Sennheiser HD 660S - Official Discussion

I also find the 6XX/650 a little too warm and dark with the RebelAmp; after EQ it’s better, but it has me considering selling the 650 and buying the 600.

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You all are crazy. I think the 6XX sounds amazing on the Rebel (currently paired with the Bifrost 2/64 which WOW). I do EQ it though; it sounds great without EQ but with EQ I like it better than a lot of more expensive things I have.

From what I understand the 6XX with EQ can be made to sound essentially the same as the 600 because they’re so similar, but I haven’t tried it myself.

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I mean, all of us audio enthusiasts are a bit crazy, yeah. :smiley:

Yeah, HD 650 sounds great with RebelAmp for sure, just a little too warm for my tastes. When using EQ though, it’s sounds better; same can be said for many headphones, though.

Tastes and individual HRTF are always going to play a role on the impressions we form, but at least we all agree that the HD 650 is an outstanding headphone; personally, I think the HD 6 series is the best value product(s) in audio.


Pick your poison. All audio products have a character and you either find a way to work with them or move on. The rough differences to my ears:

  • HD 600: Limited bass volume and limited bass extension. Strong, smooth, and pleasant mid-range and vocals. A little bit too forward in the upper mids. Treble ranges from harsh and scratchy (noisy solid state amps) to controlled and semi-airy on balanced or a well-matched tube amp. It’s always a bit soft, fuzzy, and rounded in the highs and lows.

  • HD 6XX/650: In an apparent reaction to the limited bass of the 600, they boosted the mid bass to the extent possible. It still doesn’t go deep and can’t be forced to go deep with EQ either. The mids/vocals suffer versus the 600, per roughness, thinness, and grain. The treble has nowhere near the harshness potential of the 600, but thereby can suffer from the ‘veil’ of muddy treble. It becomes a different beast with the right tube amp, as non-technical, warmish and harmonics-crazy. I like that presentation better than on solid state. It’s a distinct, unique flavor.

  • HD 800S: No more bass than the 600 and sounds bit thin on a neutral solid state amp. It’s so wide/spacious that it’s almost as if the headphones are playing in a room next door. However, it comes alive when you add bass (Class A amp; EQ with max deep bass) and on tubes. Tubes thicken the timbre while preserving far better treble details and location information than either the 600 or 6XX.

My preferences: HD 800S on EQ and/or tubes > HD 600 on balanced > HD 6XX on tubes


As usual, my ears are in 100% full agreement with generic’s ears on both of these.


Posted my impressions today on youtube unfortunately not allowed to post them here.

All good, they are a step ahead and could very well be the 650 upgrade so many were waiting for and an upgrade to the of 660s. You can find those impressions on HeadFi.

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You’ve been spoken to multiple times about this in private. We ask for the bare minimum of participation in order for content creator’s to post their videos on this forum. Our forum is not a link dumping ground.

5 of your last 6 posts have just been links to videos over the last 3 months with one of them being a passive aggressive shot towards the mod team that has extended nothing but leniency around our forum rules.

We don’t care if you’re a store, a manufacturer, etc…

The rules are, you need to participate in the community in order to advertise your content.


I hear ya all good, my contribution is the quality of the video and the impressions from the videos I create no different from the contributions I made when I was an affiliate for you which were allowed, only difference is it’s tied to a store that isn’t you.

It’s your website however and I understand you not wanting the video up but you have a strong enough following that it shouldn’t be an issue for others to see a different take, if they are going to buy from you they will and I am sure they do.

Again I hear ya though and will try to contribute to the forum in other ways. Although typing words on a forum can’t bring the same level of quality that a video I create can.

I think if you just provide some additional written commentary, like even some short form bullet points or quick thoughts on the subject of the video - something else in addition to the links - it would be fine. If it’s just links it becomes difficult to apply moderation rules evenly.

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I can totally do that and thank you for this explanation as it was never communicated to me like this, and that makes perfect sense. Thanks @Resolve

Ok, for reals why was my post deleted? I am not associated with any store front, I’m an independent “YouTube” creator… and member of the forum… I was just sharing the video for anyone curious what you all were discussing…

Seems awful contradictory to the above comments…

Edit for clarification* I posted Marcello’s video saying “for anyone curious about what this was about” with a link to his video


Posted in that format on the new thread.


Thanks for the impressions!

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Thank you for the specific clarification on how to post within the guidelines. Appreciate you!

Nicely done, thank you.

My soft spot for Sennheiser may have me picking up a pair of the HD660S2 … and that’s a point where the only headphones I thought I might add to my collection any time soon would be a set of stabilized/resin ZMF Caldera if/when they exist (I’d do the Red Heart LTD right now … if the rods and grilles were stainless steel).

While I preferred the HD650 and HD600, in that order, over the HD660 - I thought the HD660 was better than most of the early impressions and reviews suggested.



Can someone explain why they would buy a 650 over a 6xx when there is such a large price difference?


  1. Not aware of Drop
  2. Not located where Drop ships
  3. Don’t like Drop as a vendor
  4. Don’t want create a Drop account
  5. Don’t like the midnight blue color scheme
  6. Shop at traditional retail stores / loyal
  7. Believe for right or wrong that the original is better than the Drop version
  8. Believe the original will have better resale value so it’ll cost the same after sold
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While I haven’t a/b’d them directly, I’m given to understand that while everyone assumes the 6XX is a rebranded 650, that’s not necessarily true in the actual listening. Neither Drop nor Sennheiser has ever confirmed or denied either way, so YMMV.

When I bought my 660s I knew very little about what I was going into. I had limited experience and was not very happy with the sound these produced connected to my Leak Stereo 130. Starting reading about it and went to a store to try and find a solution, which could’ve ended up with me trading in the 660s for something different. The guy at the store advised against turning the headphones in. “They’re really good”, he said, “but need proper amplification. Don’t be fooled by the 150 ohms tag. They need a dedicated amplifier to sound at their full potential.” Given my budget, he recommended the IF Zen Can Signature, tuned for the 6xx. And boy, what a dramatic change. Suddenly, bass was deeper but still fast, mids where full and highs were so detailed. This is when I really started to get hooked to this hobby. Expensive, but so satisfying. I love my 660s. What a difference good counsel makes.