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Sennheiser HD660S Review (Headphone)

Rate this headphone:

  • 1. Poor (headless panther)

    Votes: 15 7.2%
  • 2. Not terrible (postman panther)

    Votes: 65 31.4%
  • 3. Fine (happy panther)

    Votes: 103 49.8%
  • 4. Great (golfing panther)

    Votes: 24 11.6%

  • Total voters
    207

MiloTheFirst

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These were the very first Audiophile tier headphones I bought. Back then I didn't know much and my logic was that the best entry point for the hobby was a set of good ol' HD 600 series and among the 600, 650 and 660s, the later would save me the need to buy an amplifier... things didn't go as well as expected. As it turns outs I was too greedy, vocals had great definition but everything else was too anemic, except for those ocassions when I listened to them in the middle of the night at very low volume (then it sounded very elegant and pleasant). I figured as time passed that maybe the issue was the lack of power from my very old PC 3.5mm jack. so I set too buy a "powerfull" dongle DAC that would cost me less than a bonafide desktop DAC-AMP combo (plus that way I could also use it with my smartphone). I decided to buy a Tempotec Sonata HD PRO (of which a non-OEM branded version was reviewed here with fliying colours across the aboard), after evaluating the specs I concluded that it might be just what I needed, but to my bewilderment the headphones still didn't sound "right", they could get extremely loud, painfully so (but so they could with my original motherboard's 3.5mm jack to a lesser degree), but it would still sound shouty and unbalanced. it wasn't until Amir reviewed a different headphone here which included a graph of the impedance across the frequency spectrum that the answer hit me, I was indeed lacking power but in a more nuanced manner. I had bought the Dongle DAC after calculating that it could deliver enough miliwats at 150 ohm, little did I know that a device impedance might vary in response to the electrical frequency (which in retrospective makes perfect physical sense). after admiting defeat, my stingy self saved up the money to buy a desktop Amp and finally close the chapter with the mistery behind these cans' not living up to their potential.

It was an adventure full of discovery and learning, but also of anguish and self doubt, at times wondering whether I was crazy or going deaf and eventually just thinking that this model just didn't live up to its predecesors and was just a design flop. ultimately I can say that these do in fact sound pretty good, I was just doing it wrong originally. Ironically, just recently I built a new PC with a higher tier mother board that advertised capability for high impedance headphones (I didn't choose it specifically beacuse of this, though), and to my surprise, yet again, the HD 660s sound perfectly acceptable when connected directly to this board.

So to those considering buying this model because it doesn't need an amp, be mindful that while on board audio has gotten really clean and well performing compared to a decade ago, it might still not have enough power to drive these cans properly depending on the motherboard in question. the same applies to a smartphone. I own an LG V50 (from the series with the quad DAC) and it can get the HD660s loud, but it only sounds balanced and proper at very low volume. in any case, without an amp they will still be serviceable if you only need to get audio out of your system to get something done, but it wouldn't be worth their price tag when used that way.

As for my subjective impression of the sound signature I will say this: They sound like a Live performance at which the mixing technician purpousefully equalized the vocals notably higher than the rest of the instuments, like there are 2 planes of depth, one for the vocals range and another for the rest of the mix. imagine as if they wanted to make the 650 but way less cluttered, as a result the instruments are less inpactful and fun but in return we get significally better instrument separation. They definitively lack bass and I specially notice it when I listen to orchestral music with plenty of cello and tuba, but for everythign else I can't avoid the feeling that having more bass would ruin the balance and be distracting. on the bright side, soundtracks and ambient music compoused mainly with acoustic guitars and piano sounds glorious on these.
 
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solderdude

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600, 650 and 660s, the later would save me the need to buy an amplifier..
The difference in sensitivity between HD650 and HD660S is just 3dB.
But agreed marketing and reviews generally would make one believe that the HD660S is better driven from portable devices.

The HD660S does not require much power, it does require more voltage equivalent to say... 100mW in 300ohm.
Certainly if one plans to boost subbass by many dB's.

little did I know that a device impedance might vary in response to the electrical frequency
The impedance nor impedance hump is of any concern/importance b.t.w. as amps deliver an output voltage which is the same regardless of the impedance.
At least for > 50ohm loads.
 

Postlan

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Too many similar headphones from the same company, and it seems there is no real improvement since HD600. It is probably very hard to improve HD600.
 

AudioSceptic

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solderdude

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Blew

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Too many similar headphones from the same company, and it seems there is no real improvement since HD600. It is probably very hard to improve HD600.
I bought the HD660S after auditioning it together with the HD600. To me the HD660S definitely sounded more revealing and had a faster response than the HD600, which by comparison had a slight veil over the sound. So I'd say that, at least with the classic rock music that I was auditioning them with, the HD660S is a clear but iterative improvement over the HD600.

They do seem to need decent power to bring the best out of them though, as I've found they sound a bit lackluster otherwise. I suspect that's why they included the balanced cable.
 

solderdude

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The difference in sensitivity between HD600 and HD660S is just 3dB in favor of the HD660S.
The balanced cable was included to appeal to audiophiles owning balanced amplifiers and to connect it to portable gear with balanced out making the max SPL twice as loud compared to a single ended HD600.
When the HD600 were to be driven from the balanced cable and the HD660S from TRS the HD600 would play 3dB louder.

Other than the extra output voltage from balanced amps there is no benefit as Sennheiser cables are always 4 wire and the impedance of the headphones is too high to matter anyway even when 3 wire cable would be used.
 

Postlan

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I bought the HD660S after auditioning it together with the HD600. To me the HD660S definitely sounded more revealing and had a faster response than the HD600, which by comparison had a slight veil over the sound. So I'd say that, at least with the classic rock music that I was auditioning them with, the HD660S is a clear but iterative improvement over the HD600.

They do seem to need decent power to bring the best out of them though, as I've found they sound a bit lackluster otherwise. I suspect that's why they included the balanced cable.
Thanks. I have not heard 660s, so I would try it in the future. I have tried several HDxxx headphones last 20 years, but I still use HD600 and actually I bought another HD600 recently. I can hear the difference, but I'm not sure if it is an improvement. I just prefer HD600. Maybe my ears are too accustomed to it. Anyway, if HD600 would be discontinued, I think the used price will go up. I know there are so many people like me...
 

AudioSceptic

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Thanks. I have not heard 660s, so I would try it in the future. I have tried several HDxxx headphones last 20 years, but I still use HD600 and actually I bought another HD600 recently. I can hear the difference, but I'm not sure if it is an improvement. I just prefer HD600. Maybe my ears are too accustomed to it. Anyway, if HD600 would be discontinued, I think the used price will go up. I know there are so many people like me...
Does anyone here know if the Drop HD6XX is closer to the HD600 or HD650? Normally I would go to Solderdude's site, where there are many Sennheiser comparisons, but I don't think he's tested the 6XX.
 

Robbo99999

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Does anyone here know if the Drop HD6XX is closer to the HD600 or HD650? Normally I would go to Solderdude's site, where there are many Sennheiser comparisons, but I don't think he's tested the 6XX.
It's always said the HD6XX is exactly the same as the HD650. Oratory has measured them and says they're the same as the HD650.
 

Phoney

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I though that saying that something is more revealing was illegal on this forum. Atleast when some random user says it, certain people will launch nukes.

But then again maybe it's just about the context of which it is used..
 

oldlurker

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These were the very first Audiophile tier headphones I bought. Back then I didn't know much and my logic was that the best entry point for the hobby was a set of good ol' HD 600 series and among the 600, 650 and 660s, the later would save me the need to buy an amplifier... things didn't go as well as expected. As it turns outs I was too greedy, vocals had great definition but everything else was too anemic, except for those ocassions when I listened to them in the middle of the night at very low volume (then it sounded very elegant and pleasant). I figured as time passed that maybe the issue was the lack of power from my very old PC 3.5mm jack. so I set too buy a "powerfull" dongle DAC that would cost me less than a bonafide desktop DAC-AMP combo (plus that way I could also use it with my smartphone). I decided to buy a Tempotec Sonata HD PRO (of which a non-OEM branded version was reviewed here with fliying colours across the aboard), after evaluating the specs I concluded that it might be just what I needed, but to my bewilderment the headphones still didn't sound "right", they could get extremely loud, painfully so (but so they could with my original motherboard's 3.5mm jack to a lesser degree), but it would still sound shouty and unbalanced. it wasn't until Amir reviewed a different headphone here which included a graph of the impedance across the frequency spectrum that the answer hit me, I was indeed lacking power but in a more nuanced manner. I had bought the Dongle DAC after calculating that it could deliver enough miliwats at 150 ohm, little did I know that a device impedance might vary in response to the electrical frequency (which in retrospective makes perfect physical sense). after admiting defeat, my stingy self saved up the money to buy a desktop Amp and finally close the chapter with the mistery behind these cans' not living up to their potential.

It was an adventure full of discovery and learning, but also of anguish and self doubt, at times wondering whether I was crazy or going deaf and eventually just thinking that this model just didn't live up to its predecesors and was just a design flop. ultimately I can say that these do in fact sound pretty good, I was just doing it wrong originally. Ironically, just recently I built a new PC with a higher tier mother board that advertised capability for high impedance headphones (I didn't choose it specifically beacuse of this, though), and to my surprise, yet again, the HD 660s sound perfectly acceptable when connected directly to this board.

So to those considering buying this model because it doesn't need an amp, be mindful that while on board audio has gotten really clean and well performing compared to a decade ago, it might still not have enough power to drive these cans properly depending on the motherboard in question. the same applies to a smartphone. I own an LG V50 (from the series with the quad DAC) and it can get the HD660s loud, but it only sounds balanced and proper at very low volume. in any case, without an amp they will still be serviceable if you only need to get audio out of your system to get something done, but it wouldn't be worth their price tag when used that way.

As for my subjective impression of the sound signature I will say this: They sound like a Live performance at which the mixing technician purpousefully equalized the vocals notably higher than the rest of the instuments, like there are 2 planes of depth, one for the vocals range and another for the rest of the mix. imagine as if they wanted to make the 650 but way less cluttered, as a result the instruments are less inpactful and fun but in return we get significally better instrument separation. They definitively lack bass and I specially notice it when I listen to orchestral music with plenty of cello and tuba, but for everythign else I can't avoid the feeling that having more bass would ruin the balance and be distracting. on the bright side, soundtracks and ambient music compoused mainly with acoustic guitars and piano sounds glorious on these.

Also a first buyer of an “audiophile headphone” here. I bought the HD660S for much the same reason as you. No need for an additional amp which pushes the cost of a setup way past the money I wanted to spend for a first try. It also comes with a balanced cable with a 4.4mm connector which fits exactly my DAP. The 660 is a product from a company with a good track record for outstanding engineering and manufacturing. I thought: great deal. I knew there are a lot of discussions going on comparing the various 600 variants, but I dismissed them as mere “religious bickering”.

My surprise when I first listened to them out of the box was quite big. Bloated bass invading and distorting the lower mids. Heavy distortion in the highs at higher sound levels. I thought for a moment that I was sold a fake product, but the build and the packaging looked genuine. Plus, I bought it from an authorized dealer. The only remedy was heavy equalizing.

They have now around 25 hours of listening. Some of the early issues have become milder, but are still present to some degree. I listen mostly to classical music with a DAP of good quality and FLAC files 44.1/16, 96/24 and 192/24.
As of today I see the following issues.

• Bass of very bad quality that has to be equalized out so as to not affect higher frequencies.
• Very audible distortion in the higher mids at louder levels.
• Audible peak around 4-6kHz producing ringing at higher sound levels if it is not equalized out.
• Limited dynamics. The distortion level increases very quickly at higher sound levels.
• Complete inability to handle complex music as some symphonic passages can be.
• The presentation of the music is quite 2D, but at the same time detailed. This creates problems with some recordings where one gets distracted from the main melodic line by overbearing secondary details. It is sometimes a very strange presentation and certainly inaccurate.
• It seems to me that equalizing also affects the timbres negatively.
• As a result, I use them to listen to chamber music and they are quite good at that. For this, I do not need to equalize and the overall performance is OK.
• Symphonic music with a high dynamic demand is best completely avoided. Some passages end up in a terrible mess.

Overall, quite disappointing. They are OK for some simple music, but add complexity at a higher sound level and they are totally unable to cope. But I suppose that you just get what you paid for.

Now that said, maybe the pairing with the DAP is wrong, but I doubt that it can be that wrong.

EDIT: I forgot to mention that the build is very good and they are very comfortable.
 
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solderdude

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• It seems to me that equalizing also affects the timbres negatively.

When this is the case you are certainly not using the correct EQ for your use case.
• Very audible distortion in the higher mids at louder levels.

This may well NOT be the headphone's fault.
• Audible peak around 4-6kHz producing ringing at higher sound levels if it is not equalized out.

Yes, agreed should be EQ'ed out. Not everyone is bothered by it.

• Complete inability to handle complex music as some symphonic passages can be.

I have heard this headphone doing complex classical to girl with guitar and rock and do not share your view.

• The presentation of the music is quite 2D, but at the same time detailed.

Yes, the same with all HD6** models.

• Symphonic music with a high dynamic demand is best completely avoided. Some passages end up in a terrible mess.

May not be the headphone's fault but at 110dB/V some 2-3V output voltage (no EQ) should be enough to work distortion free. Amir tested it at 114dB so with 1.6V on it and there was no distortion in the mids but note that distortion in the bass will create IM products and affect the mids.
Not visible with current standard measurements though.
We would need dual tone to see how bad it becomes (say 70Hz and 4kHz in 1:10 ratio or so). No such measurement signal is used though.
 
Last edited:

ichliebes

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I bought HD600, 650, 660s and DT1990Pro, using Element III from JDS Labs to drive them, equalized to Oratory1990 Harman Target. Overall, the equalized 650 is my favorite, I can enjoy listening to all CDs in my collection with it. But my 650 has a slight mismatch in the low end, about 0.5-1.5db. 660s has the best match of the four, DT1990Pro has the worst (and I returned it immediately). I'd love to keep my 650, but the mismatch is kinda annoying... I understand it's hard to get a headphone with nearly perfect channel match. So is there any way to make 660s sound similar to 650?
 

threni

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I bought HD600, 650, 660s and DT1990Pro, using Element III from JDS Labs to drive them, equalized to Oratory1990 Harman Target. Overall, the equalized 650 is my favorite, I can enjoy listening to all CDs in my collection with it. But my 650 has a slight mismatch in the low end, about 0.5-1.5db. 660s has the best match of the four, DT1990Pro has the worst (and I returned it immediately). I'd love to keep my 650, but the mismatch is kinda annoying... I understand it's hard to get a headphone with nearly perfect channel match. So is there any way to make 660s sound similar to 650?
You could consider fixing the mismatch via EQ.
 

DUKE-DUKE

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Compré HD600, 650, 660s y DT1990Pro, usando Element III de JDS Labs para conducirlos, igualado a Oratory1990 Harman Target. En general, el 650 ecualizado es mi favorito, puedo disfrutar escuchando todos los CD de mi colección con él. Pero mi 650 tiene un ligero desajuste en el extremo inferior, alrededor de 0.5-1.5db. 660s tiene la mejor coincidencia de las cuatro, DT1990Pro tiene la peor (y lo devolví de inmediato). Me encantaría mantener mi 650, pero el desajuste es un poco molesto ... Entiendo que es difícil conseguir un auricular con una combinación de canales casi perfecta. Entonces, ¿hay alguna manera de hacer que los 660 suenen similares a los 650?

Sennheiser HD 650 ParametricEQ.txt

11 lines (11 sloc) 482 Bytes

Preamp: -6.3 dB
Filter 1: ON PK Fc 24 Hz Gain 6.3 dB Q 0.38
Filter 2: ON PK Fc 172 Hz Gain -3.4 dB Q 0.57
Filter 3: ON PK Fc 2022 Hz Gain 1.6 dB Q 3.53
Filter 4: ON PK Fc 4361 Hz Gain 2.8 dB Q 3.98
Filter 5: ON PK Fc 8661 Hz Gain 4.7 dB Q 1.71
Filter 6: ON PK Fc 3129 Hz Gain -1.4 dB Q 5.51
Filter 7: ON PK Fc 11658 Hz Gain 1.1 dB Q 0.47
Filter 8: ON PK Fc 12016 Hz Gain 1.8 dB Q 1.75
Filter 9: ON PK Fc 19531 Hz Gain -6.5 dB Q 0.34
Filter 10: ON PK Fc 19869 Hz Gain -4.9 dB Q 0.60


 

ichliebes

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Sennheiser HD 650 ParametricEQ.txt

11 lines (11 sloc) 482 Bytes

Preamp: -6.3 dB
Filter 1: ON PK Fc 24 Hz Gain 6.3 dB Q 0.38
Filter 2: ON PK Fc 172 Hz Gain -3.4 dB Q 0.57
Filter 3: ON PK Fc 2022 Hz Gain 1.6 dB Q 3.53
Filter 4: ON PK Fc 4361 Hz Gain 2.8 dB Q 3.98
Filter 5: ON PK Fc 8661 Hz Gain 4.7 dB Q 1.71
Filter 6: ON PK Fc 3129 Hz Gain -1.4 dB Q 5.51
Filter 7: ON PK Fc 11658 Hz Gain 1.1 dB Q 0.47
Filter 8: ON PK Fc 12016 Hz Gain 1.8 dB Q 1.75
Filter 9: ON PK Fc 19531 Hz Gain -6.5 dB Q 0.34
Filter 10: ON PK Fc 19869 Hz Gain -4.9 dB Q 0.60


Hey Duke, thank you so much for your reply.

I see this is Parametric EQ settings for HD650 to Harman Target (from AutoEQ, with measurements from Oratory1990).

I was wondering If I could make 660s sound similar to what 650 did after equalizedwill try to figure it out.

My main problem with 660s is that it sounds not smooth enough, sometimes the high frequency sounds like broken glass... And overall the bass sounds strange.

Update: just find out I can use autoeq.py to make a headphone sound like another. Will try it tomorrow.
 
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DUKE-DUKE

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Hey Duke, thank you so much for your reply.

I see this is Parametric EQ settings for HD650 to Harman Target (from AutoEQ, with measurements from Oratory1990).

I was wondering If I could make 660s sound similar to what 650 did after equalizedwill try to figure it out.

My main problem with 660s is that it sounds not smooth enough, sometimes the high frequency sounds like broken glass... And overall the bass sounds strange.
Hi. Try equalizing the HD 660s with the HD 650 EQ.txt Parametric table and then let us know what you think.

In my case I use the Parametrica EQ.txt table of different headphones to find the sound I like the most and that way I adjust the headphones I don't like to use them out of the box.

Here is the link with all the brands and models: https://github.com/jaakkopasanen/AutoEq/tree/master/results so you can try them out, I hope you find the sound you are looking for in your HD 660s.

Best regards.
 
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