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Sennheiser HD660S Review (Headphone)

Rate this headphone:

  • 1. Poor (headless panther)

    Votes: 14 7.1%
  • 2. Not terrible (postman panther)

    Votes: 64 32.5%
  • 3. Fine (happy panther)

    Votes: 98 49.7%
  • 4. Great (golfing panther)

    Votes: 21 10.7%

  • Total voters
    197

AudioSceptic

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It does belong in an entirely different family.

Different baffle, different construction, different driver, angled vs not angled driver, dual entry vs single entry, weight, clamping force and comfort differ. Different pads as well.
The HD660S is similar in build to the HD6** series and HD560S is based on HD5** chassis.
HD660S feels 'solid/serious' where the HD560S feels like a toy (comparatively).
HD660S comes with balanced cables as well, HD560S does not (6.3mm only).
And yet, the 58X looks like it's in the HD6** family.
 

solderdude

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And yet, the 58X looks like it's in the HD6** family.

Correct. This is because it was referencing to the original HD580 (precision) which is what ultimately started the HD6** series.
 

I0000dayz

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HD660s is one of the best headphones ever with EQ in my opinion. Their mids section shows a technical tour de force, with perfect timbre, speed and dynamics. It's sad to see that their bass distortion levels are so high, but expected.

After EQ there are two problems remaining:
- weak bass extension; they barely reach 30-35hz - some electronic music just doesn't sound complete
- (subjective) they sound too "tiny"; the instruments and vocals sound so small compared to other headphones of mine like the Audeze LCD-2C, Sundara, Elear and AKG K702; it kind of takes away from the experience, it is like listening to a small pair of desktop speakers
 
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solderdude

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After EQ there are two problems remaining:
- weak bass extension; they barely reach 30-35hz - some electronic music just doesn't sound complete
Consider the fact that the used EQ is not the correct one.
I have EQ'ed HD650 and HD58X to be flat to 20Hz and they are perfectly capable of that to at least impressive levels.
 

Exprymer

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Is it only my opinion or the AKG k371 it's better in all regards except for maybe material and construction?
 

I0000dayz

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Consider the fact that the used EQ is not the correct one.
I have EQ'ed HD650 and HD58X to be flat to 20Hz and they are perfectly capable of that to at least impressive levels.
I never use EQs from ASR review threads, they do their job but they're made by eye.
I don't know about the HD650 and the HD58X, but the HD660s lacks sub-bass regardless of how much you boost it, it's not gonna reach those deep -45hz frequencies unless you apply a ridiculous 12-15db boost, which creates distortion. I've compared it directly to AKG K702 which becomes subwoofer like when boosted +7db in that region, even my 10 years old HD598 can rumble nicely with +6db.
 

MacCali

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Had all 3, 660S has by far the least veil.
Really, I’ve listened to both at shows and honestly found the 650 better even though this is strictly subjective and may not be on veiled performance.

The 650 is also cheaper eh

@Exprymer honestly I bought those because they follow the target Harman curve. Also did the EQ to make them better, which does make them sound better.

I feel like the closed enclosure hurts those headphones. I own a focal Elegia and with or without EQ and massive distortion at higher volume they sound better to my ears. Not sure if that’s based on interior reflection design or what
 

usern

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it's not gonna reach those deep -45hz frequencies unless you apply a ridiculous 12-15db boost, which creates distortion.
Do you think this distortion is audible at, let's say, 75 dB listening level?
 

I0000dayz

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Do you think this distortion is audible at, let's say, 75 dB listening level?
I think so, it's not extremely obvious but it makes the bass sound "crunchy" at times, just not very smooth and lacks texture. It certainly sounds a bit unnatural for the headphone to produce these very low frequencies. Their mid bass is absolutely wonderful though... :)
 

Robbo99999

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Do you think this distortion is audible at, let's say, 75 dB listening level?
Well, 75dB listening level, would we say 75dB at 1kHz then....which would mean +15dB boost on the bass which would put it at an equivalent 90dB distortion measurement in the bass (75+15 = 90). Which would mean it would be below the blue line in the following distortion graph in terms of distortion in the bass:
index.php

At which point people would say you probably won't hear that distortion if it's under that blue line. I did take some measurements of my own headphones though using my miniDSP EARS and my HD600 came out with (similar'ish to the graph above) more distortion in the bass than my HD560s and one of my K702 and I'd always thought the HD600 had woolly bass when EQ boosted in comparison to my other headphones even before I bought the miniDSP EARS, so praps you can hear it. Most would say under than blue line in the bass would be fine though.
I think so, it's not extremely obvious but it makes the bass sound "crunchy" at times, just not very smooth and lacks texture. It certainly sounds a bit unnatural for the headphone to produce these very low frequencies. Their mid bass is absolutely wonderful though... :)
 

usern

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I think that there seems to be misunderstandings of boosting bass at reasonable volumes and if you do it correctly with digital EQ then there should be no problems with distortion until you turn the volume up pretty loud.

@Robbo99999 I did actually choose 75 dB to stay under 90 dB when boosted :). And you explain well how it should stay below audible threshold. My 660S is software boosted 15 dB and bass is clear and can hear very low frequencies. Actually, everything else is toned down 15 dB (applied the boosts and used -15 dB preamp) to avoid digital clipping which perhaps @I0000dayz is hearing.

And yeah, 560S has less distortion so can go louder with boosted bass. And the distortion is more gradual than 660S. 660S starts to distort very suddenly when enough gain is applied. Can still go stupid loud before it happens though.

In general, the tonality of my 660S sample is very good with @oratory1990 EQ. I like it a bit more than equalized 560S.
 
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Robbo99999

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I think that there seems to be misunderstandings of boosting bass at reasonable volumes and if you do it correctly with digital EQ then there should be no problems with distortion until you turn the volume up pretty loud.

@Robbo99999 I did actually choose 75 dB to stay under 90 dB when boosted :). And you explain well how it should stay below audible threshold. My 660S is software boosted 15 dB and bass is clear and can hear very low frequencies. Actually, everything else is toned down 15 dB (applied the boosts and used -15 dB preamp) to avoid digital clipping which perhaps @I0000dayz is hearing.

And yeah, 560S has less distortion so can go louder with boosted bass. And the distortion is more gradual than 660S. 660S starts to distort very suddenly when enough gain is applied. Can still go stupid loud before it happens though.

In general, the tonality of my 660S sample is very good with @oratory1990 EQ. I like it a bit more than equalized 560S.
That's good re your HD660s and the boosted bass being fine for you, and interesting correlation re your impressions of bass potential of HD660s & HD560s which agrees with the measurements. I'm surprised you like your EQ'd HD660s more than your EQ'd HD560s as the latter has a more EQ'able frequency response and lower distortion as well as angled drivers to improve soundstage.........but headphones can be very personal, and additionally it will also come down to unit to unit variation and how close your samples are to the measured unit(s) upon which the EQ was based (and the accuracy of left & right channel matching as a related variable), so that's a factor too.
 

I0000dayz

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My 660S is software boosted 15 dB and bass is clear and can hear very low frequencies. Actually, everything else is toned down 15 dB (applied the boosts and used -15 dB preamp) to avoid digital clipping which perhaps @I0000dayz is hearing.
I apply preamp to avoid clipping, it isn't that. I always EQ all of my headphone to match the Harman curve and audition them carefully. The HD660s simply doesn't take it too well in the sub-bass region. Robbo99999 says bass distortion can be audible with the 600 series, I don't know, but if it isn't distortion that I hear (2.5-5% distortion at 90-95db is probably barely audible) that means the technicalities of the headphones in that area are just bad, and maybe that is why Sennheiser choose to tune it the way they did (?). The AKG K702 with a similar bass profile sounds like a quality subwoofer (in the limits of what a headphone can do) compared to the HD660s, the HD598's sub-bass sounds also much better. It's weird, because the mid-bass sounds extremely clean and fast on the HD660s, it's just the lowest bass extension which struggles.
 
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rkt31

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I noticed the New Flamenco guitar player Jesse Cook uses them. One of the reviewers described R70x as boring and uninspiring (?). Others describe them as smooth, tonally correct, with good image.
Flat response may sound boring if people are habitual of v type or w type sound signature.
 

Blew

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Try the headphone on another system directly from a phone, tablet, PC, laptop, integrated amp or other device first before trying anything else.
This way you can rule out the headphone/cable.
As I mentioned, the headphones exhibit the crackle/popping on other headphone systems too, and have done so for a while. Also, my HD599S don't exhibit it on this system either. So I think it's something to do with the headphones themselves. It's mostly the left ear but does happen in the right too. It seems to happen when playing music with a lot of heavy guitars, such as heavy metal.

Could it be IMD caused by the lower frequencies distorting the driver while playing certain other frequencies in combination and making it crackle? Could the drivers be damaged?

However, I've done a frequency sweeps and the THD tests on audiocheck.net which all sound fine. I can still determine a difference between the 0.01% and 0.05% THD tests on there, so the drivers sound ok otherwise.
 

solderdude

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Sounds like a similar thing as reported by 10000dayz.

The (brief) period I heard the HD660S I did not notice anything wrong but also did not EQ it.
Maybe it is faulty in some way, maybe it is too revealing and 599 smooths things over (comparatively).

Perhaps try to audition another HD660S or buy one with the right to return without costs ?
 

Blew

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Maybe it is faulty in some way, maybe it is too revealing and 599 smooths things over (comparatively).
I finally sat down and spent some time testing it properly over multiple systems (DACs, amps, headphones, computers/players), and discovered that it does actually happen on every system I tested, including the HD599SE headphones! I guess you're right about the HD660S being so revealing that it's just a lot more noticeable on them. It's definitely more noticeable on headphones than on speakers.

Searching further I found this thread about the exact same issue here:

During testing I also noticed that the sound of the headphone pads moving against my hair can make a similar sound that from time to time I've probably assumed is the same issue. So I've now fallen back in love with the HD660S. Apologies for the thread pollution!
 
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