[wantan]

I can only conclude that the HD660S that Sonarworks reviewed, and more than likely all of the early units, were considerably brighter than the more recent production and that Sennheiser has at some point done a silent revision. That, to me, seems to be the only logical conclusion.

That would be interesting to confirm, they must have measured more of them since they wrote this review. I had a HD660 with drivers build december 2018 which was too dark and sounded off. Cymbals lacking shimmer and a bit dull sounding altogether. My new one (august 2019 drivers made in romania but old design) sounds correct, compared to two other sets, and in line with the measurements.

I agree with your obeservations about the sound differences, I hear the same. What makes the difference IMHO is the raise in FR range of the 660s between 2 and 6 kHz that follows the dip. I think a rise in FR alway adds excitement and detail to the sound. A downwards slope is extremely difficult to hear, it's the rise that makes the audible difference because it's easier to hear when something is emphasised. The 660s is darker but more exciting with more clarity than HD650.
My guess is Sennheiser wanted to get rid of the "sennheiser veil" stuff and the "shouty midrange" that was linked to the HD650/600 in the past and the 660S frequency response is doing this very well.
It's just a nicely done headphone which is totaly underrepresented. Well you could buy all three of them and still save compared to a single Focal Clear.

 

[donlin]

That would be interesting to confirm, they must have measured more of them since they wrote this review. I had a HD660 with drivers build december 2018 which was too dark and sounded off. Cymbals lacking shimmer and a bit dull sounding altogether. My new one (august 2019 drivers made in romania but old design) sounds correct, compared to two other sets, and in line with the measurements.

I agree with your obeservations about the sound differences, I hear the same. What makes the difference IMHO is the raise in FR range of the 660s between 2 and 6 kHz that follows the dip. I think a rise in FR alway adds excitement and detail to the sound. A downwards slope is extremely difficult to hear, it's the rise that makes the audible difference because it's easier to hear when something is emphasised. The 660s is darker but more exciting with more clarity than HD650.
My guess is Sennheiser wanted to get rid of the "sennheiser veil" stuff and the "shouty midrange" that was linked to the HD650/600 in the past and the 660S frequency response is doing this very well.
It's just a nicely done headphone which is totaly underrepresented. Well you could buy all three of them and still save compared to a single Focal Clear.

How can you tell what month/year the drivers were built? Is it printed somewhere on the driver?

 

[Mike F]

How can you tell what month/year the drivers were built? Is it printed somewhere on the driver?

Yes, it’s on the inside of the driver. Just take the ear pad and foam off and you can see it.

 

[donlin]

Thanks!

 

[boodi]

@wantan
I'm worried that such differences may be there in the production/s line/s for 400$ ( audiophiles?) headphones , if we are in this case - who knows.... happenings that are hard to spot and to come by even in years of consumer distribution

apart that , I've noticed that lately more and more brands went designing faster and darker and dark-blue sounding drivers, or darker then before .. in other words they are leaving oomph and warm headphones and designs behind and favoring more snappy east fun presentations ( akin to low ohm too...btw) , ...in a dark tone sauce . call it fun factor or need for blacker blacks or anything else, there might something in the ears' audience that has to do with it . I quite like it too

it might be the case of 660 also ( colored sound signature ? , I do not have them and do not plan buying them at all )

650 are slighty faster and slighty more resolving then hd600 , but they have that bordeaux or "deep reddish" veil ( an added warmness on any piece of music they play that is quite easy to hear ) which makes their sound too fat fatclose at times



even former Grados designs which are fast headphones , almost too snappy or aggressive many of them , are not tailored with this late color that many headphones seem to share

 

[Mike F]

That would be interesting to confirm, they must have measured more of them since they wrote this review. I had a HD660 with drivers build december 2018 which was too dark and sounded off. Cymbals lacking shimmer and a bit dull sounding altogether. My new one (august 2019 drivers made in romania but old design) sounds correct, compared to two other sets, and in line with the measurements.

The four I tried were made between 1.19 and 10.19. There were minor differences - some a bit bassier and others a bit brighter, but the differences were within what I would expect from sample variation.

I agree with your obeservations about the sound differences, I hear the same. What makes the difference IMHO is the raise in FR range of the 660s between 2 and 6 kHz that follows the dip. I think a rise in FR alway adds excitement and detail to the sound. A downwards slope is extremely difficult to hear, it's the rise that makes the audible difference because it's easier to hear when something is emphasised. The 660s is darker but more exciting with more clarity than HD650.
My guess is Sennheiser wanted to get rid of the "sennheiser veil" stuff and the "shouty midrange" that was linked to the HD650/600 in the past and the 660S frequency response is doing this very well.
It's just a nicely done headphone which is totaly underrepresented. Well you could buy all three of them and still save compared to a single Focal Clear.

I agree with you about the above. The first highlighted part could explain why some people hear the HD660S as brighter and more exciting without it actually having more treble presence in that region, but it wouldn't explain the discrepancy between Sonarworks graph and the other one I posted, nor Sonarworks statement that the HD660S had the sort of (increased) treble that would make mix decisions more difficult in that region than on the HD650......

 

[Mike F]

@wantan
I'm worried that such differences may be there in the production/s line/s for 400$ ( audiophiles?) headphones , if we are in this case - who knows.... happenings that are hard to spot and to come by even in years of consumer distribution

I'm talking about differences that you would never notice unless you had two units side by side, and then such small differences that most people simply wouldn't notice them.

 

[boodi]

I'm talking about differences that you would never notice unless you had two units side by side, and then such small differences that most people simply wouldn't notice them.

sure
one would never expect that in 500$ headphones . imo .
I'm sure when you buy 2 Focal Utopia you pretend they sound identical but I would expect the same on 500$ audio gears.

 

[CaptainFantastic]

sure
one would never expects that in 500$ headphones . imo .
I'm sure when you buy 2 Focal Utopia you pretend they sound identical but I would expect the same on 500$ audio gears.

They very likely don't. High-end Audeze are known to have variances, likely bigger than the minor ones the Sennheiser 6-series does. Again, to be clear, we are saying it seems that the bigger differences are accounted by actual voluntary changes from the company. Once they go with a driver version, the differences are very, very... very small. This is normal.

 

[boodi]

could even be more worrying to someone that they know they change sound for a model -slightly ,and willingly- and they do not release it publicly

but then you know we are head-fiers .. / I wouldnt be surprised though that anyone owning more then 1 pair of cans -portables apart- is not user here

 

[HipHopScribe]

Silent revisions and variability are a reality of almost any type of manufacturing, it's really nothing to worry about unless there's a big documented history of issues. There are also defective HD660s out there that probably sound way off, it's just a reality that a certain number of products are gonna have issues

 

[boodi]

sill I wouldn expect my 500$ pair sounding off ( I'd return it obviously - but they 'd need to be qc before living the factory )..

or wouldnt expect a range of revisions soundwise ; it is something I'd rather not live with if I can choose
there's also case for revisions , printed on headphones names too , when the drivers remain the very same ..so ..

lucky enough I'm set with a few keepers , happy and off headphones research from a time apart some spare curiosity ; + hardly going to buy many more Sennheiser in life

 

[HipHopScribe]

sill I wouldn expect my 500$ pair sounding off ( I'd return it obviously - but they 'd need to be qc before living the factory )..

or wouldnt expect a range of revisions soundwise ; it is something I'd rather not live with if I can choose
there's also case for revisions , printed on headphones names too , when the drivers remain the very same ..so ..

lucky enough I'm set with a few keepers , happy and off headphones research from a time apart some spare curiosity ; + hardly going to buy many more Sennheiser in life

I'm sure Sennheiser has a robust QC process, but realistically given their production volume a QC process is not gonna catch 100% of problem units before they go out

 

[HipHopScribe]

Also, this should go without saying but human ears and brains are not in any way reliable measuring equipment, so someone thinking 2 pairs of 660s heard at different times sounded different is interesting but virtually meaningless information in the larger scheme of things. Even different measurements don't necessarily mean much unless they were taken on the same exact equipment with as close to the same set-up and positioning as possible. The same headphone is liable to measure differently even on the same equipment even with just a small change in positioning that affects the seal the earpads form. That's why such measurements should only be taken as a rough comparative guide at best

 

[Mike F]

I would be surprised if there were any really ‘rogue’ examples of 6 series headphones. I think that the production numbers and tolerances would make that very unlikely. Sample variation though for sure, and in fact guaranteed when you have driver matching (which of course is a good thing) going on.