The Sennheiser HD 660 S are wired over-ear headphones. Positioned in the middle of Sennheiser's audiophile range of headphones, the dynamic drivers in these open-backs sound like what we've come to expect from the brand. Though they've been replaced by the Sennheiser HD 660S2 in the company's lineup, you can still find them in stores, and they are worth considering if you're in the market for accurate, neutral-sounding headphones.
Our Verdict
The Sennheiser HD 660 S are very good for neutral sound. Overall, their sound follows our Harman-based target curve so vocals and instruments are reproduced accurately, but they do lack a little thump and punch in the bass region. They have somewhat inconsistent treble performance, with peaks and dips that can render sibilants both dull and piercing, and their frequency response consistency isn't the best, so it's worth taking some time to ensure these sit well on your head so that you get a consistent sound with each wear.
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Comfortable, stable fit.
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Very good frequency response consistency.
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Terrible noise isolation.
The Sennheiser HD 660S are bad for commuting and travel. As open-backs, they are not designed for this purpose, so they have terrible noise isolation that provides little attenuation of nearby conversations or the rumble from public transit engines.
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Comfortable, stable fit.
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Terrible noise isolation.
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Leak a lot of audio.
The Sennheiser HD660S are inadequate for sports and fitness. Though comfortable and stable when used for their intended purpose, they are too bulky and large for sports use. Their open-back design means they also leak a lot of sound, and their components are more susceptible to damage from sweat or moisture.
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Good build quality.
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Terrible noise isolation.
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Leak a lot of audio.
The Sennheiser HD660 S are poor for use in a shared office. While comfortable, their open-back design provides little isolation against office sounds, and they leak a lot of audio, too. They'd be fine in a private or home office, though, where their accurate presentation of voices will be useful when taking calls.
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Comfortable design.
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Terrible noise isolation.
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Leak a lot of audio.
The Sennheiser HD660 S are wired; you can't use them wirelessly.
The Sennheiser HD 660S are acceptable for wired gaming. Their detailed and balanced mid-range will ensure dialogue is rendered clearly and accurately, though their slightly attenuated low- and mid-bass regions will rob explosions and effects of some thump and power. They don't have a microphone but are worth considering if you don't need or already have a standalone one.
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Comfortable, stable fit.
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Excellent mid-range accuracy.
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Terrible noise isolation.
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Lack low bass.
The Sennheiser HD660S don't have an integrated microphone, but you can use them with a standalone mic. In that situation, their comfortable fit and accurate reproduction of voices is useful, but their poor isolation and leakage performance will be a nuisance: people nearby will be able to hear your conversation, and noise around you might make it difficult to hear your conversation partner.
- 7.9 Neutral Sound
- 3.7 Commute/Travel
- 5.4 Sports/Fitness
- 4.3 Office
- 4.3 Wireless Gaming
- 6.3 Wired Gaming
- 1.6 Phone Calls
- Updated Jun 27, 2024: We've updated this review's text to keep it up-to-date and accurate.
- Updated Mar 08, 2023: We've added a comparison between these headphones and the Sennheiser HD 660S2 in Compared To Other Headphones.
- Updated Jul 07, 2021: Converted to Test Bench 1.5.
- Updated Feb 17, 2020: Converted to Test Bench 1.4.
- Updated Nov 21, 2019: Converted to Test Bench 1.3.1.
- Updated Nov 21, 2019: Converted to Test Bench 1.3.
- Updated Aug 12, 2019: We've updated the Comfort score to better reflect how tight these headphones are.
- Updated May 08, 2019: Review published.
- Updated May 06, 2019: Our testers have started testing this product.
- Updated May 06, 2019: Early access published.
- Updated May 04, 2019: The product has arrived in our lab, and our testers will start evaluating it soon.
- Updated Apr 29, 2019: We've purchased the product and are waiting for it to arrive in our lab.
Differences Between Sizes And Variants
The Sennheiser HD660S headphones come in one color variant: Black. If you encounter another variant of these headphones, please let us know in the comments, and we'll update our review.
Compared To Other Headphones
The Sennheiser HD 660S are wired, open-back headphones designed for a range of pro audio applications and audiophile listening. They're the previous generation of the Sennheiser HD 660S2 which, like the Sennheiser HD 6XX, have more punch and thump. Of the three, the HD 6XX have the most speaker-like passive soundstage, but their fit isn't quite as stable as the HD 660S. If a sound that closely mimics our target Harman-based curve is important to you, consider the HiFiMan Edition XS, which have better bass and treble accuracy than any of the Sennheisers, as well as a much wider passive soundstage. However, the HiFiMan use planar magnetic drivers, which are heavier than the Sennheisers' dynamic drivers.
If you're looking for more headphones, check out our recommendations for the best audiophile headphones, the best wired headphones, and the best headphones for studio use.
The Sennheiser HD 560S and the Sennheiser HD 660 S are similar-performing open-back, over-ear headphones, with the HD 560S slightly better for most listening applications than the HD 660 S. The HD 560S feel notably more comfortable, and they also have a wider passive soundstage than the HD 660 S. However, the HD 660 S are better built and come with an extra cable.
The Sennheiser HD 660 S and the Beyerdynamic DT 990 PRO are over-ear headphones that deliver a balanced sound. Both headphones feature a slightly tilted bass response, with an overemphasis in the high-bass that helps compensate for the lack of low-bass; something that's commonly seen with open-backs. While both have balanced mid-ranges that help bring out the detail in vocals, the Beyerdynamic have a slight peak in the low-the mid-treble that can add sharpness to sibilants, whereas the Sennheiser sound more veiled in this range. The Beyerdynamic are more comfortable and better built though, which makes them better suited to extended use.
The HiFiMan Edition XS are better audiophile headphones than the Sennheiser HD 660 S. The Sennheiser have a dip in the treble range that can make audio sound slightly veiled. By comparison, the HiFiMan have a much more neutral treble range and have more low bass, so kick drums and basslines have more thump and punch than the Sennheiser. Despite both headphones being over-ear open-backs, the HiFiMan have a far superior passive soundstage, producing a much more speaker-like sound than the Sennheiser. That said, the Sennheiser are slightly cheaper.
The Beyerdynamic DT 1990 PRO and the Sennheiser HD 660 S are both very good open-back audiophile headphones, each with their own different sound signature. The Sennheiser have a warm, smooth sound but lack thump and punch in the bass and clarity in the treble. The Beyerdynamic have a fuller, brighter sound, but they can also make sibilants and cymbals seem rather piercing. Listeners who prefer a more speaker-like passive soundstage will prefer the Beyerdynamic, which are also a bit more comfortable. On the other hand, the HD 660 S are cheaper.
The HiFiMan Sundara 2020 and the Sennheiser HD 660 S are both over-ear headphones designed for neutral sound reproduction. The HiFiMan do a better job at this, producing bass with more thump and punch than the Sennheiser, as well as treble with more clarity and detail. That said, both are very well-balanced throughout the mid-range, so vocals and instruments should sound present without being honky. Though they are both open-backs, the HiFiMan have a significantly more speaker-like passive soundstage and are more comfortable than the Sennheiser, but the latter are more stable on the head, which might be important if you like to headbang while listening to music.
The Sennheiser HD 660S2 are the next generation of the Sennheiser HD 660 S. While they share the same style, build quality, and comfort, the second generation have a warmer sound that delivers more thump and punch. Their treble range has also been adjusted, so vocals and instruments are a bit more veiled in the sequel, while sibilants become a bit more aggressive due to a dip in the mid-treble region. The 660S2 also come with a dust pouch, so you can store the headphones when not in use.
The Sennheiser HD 600 and the Sennheiser HD 660 S are similar over-ear, open-back headphones, but the HD 600 are a better choice for audiophiles who prefer a more balanced sound and a wider, more speaker-like soundstage. Their bass- and mid-range responses are comparable, but the HD 600 have a brighter and more present treble, while the HD 660 S' veiled treble range can sound dull. The underemphasized treble of the HD 660 S may be preferable if you find sounds in the higher frequencies particularly piercing or painful, but audiophiles will likely find the HD 600 sound more balanced.
The Sennheiser HD 660 S and the Sennheiser HD 490 PRO are similar open-back, over-ear headphones. The HD 490 PRO have a more speaker-like passive soundstage. They're also designed for audio professionals and come with two sets of pads: one for producing and one for mixing. While the HD 490 PRO are the superior headphone, the HD 660 S are slightly cheaper and still a worthy set of well-made audiophile headphones.
The Sennheiser HD 6XX and the Sennheiser HD 660 S are similar over-ear headphones, but the HD 6XX are better if you're looking for a neutral sound. Both cans perform superbly in the mid-range, but the HD 6XX have a little more bass, giving kick drums and basslines more thump and rumble. Although they both have open-back designs, the HD 6XX have a much more open passive soundstage. On the other hand, the HD 660 S have a more stable fit and come with a longer audio cable.
The Sennheiser HD 599 and the Sennheiser HD 660 S are very similar over-ear headphones. Despite both being open-backs, the HD 599 have a much more speaker-like passive soundstage performance, as well as a bass and treble response that more closely resembles our target Harman-based curve. This makes the HD 599 a bit better for audiophiles looking for a neutral sound, They're also more comfortable and breathable. On the other hand, the 660 S have a much better build quality and a more stable fit on your head.
The Sennheiser HD 650 and the Sennheiser HD 660 S are very similar-performing over-ear, open-back headphones. With almost identical sound profiles and build qualities, there is little to choose between these cans. The biggest difference is comfort: despite identical clamping forces, the HD 650 don't feel quite as tight as the HD 660 S, so listeners with a larger head or who enjoy very long listening sessions might prefer the HD 650s.
The Beyerdynamic DT 770 PRO and the Sennheiser HD 660 S are somewhat comparable over-ear headphones with slightly different sound signatures. The Sennheiser have a small dip in the treble range that can make vocals sound slightly veiled, while the Beyerdynamic have a peak in the high-treble that can make cymbals and sibilants sound piercing. At the other end of the spectrum, while the Beyerdynamic have superb bass that accurately conveys the thump and punch of kick drums, the Sennheiser are slightly lacking in this area. That's to be expected as the Sennheiser are open-backs, which typically have less bass than closed-backs like the Beyerdynamic. That design different also means the Sennheiser have a more open passive soundstage than the Beyerdynamic.
The Sennheiser HD 800 S are better headphones than the Sennheiser HD 660 S if you want a bigger and wider soundstage. The HD 800 S are more comfortable and noticeably better built. There's also a big difference in soundstage, as the HD 800 S create a wider, more out-of-head audio experience. However, the HD 660 S are much less expensive and may offer better overall value for money.
The Sennheiser HD 660 S and the Sennheiser HD 58X Jubilee are similar open-back, over-ear headphones. While they both have a neutral sound, the HD 58X have a touch more low- and mid-bass, giving kick drums and basslines slightly more thump and punch. The HD 58X also have a slightly more speaker-like passive soundstage. They both have terrible noise isolation. The HD 58X are cheaper and better value for money but are only available on the Drop website as they're a special collaboration between Sennheiser and Drop.
Test Results
The Sennheiser HD 660S are good-looking headphones that resemble other premium Sennheiser cans, like the Sennheiser HD 650 and Sennheiser HD 600, but with a black matte finish. The grille on the outside of the large oval ear cups shows off their drivers, and the pads are covered with a microfiber-like fabric that gives the headphones a premium feel.
These headphones are decently comfortable, if a little tight. If you have a larger head or prefer a looser fit, these might not be the most comfortable for you. For reference, they have about double the clamping force of the Sennheiser HD 598. On the other hand, the microfiber-like fabric on the ear cup padding is soft and feels nice to the touch, and the cups themselves are very large and suitable for most ear sizes and shapes. Their headband design is more comfortable than the Sennheiser HD 600, as it distributes weight more effectively across the whole headband.
While not as breathable as other Sennheiser headphones with a lighter clamping force, like the Sennheiser HD 598, the open-back design of the Sennheiser HD660 S means they still have acceptable breathability. They create a good seal around your ears that does trap some heat under the ear cups, but the grille design helps with airflow.
These audiophile headphones aren't designed to be very portable. They're bulky and large, and you can't fold them into a more compact format or lay the ear cups flat. They also don't come with a dedicated case or pouch to carry the headphones in, which is slightly disappointing, but it's unlikely that you'll be on the go much with these cans.
These headphones have a good build quality. Like the Sennheiser HD 6XX, they are mostly made of plastic, with a metal headband and metal grilles covering the drivers. The headband feels durable but isn't very flexible, and the joint that connects the headband to the ear cups feels susceptible to breaking under stress. The cables are detachable and thus replaceable if broken.
These headphones maintain a very stable fit on the head when used for their intended purpose of indoor listening, but vigorous headbanging may cause them to slip off. It's also possible their wire might snag on something if used on the move.
- Sennheiser HD 660 S headphones
- 1/4" audio cable
- 0.17 inch (4.4 mm) balanced audio cable
- 1/4" to 1/8" adapter
- Manuals
These headphones are generally well-balanced with excellent accuracy in the mid-range, so mixes sound even, and vocals are present without being honky or harsh. A dip in the low-treble and a small boost in the high-bass regions gives them a slightly warm and mid-forward sound. That said, as open-backs, they lack some low bass, so fans of bass-heavy genres like EDM might be slightly disappointed by the Sennheiser HD660 S's lack of thump. Their successor, the Sennheiser HD 660S2, are better for listeners who prefer a touch more boom.
These headphones have very good frequency response consistency, with stellar performance across the mid-range in particular. Bass performance is excellent, too, with minimal deviation throughout the entire bass region. Treble consistency is another story, with peaks and dips depending on the headphone's fit and seal, so it's worth taking some time to ensure these sit well on your head.
These headphones have decent bass accuracy. Like many open-back headphones, their low bass is slightly attenuated, so they don't accurately produce the thump of a kick drum, and they're short of mid-bass, so bass sounds lack a little punch. That said, they make up for this somewhat with a small boost in the high-bass region, which helps give these cans their warm tonality and keeps basslines feeling present and full.
These cans have outstanding mid-range accuracy. With an even and flat response across the entire range, vocals, instruments, and effects sound natural and present, with little honk or harshness. When listening to songs like Dua Lipa's 'New Rules,' her vocals come across as loud and powerful without overwhelming the song's drums or synths, just as you'd expect from a pop song.
These headphones have a decent treble response. The lower end of the low treble is fairly flat, so instruments and vocals sound present and detailed. However, a dip from the higher end of this range progresses into the mid-treble, which veils higher harmonics and dulls cymbals and sibilants. The headphones' fit and seal also slightly affect the mid-treble region.
These headphones have a very good peaks and dips performance and generally follow their sound profile well. The peak in the high-bass helps keep basslines audible despite the headphone's relative lack of punch and thump from the low- and mid-bass, but it can also make already-warm content sound a touch muddy. On the other hand, the dip between the low- and mid-treble regions dulls sibilants and cymbals, and the peak in the mid-treble can make some audio sound harsh or piercing.
The imaging performance of these headphones is superb. Sennheiser's audiophile headphones are usually subject to excellent quality control, and while imaging varies between units, our Sennheiser HD 660 S lives up to the Sennheiser reputation. The group delay response is inaudible, resulting in a tight bass. Our unit's left and right drivers are closely aligned in amplitude, phase, and frequency throughout the mid and treble ranges. This means objects like voices, instruments, and effects are accurately placed within the stereo image.
The Sennheiser HD 660 S have an okay passive soundstage. They're open-back headphones and interact greatly with your environment, giving them a more natural and spacious sound than closed-back designs. On the other hand, the sound doesn't seem like it's coming from outside the listener's head, nor does the soundstage feel very large.
These headphones have a very good weighted harmonic distortion performance. While distortion rises slightly at moderate volumes between the low- and mid-bass and between the high-mid and low-treble ranges, this will not affect the purity of your audio unless you are an incredibly discerning audiophile.
These are the settings used to test these headphones, and our results are only valid in this configuration.
These headphones have very bad noise isolation. This is unsurprising, as open-backs leak audio by design to create a more immersive passive soundstage. That said, they provide no isolation in the bass range, where the rumble of a plane engine lives, nor do they block any mid-range noise, so the sounds of speech and other office sounds aren't attenuated. They block some treble out, so they'll reduce piercing sounds in your vicinity a little, but you'll still hear them.
As these headphones are designed to leak audio and interact with your environment, their terrible leakage performance is to be expected. Although bass sounds won't be especially audible to anyone around you, the broad peak between the high-mids and high-treble range means most audio content, like dialogue or music, will be heard by those around you, even at moderate volumes. These headphones are designed primarily for people listening in private, enclosed spaces.
The Sennheiser HD 660S are wired headphones that come with a 1/4" (6.35 mm) TRS audio cable and an adapter for use with 1/8" (3.5mm) input devices. They have an impedance of 150 ohms and a sensitivity of 104dB (1 V), so you may want to consider adding an amp to get the most out of them.
You can plug these headphones into any 3.5 mm jack on your computer, but they don't have a microphone, so you can only receive audio.
These headphones are compatible with your PlayStation controller's 3.5 mm jack. Since they lack a microphone, you can only use them to hear audio.
You can plug these headphones into your Xbox controller, but you can only receive audio as they don't have a built-in microphone.
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Comments
Sennheiser HD 660 S: Main Discussion
Let us know why you want us to review the product here, or encourage others to vote for this product.
- 21010
thank you!
However, I’m confused because I thought the 2022 in the RTINGS review said it had flicker even though the flicker graph was flat while the 2021 review indicated no flicker but then it’s flicker graph had bumps in it. Wondering if both reviews were off to start, and were both years reviews updated or just the one? Also do you know if there are any iPhones and also any iPads that would work for me at certain brightness settings, that is without flicker? I want one of each. And do you do any consulting away from RTINGS. If I were to buy a MacBook Air (or iPhone/iPad) could we have it shipped to you and have you test it for flicker (within the return window) and maybe configure it, of course for a fee?Hi,
I think there’s a bit of confusion regarding the actual model. There’s no 2021 MacBook Air. The M1 came out in 2020, while the M2 came out in 2022, and the M3 came out in 2024. Are you referring to the MacBook PRO from 2021?
As for iPhones and iPads, most recent models flicker as far as I’m aware. Unfortunately, we don’t do any consulting work to test specific products.
- 21010
thank you!
However, I’m confused because I thought the 2022 in the RTINGS review said it had flicker even though the flicker graph was flat while the 2021 review indicated no flicker but then it’s flicker graph had bumps in it. Wondering if both reviews were off to start, and were both years reviews updated or just the one?
Also do you know if there are any iPhones and also any iPads that would work for me at certain brightness settings, that is without flicker? I want one of each.
And do you do any consulting away from RTINGS. If I were to buy a MacBook Air (or iPhone/iPad) could we have it shipped to you and have you test it for flicker (within the return window) and maybe configure it, of course for a fee?
- 21010
Thank you for all this information. Can you tell me what other sizes the M2 2022 Macbook comes in besides 13"? And what memory options, and where to buy?
Hi,
The M2 MacBook Air is available in a 13- and 15-inch. However, the 15-inch has been discontinued, so you can only get it from a thrid-party seller or marketplace like Amazon or Bestbuy. The 13-inch is still available from Apple and other retailers. RAM options vary from 8GB up to 24GB. Apple has recently discontinued the 8GB model and made the 16GB the baseline spec, though you can still get the 8GB from third-party sellers.
- 21010
Thank you for all this information. Can you tell me what other sizes the M2 2022 Macbook comes in besides 13"? And what memory options, and where to buy?
- 21010
Did the iPad Pro M4 measure any flicker? Is there any super simple “no set up” tool to measure flicker at home? Rereading your comments, still some confusion whether the 13" MacBook from 2021 or 2022 measured flicker-free, or if both measured flicker-free? When you say “IF” the 2021 13" MacBook is flicker-free then according to the Apple Tech the larger variants from that year should also be flicker-free, it is the Rtings review of the 2021 13" MacBook that says it is flicker-free, so are you thinking it is possible there is flicker on that model but the Rtings review measurement tool just was not able to pick it up, or how should I understand the “IF”?
Yo! The iPad Pro M4 does measure with flicker at 480Hz.
Opple Lightmaster meters are a consumer-grade luminance tool that will give you a bunch of information on the display (brightness, color temperature, flicker, etc). I’ve not personally used one as I have access to much more sophisticated tools, but the reviews seem to be positive about the tool itself, but the app being more of an annoyance than anything. I’m hesitant just because it doesn’t tell me all the thresholds for it’s reading capability, so I’m concerned it wouldn’t be able to identify flicker above a certain cap, which they don’t tell us.
Another method is to use a camera and set the shutter speed to 1/4000 and you might be able to identify it. The thing you’ll see more of with this method is the stroboscopic visibility, which would be the seen as wide gaps in the line. The Macbooks don’t have a wide stroboscopic visibility so this method isn’t really useful for you in this particular circumstance.
Sorry, I’ll try to make it a bit clearer. It does get a bit confusing.
So, the M1 Macbook Air we tested from 2021 does have flicker (this should be updated in the review soon). The M2 Macbook Air from 2022 does not have flicker.
What I meant by “if” was more a reference to the information I received from the Apple Store genius. I can confirm what I have here but any variants of our products (so in this case a larger M2 Macbook from 2022), I cannot verify. I can only say what Apple employees have told me. So the “if” is a lack of my ability to 100% guarantee that information. What I can guarantee is that the M2 Macbook Air 13" 2022 does not have flicker.
- 21010
Thank you so much again! You are going above and beyond to help me figure this out, and I really appreciate it. I hope they give you a raise because it sounds like you deserve it haha. There’s not much more I can ask of you, other than if there’s any way to find out if the larger 2022 MacBooks also have a flicker-free screen like the 13-inch one. I tried going to the Apple Store, but they had no idea. I also tried calling customer support, and I don’t think they even knew what flicker was. If there is some Apple customer support number to actually talk to their engineers, then maybe I could get an answer myself, but I don’t know if there is or who to contact. Do you know anyone who owns that model and could measure it, or, if not, do you have any way to do it? Please let me know, or if you have any ideas on who I could contact. If you can do it, great, but if not, I understand.
Did the iPad Pro M4 measure any flicker?
Is there any super simple “no set up” tool to measure flicker at home?
Rereading your comments, still some confusion whether the 13" MacBook from 2021 or 2022 measured flicker-free, or if both measured flicker-free?
When you say “IF” the 2021 13" MacBook is flicker-free then according to the Apple Tech the larger variants from that year should also be flicker-free, it is the Rtings review of the 2021 13" MacBook that says it is flicker-free, so are you thinking it is possible there is flicker on that model but the Rtings review measurement tool just was not able to pick it up, or how should I understand the “IF”?
- 21010
It’s all good! It wasn’t a waste or anything, so no worries about that. :) If the information I received from Apple is correct, than if one of the models is flicker-free than all models regardless of size within that same category should be flicker free as well. So the 2021 13" Macbook Air being flicker free should mean that the larger sizes of the Macbook Air from that year should be the same. I hope that answers your question!
Thanks so much! If you ever get a chance to confirm this by measurements or some other means let me know, otherwise thanks again for your time and help.
- 21010
I’m sorry but I think I goofed. I just looked on rtings.com at the 2021 13" macbook air review and that is the model that is flicker free, so I was hoping you could find out if the larger models were also flicker free for that year. I realize you’ve already spent quite a bit of time on this.
It’s all good! It wasn’t a waste or anything, so no worries about that. :)
If the information I received from Apple is correct, than if one of the models is flicker-free than all models regardless of size within that same category should be flicker free as well. So the 2021 13" Macbook Air being flicker free should mean that the larger sizes of the Macbook Air from that year should be the same.
I hope that answers your question!