Sennheiser HD660s2 Open-Back Headphones - Official Discussion Thread

This is the thread to discuss the new (as of February 8th, 2023) Sennheiser HD660s2, Sennheiser’s latest update in their 600 series lineup of headphones.

From Sennheiser

Enjoy your music on a completely new level with the Sennheiser HD660s2, the latest update in Sennheiser's legendary 600 series lineup of headphones. An intimate, relaxed sound signature combines with outstanding precision and exceptional comfort — and now, extended sub bass — for a deeply moving experience.


  • Open-Back, Dynamic, Over-ear Headphones with High Fidelity sound
  • Ultra-light aluminum voice coil with 300Ω impedance for excellent impulse response
  • Uniquely powerful vented magnet system for minimized distortion
  • Outstanding quality designed in Germany, made in Ireland
  • Intimate and precise yet non-fatiguing sound with great timbre and deep, accurate sub bass
  • Plush ear cushions and open design for maximum comfort


  • Transducer Principle: Dynamic, openK/li>
  • Transducer Size: 38mmK/li>
  • Frequency Response: 8 Hz - 41,500 HzK/li>
  • Impedance: 300 ΩK/li>
  • Sound Pressure Level (SPL): 104 dB (1V)K/li>
  • Total Harmonic Distortion (THD): < 0.04% (1 kHz, 100dB)K/li>
  • Weight: 9.17 oz (260g)K/li>
  • Magnetic field: 2.5 mTK/li>

An improvement over the 660s headphones and could be what many have wanted for a true upgrade to the legendary 650! Thanks for creating the thread, definitely worth an audition. There will be a loaner tour on HeadFi

anyone interested should sign up!

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The new 660s2 a worthy upgrade to the 660s and, quite possibly, the 650 replacement so many have been waiting for.

Quick impressions-more in-depth and tech in video below vs 660s

*better detail retrieval
*better sub bass extension
*tighter bass signature
*better separation of instruments on the sound stage
*better separation of the bass regions to the midrange
*more natural timbre
*less peaky treble execution
*660 still a great sounding headphone just a step behind technically now
*660s will still be a go to for easier to drive and used market should present some good buying opportunities.
*300 ohm headphones preferred by many tube amp lovers.
*more comfortable than 660s both in clamp and headband.

It’s a definite upgrade for my preferences over my owned pair of 660s and I will be selling my 660S in order to purchase a pair of the 660S2

Sennheiser HD660S2 300hm new updated headphones compared to the original 660s headphones!


Great impressions and great video so far! I’m only about half way through it but some great shots in there. Curious to know what source gear you were pairing with it?

I’ve got a pre-production unit on my desk that I’ve been using with the Envy and it’s definitely a warmer combination. I agree that it’s an upgrade over the regular 660s. I don’t think this is going to dethrone the 600 / 650 for the people who enjoy those headphones but it definitely gives an alternative tuning for those looking for a bit more flavour from those headphones with a little more punch.

We’ve got another unit that should be arriving today just to make sure the pre-production matches the production unit and then I’m planning to run it through the gauntlet of source gear from the Piety to the HM1 to see if there are any noticeable changes with Sennheiser going back to 300 ohms on the driver.


Thanks man! I discuss the source equipment right before the impressions the main source components used for my impressions were the TT2, MHA200 fed by TT2 as the DAC, also my BHC with Speedball fed by TT2. I also listened via two of my integrated speaker amps with headphone outs the Marantz 40n and Michi X3.


Great. Looking forward to some more measurements.

And… Which driver is this? Is it an existing one (600/650’s) or a new development altogether?

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Here are the measurements of the Sennheiser HD 660 S2 on the B&K 5128. For our target we use Diffuse Field with an 8dB slope applied to match listener preference research.



HD 660 S2 vs HD 600 (both with fresh pads)

Channel Matching

Here’s an initial EQ profile done subjectively. I don’t think I can fix the 4.5khz dip as that seems to be a deep phase cancellation issue, but… I’m not really that fussed since it’s fairly narrow.


And here’s the result with these changes.

My take at the moment is that the HD 660 S2 is very similar to the HD 600 and HD 650, just with a more relaxed tuning in the upper mids. So for those who found the other two to be a bit shouty, the HD 660 S2 will be a good alternative. Personally I still prefer the HD 600 and HD 650.


I would like to know the difference between the new S2 and 660s with the oratory1990 eq that I use, my 660s sound very good with that eq profile and have more than enough bass, I even lowered the low-shelf bass by 2db from the oratory1990 as it in my thought was too exaggerated, so I really wonder what I have to gain by upgrading to S2?

If you own the original HD 660 S… I think you’re better off just going with the HD 600. The S2 is more for folks who aren’t looking for neutrality and are instead after a more relaxed, thicker presentation.


Gras measurement when?


I’m still waiting for graphs of them together with hd660s. Official graphs look a bit exaggerated.

@Resolve Has them. Maybe he’ll post them today if we poke him enough times!

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I’m in meetings though!

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They don’t appear exaggerated for that comparison - or at least close enough within unit/pad variation:

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It’s a new driver.

Same 38-mm diaphragm/42mm overall size as the HD6XX line, but a new voice-coil (higher magnetic impulse … i.e., more force and better damping/less overshoot), an optimized air-gap for the magnet/“motor”, and a new, more compliant “surround” (shifts the driver’s resonant frequency down).

This will have the effect of changing the response to higher-impedance sources, as well as the frequency where impedance spikes, so there is the potential for somewhat different behavior with familiar amplifiers vs. the HD600, HD650 and HD660S.

I’m intrigued enough that I pre-ordered a set … and very much looking forward to hearing how it sounds with the HM1 …


Wonder how they compare to 650 though, if the difference is heard immediately, or only just.

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@Resolve I already owned a hd660s. I was thinking to upgrade my hd660s when I saw the release news of hd660s2, but it seems to be an additional variation instead of an upgrade. Then I saw you recommend that if I already have a hd660s I’m better off just going with the hd600. I would like to ask which one you would recommend if it is hd600 compared to Hfiman Sundara? Which one is better if I would like to have a different listening experience compared with hd660s?

Hard to say, but… both are good. On the one hand it’s worth having an HD 600 for ‘reference’ sound. On the other it’s worth having one dynamic and one planar for different presentations. Also the Sundara takes to EQ better than the Sennheisers.


Hi Andrew. Do you have a link to a list of your eq settings, specifically the HD 600? I pretty much just add a 3 db low shelf at 80 hz and sometimes lower 3300 hz by a couple db.

Probably a dumb question but is there a way to eq the HD600 to perhaps create or simulate soundstage? To me it’s the only thing missing from the 600 that keeps it from being a complete end game headphone.


Here’s the review for folks who have been waiting on that: