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Harman preference curve for headphones - am I the only one that doesn't like this curve?

thewas

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FYI, it's discussed a bit further here (s. 2.7).
Thank you for the hint, just had a look at it and have though two objections where @Sean Olive might be able to help.

Firstly, the second order high shelving 2500Hz filter they used has a quite different shape to a nominal same one at REW, below both for -10 dB

1611753616263.png

1611753850002.png

the paper one starts much lower and does not shows the typical "kink" around its nominal frequency.

Secondly I find it questionable they defined their total target values including their 3 inexperienced to the 8 experienced ones while both groups had an almost 6dB(!) deviation in the desired treble of loudspeakers (1.8 vs -4.0 dB).
 

Robbo99999

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Those measurements on the Drop site were by Jude of Head-Fi. Speaking to Oratory about them he agreed with me that he likely didn't get a good seal when measuring the headphones. Oratory's measurements show better bass extension. As for distortion, it's pretty low across the entire frequency range, not only according to Head-Fi's (90dB@1kHz) but also Innerfidelity's measurements. Subjectively, I don't hear any distortion at all boosting mine up to the Harman target - in fact it's some of the cleanest bass I've heard.



This is an important (and often overlooked) point. Some companies' / models' unit variation does seem better than others though, sometimes belying their price. For example, as @Robbo99999 mentioned, Oratory, who's said most of his posted measurements and EQ profiles are based on multiple units by now, found the HifiMan HE4XX's unit variation to be very low. Direct quote:


That's a $180 planar magnetic headphone (despite planars usually being more expensive than dynamic driver models - I actually got mine for just $140 on promotion, and they've been as low as $120), which has low enough variation between units that individual EQ settings wouldn't even make sense, presumably due to this unit variation being around the same or less than placement variation.

Talking of placement variation, this seems to be another often ill-considered factor when it comes to using headphone measurements for developing EQ profiles, sometimes only a single-placement (and single-unit) measurement being used to base EQ settings on for all users and their units, when in reality every time a pair of headphones is put on the variation in placement will alter the frequency response somewhat. That's why professional measurements take an average of at least 3 (or more, Oratory takes 5 as I believe Harman does) re-seats and average them. (I see this as analogous to the listening window averaging being included in the predicted in-room response calculation for loudspeakers in order to account for multiple seating positions / head movement.) This is another area in which HifiMan's headphones seem to do well e.g. here is the frequency response variation of the HE400i with multiple re-seats as measured by Rtings, which combines in-ear mic measurements of several real people wearing the headphones for the bass (including subjects wearing glasses) with HATs measurements in the mids/treble.

I believe useful measurements to base EQ settings on that will work for the majority of users and their specific units and placement on their heads can be achieved, if care is taken to average both several units and placements (as long as variation in both is reasonably low) in order to mitigate all these potential issues.
What you say makes sense.
In that case I might send my HE4XX to Oratory at the same time I send him my K702, because I find it quite surprising that the HE4XX sounds the most different to my other headphones when all are EQ'd to the Harman Curve - if it's shown to have a significantly different frequency response to his other tested units then it would rule out my hypothesis that the HE4XX is reacting unpredictably with my ear & head physiology (unlike my other headphones) and throwing off my normal experience of the Headphone Harman Curve that I know from my other headphones.
 

raistlin65

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Am I alone here in really not liking Harman preference curve? Like really not liking it :eek:

Here's an interesting question. How many people that swear by HTR have done DBT to determine that they do prefer it?

And have they used DBT to compare variances of HTR to the stock sound? As they might be responding to the smoothing of the frequency response, rather than the particular curve emphasis.

Could be some of them are being influenced by expectation bias.
 
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Music1969

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Here's an interesting question. How many people that swear by HTR have done DBT to determine that they do prefer it?

And have they used DBT to compare variances of HTR to the stock sound? As they might be responding to the smoothing of the frequency response, rather than the particular curve emphasis.

Could be some of them are being influenced by expectation bias.

Fair points indeed. Cannot argue with that.

I do need to see how I go with DBT , would be very interesting for myself.

Will the differences be as huge as my sighted testing? Not as huge? No differences? All good questions.
 

raistlin65

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Fair points indeed. Cannot argue with that.

I do need to see how I go with DBT , would be very interesting for myself.

Will the differences be as huge as my sighted testing? Not as huge? No differences? All good questions.

And you might not want to listen to your speakers for a day or so first. HTR EQ tuned headphones only. Give your brain a chance to adjust.
 

Sean Olive

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In that case I might send my HE4XX to Oratory at the same time I send him my K702, because I find it quite surprising that the HE4XX sounds the most different to my other headphones when all are EQ'd to the Harman Curve - if it's shown to have a significantly different frequency response to his other tested units then it would rule out my hypothesis that the HE4XX is reacting unpredictably with my ear & head physiology (unlike my other headphones) and throwing off my normal experience of the Headphone Harman Curve that I know from my other headphones.
This is an open-back headphone so you would think that it's not related to acoustic impedance. What else could explain it? But getting accurate measurements would rule out accuracy of the EQ.
 

Sean Olive

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Here's an interesting question. How many people that swear by HTR have done DBT to determine that they do prefer it?

And have they used DBT to compare variances of HTR to the stock sound? As they might be responding to the smoothing of the frequency response, rather than the particular curve emphasis.

Could be some of them are being influenced by expectation bias.


Completely possible. Of course, all of our research is based on controlled DB tests.

Otherwise, I wouldn't have believed I like a 10 dB bass shelf for an in-ear headphone unless I did the test myself. I would be embarrassed to admit that's what I consider neutral. I would have said "that is something a 16-year old gamer with no music/ audio training might like" and completely dismiss it.

It turns out my tastes are not that different from average trained and untrained people. But I never would have known unless I did a blind test.
 

raistlin65

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Completely possible. Of course, all of our research is based on controlled DB tests.

Otherwise, I wouldn't have believed I like a 10 dB bass shelf for an in-ear headphone unless I did the test myself. I would be embarrassed to admit that's what I consider neutral. I would have said "that is something a 16-year old gamer with no music/ audio training might like" and completely dismiss it.

It turns out my tastes are not that different from average trained and untrained people. But I never would have known unless I did a blind test.

Not that you don't have enough to do. But it would be interesting if Harman took a couple of music files. EQ'd the files for the K371 to match the target. And then a couple of the most likely variations from target.

Create an interactive website that let K371 owners do DBT tests with no EQ and the different EQ options. Then report the results to the user. You might get some interesting data out of it.
 

bobbooo

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This is an open-back headphone so you would think that it's not related to acoustic impedance. What else could explain it? But getting accurate measurements would rule out accuracy of the EQ.

It's open-back but I believe it has a closed front volume, so I think acoustic impedance effects could still be a factor here.
 

Sean Olive

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Thank you for the hint, just had a look at it and have though two objections where @Sean Olive might be able to help.

Firstly, the second order high shelving 2500Hz filter they used has a quite different shape to a nominal same one at REW, below both for -10 dB

View attachment 108727
View attachment 108733
the paper one starts much lower and does not shows the typical "kink" around its nominal frequency.

Secondly I find it questionable they defined their total target values including their 3 inexperienced to the 8 experienced ones while both groups had an almost 6dB(!) deviation in the desired treble of loudspeakers (1.8 vs -4.0 dB).
This was an test early on, almost what I would call a pilot experiment with only 9 listeners. The Harman Target Curve for headphone came from a later test involving over 250 listeners.

Just spoke with Todd and the shelving filters in the MOA experiment were specified based on Q not order. The Q was 0.3. In EW apparently you can only specify slope as 6 db or 12 dB. That could explain the differences.


Not that you don't have enough to do. But it would be interesting if Harman took a couple of music files. EQ'd the files for the K371 to match the target. And then a couple of the most likely variations from target.

Create an interactive website that let K371 owners do DBT tests with no EQ and the different EQ options. Then report the results to the user. You might get some interesting data out of it.

That would be interesting, and we've discussed doing something like this a couple of years ago. Turns out management doesn't see a sufficient ROI on the effort so I would have to do this on my own time, maybe when I retire.

With COVID, Harman -- like all audio companies - has been seriously impacted in terms of subjective listening panels. -- so remote or online tests are becoming more feasible. At the recent SenseCamp 2021 this was a topic of discussion, and certainly the efficacy of testing preferred target curves is better than say evaluating loudspeakers or automotive audio systems.

Assuming the QC is sufficient, limiting the tests to AKG K371 users would make it somewhat controlled. With enough users the noise in the data would decrease. Playback level would need to be controlled since that is a variable also.
 
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PH73

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@Sean Olive, would you care to speculate as to why the preferred headphone curve equates to the Harman speaker room curve? I thought that the preferred room curve was related to the inverse of the speaker's directivity. In effect there should be a different preferred room curve for speakers with different directivity patterns. Is it just coincidence that the preferred headphone curve happens to match this particular room curve or something else?
 

Sean Olive

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@Sean Olive, would you care to speculate as to why the preferred headphone curve equates to the Harman speaker room curve? I thought that the preferred room curve was related to the inverse of the speaker's directivity. In effect there should be a different preferred room curve for speakers with different directivity patterns. Is it just coincidence that the preferred headphone curve happens to match this particular room curve or something else?
Speculation can get you in trouble.

That's the first time I've heard the preferred in-room target expressed as the inverse of the speaker DI If that were true then yes you would require a different in-room curve for every speaker DI. Are you aware of any research where they actually tested this ?
 

Feelas

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Not that you don't have enough to do. But it would be interesting if Harman took a couple of music files. EQ'd the files for the K371 to match the target. And then a couple of the most likely variations from target.

Create an interactive website that let K371 owners do DBT tests with no EQ and the different EQ options. Then report the results to the user. You might get some interesting data out of it.
It is most interesting, that K371's filters (at least how Amir proposed them) are mostly opening up the soundstage & widening the percepted sources. I have a theory myself, that smoothness of FR lets the real reverb come through & Haas effect happens, since first reflections of recording aren't masked by any erratic peaks in response.

@Sean Olive if I may interrupt - did you assess how angling of headphone pads affects the percepted soundstage? Some here extensively speculate, that indeed the angling & pads deepness contribute mostly to the percepted soundstage - could you please try to tell us what You know, did you check anything in regards to other factors than FR, i.e. during other studies?
 

thewas

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This was an test early on, almost what I would call a pilot experiment with only 9 listeners. The Harman Target Curve for headphone came from a later test involving over 250 listeners
Thank you, was there also a later larger study made for the loudspeaker targets?

Just spoke with Todd and the shelving filters in the MOA experiment were specified based on Q not order. The Q was 0.3. In EW apparently you can only specify slope as 6 db or 12 dB. That could explain the differences.
In REW you can also define a HSQ and with 0.3 it actually also looks very similar to the paper one, it invalides though the argument in the paper about its choice:

The treble filter frequency of 2.5 kHz was chosen because this is a common midrange-tweeter crossover frequency where the directivity of the loudspeaker begins to increase, and the in-room response of the loudspeaker begins to fall downwards (see Fig. 2).

as it starts increasing already around 400-500 Hz, although it must be also said on common 5-6.5" midwoofers it already starts increasing around 1kHz as it can be akso seen at the F208 LP measurement of Fig. 2.

That's the first time I've heard the preferred in-room target expressed as the inverse of the speaker DI If that were true then yes you would require a different in-room curve for every speaker DI.
But the variation of the preferred curve is logical if the preferred target above transition frequency is a flat direct sound and is also described in the same paper:

The exact amount of high frequency drop will depend on directivity of the loudspeaker, the ratio of direct-reflected sounds at the listening seat, and the absorption characteristics of the room.
 
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raistlin65

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That would be interesting, and we've discussed doing something like this a couple of years ago. Turns out management doesn't see a sufficient ROI on the effort so I would have to do this on my own time, maybe when I retire.

With COVID, Harman -- like all audio companies - has been seriously impacted in terms of subjective listening panels. -- so remote or online tests are becoming more feasible. At the recent SenseCamp 2021 this was a topic of discussion, and certainly the efficacy of testing preferred target curves is better than say evaluating loudspeakers or automotive audio systems.

Assuming the QC is sufficient, limiting the tests to AKG K371 users would make it somewhat controlled. With enough users the noise in the data would decrease. Playback level would need to be controlled since that is a variable also.

I would think that you would not want to control for playback level. Encourage the user to choose the volume they are comfortable with. If multiple music files, encourage them to recalibrate the volume to their tastes for each song before testing.

After all, that is how they will use their headphones. And given how easy the K371 are to drive, the very large majority of users that listen loud should be able to reach their preferred level without clipping.
 

Sean Olive

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Thank you, was there also a later larger study made for the loudspeaker targets?


In REW you can also define a HSQ and with 0.3 it actually also looks very similar to the paper one, it invalides though the argument in the paper about its choice:

The treble filter frequency of 2.5 kHz was chosen because this is a common midrange-tweeter crossover frequency where the directivity of the loudspeaker begins to increase, and the in-room response of the loudspeaker begins to fall downwards (see Fig. 2).

as it starts increasing already around 400-500 Hz, although it must be also said on common 5-6.5" midwoofers it already starts increasing around 1kHz as it can be akso seen at the F208 LP measurement of Fig. 2.


But the variation of the preferred curve is logical if the preferred target above transition frequency is a flat direct sound and is also described in the same paper:

The exact amount of high frequency drop will depend on directivity of the loudspeaker, the ratio of direct-reflected sounds at the listening seat, and the absorption characteristics of the room.

The only other study that was published was the Room Correction AES paper where we compared different room corrections that had different targets versus one of ours. It only had 9-10 trained listeners.. Also, Linda Gedemer while doing her PhD research at Harman on Cinema Speaker Calibration did a comparison of Harman Target vs SMPTE X-curve. That paper is available at AES elibrary and discussed in Floyd Toole;s open access paper in J.AES.


I agree that the DI transition begins sooner than 2.5 kHz and will depend on the particular array of drivers used and how they are crossed over.

Finally. I don't claim the Harman In-Room Target is the last word in what it should be. The results of the paper cannot be generalized to conditions beyond those tested in the paper. There remains many open questions that need further research including the influence of speaker DI, spatial averaging used, what sort of window length is optimal, and the influence of the ratio of direct/reflected sounds in the room. etc.. We know from a few controlled tests, years of empirical experience in the field (both small and large rooms,) as well as cars that we are in the ballpark.. There is also some broad consensus with others who have contributed to this topic. Much of this is all discussed in Floyd's paper: http://www.aes.org/e-lib/browse.cfm?elib=17839
 

Sean Olive

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I would think that you would not want to control for playback level. Encourage the user to choose the volume they are comfortable with. If multiple music files, encourage them to recalibrate the volume to their tastes for each song before testing.

After all, that is how they will use their headphones. And given how easy the K371 are to drive, the very large majority of users that listen loud should be able to reach their preferred level without clipping.

Their choice of preferred EQ is likely dependent on volume so if you don't control that variable you are comparing apples vs oranges. I would only allow them to adjust volume if that is treated as a measured variable. So maybe they adjust the EQ to preference at some standardized low/medium/high volumes. It would be interesting to know what their preferred volume is although that data exists somewhere.
 

richard12511

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The analogy wasn't with the cuisine type, but traditional (family owned Italian) / niche vs mass market compromises thereof (Olive Garden)

Think local soul food / bbq restaurant vs the McRib.

Except most people would likely prefer the local soul/bbq over the McRib under blind conditions, which would make the Harman curve more similar to the local soul/bbq.

I get what you mean, but I see it as different. The Harman curve is what most people will prefer under blind conditions. Having been to both, I have a hard time believing that most would prefer Olive Garden's Lasagna over Trattoria Lisina's ;).

That said, I do love Olive Garden, and McDonalds can certainly hit the spot at times, and you're making me hungry now :p.
 

richard12511

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Unfortunately we only tested the hearing of the trained listeners, and not the untrained. So we can't really separate out hearing loss with the other variables Females did on average headphones with less bass but the sample size I feel is too small to make any generalized conclusions.


I recently saw a large study of hearing loss/sensitivity up to 18 kHz and females have less loss with age than males.

Your research has shown that older listeners tend to prefer more treble. Do you believe this is due to HF hearing loss? or some other factor?
 
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