Well, finally I’ve had the chance to listen to the HD660S! After well over a year of speculation as to what it might sound like and whether I would like it, I now know. Spoiler and warning; if you love the HD660S and don’t want to read an alternative opinion or have your views challenged, look away now! If you do continue to read then I would like to make it clear from the beginning that these views are my own personal opinion based on my listening experience with my equipment to my music according to my taste and affected by my own physiology.
Having waited so long to get the HD660S I found myself eagerly awaiting its arrival when I finally ordered it. First impressions didn’t disappoint. The matt black finish and the new shaped grill with the Sennheiser logo make it look something special, and the new driver just looks the business! I was really hoping that with Sennheiser’s know how and with the installation of the new better driver that all of the good reports about the sound would be true.
I have to say that I think the title of this thread is somewhat unfortunate. Had it been ‘Sennheiser HD660S..... Finally a worthy addition to the 6 series?’ I might have given a qualified ‘yes’, but a worthy successor? No. Sorry, but no.
I’m not going to attempt to do a full review - there have been plenty of those from people better able to do that than me, but I would like to explain why I came to that conclusion and also my listening methods and material.
I did most of my comparison using a chain which I am extremely familiar with. Namely, a Marantz CD12 DA12 (with the famous TDA1541A-S1 converters) and Lehmann Black Cube Linear. The transport and DAC are connected with a Van Den Hull The First Ultimate and the DAC and amp are connected with Nordost Blue Heaven cables. More casual comparison was done with a Sennheiser HDVD800 with lossless files from my Mac. Most listening was done single ended, although I did compare them in balanced mode. Balanced operation benefited both phones similarly with perhaps a slight advantage to the HD650. There was of course, unfortunately, a volume difference between the two, but with a lot of switching I became comfortable with matching the volumes to my satisfaction. I also listened both for extended periods of several tracks at a time and switched as directly as possible between them.
I listened mostly to material with which I am very familiar with and in most cases have known and used as test material as well as listening for pleasure for many years. Those CD’s included; Jan Garbarek Visible World 1996 ECM, Fauré Requiem, 1994 Philips, Gator Barbieri Que Pasa,1997 Columbia, and
The Hunchback of Notre Dame Studio Cast Recording 2016 Ghostlight records.
Listening to the Jan Garbarek - the recording with which I am most familiar, revealed almost everything. This recording has that wonderful acoustic and sometimes ambient sound stage that ECM is famous for. Jan Garbarek’s tenor and soprano sax is set in an enormous soundscape with Marilyn Mazur and Manu Katche’s drums and percussion coming from all around the listener, Rainer Brüninghaus’s piano beautifully clear and articulate and Eberhard Weber’s electric acoustic bass providing both high melodic and low luscious bass sounds.
The first thing to note, and very significantly I think, is that the HD650 and HD660S sound far more similar, on higher end equipment at least, than they do different. That firstly makes one wonder why they bothered and at the same time focus on the differences that exist much more closely.
The first thing that became apparent to me when switching to the HD650 was how smooth and effortless it sounds by comparison. When I had listened to the HD660S on my phone (the only source I had for several days) it didn’t occur to me that the sound was harsh in any way, and indeed I would still not describe it as such, but in comparison to the HD650 it simply lacks that headphones smooth and effortless presentation. Gone was the silky smooth, inky black ECM soundscape on Jan Garbarek’s Visible World. It occurred to me then that it was this that has lead some to describe the HD660S as grainy. Unfortunately, having noticed that and made the connection, it was impossible to un-hear. I’m sure it’s true to say that one man’s smooth is another man’s veil, and similarly that one man’s grain is another man’s detail, but there you go.......
However, talking of detail I didn’t find the HD660S to be more detailed. Certainly it has more treble energy, but more detail - no. In fact if anything the slightly harsher and more obvious presentation of the upper treble seems to me to make it harder to hear the fine details which are present in the mids and upper mids - the area where most of that information exists, and that area is slightly recessed on the HD660S so for me it’s a bad combination. Resolution of fine detail is so important to me - more important ultimately than a lively and dynamic sound.
The next thing which I noticed and couldn’t shake off no matter how many times I switched headphones or changed tracks, was the impression that the soundstage seems smaller. Only a bit, but definitely smaller. Not as wide, high or deep - less three dimensional in fact. This, combined with the dynamic drive of the HD660S (which is arguably better, particularly in the bass) may very well be an advantage for many, depending on genre, but for well recorded acoustic music, and especially large scale orchestral music, it is not.
The other issue for me was the tonality and naturalness of the sound. Again, the differences between the headphones is not great, but for me, and knowing the recording as I do having listened to it for years on many good to great transducers (and having heard it live four times) Rainer Brüninghaus’s piano on Visible World has a hard edge to the sound which was somewhat unnatural. The sound after the initial attack was also coloured in a slightly unnatural way. I found the same with the string sounds on the recording of Fauré’s Requiem, for instance at the beginning of the second track where the cellos sounded somehow more metallic, for want of a better description. The same was unfortunately true of Jan Garbarek’s saxophone - an instrument which I play and therefore have a very critical ear for. Still, the HD660S faired a lot better in this respect than some other well regarded and more expensive headphones that I’ve tried - just not quite as well as the headphone it set out to be better than.
I’m sure that the HD660S could be regarded as (and quite possibly sound) better on a DAP or lower end amp than the HD650 (which is admittedly notoriously difficult to drive properly), but it would be better in the same way that a nice ice cold Coca-Cola is better with hamburger and fries than a good glass of red wine would be. However, go for a nice meal at a proper restaurant and the good red wine will be on the table.
It could well be largely a matter of my musical preferences combined with the fact that I generally listen at fairly low volumes, but I honestly couldn’t find anything which I thought sounded better on the HD660S than the HD650, sadly. And sadly it is, because as I look at the HD660S on the table in front of me waiting to be sent back, it’s very easy to be seduced by the sleek good looks and that driver which looks so special. In the end, despite all of my previous reservations, I had sincerely hoped that it would sound as good as it looks. Unfortunately, for me, it is not the case. I’ve even considered keeping them just to own all of the 6 series headphones, but I just can’t bring myself to spend nearly €400 on a headphone which is remarkably like the HD650 but isn’t quite as good. Sennheiser seems to have succeeded in producing a headphone that sounds very similar to the HD650 whilst making it more amp friendly and with tweaks to the sound which will appeal to many. If that was Sennheiser’s aim then they succeeded. If they genuinely tried to produce something better than the HD650, they failed.
It’s revealing, I think, that Sennheiser seem to have acknowledged that themselves. After the persistent rumours and reports, often from Sennheiser reps, that the HD650 would be discontinued in favour of the HD660S it has now become clear that they, along with the HD600, will continue in production with the new look design at Sennheiser’s factory in Romania. It’s good to know that Sennheiser is listening to the feedback!
