Finally a decent review that makes sense and is not full of BS...
:>)
Great Job!

Hey, thank you! Always trying to do my best!

I was thinking of these, and put on my 650's today and then the D8000 Pros....well I guess I will just stay with the D8000 Pros for now...
:>)

Not a fair comparison!

Ha! For sure...

"Outside the Sennheiser ecosystem, the HD660S2 is an undeniably excellent sounding headphone with supreme technicalities and a balanced, realistic tuning"

This comment finally pushed me over the edge into the purchase. I've been on the fence for the last few years about adding a Sennheiser over-ear to my collection, but the lack of sub-bass in their over-ear Hi-Fi line has always been a dealbreaker. I love their overall timbre and mid-range in the IE900 and even the consumer Momentum line. Then on top of that, figuring out the "which is right for me" situation that is the many variations of the 6 line left me even more on the fence.

Then seeing the close of your review, plus the D8k Pro comment made me realize regardless of my other gear, this is the best shot I've got at getting a Sennheiser into my collection that has some attention to the sub-bass.

Thanks for your thoughts!

Thank you very much!
I think that it is very abstracting to keep continuously comparing the HD660S2 with the 6xx line of headphones.
In the end who cares if it is the successor to the 650 or an upgrade or downgrade or whatever.
This is an entity on it's own and ought to be compared to the competition from other brands.
And this regard is a very competitive and excellent sounding headphone period with a sound signature that is going to appeal to many people.
The whole HD660S2 thread has become completely disoriented because all the talk is about how it compares to the rest of the family.
Wrongly.

So the S2 has a smoother and less bright tuning throughout the upper mids and lower treble?

"The whole HD660S2 thread has become completely disoriented because all the talk is about how it compares to the rest of the family. Wrongly.”
Wrongly is not, according to me. It is absolutely natural to do that since the design and the naming.
And, yep, comparing it to competition is to be done but the 6xx line owners and the community (in general) are judging also this launch like a kind of attitude to them. The package, the replay, the price - that is attitude and I think Senn underestimated that side of a launch since if they look at us like "market"!? - I will not elaborate.
Probably they had to name it hd6neo.

@Mhog55

In my opinion, yes, this is how I am hearing it compared to the HD650.

@Sharppain

I don't know, maybe wrong marketing from Sennheiser.
The thing is that this is a new headphone with it's own tuning and virtues.

Agree, it is a new phone.
But what new is delivered? It is 100% a marketing failure - the name is like 'the next in line', and it delivers cosmetic changes, the biggest issue is not solved, and they noticeably increase the price.

What is the biggest issue that should be solved?

Oooo, the moment I wrote that I knew I will get that Q!
According to me, it is not in the FR, it is in the technicalities - the sound stage presentation is deal breaker for some. It is narrow as in iems, even narrow than that of some iems. I know, I know, it is called 'intimate presentation' but according to we the sound stage presentation is part of the fidelity - if I am listening to a concert in a stadium it should be replayed like that, if it is in a hall it should sound again big but different than a stadium, if it is a studio recording - well let it sound like that; but I rarely get David Gilmour and Ian Gillan singing in my ear!!!
I am a big fan of Senn approach to sound and replay and I have big collection of Senn iems and headphones, even the most polarizing (like HD700) but the 'intimate presentation' is a big issue, according to me, and they didn't solve it.

According to their literature, the soundtage and the whole presentation are intimate on purpose, this is how they wanted it to sound.
Anyway, this is pretty subjective, you don't like it but there are people who are on such type of approach.

Agree, it is a deliberate choice - I guess they want to keep the room for the HD700 mk2.

I think that a headphone alone cannot really reproduce a real sense of various room and spaces (stadium, hall etc). Yes, it can reproduce all kinds of reverberation accurately respectively to time and frequency parameters, but two drivers, one over each ear, will never fool our hearing/mind to think that music is coming from a distance. Advance processing (crossfeed type) is needed to bring some nice results horizontally but still not enough to make you turn your head up or down. "Height" is a term that many like to use but actually it is non existent with headphones (or ear-level loudspeaker systems). Most people by "height" mean any reverberation related to height of a hall or other recording place, but in replay it never actually comes from above or below without the use of extra transducers at different heights/angles, also reacting with our head shape and upper body.

Thus, I would not expect from a headphone to recreate a full 3D sense, neither would I judge it by this. Instead a full and neutral enough balance with precise horizontal positioning is a very good start to allow special recordings (binaural) or processing to create some successful 2D effect.
I think that another crucial factor is a headphone design that does not transmit vibration through the earpads on the head, destroying any illusion of distance. This is already hard to achieve with common headphones with listening levels above medium. Very large earpads and low pressure on the head are needed to avoid this effect. Maybe this is a most important factor of the HD-800S recipe for its unique soundstage ability.

"... a headphone alone cannot really reproduce a real sense of various room and spaces."
Well, yep, you need a decent transport/streamer - very good dac - very good amp.

And Really?!!! To what extend this phenomena is possible, check here: https://support.beyerdynamic.com/hc...eld-equalisation-and-free-field-equalisation-
And do not forget: I do not see it doesn't mean it doesn't exist

We must note that the above article has nothing to do with sound directivity when reproduced by headphones or anything about soundstage. It is only about tuning/equalizing a headphone frequency response using a clever technique of sounds (frequencies) coming from every possible direction or from a "diffuse field chamber" (averaging the intensity of a frequency coming from many various directions to decide the final intensity of reproduction for that frequency). It is not a method to make a headphone able to reproduce soundstage or directionality.
This is also very clear in the final paragraph of the article:
"To equalize the headphones, they are placed on the dummy head and the frequency response is adjusted so that the measured frequency response corresponds to that in the diffuse field".

MMMM, so the singer room, the home room, the orchestor stage, the hall are no acting like a diffuse field chambers!!!!?
Yep, the tuning and the capability of the driver are highly important and this is what I was also referring to. But the fact that some 6line series headphones are using the HD700 driver and do not have any of the spatial presentation of the HD700 is also due to the around the year 'chamber' (its size, form, dumping,...). It is not buy chance the most spacious caps headphones have large soundstage replay (Amanda, XS, Arya, HD700, HD800, ZMV models).
Second, I do not say that Senn do not know that the 6series has weak spatial characteristics - of course they do know. And of course they say it is intended - the story of the 'intimate presentation' is accepted buy some and the 'in the head' is Ok. What I say is that Senn sell cheap design for more money (no effort, no cost, no material no cost) and with the 660S2 they crossed the red line.