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 Though they've been replaced by the Sennheiser HD 660S2 in the company's lineup, you can still find them in stores, and they are worth considering if you're in the market for accurate,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.
- Comfortable, stable fit.
- Very good frequency response consistency.
- 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.
- Comfortable, stable fit.
- Terrible noise isolation.
- 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.
- Good build quality.
- Terrible noise isolation.
- 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.
- Comfortable design.
- Terrible noise isolation.
- 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.
- Comfortable, stable fit.
- Excellent mid-range accuracy.
- Terrible noise isolation.
- 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.
Changelog
- 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.
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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.
Popular Headphones Comparisons
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, but the HD 660 S are better built and come with an extra cable.
The HiFiMan Sundara 2020 and the Sennheiser HD 660 S are both over-ear headphones designed for critical listening. The HiFiMan do a better job at producing low-bass with more thump and punch than the Sennheiser, as well as treble with a little 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 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 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.
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