Sennheiser HD 6 Series Comparison Thread

Resolve has just put out a video comparing all of the currently available headphones from the 6 series (as well as one from the 4 series), so I thought it prudent to have a place to discuss the topics addressed in the video as well as anything else surrounding the comparisons between all of these headphones.

Below you can find all of the measurements included in the video, as well as a few others I’ve taken the liberty of adding.

Individual Frequency Response Measurements

Sennheiser HD 600

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

GRAS 43AG with KB50xx pinnae — Raw

B&K 5128 — DF-Calibrated, pad wear effects shown

Sennheiser HD 650

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

GRAS 43AG with KB50xx pinnae — Raw

B&K 5128 — DF-Calibrated, pad wear effects shown

Sennheiser HD 6XX

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

B&K 5128 — DF-Calibrated, pad wear effects shown

Sennheiser HD 620S

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

GRAS 43AG with KB50xx pinnae — Raw

Sennheiser HD 660S2

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

B&K 5128 — DF-Calibrated, pad wear effects shown

Sennheiser HD 490 Pro

B&K 5128 — DF-Calibrated

B&K 5128 — Raw

Impedances of the HD 6 series (and HD 490 Pro) compared

Total Harmonic Distortion measurements

HD 600

HD 650

HD 620S

HD 660S2

HD 490 Pro

Excess Group Delay

HD 600

HD 650

HD 620S

HD 660S2

HD 490 Pro

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I see that you are testing both a 650 and a 6xx, and that they appear to have some differences. Are these within expectations for unit variations, age of units, ear pads and wear, or does it appear that despite the hype, that these are truly different units?

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In the video this thread is referencing, Resolve mentions that we should probably still think of them as the same headphone, as with the same earpads they measure near-identically both in terms of Frequency Response as well as impedance.

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Gras mic drop.
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No need for any more Sennheiser HD 600 series videos for the next couple of years from anyone else as this video is spectacular. Even though I would place Drop HD6XX in D tier, Resolve is spot on coming from the subjective perspective. Props! Bravo Resolve!

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This image is now a thing that exists on the internet… The horror

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Very well done. I like it when @Resolve gets enthused. :grinning:

Been thinking about dipping into the Sennheiser pool. I’m leaning toward the 490 Pro, I’ve got some other “Pro” styled headphones ( Yamaha, AKG ) and this looks like it would be a good fit with my wonky ears.

Mark Gosdin

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Great video - I do like that the HD490 Pro was included as I do really like that headphone after having used it for a few weeks now.

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Your video was solid, @Resolve. Great job. :clap:

This is the first time I see an impedance plot for the 660S2. Quite an elevated one.

Anyway, since I am in the brain burn-in camp, and after owning the 600 for 4 years and the 660S2 for almost a year, I can comfortable state that even though the 600 sounds more natural in the first couple of songs, the 660S2 gives me a better experience in the long run, i.e., after my ears adjust to its FR. But we’re living in the instant dopamine era, so the 600 will always be easier to recommend. :man_shrugging:

To my ears – while in longer listening sessions: 660S2 > 650 > 600 > 660S

Cheers. :beers:

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Thanks for this survey of the 6 (and one 4) series headphones, Resolve!

I’ve flirted with the idea of a 6 series headphone for a long time. But guess the lack of sub-bass and maybe also soundstage has kept me away. The 490 Pro looks like a fairly nice additional though to Sennheiser’s Pro lineup. And perhaps one I might consider.

I’m tryin to get away from EQ though. And the 490 Pro looks a tad bright in the low treble, not unlike my current Beyer DT-770. If you do another vid on the 490 Pro, it might be interesting to see a comparison with Focal’s new Hadenys, and maybe a couple other recent open backs that also extend well into the bass.

I know you’re not really the tech guy at Headphones.com, btw. But there are a few issues along more technical lines that I’d push back on, or want to know more about in the 6 Series Comparison video. I don’t agree that a midrange/BBC dip = soundstage, for example. And don’t necessarily agree that more “heads” are better, unless they’re close to the anthropomorphic/metric characteristics of a rig like the 5128. (The 5128 manikin still needs some work tho imo.)

I’d also like to know more about how a DF HRTF curve was computed for the GRAS 43AG, because accurate free field and diffuse field HRTF measurements normally require a manikin with at least a head and neck that interacts with the sound field. And I don’t see how you’d get those, or translate them correctly to over-ear measurements made on a system with a flat plate and no head, like the 43AG.

IAC, I’ll be interested to see how your efforts to correlate measurements between rigs proceed. And look forward to maybe hearin a few more thoughts on the 490 Pro, if you do another vid on this.

Re the DFHRTF, this would’ve been from Oratory taking the KEMAR to “a facility” as I called in a recent live stream haha. My understanding is that this was calculated from FF (power weighted average). But this is where @Mad_Economist would have to fill in the rest of the details. I will say, it has yet to be independently validated, but it’s what we’re moving forward with currently since it lines up with the measured result as well.

Regarding the different heads thing, this is something we’re currently researching. But there’s already a lot pointing to HpTF variation across real heads being a far more significant factor than even we had previously considered. So I’d say just keep an eye on what we’re doing there. Once we have something more concrete to share on that front I’m sure we’ll make a video.

Re the soundstage effect, I don’t think it’s just a dip around 1.5khz. I think it’s a combination of that dip with certain extra presence in the treble. But in just about all headphones that are seemingly well received for this effect, these features are present.

Edit: not Struck method

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Thank you very much for the detailed reply, Resolve. And happy July 1st or 4th, whichever is most applicable in your cases. I wanted to give your 6 series comparison video another look before responding to the above and maybe givin a more in-depth take on some of this, because there’s alot of ground covered in this video, in a relatively short space of time.

I also like to quibble about some of the technical stuff. But overall, I think you and DMS are doin a pretty decent job on most of your measurements and reviews. And I find myself agreeing with more of your takes than not. I hope both of you will continue to post your raw/uncalibrated/uncompensated measurements though, since I prefer to use my own methods of compensation and reference curves, rather than the ones Headphones.com is currently offering.

For me, the most logical baseline or reference point for a headphone’s FR is still the in-ear FR of a pair of good neutral speakers in a typical semi-reflective room. And I hope that you, DMS, or some other kind soul at Headphones.com will make a run at this at some point, so we can see how this type of in-ear response compares to the raw headphone measurements. I know some on your staff think DF is the best way to go. But for me, it’s just a stepping stone to get a little closer to the above, until some better in-ear measurements of speakers are available.

I have some gripes about the way y’all are doin DF compensation as well, but will save most of those for another time or place. I like the results I’ve been gettin recently with HBK’s original 1/3-octave 5128 DF measurement though. And would like to try posting a few examples of this in another topic here, maybe in the Technical Forum.

The comparisons of new and worn earpads was very interesting. I wasn’t expecting that much variation in the before and after on these headphones. But my experience with other headphones has been similar. As the pads wear, and become more compressed (and your ears get closer to the drivers), the FR seems to get warmer sounding. This may not be true for all headphones though.

I’ve been wondering about the potential influence of pad flap on some of the closed back measurements as well. So I’m glad you threw in the slide of the HD620S with increased clamp for comparison. And hope this is something you’ll continue to look at, and try to understand better. I know you need fairly high dBs when doing measurements to filter out the background noise. But I wonder if that could be adversely (and maybe unfairly?) effecting the bass measurements on some closed-backs, since it may not necessarily represent the responses at more typical listening levels. And I seem to be noticing a bit less mid-bass emphasis in some of Jude’s (and maybe also the Sound Guys’?) closed-back measurements by comparison.

Tyll put his old Head Acoustics rig in a small insulated box when doing his headphone measurements. And I wonder if that might be something to consider as well. Seal or leakage issues around the 5128’s cheeks might be something else to look at.

On the subject of HpTF variation, I think you’ll have to explain what this refers to a little more, and why you think it’s important… I expect headphones to measure differently on every head, ear, and ear canal. This is more of a problem, imho, with IEMs than with over-ear headphones though (even though some of the technical research seems to contradict this), because an individual’s HRTF interacts much less with an IEM, making it harder to filter out the HRTF effects, and produce a reliable, predictable result. This is why I only use over-ears for my critical headphone listening.

I still expect some variation with over-ears. Assuming we all fall within a more or less normal range of human physical characteristics though, compensation should take care of alot of that. That is really the point of compensation, in fact! To filter out the individual effects of a person’s or rig’s transfer characteristics, so that measurements on two or more individuals or systems can be more easily compared. This is one of the main reasons we do compensation, or “calibration”, as you refer to it in the video.

Re soundstage, since this is largely a subjective effect, I think it’s difficult to actually pin down precisely what’s responsible. I think Tyll and probably also some of the more informed developers and subjective listeners in the hobby would probably say that it’s a bit more involved than just a midrange dip and some extra treble though. This might also be a good topic for another thread though.

I think that a slight dip in the upper midrange can potentially improve the timbral and tonal balance of some recordings though, because the speakers used for mastering recordings will often have a dip or depression in their in-room response due to cross-over and directivity issues in the same frequency range. A good example of this is the Adam T8V…

https://www.spinorama.org/speakers/Adam%20T8V/ASR/index_asr.html

The in-room response of the T8V has a fairly pronounced dip at around 2 kHz in the upper midrange. And it also rises up fairly significantly in the low treble before descending back down again in the higher frequencies. To properly decode a recording mastered on a speaker like this, you’d need a headphone with a similar dip and rise in the same ranges. This might improve the perception of soundstage as well. But it may only be because the headphones are doing a better job of matching the tonal and timbral balance of the transducers used to produce the recording.

The Adam is a somewhat extreme case, but there are many other well-regarded speakers with a similar dip or depression in their in-room/off-axis response, at the cross-over of the midrange and tweeter drivers. So this is not an uncommon thing. Recent speaker designs (with DSP and improved cross-overs) are beginning to address this issue though. And getting much closer to acheiving a linear in-room slope from F0 in the bass to the treble.

Sorry to hear you’re under the weather in the livestream btw. Another thought also occurred to me though on the subject of pad wear, after watching the 6 series video…

If you have a good, reliable in-ear mic, like maybe the one used to measure the difference in response between the HD 600 and 650 on your own ears, perhaps that could be used to document any changes in your headphone’s response over time, due to pad wear and other factors, so appropriate adjustments could be made in your EQ settings to compensate for those effects. For this to work most effectively, you’d probably need measurements with an in-ear mic and also a good HATS (like the 5128) made while the pads and headphones are still brand new, so you have a good baseline to begin with for comparison and any future tweaks.

The pad wear effects on the 6 series seem to be confined primarily to the higher frequencies though. So perhaps that could be tweaked with just a simple high frequency shelf control.

There’s no guarantee that changes in FR due to pad wear or aging would measure the same at the eardrum reference point (of a HATS) as they due at the entrance to the ear canal, btw. But an in-ear mic might give at least a general idea of what’s goin on there for the purpose of doin some basic EQ adjustments.

Hope you’re feelin better soon.