Compendium updated: February 3rd, 2021
The Sennheiser HD line has long since reached legendary status in audiophile circles. Newcomers to the hobby are often told to “just get a Sennheiser” as if owning a pair is a required step in mapping the modern headphone landscape.
The HD 660 S has elbowed its way into the middle of the Sennhesier pack (in terms of price) but hasn’t had any trouble standing out. We’ve compiled reviews from across the web for your reference. What you’ll find here are the TLDR versions of the full reviews (which you can access with the provided links). We’ll continue updating this compendium as reviews come in.
From DMS's review of the Sennheiser HD 660 S, first published on March 6th, 2020:
“The HD660 S is a phenomenal headphone, and if you get it I don’t think you’ll be disappointed.”
From Z Reviews' review of the Sennheiser HD 660 S, first published on February 27th, 2018:
“These are oh my god headphones.”
“They’re so natural-sounding. It doesn’t even sound like a headphone.”
From Joshua Valour's review of the Sennheiser HD 660 S, first published on June 11th, 2018:
“Are they worth $500? Yes. They sound like $500. That’s the short, clean, and dirty answer.”
“All in all, I would say [my rating] is a 9/10.”
From RTINGS.com's review of the Sennheiser HD 660 S, first published on May 8th, 2019:“Good for neutral listening. Their bass is very good, consistent, and punchy, the mid-range is well-balanced and clear, and their treble is very good as well. However, their bass lacks a bit of thump and is a bit muddy; they also sound a bit mid-rangy and forward. Also, their treble lacks a bit of detail and might sound slightly veiled. Overall, they are great versatile headphones for a wide variety of music genres but their sub-bass might be lacking a bit for bass-heavy music.”
From Headphones.com's review of the Sennheiser HD 660 S, first published on July 1st, 2020:
“I mentioned earlier in this review, that I considered value a very important factor when talking about the HD 660S. The reason for this is that, although they are a very good headphone, at their MSRP of $499 they are not as competitive when compared to some of the other options currently in the market. I think mainly of the HiFiMan Sundara and DROP X Sennheiser HD 6XX which greatly undercut the HD 660S in price while delivering tonal and technical performance parity or something close to it. The HD 6XX is available on DROP at $220, which is roughly half the price of the HD 660S’ MSRP. At $220, the HD 6XX achieves what I would consider to be a very close experience to that of the HD 660S. Then there is the Sundara, which at $349 has slightly better soundstage, significantly better bass, similar level of detail and an overall tonal balance that I think will keep up a bit better across more genres. For those reasons, I find it hard to give the HD 660S a strong recommendation despite them being really enjoyable and well-performing headphones. Should the HD 660S come down in price to around the $399 mark, I think they become a much more compelling option as they are an excellent set of headphones that I sincerely believe most listeners will enjoy.”
From Headfonia's review of the Sennheiser HD 660 S, first published on March 4th, 2018:“Is the Sennheiser HD660 S a good headphone? Absolutely! Is it a great headphone? Yes, with the proper source it definitely is. Is it as good, if not better than the HD600 and HD650? Well, there it becomes more difficult. The HD660 S is a great headphone if you want a bit of both the HD600 and HD650, but in my personal opinion it won’t ever be as iconic as the HD600 and HD650 already are. In 10 years’ time people will still be talking about those two Senns, but I’m not sure they’ll remember the HD660 S. Only time will tell if I’m right or wrong.
“It is a fact that the HD660 S now is easier to drive, and it performs really great with the Sony WM1Z in balanced mode, but the headphone still scales up nicely with a good desktop sized amp, yet not as much as before.
“I have been using the HD660 S for about 3 weeks non-stop now in my office and while I liked it from the beginning, I like them even more now. So yeah, the HD660 S is a job well done and it will please a new group of listeners that couldn’t find their ideal sound signature in either the HD600 and HD650. I don’t think that those who love their HD600 and HD650, will be replacing their beloved headphone for the HD660 S, but if you have to start from zero, the HD660 S might just be that one for you with a bit of the best of both worlds.”
From Business Insider's review of the Sennheiser HD 660 S, first published on August 14th, 2020:
“The Sennheiser HD 660S headphones aren't made to go up against brands like Beats or Sony, and neither do they challenge a pair of good Bluetooth headphones for versatility. If you're thinking of these as everyday headphones for your commute, then it's better to go with a more mainstream set. If you're looking for headphones to explore your hi-res music collection at home, and you either own or don't mind buying a headphone amp of some kind, then you'll be floored by the sound produced by these stunning headphones.
“If you want to move on from your Bluetooth headphones, no matter how good they are, and take a gentle first step into the audiophile world, the Sennheiser HD 660S are a relatively reasonably priced way of doing so, just remember that it's not the only cost you'll incur if you want to get the best out of them. In other words, they're not cheap, but they're absolutely worth it.”
From Trusted Reviews' review of the Sennheiser HD 660 S, first published on October 1st, 2018:
“Comfort and great sound quality make these excellent at-home headphones. 4.5/5 stars.”
From Headphone Guru's review of the Sennheiser HD 660 S, first published on July 10th, 2018:“Overall, the Sennheiser HD 660S represents a stronger, and arguably better version of its predecessor, the HD 650. It retains the smooth signature but imparts more spirit into it this time around. This change isn’t for everyone, but I found it for the better as it gave songs and genres that previously needed that oomph the ability to shine; it was that little bit that was missing that the 660S brings to the table.
“The legend continues, but this time transformed, just like the 660S has changed, as the torch is passed. The HD 660S diverges from the path carved out by the HD 650 ever so slightly and that has made all the difference. A new legend starts today.”
From Soundnews' review of the Sennheiser HD 660 S, first published on February 13th, 2019:“If you liked the HD 650 and the HD 600, it’s impossible not to like the new HD 660 S.
“I’ve seen opinions according to which the HD 660 S is inferior to the HD 650 model, but I couldn’t figure out what they are based on.
“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.
“The built quality is already well known for 26 years. The matte black color is welcome, as well as the 2 cables in the box. I hope other manufacturers will adopt the new Pentaconn 4.4mm balanced jack. I think this is the future of balanced connection; we’ll live and see.
“The official price seems correct, exactly the price of the HD 650 14 years ago. If we factor in for inflation, they can be considered cheap for the current year.
“In my opinion, the legend continues with HD 660 S, being a fierce contender in its price category.”
From The Audiophile Man's of the Sennheiser HD 660 S, first published on February 22nd, 2018:“Anyone who has been brought up on the classic 650 headphones will be familiar with the basic approach of the 660 S models. The 660 S do move the sound quality up the ladder by a couple of rungs though in terms of detail and insight. The new 660 S phones can also successfully judge what detail to highlight and when. There’s a tremendous sense of midrange perception with this design. That is, you always feel that you’re getting a good, honest performance from the music your hearing. Some headphones can make you feel that the artist has turned up to fulfil a loathsome contract date. Not the 660 S, the performer always seems on top form. Mainly because the Sennheisers bring you into the action. Wholly involving, engaging and absorbing, the Sennheiser 660 S headphones will never let you down in a musical crisis. They are, in fact, the headphones version of Lassie. Dependable, responsive, speedy, full of enthusiasm and always able to tell you that Jimmy has fallen down the well (actually Sennheiser is still working on the last bit).”
Editor’s note: Emphases ours.