Master Complaint Thread About Headphone Measurements

[amirm]

One thing that also needs to be taken into consideration on this is the users' ability to "self-correct" the sound of the different headphones on their own head, if they sound off, by shifting the headphones around a bit, or adjusting the seal, headband, and so forth. Which is something that's probably not so easily take into account in such a study.

Except for extreme situations, I find that listeners are far more forgiving of headphone seating on their heads than measurements are. On some headphones variations in measurements are quite large but when I wear them, I don't sense this at all.

 

[MayaTlab]

I have looked at the research that Maya has posted elsewhere, btw, that explored this idea of using the differences between multiple headphones to compute a correction curve for different individuals. And while I think there could be some slight problems with it. I wasn't really convinced by the study that the differences in the computed correction curves between different headphones that were showing up with some headphones on the same individual were either substantial or consistent enough in their irregularity to be of much consequence. Perhaps this was the sort of thing you were referring to with regard to HpTF?

They're not substantial enough to invalidate the use of dummy head measurements, far from it, or any research of the Harman type, but they most likely are substantial enough to be audible (1dB across a large bandwidth is enough unless I'm mistaken, and at higher frequencies the differences, while only across narrower bandwidths, are much more severe) and probably to make Harman type research quickly loose its predictive value once we compare two headphones either very close to each others or to the target (I don't think that anyone at Harman would have the pretence to tell us that they can reliably predict whether a majority of people will prefer the HD560S over the HD650 or vice-versa - even though even with a virtualised pair of headphones most people would probably be able to tell them apart).

It's all a question of degree, it isn't black and white .

There's also this one BTW (free access) : https://vbn.aau.dk/ws/portalfiles/portal/227875204/1995_M_ller_et_al_AES_Journal_b.pdf

Some of these HPTF variations may be desirable as they match the sort of HRTF variations we would get when listening to "decent speakers in a decent room", but not all of them are, which is logical given that headphones don't operate like speakers at all relative to our ears.

So when you add undesirable HPTF variations to variations caused by pad wear, sample variation, etc... it makes a compelling case IMO for attempting to measure headphones on your own head (which carries its own inexactitudes), particularly since, if you EQ based on measurements done on a dummy head, you also have to take into account variations in the test rig setup and the operator's methodologies.

If you are dealing with a more troublesome headphone design though, then determining an accurate correction or translation curve from something like that will likely be much more challenging. I believe Maya has also commented on this, and determined that some open headphones are probably more reliable for this type of thing, because they produce more consistent results between usages in her measurements. (Hopefully she'll correct me though, if that's not right.)

I didn't determine anything, I'm just a dumb idiot.

But at least at lower frequencies, it's plainly apparent looking at Rtings's measurements, which measures bass response on five real humans at lower frequencies, that some designs are more susceptible to have a significant variance between listeners than others.
This is very significant variance (as in "completely changes the sound of the headphones" and "makes any prediction invalid") : https://www.rtings.com/headphones/1-3-1/graph#669/3185
Open headphones of the HD600/HD800 type are reasonably consistent.
Some ANC headphones on the other hand are superbly consistent for closed backs thanks to their ANC feedback circuit : https://www.rtings.com/headphones/1-5/graph#16490/7913
The latters basically solve the HPTF variation problem at lower frequencies : regardless of pad compression / wear / seal quality, everyone gets the same response (which, combined with a simple EQ shelf adjustment to match individual preferences, IMO is the right approach at lower frequencies, as HRTF modulation only starts to appear at higher frequencies - where you'll definitely want to see some differences between listeners, albeit only of the "desirable" kind).

Here is the link to the study I was referring to above, and some of the relevant plots from it (courtesy of Maya's post in another topic).
https://www.aes.org/e-lib/browse.cfm?elib=16877

One thing that I take away from that study (or the other one above) is that there isn't a constant transfer function between individuals, ie the response of the headphones at their eardrum can't be calculated based on an hypothetical constant HPTF per individual and is difficult to predict. While there are some trends ("subject A's response in the ear canal gain region tends to peak at x Hz, subject B at y Hz"), possibly related to desirable aspects of HPTF variation, the STD isn't constant per frequency for all headphones and the relative differences between the individual squiggly lines aren't constant (as you'd think you'd see if that study had measured different speakers in an anechoic room instead, where theoretically the only variation would be the listener's HRTFs and where you would expect the speakers' relative differences to stay constant across all listeners, even if their absolute results would be shifted by each individual's own HRTF).
It's not necessarily huge, but possibly (IMO probably) audible, particularly at the two extremes.
This type of study has a degree of inexactitude as well.

 

[MayaTlab]

Except for extreme situations, I find that listeners are far more forgiving of headphone seating on their heads than measurements are. On some headphones variations in measurements are quite large but when I wear them, I don't sense this at all.

Sometimes maybe it's just that there actually isn't that much variance ?

This is using mic n°2 below :

With a pair of HD650 + Dekoni Elite Velour pads, several individual seatings ("seatings" means to me completely removing and repositioning the headphones on my head, as I normally would - I'm not trying unrealistic seatings) during the same session ("session" means to me that the mics weren't moved between the measurements) :

The other benefit of the above is that they also stay glued on my head regardless of how much I lean forward / backwards / move about.
this on the other hand, is my pair of K371 with me trying to be as steady as possible :

Things quickly get way worse as soon as I move even slightly (like leaning forward to look at my computer on the table) and the incessant variation in FR is very noticeable (perhaps more than a pair of HPs that varies a bit from seatings to seatings, but doesn't shift / change position once it's on one's head).

 

[ADU]

Retracted.

 

[Robbo99999]

Howdy again, Robbo99999.

I am not as into to all the fancy new DSP and HRTF-related stuff for headphones that's out there right now as some other folks seem to be. So you (and Maya) may be much better informed in these areas than I am, Robbo. And feel free to correct me again, if you think I'm looking at any of this incorrectly, or through too rosey-colored glasses. That does not mean I have anything against such things though, or those who are into it. (Quite the contrary, in fact.)

My primary objective though in this is NOT to determine the best sound signature, or HpTF (if I'm understanding that term correctly) for my own particular ears. It's to determine, as well as can possibly be done within the limited means available to me, what a neutral, accurate HRTF-independent response curve should look like for a pair of over-ear headphones. That is, one which is NOT reliant on customization to an individual person's particular ears. And I believe that using DF compensation is one potential way to accomplish this (albeit a somewhat imperfect one).

That isn't the whole point of why I'm using DF compensation. But it is certainly one of them.

Alot of folks in the headphone community unfortunately seem to be under the false impression that there is only one diffuse field curve (like in The Highlander... THERE CAN BE ONLY ONE!!!!! Aaaaaahhh!) that you can use on any measurement system to get that groovy, bright "diffuse field sound", baby! But it dudn't quite work like that.

The diffuse field is not a "generalized target" like the Harman curve in this sense. It's a compensation or correction or calibration curve which is based on a common or reference stimulus. And not one particular curve... Which means that the DF compensation is different for every different HATS rig. And tailored specifically to each of their HRTFs.

It seems like you sort of get this, Robbo. But some of the objections you keep raising lead me to think that maybe you're not quite seeing the connection between this, and HRTF compensation or correction. As far as I'm concerned, DF compensation is HRTF compensation or correction! Because it's different for each individual rig.

You can certainly make the argument that it's poorly standardized. And not reliable or accurate because the DF measurements may not all be performed exactly the same way, and with the same type of equipment, on different rigs by different manufacturers. And that's something I'd probably accept and have to agree with to some extent. But arguing that it is somehow not a form of HRTF compensation or correction seems a bit of a stretch to me. (It may not be a particularly GOOD form of HRTF compensation!... But it is HRTF compensation in my book.)

Maybe I'm still missing or not fully grasping something in what you're saying though. And the confusion is more on my end on this. And if you think that's the case, then I'm asking you to please try to clarify it a little better, or point it out to me, if you can.

There are some other potential methods of performing this type of HRTF compensation, btw, which Jaakko apparently used to adapt the Harman target to several different sets of measurements made by different graphers for his AutoEQ project. And I believe this was actually done by comparing the measurements of the same set of headphones (I don't know how many though) on the different rigs. And then computing an average correction curve for each rig, based on the differences in the measurements between that rig, and the GRAS rigs used by Harman, Crin and Oratory.

This is a technique I also experimented with briefly, back when Tyll was trying to adapt the Harman curve to his raw Inner Fidelity measurements. I didn't have a whole lot of time to dedicate to plotting back then though, so it was extremely slow going. And when Jaakko posted his AutoEQ results, it made most of my efforts along a similar lines largely irrelevant. And I don't think I ever got to the point where I shared any of my results on this with anyone at IF. (I think a few us of may have discussed it as one possible solution though. And perhaps that's where the AutoEQ project began? It is very possible that Jaakko is the one that first brought this idea up though, because he was working on something along those lines already... I honestly don't remember though.)

It employs basically the same principles as diffuse field HRTF compensation though. Namely, using a common sound stimulus (a specific model of headphone in this case, instead of a diffuse sound field) to compare, and then calculate the differences in response between two different measurement rigs. And then to use that difference curve to adapt a target curve developed on one rig for use by another.

It may not work 100% perfectly all the time (as Jaakko's AutoEQ project has demonstrated), possibly due to unit variation, differences in measurement technique, seal, and so forth. But, in theory, the principal is sound. And is also something that could potentially be used to adapt a reference response curve, like the Harman target, for use with measurements made on other systems. Including possibly also the kind of in-ear measurement systems that Maya is using.

A slight drawback to using a headphone or headphones for this reference stimulus is that it is perhaps not quite as easy to relate back to something a bit more concrete, like the sound power response of a loudspeaker, as DF compensation seems to be... Unless you're willing to accept on faith and evidence that something like the Harman curve, or a headphone with a similar response such as the AKG K371, is an appropriate and sufficient model for something like that... Which I regrettably do not.

There are some headphones (or combinations of them) that I think might get pretty close to this though. And one of the advantages of an approach like this is that the stimulus being used as a reference for adapting other measurements is a bit closer in character and response to the other stimuli or sound sources (headphones, presumably) that you're intending to measure and correct with this info, than the rig's DF curve would be. (I assume that this is probably one of reasons that Jaakko preferred this approach to using DF or FF compensation for his AutoEQ project. Though perhaps he just couldn't find the DF/FF sound field data for all the different measurement systems in his project.)

If you do believe that the Harman curve (or something similar, such as the K371) is the last word, or at least a sufficient model for a "room sound" (or whatever sound it is that you're personally going for), then calibrating your measurements to that target by comparing various other headphone measurements made on your own personal rig or in-ear setup to the measurements of the same headphones on a GRAS rig similar to Harman's may be enough to get the job done.

I apologize, btw, if this has again been too much to take in, in just one post. But it seems as though some here may already have been down some similar roads. And already formed some other opinions on this. And since we seem to moving a bit more out of the kiddy pool, and more into the adult swim, I figured maybe some of this was ok to throw out there. If I'm somehow way off base though on this, then please feel free to say so. Or tell me to go jump in a lake!

I don't buy into the idea that the response of an over-ear headphone has to be specifically tailored to each person's individual HRTF to sound acceptable or accurate though. Because it just doesn't hold that much water in my opinion. (Hmm... lots of aquatic references today, must be the Olympics or somethin.) And I think perhaps your experience with using the Harman target for compensation, Robbo, seems to demonstrate that to some degree... At least maybe for you.

It's also possible that this all boils down to just questions of degree though, and determining which differences in these things actually make a difference to a person's audio enjoyment. Those are probably also some valid things to consider as well imo.

Just to be clear though, I'm not really saying that individual HRTFs should simply be ignored, or do not matter. What I'm sayin is that I believe that diffuse field HRTF compensation, and calibration to a common stimulus by this method (or possibly some other similar method using several pairs of well-designed & well-fitting headphones), will probably be adequate for my purposes for the time being. And enough to factor out the differences between different rigs or HRTFs, so that they're not a significant impediment to determining a general neutral response for a pair of circumaural headphones.

This is just my 2c on the subject though. And your mileage may certainly vary on this. (Another pretty long post folks, so my apologies for that.)

HPTF, my understanding is that this describes the interaction between any given model of headphone and your ear structures when it's placed on your head. In other words as a practical demonstration of this, if you EQ two different models of headphones to the same curve on say a GRAS unit, then if you were to then wear both of those EQ'd headphones and were able to measure the frequency response at your eardrum you'd find that there were some differences in the frequency response between them, even though of course they were EQ'd to exactly the same curve on the GRAS unit. So that's a hypothetical practical demonstration of HPTF in action.

Whereas HRTF in my understanding describes the frequency response received at your eardrum when exposed to speakers in a room, and is therefore describing the Target Curve that you'd want to aim for. So HRTF takes into account your head structure as well as your entire ear structures.

So that's my understanding of the differences between HPTF & HRTF, and I see those are the two things that headphone manufacturers would have to determine for an individual in order to get successful personalised targets for people, I see that as the future.....somekind of scanning or other means for them to determine this for the individual, as long as it's cost effective, quite accurate, and easy for the customer to implement. This is also what the Impulcifier Project aims to do. As to all the other stuff we've talked about your Diffuse Field Compensation Graphs, I can't add anymore to that, I've already given you my thoughts on that.

 

[ADU]

Thank you for taking the time to explain this a little better, Robbo99999.

I'll give you my opinions on some of the above, and then you can tell me if you agree, or not with any of it.

This is a plot that I'm sure you're probably familiar with showing how different parts of the human anatomy can effect the frequencies of a sound source when it's measured at the eardrum. The source in this case is a free-field point source positioned at a 45-degree angle to the head, most likely measured in an echo-free room. (So there is no "room gain" included in the above plots.) The curve labeled "Ear Resonance" represents the sum total of the 5 other curves combined, as measured at the eardrum. This would also be what some like to refer to as the "head-related transfer function", or HRTF for a point source at a 45 degree angle, with no ambient or reflected room noise. It's technically a head AND torso AND ear transfer function, because it includes all of these different parts of the body in its response. But in the current vernacular, it's usually just referred to as "HRTF".

-------------------------​

Okay.

Based on what you've said above, it seems like a headphone-related transfer function would have to be some subset of the above curves. Because unlike a source in a room, the sound that's coming out of a headphone does not interact with the body or the general shape of the head. Its primary interaction is just with the ears.

So instead of adding all 5 curves above together, for the headphone-related transfer function, you would probably just add together the 3 curves for the pinna flange, concha, and ear canal... And omit the head and torso curves. This would be for a fullsize over-ear (aka circumaural) headphone, that completely surrounds the outer ear.

The effects of an on-ear and in-ear headphone would be different though. An on-ear headphone would have less interaction with the outer parts of the pinna than a circumaural headphone would. So you'd probably have to subtract the pinna flange curve from its response as well. Leaving just the concha and ear canal curves.

An in-ear headphone or IEM has the least interaction of all with the list of different "parts" above. So the only curve that might possibly be relevant, to some degree, would be a portion of the ear canal effects, depending on how deeply the IEM is inserted inside the ear.

The resonant frequencies in the ear canal might also change from what's shown above, because 1) a closed or blocked ear canal has different resonances than one which is open, and 2) the length and volume of the ear canal also effects its response. And an IEM inserted into the ear can potentially effect both of these things.

To adequately describe just these three specific cases above, you would probably need three different headphone-related transfer functions: an over-ear function, an on-ear function, and an in-ear function.

However, for all three of the above headphone cases to sound the same as a source in a room, they would have to produce a measurement at the eardrum that is substantially similar to the combined result of all of the curves shown above, which is the curve labeled "Ear Resonance".

-------------------------​

If this is all correct, then there are a couple other things that I think you can also deduce from the above.

Since an IEM has the least amount of interaction with the different parts of the anatomy described above, it is likely to require the greatest amount of individualization or customization from person to person to achieve the same sound which is described in that top overall curve, from one individual to the next. And it would therefore also follow that a fullsize over-ear headphone, that completely surrounds the ear, would probably need the least amount of individualization/customization of the headphone types for different individuals to achieve the same sound. Because the sound from an over-ear headphone interacts with more of an individual person's anatomy than the other two headphone types.

The fullsize over-ear headphone might still possibly need a small amount of customization though, to account for some variances in the shape and size of an individual's head and torso, which would be missing from the headphone's transfer function measured at the eardrum. However, as long as the different individuals' heads and torsos are not drastically different in size and shape, the effects of those variations on the measured response at the eardrum are likely to be rather broad in bandwidth and small in amplitude, based on the shapes of the head and torso curves shown above. The long dotted curve that represents the head's transfer function might shift or tilt slightly higher or lower in amplitude. And the same would probably be true for the torso and neck curve.

Just looking at the graph above, it would be hard to predict what the combined effect of those two curves changing might be on the perceived sound at the eardrum. And how noticeable it would be. They might just produce a small change in the overall volume. Or they might have a small effect on the perceived "tilt" or tonal balance. Or they might have no discernible effect at all, depending on the different shapes of the individuals. You could probably make the assumption that the effects of different head and torso shapes would be more noticeable though when comparing individuals who are at more polar opposites of the body-type range... I suppose.

The main crux of what I'm saying above though is just that IEMs would likely require the most customization or individualization to produce a similar sound from person to person, because there is less of an interaction between the IEM and an individual's particular HRTF than with the other headphone types (or a sound source in room).

-------------------------​

If this is indeed the type of thing that you're talking about with regard to different HPTFs (and I think there's a good chance it is), then I think you could probably also make the following assumptions as well...

If you're comparing the headphone-related correction curves for two different headphones on two different individuals, then you are probably more likely to see a difference between those two correction curves if the two headphones are also of different types, and one is a full-sized over-ear headphone, for example, and the other is an IEM. Because the different headphone types would interact with different portions or degrees of the two individuals' overall head (and torso, and ear) related transfer characteristics.

If you're comparing two headphones of the same type with a similar fit and construction (so two over-ears, or two IEMS, rather than an over-ear & an IEM) on the two individuals, then I think the correction curves for the two headphones would also have to be more similar.

 

[ADU]

One last addendum that I'll add to the above is that I don't think there's a single universally agree upon definition for how an "HRTF" needs to be measured. So it could potentially be done using various sources and methods. Including point or diffuse sources, from various angles, and in different kinds of rooms which are either echo-free, or more reflective.

If the HRTFs are measured using speakers in a room, then they would technically be room AND head (and torso, and ear) transfer functions. Because they'd also incorporate the reflective and distortive sound characteristics of the room, as well as some of the speaker's design (if you're comparing room/HRTF characteristics for different speakers). An echo-free or anechoic room removes the room effects though, so you are looking more at the response of just the head, torso and ears.

As far as I know though, there is no particular set method for any of this. It would probably help though, if you described which type of HRTF you're specifically referring to, and whether it's from a point, or diffuse source. Or from multiple points or speakers. And whether its "anechoic", or also incorporates the room effects.

Maybe I'm wrong though about this.

 

[Deleted member 16543]

You're not wrong. This is what I would have liked to see ASR do (if they had taken the path of expanding current research):

1) (Since we know what a well balanced speaker measures like in a room) Place a proper binaural microphone at the listening position of a stereo system and measure the FR.
2) Measure headphones with the same binaural microphone and try to match to the FR obtained at step 1.
3) Investigate listeners preference in relation to closeness to that FR

Both measurements would have to be done with appropriate gating based on human perception.
Maybe allow for some extra correction EQ due to the fact that the expected sound balance out of speakers might not be the expected sound balance when listening to headphones.
I think this method is basically what you're describing as well, but without breaking down the HRTF in its various components.

 

[solderdude]

1) (Since we know what a well balanced speaker measures like in a room) Place a proper binaural microphone at the listening position of a stereo system and measure the FR.

gated ? not gated ? What specific room ? What speakers ? in what positions ? What is the listening position ? Will this work for everyone in their own home ? Nearfield or specified distance ? What 'binaural' microphone ? What correction should be used ?

Why would speakers measured in a room with sounds coming from meters away with inter-aural delay be compared to 2 speakers a few cm away from a specific HATS be as accurate as large multi driver speakers in 'a' living room ?
What if the pinnae were changed how much effect on both types of measurements ?

How does one go about ranking preference ? Does one invite folks over ? Who to invite ? would those individuals have to be screened for knowledge about real life sounds ? Pick people from the street ?
When we let folks define their own preference in bass and treble lift... what filters are going to be used ? predefined or let people change Q and frequencies ?

Hmmm the above sounds a lot like it already has been done but with some pre-determined sets of things.
Peer review Harman Research ?
Repeat many, many years of research ? Who owns the equipment to do all this ? One type of HATS ? multiple ones ? What speakers ?

 

[Robbo99999]

Thank you for taking the time to explain this a little better, Robbo99999.

I'll give you my opinions on some of the above, and then you can tell me if you agree, or not with any of it.

This is a plot that I'm sure you're probably familiar with showing how different parts of the human anatomy can effect the frequencies of a sound source when it's measured at the eardrum. The source in this case is a free-field point source positioned at a 45-degree angle to the head, most likely measured in an echo-free room. (So there is no "room gain" included in the above plots.) The curve labeled "Ear Resonance" represents the sum total of the 5 other curves combined, as measured at the eardrum. This would also be what some like to refer to as the "head-related transfer function", or HRTF for a point source at a 45 degree angle, with no ambient or reflected room noise. It's technically a head AND torso AND ear transfer function, because it includes all of these different parts of the body in its response. But in the current vernacular, it's usually just referred to as "HRTF".

-------------------------​

Okay.

Based on what you've said above, it seems like a headphone-related transfer function would have to be some subset of the above curves. Because unlike a source in a room, the sound that's coming out of a headphone does not interact with the body or the general shape of the head. Its primary interaction is just with the ears.

So instead of adding all 5 curves above together, for the headphone-related transfer function, you would probably just add together the 3 curves for the pinna flange, concha, and ear canal... And omit the head and torso curves. This would be for a fullsize over-ear (aka circumaural) headphone, that completely surrounds the outer ear.

The effects of an on-ear and in-ear headphone would be different though. An on-ear headphone would have less interaction with the outer parts of the pinna than a circumaural headphone would. So you'd probably have to subtract the pinna flange curve from its response as well. Leaving just the concha and ear canal curves.

An in-ear headphone or IEM has the least interaction of all with the list of different "parts" above. So the only curve that might possibly be relevant, to some degree, would be a portion of the ear canal effects, depending on how deeply the IEM is inserted inside the ear.

The resonant frequencies in the ear canal might also change from what's shown above, because 1) a closed or blocked ear canal has different resonances than one which is open, and 2) the length and volume of the ear canal also effects its response. And an IEM inserted into the ear can potentially effect both of these things.

To adequately describe just these three specific cases above, you would probably need three different headphone-related transfer functions: an over-ear function, an on-ear function, and an in-ear function.

However, for all three of the above headphone cases to sound the same as a source in a room, they would have to produce a measurement at the eardrum that is substantially similar to the combined result of all of the curves shown above, which is the curve labeled "Ear Resonance".

-------------------------​

If this is all correct, then there are a couple other things that I think you can also deduce from the above.

Since an IEM has the least amount of interaction with the different parts of the anatomy described above, it is likely to require the greatest amount of individualization or customization from person to person to achieve the same sound which is described in that top overall curve, from one individual to the next. And it would therefore also follow that a fullsize over-ear headphone, that completely surrounds the ear, would probably need the least amount of individualization/customization of the headphone types for different individuals to achieve the same sound. Because the sound from an over-ear headphone interacts with more of an individual person's anatomy than the other two headphone types.

The fullsize over-ear headphone might still possibly need a small amount of customization though, to account for some variances in the shape and size of an individual's head and torso, which would be missing from the headphone's transfer function measured at the eardrum. However, as long as the different individuals' heads and torsos are not drastically different in size and shape, the effects of those variations on the measured response at the eardrum are likely to be rather broad in bandwidth and small in amplitude, based on the shapes of the head and torso curves shown above. The long dotted curve that represents the head's transfer function might shift or tilt slightly higher or lower in amplitude. And the same would probably be true for the torso and neck curve.

Just looking at the graph above, it would be hard to predict what the combined effect of those two curves changing might be on the perceived sound at the eardrum. And how noticeable it would be. They might just produce a small change in the overall volume. Or they might have a small effect on the perceived "tilt" or tonal balance. Or they might have no discernible effect at all, depending on the different shapes of the individuals. You could probably make the assumption that the effects of different head and torso shapes would be more noticeable though when comparing individuals who are at more polar opposites of the body-type range... I suppose.

The main crux of what I'm saying above though is just that IEMs would likely require the most customization or individualization to produce a similar sound from person to person, because there is less of an interaction between the IEM and an individual's particular HRTF than with the other headphone types (or a sound source in room).

-------------------------​

If this is indeed the type of thing that you're talking about with regard to different HPTFs (and I think there's a good chance it is), then I think you could probably also make the following assumptions as well...

If you're comparing the headphone-related correction curves for two different headphones on two different individuals, then you are probably more likely to see a difference between those two correction curves if the two headphones are also of different types, and one is a full-sized over-ear headphone, for example, and the other is an IEM. Because the different headphone types would interact with different portions or degrees of the two individuals' overall head (and torso, and ear) related transfer characteristics.

If you're comparing two headphones of the same type with a similar fit and construction (so two over-ears, or two IEMS, rather than an over-ear & an IEM) on the two individuals, then I think the correction curves for the two headphones would also have to be more similar.

I think we're going into too much detail & getting off track from you initial request of including Diffuse Field Compensation Graphs in Amir's reviews.....yet we've already talked about that subject & I've offered all my thoughts on that already.

For your graph you showed in your post, for headphones I don't think you can just omit the head and torso curves and then assume it's gonna be the rest of them combined because the directional sound source of headphones is different to the graph you showed so it's not comparable. The good thing about IEM's if manufacturers ever go down the personalised HRTF scanning route is that it removes the variance of the outer ear structures from person to person, so manufacturers wouldn't have to consider HPTF to the same complication, I would think. No, but anyway, I think we're getting a bit off topic from your first post in this thread, but we've already talked about that too.

 

[amirm]

You're not wrong. This is what I would have liked to see ASR do (if they had taken the path of expanding current research):

What's the motivated for expanding research? I have now tested over 60 headphones. In every case optimizing them to target with EQ results in substantial improvement. With many headphones, the sound becomes to die for. Given the fact that we are never sure of the frequency response of the recording venue, there is only so much accuracy we need in this affair. Our work is best spent getting the industry to get closer to a single target than messing with new ideas that don't have justification.

 

[Deleted member 16543]

gated ? not gated ? What specific room ? What speakers ? in what positions ? What is the listening position ? Will this work for everyone in their own home ? Nearfield or specified distance ? What 'binaural' microphone ? What correction should be used ?

Why would speakers measured in a room with sounds coming from meters away with inter-aural delay be compared to 2 speakers a few cm away from a specific HATS be as accurate as large multi driver speakers in 'a' living room ?
What if the pinnae were changed how much effect on both types of measurements ?

How does one go about ranking preference ? Does one invite folks over ? Who to invite ? would those individuals have to be screened for knowledge about real life sounds ? Pick people from the street ?
When we let folks define their own preference in bass and treble lift... what filters are going to be used ? predefined or let people change Q and frequencies ?

Hmmm the above sounds a lot like it already has been done but with some pre-determined sets of things.
Peer review Harman Research ?
Repeat many, many years of research ? Who owns the equipment to do all this ? One type of HATS ? multiple ones ? What speakers ?

Yeah, that's called doing research. Obviously the three points I wrote down are a very simplified version of what this research would entail.
But to answer at least a few of your questions, the speakers would have to be equalized to a target curve using psychoacoustic based measurements (gating). There's many people doing this already for their systems, so at least this part is not that difficult.
Read the book I linked to earlier, for example.
The point being, it's a lot of work.. but that didn't seem to have scared Harman in the past (although their procedure and equipment was different).
That's why I specified (if they had taken the path of expanding current research)

 

[Deleted member 16543]

What's the motivated for expanding research? I have now tested over 60 headphones. In every case optimizing them to target with EQ results in substantial improvement. With many headphones, the sound becomes to die for. Given the fact that we are never sure of the frequency response of the recording venue, there is only so much accuracy we need in this affair. Our work is best spent getting the industry to get closer to a single target than messing with new ideas that don't have justification.

Motivation to expand research? Curiosity, science, making things a little better.. there's many reasons to expand research, otherwise we would be still waiting for lightening storms to hit a tree to get some fire.
I'm not saying that there isn't value in saying "this is good enough for me", but that substantial improvement you talk about could be even better.

We can absolutely measure the frequency response of a recording venue (with a set of sources in specific points of the room, at the listening position). People do it all the time.
How you chose to spend your time is your own business, but to not see any justification for this expanded research (even if it's just for a slight increase in performance) is quite condescending for somebody that named his site Audio SCIENCE Review, don't you think?

So you're not doing this work (fine, completely understandable). I'm not doing it either.
But.. somebody will do it, sooner or later. Such is the nature of competition. You always have to one-up similar products in the market and come up with something new. This is one of the rare occasions in audio where the new thing would also be more accurate (maybe marginally, maybe not), so as far as I'm concerned it would represent a breath of fresh air in an industry full of snake oil salesmen. But I digress.

 

[solderdude]

The point being, it's a lot of work.. but that didn't seem to have scared Harman in the past (although their procedure and equipment was different).
That's why I specified (if they had taken the path of expanding current research)

And you are basically asking Amir to repeat all the research already done by Harman but in his home using his HATS ?
The guys at Harman were being paid by a large company.
Who is going to pay Amir and when is he supposed to do all this work alongside his garden, reviews and family ?
How many different test fixtures would need to be used ?

DF as well as FF are both not suited for headphones. If it were Harman would have ended up with the same curve as the DF curve (which Amir has but there is no reason to use it)

What does Harman research need to expand on ?

Besides.. I have done my own research and built my own test fixture and target curve and came rather close to Amir's results (at least with non angled headphones) but using a very different approach in obtaining results.

 

[don'ttrustauthority]

There is no objective method for studying headphones.

Here they are trying to have a consistent, repeatable set of measurements. You can compare headphones that have been tested similarly. You can also compare how others have tested the same headphones and try to see if there is anything revealed though multiple testing.

 

[Deleted member 16543]

And you are basically asking Amir to repeat all the research already done by Harman but in his home using his HATS ?
The guys at Harman were being paid by a large company.
Who is going to pay Amir and when is he supposed to do all this work alongside his garden, reviews and family ?
How many different test fixtures would need to be used ?

DF as well as FF are both not suited for headphones. If it were Harman would have ended up with the same curve as the DF curve (which Amir has but there is no reason to use it)

What does Harman research need to expand on ?

Besides.. I have done my own research and built my own test fixture and target curve and came rather close to Amir's results (at least with non angled headphones) but using a very different approach in obtaining results.

I think I made my position clear enough when I stated that some of us WOULD HAVE LIKED this research to be done by ASR, and right after I specified that the fact that he chose a ready made research to make his measurements bears NO MORAL JUDGEMENT on my part whatsoever.. What are you getting all defensive about?

I have no idea (nor do I care to know) about Amir's or ARS's means and time availability. Can I just wish that there would be better research done by somebody, or do I need your permission?

I already explained to you somewhere else why your method is not that great. Harman method is better (way better). An anathomically accurate binaural microphone would be even better. And probably that too will be topped by something else in the future.
Harman's research doesn't NEED to expand on anything. They made their assumptions, used the equipment of their choice, carried out their research and came up with very good results. Good for them.
It's just that now there's better equipment out there.

 

[solderdude]

Ah... sorry.. you meant some ASR members just WISHED someone at ASR had taken the task to do Harman's research from scratch and improve on it with newer equipment that would, in the end, have created yet another EQ that maybe could be more accurate and possibly be correct for every headphone.

I wish I had the time, the needed funds (several hundred K€ at least) to buy/rent the needed equipment and quit my job but alas no one is going to fund this... my test equipment just merely cost about € 100.- or so, sooo yeah.. it isn't as accurate for sure nor do I think it is needed for the job at hand.

I was getting defensive because it is so easy to ask for research from behind a keyboard, throw in some random not well thought through remarks and expect wish someone (or more folks) just spend a few years of research just so ASR members can get a slightly different (maybe better) EQ acc. to yet another not official standard which is not comparable with other research.

Just as if someone in his living room with a newer HATS on a listening position and just measuring a handful of headphones would be all that is needed.

 

[Deleted member 16543]

Ah... sorry.. you meant some ASR members just WISHED someone at ASR had taken the task to do Harman's research from scratch and improve on it with newer equipment that would, in the end, have created yet another EQ that maybe could be more accurate and possibly be correct for every headphone.

I wish I had the time, the needed funds (several hundred K€ at least) to buy/rent the needed equipment and quit my job but alas no one is going to fund this... my test equipment just merely cost about € 100.- or so, sooo yeah.. it isn't as accurate for sure nor do I think it is needed for the job at hand.

I was getting defensive because it is so easy to ask for research from behind a keyboard, throw in some random not well thought through remarks and expect wish someone (or more folks) just spend a few years of research just so ASR members can get a slightly different (maybe better) EQ acc. to yet another not official standard which is not comparable with other research.

Just as if someone in his living room with a newer HATS on a listening position and just measuring a handful of headphones would be all that is needed.

Apparently I DID need to ask for your permission..
Just to put things in perspective when you accuse somebody of expecting people to do work they would like to see done..
I'm the guy that made anatomically accurate ears a good 3 years before the B&K 5128 came around... On my own.
You're the guy that put a capsule on a piece of plywood.. and now gets offended that somebody has the audacity to suggest there are better ways to do it..
Buh-bye

 

[solderdude]

Apparently I DID need to ask for your permission.

What nonsense.

I'm the guy that made anatomically accurate ears a good 3 years before the B&K 5128 came around... On my own.

Excellent... I put a capsule on a piece of wood. Also on my own and more than 3 years before the B&K came around.
Together we can rule the headphone measurement world !

 

[Robbo99999]

@ADU , you could always start a new thread somewhere if you wanna discuss your ideas. I can't promise I'll jump in as I don't always want to tax my brain with theory, but this thread is more about asking for stuff to be included in the reviews or done differently in the reviews, etc.