena, I am using the IFI Zen air line of products, the Air dac and Air can, both awesome to start with, and you probably won't need to upgrade for some time, key word is need, want is different. lol. For gaming I use the PC38x Sennheiser/epos, the epos H6Pro, Steel series Nova Pro wired with DAC. Sennheiser Game zero, and Audeze PenroseX, Gaming Dacs are the sound Blaster GC7, and G6 love them both but prefer the GC7 in case anyone is looking at the two. Good luck, and good listening!

This is my first pair of open-back headphones. I purchased them to study in a basic audio mixing course I'm taking. I'm not an audiophile by any means and for my 50+ year old ears, these sound quite good. I needed a pair of reference headphones that don't color the sound, so that as I learn mixing, I can make sensible decisions once I get to the part in the course where mixing in headphones is covered. Overall, I think the sound is great given the concerns that many people have expressed in Sennheiser's frequency response chart on the product page of their website in that there's a trough around 5K. That could certainly be a deterrent, but I think the overall balance is good without the sound being too exhausting over long periods of time. The pads feel great and are very comfortable even with my glasses on with not too much pressure. I have a lot of hair on the top of my head, so I don't really notice any pressure on the crown of my head either. My only gripe is regarding the choice of cables. First, they offered a balanced 4.4mm plug, but an unbalanced 6.35mm plug and a dongle for a 3.5mm plug for mobile devices. At this price point, it would've been nice to include a balanced XLR option. Second, the cables are too short for my liking. I recently purchased a DAC and headphone amp along side this purchase and positioned it on my desk next to my monitor controller. Because I have an 88 key MIDI controller directly in front of me for my music production, I couldn't flop the cable on top of the keyboard, and the cable was too short to run around the edge of the keyboard. So I ran the cable under the platform the keyboard sits on and it was just long enough to reach. But if I sat back in my chair, it would tug on the cable. Fortunately, I also purchased a replacement cable with an XLR plug and it's longer and that leads to...... Third, the cables that come with the headphones are non-microphonic until you get to the part where the wires separate to each cup. The part of the cable that extends to each cup is susceptible to annoying noise when it touches anything from clothing to fingers. A slight move of your head transfers any contact with the cables straight to your ears. Not acceptable in my opinion for this price. But overall, I am pleased with the purchase and plan to use them for years to come.

The Sennheiser HD 660S2 is one of those headphones that reminds you why the Sennheiser name carries so much weight in the audio world. The sound is exactly what you expect from their 600‑series lineage: smooth mids, natural vocals, polite treble, and a relaxed, non‑fatiguing presentation that’s perfect for long listening sessions. Voices are lifelike, the treble never gets harsh, and the overall tuning is detailed without ever becoming shouty. Comfort is another strong point. The velour pads are soft, breathable, and great for extended use. No hotspots, no heat buildup, and no pressure issues even with glasses. They’re lightweight and disappear on your head in a way many premium headphones don’t. Where my experience was mixed was the packaging. The pair I received didn’t feel completely “factory fresh” — the presentation was a bit barebones and had that “possibly handled before” vibe. It didn’t affect the sound, but it did take away from the premium feeling you expect at this price. My advice: buy from a seller known for clean inventory and careful handling. That said, the current $359 sale price is an outstanding bargain. At that price, the HD 660S2 delivers sound quality that normally sits in a much higher tier. If you can grab them at $359, the value is genuinely hard to beat. Once you get a truly new unit, the HD 660S2 is everything people say it is: beautiful, natural sound, zero fatigue, and built to last. A true classic in the audiophile world. If you’re after pure sound quality and long‑term comfort, these are an easy recommendation — especially at the $359 price point.

I don’t consider myself an audiophile, but I do enjoy listening to my music the best way I possibly can and getting as much detail out of my recordings as possible. I use the HD 660S2 primarily with my vinyl setup through a JDS Labs Atom Amp 2, as well as a FiiO KA17 for my cellphone and laptop. The Sennheiser HD 660S2 exceeded my expectations. The sound is detailed, natural, and balanced, with excellent instrument separation and a deep, controlled bass response that never overwhelms the music. Vocals sound lifelike, acoustic instruments are beautifully rendered, and the headphones handle everything from rock and hip-hop to jazz and classical with ease. The imaging and soundstage create an immersive listening experience that keeps me discovering new details in albums I’ve heard many times before. Comfort is another strong point. The headphones are lightweight, well-built, and comfortable enough for long listening sessions without fatigue. The open-back design provides an airy, spacious presentation that makes music feel alive. If you’re looking for a headphone that helps you hear more of your music without sacrificing comfort or natural sound, the HD 660S2 is an easy recommendation. They’re worth every penny, specially if you can catch them on sale like I did.

While the entire headphone-buying population is busy searching for a pair of HD 600 with further bass extension, they may be hiding in plain sight. For reference, I own every major ANC headphone that’s been made over the last 7-8 years, the Dan Clark Auidio Noire X, the HD 600, the HD 490 Pro, the Hd 660S2 and the Sony MDR-M1. The 660S2 are becoming my daily drivers. Make no mistake, my DCA are the technically-superior headphone. They offer far better detail retrieval, tighter, more accurate bass, better imaging and a more expansive soundstage. They’re also about triple the price! Nonetheless, the 660S2 are just more fun. I just enjoy my music more with the 660S2 over everything else I own. Moreover, I do not have to drag them out of a case and hook up the wires every time I want to use them like with the DCA. I guess I should mention that I’m using a FiiO M21 DAP/DAC line out into an Apos Gremlin with Gold Lion tubes. The Gremlin is a hybrid solid state /tube amp, which provides just a little bit of added lush and warmth to the mids. While there is no question that the 600 is the more accurate headphone, and it wins in the mids and timbre department hands down, but the 660S2 gets you 90% of the way there, except the bass extends far below 80 hz. Moreover, the upper treble is more relaxed, which makes for a less-fatiguing listen in my opinion. In short, they sound phenomenal. They make me want to keep listening in a way that no other headphone I own does. Altogether, in my opinion, it makes for a listening experience that is just a lot more fun than the 600. I find myself getting lost in the vocals (Stevie Nicks “Landslide” for example), which just sound both richer and fuller than on the 600. Moreover, the 660S2 are far more forgiving than the 600 (and especially the DCA, for that matter). There are some songs that I just skip over because they are retched recordings and the DCA and 600 expose the technical imperfections a lot more than the 660S2. The comfort and build quality are identical to the 600—until they stretch, it’s going to feel like your head is in a vice grip! Relax, it’s temporary. Eventually, they will conform nicely and become very comfortable. I expect the 660S2 to be just as durable as the 600, both should provide years of listening. The pads on both are easily replaceable. Also, the 660S2 comes with a 4.4 mm balanced wire in addition to the 3.3 mm unbalanced wire, which saves you $30+. While I’m still going to keep my HD 600, I find I’m reaching for them less and less. If you found this review helpful, please press the help button so that I know I’m on the right track with the info I’m providing.

EXCELENTE! Finalmente encontrei o headphone versátil definitivo! Ja tive Beyerdynamic DT 990 PRO, ja tive o DT 900 Pro X (muito inferior ao 990 PRO), ja tive monitores Extreme Ears moldados especificamente pra mim…nada foi tao versátil (musica, games, edição…) pra mim quanto o HD 660S2. A EQ dele é impecavel, boa quantidade de graves, e medios e agudos bem balanceados!

Son exceptionnel

Well…a few hours in and let’s say I am not overwhelmed. Very little difference between these and XM5s and maybe not so good. Returning.

Typisch Sennheiser sehr gute Qualität

Ok.The Skinny of it... A little rough in the edges but..still acceptable by listening standard. Compared to AT WP 900 this model is on the softer side and rougher on the highs. Compared to Grado SR60 the sound is compressed with this headphone. Compared to Sony MZR 2 the 1k version that is opened and not compress but you feel you want to play it louder. But no complains if you want to pamper yourself. Finally compared to the top of the line Focal 6k model. This one is bar none. Dynamics highs mid and tonal separation this is serious stuff. But Seriously all running on the same LG V60 as source with Tidal and with USB audio pro meaning it is forced to output 16bit. Not 48.... Final word for the price...we have to be fair for the quality of sound on the price. If you were to compare it with the AT WP900 same price but now with the promo the Senheiser is reasonable value for money. Atleast if you are thinking about giving this to your teenage kids.Fine with it. No complaints. Cause if you look at it in this way every 6months they will end up buying new cans. Cause the wires just snap but with the Senheiser you can easily replace them. All the parts sponge head sponge and the cables you can swap them when wear and tear approaches.Besides you only have 1pair of ears so either you take good care of them for the better part of your life or you end up loosing to be deaf as time and age passes by. Your choice. For me I will this model. It is fine for daily use.Reasonable.