Thoughts/discussion on The Headphone Show & other audio-related livestreams

[ADUHF]

I don't see how the Harman curve can have errors. It's an averaged preference of a wide range of people. It isn't intended to be an absolute thing. It is what most people prefer. Are you saying most people don't prefer the Harman target?

If you think the Harman target is attempting to replicate the experience of listening to a speaker system, then yes it's riddled with errors. Headphones can only replicate certain aspects of speakers. The most important and unique aspects of speaker listening are impossible to reproduce using headphones without heavy digital signal processing, head tracking and custom HRTF. Response may be the most important aspect of headphone listening, but with speakers, that is only half of it. There are many more things that affect timing and directionality and the way each person hears that are completely beyond the realm of headphone listening.

I think the attempt to make headphones sound like speakers is kind of like having your cake and eating it too.

Thank you for the reply. You have some good thoughts here which I mostly agree with. But I think you are confusing the issue a bit by potentially mixing together two different concepts or concerns. One being the subjective nature of the Harman target, and (I assume) its relevance or lack thereof as a neutral response curve. And the other being the inadequacy of frequency response curves generally as a way of approximating all the characteristics of a loudspeaker in a room.

I think I've already responded to the latter in previous discussions. And basically agreed with you that it is not possible to approximate all the characteristics of a loudspeaker's behavior in a room by simply adjusting a headphone's frequency response. And that is still my position. So we probably agree on that much.

Re the subjective nature of the Harman curve, I do not dispute that it is the average preference of the test subjects in the Harman study. I question its usefulness and precision though, in some ways, with most of the currently available measurement data. And also its accuracy as a model for the steady-state frequency response of a neutral loudspeaker in a typical semi-reflective room. Which may not have been its sole or original purpose. But one which it ultimately seems to have acquired (at least in some people's minds) through its ubiquity.

 

[bigshot]

I don’t think it’s intended to be a model for a neutral speaker system and room. That was just a general baseline to start with, since most people prefer the sound of speakers to headphones. It shifted to match the input of the test respondents.

 

[ADUHF]

I don’t think it’s intended to be a model for a neutral speaker system and room. That was just a general baseline to start with, since most people prefer the sound of speakers to headphones. It shifted to match the input of the test respondents.

Whether it was or was not intended for that purpose, that is how alot of people seem to be treating it. So it's a relevant subject for debate and discussion imho.

 

[ADUHF]

The notion that frequency response is somehow less predictable or more subjective below a certain frequency or range is not a new one btw.

This comes from the concept of the Schroeder frequency. Which is the frequency range below which the resonant characteristics of a room (aka room modes) begin to exert more of the control over a speaker or other sound source's frequency response. The smaller the room is, generally speaking, the higher the Schroeder frequency will be, since it is based on both the size of the room (in cubic meters) and also its reverberation time.

Floyd Toole also discusses these room effects (and the Schroeder or room cross-over frequencies), and when they start to become more relevant with different sized rooms in this video, beginning somewhere around the half hour mark. (And I've cued the video to the approximate spot where this discussion begins)...



In this video, Mr. Toole suggests that the spinorama data is accurate in terms of its predicted in-room response down to about the 300-400 Hz range. Which is quite a bit lower than the 900 Hz range that Resolve, and some others have suggested for headphones. According to some other sites on the web though, the general rule of thumb for the cross-over (aka Schroeder) frequency of a typical domestic listening space can be anywhere between about 100 to 250 Hz. And its thought that below this range the frequency response of the speaker is largely dominated or dictated by the behavior of the room. There is generally about a two octave range above this frequency where both the room and speaker share some degree of control of the response though. And it's above this so-called transitional range where the response tends to be more heavily controlled (and hence also generally more predictable) by the speaker itself.

As mentioned in one of my previous posts though, there is no great mystery about what the general trendlines are (or should be!) in a speaker's in-room or sound power response in the lower frequencies. The data is actually very unequivocal on this. And there is also no great mystery about what the manufacturers of the best loudspeakers are trying to achieve in that range. Because what they're attempting to do is exactly what Floyd Toole describes in the above video. Namely, achieving the smoothest, most uniform, and also the most linear response in a speaker's off-axis response possible, for greater timbral consistency.

And you can easily see their endeavors in this regard in the sound power curves of some of the more expensive, and also technically sophisticated designs of the better speaker manufacturers. In speakers like the KEF Reference 5 and Genelec 8341A, for example...

https://pierreaubert.github.io/spinorama/KEF Reference 5/KEF/index_vendor.html
https://pierreaubert.github.io/spinorama/Genelec 8341A/ASR/index_asr-vertical.html

And also in many other of the higher end models at the above link. Speakers like the Reference 5 and 8341A are the flagship designs which will be setting the standard for speaker designs and development in the near future, both on the high end and also at the lower end. And you can also see this trend beginning to reach down into the design and response curves of some of the latest mid and lower-cost speakers intended for studio monitoring. Like the recently released Kali IN-5 and IN-8, for example. Which appear to be targeting a linear sound power response similar to the flagship models above...

https://pierreaubert.github.io/spinorama/Kali IN-5/ErinsAudioCorner/index_eac.html
https://pierreaubert.github.io/spinorama/Kali IN-8/ASR/index_asr.html

So, far from being unpredictable, both the objectives and the general trend lines for the response in the lower frequencies are actually quite clear from looking at the available speaker data. Moreso, I would suggest, than in the upper frequencies, where the actual responses of speakers still tends to be more heavily-dependent on their internal cross-over designs, and the directivity or dispersion of their drivers. Especially the dispersion in the higher frequencies of the tweeter.

There is enough similarity and data available though for the responses in both the upper and lower frequencies that we can fairly easily determine (and make some broad assumptions about) the general/average response of a speaker's entire frequency range from the anechoic spinorama data. So there is no need to be "in the dark" any longer about what this is, imho.

 

[InvisibleInk]

However, it seems he’s got contradictory views about DACs and amps, because he claims to hear differences between DACs, and honestly I think he’s full of it, or he’s just lying to himself.

I don't hear that from him at all. Quite the opposite, I feel he believes DACs don't matter much at all.

 

[bigshot]

Whether it was or was not intended for that purpose, that is how alot of people seem to be treating it. So it's a relevant subject for debate and discussion imho.

Well, you can feel free to debate it until someone points out that it just isn't intended to serve that purpose! I don't see any point at all in debating misconceptions.

A lot of audiophiles have massive misconceptions about a lot of things. One of those is that there is a "ONE AND TRUE RESPONSE CURVE" for transducers. That just doesn't exist. For headphones the shape of your own ears is unique and has an effect on the response, making it a matter of "one man's meat is another man's poison." And with speakers in a typical living room, the room has a massive effect on the sound, and the object is more a matter of balancing response at different points in the room to achieve a compromise that works for the way you live. You can go ahead and get a totally precise response from a specific listening position, but sit on the couch a foot to the left and right, and it might not be precise any more. There are a LOT more different sounding rooms than there are different sounding headphones or speakers. One size does not fit all, and most people don't have the luxury of tearing down their house and rebuilding it to acoustically suit their stereo system. You have to strike a balance that works for you and your situation. You can use science to help you get close to that target, but you can't entirely ignore the purely subjective and situational aspects.

On top of this is the matter of personal taste. The purpose of a home audio system is to provide an enjoyable listening experience for music. In fact, that is probably the primary goal, trumping any retentive compulsions to achieve some sort of absolute calibration setting. In a high quality restaurant, they still put salt and pepper on the table. You taste the food as it is presented, but you are free to adjust to your own palette. When human beings listen to music, I'm afraid science has to take a back seat to pleasure, because pleasure is the whole point of listening to music.

 

[ADUHF]

Well, you can feel free to debate it until someone points out that it just isn't intended to serve that purpose! I don't see any point at all in debating misconceptions.

So you have said... Or maybe I just inferred this from some of your other comments above. IAC, I've explained my reasoning for doing so already. And don't really see much need to further justify it.

There have been various other proposals for what a neutral response should look like though, when measured at the eardrum. And with the possible exception of the diffuse field curve, none of them have been as widely publicized and accepted as the Harman target. Which is why I continue to point out what I believe are some of its flaws and shortcomings in this regard.

Whether the Harman curve was or was not designed as a model of a neutral response, and whether people have misconceptions one way or the other about this is largely irrelevant imo. Because that is the way many people continue to use and view it.

A lot of audiophiles have massive misconceptions about a lot of things. One of those is that there is a "ONE AND TRUE RESPONSE CURVE" for transducers. That just doesn't exist. For headphones the shape of your own ears is unique and has an effect on the response, making it a matter of "one man's meat is another man's poison." And with speakers in a typical living room, the room has a massive effect on the sound, and the object is more a matter of balancing response at different points in the room to achieve a compromise that works for the way you live. You can go ahead and get a totally precise response from a specific listening position, but sit on the couch a foot to the left and right, and it might not be precise any more. There are a LOT more different sounding rooms than there are different sounding headphones or speakers. One size does not fit all, and most people don't have the luxury of tearing down their house and rebuilding it to acoustically suit their stereo system. You have to strike a balance that works for you and your situation. You can use science to help you get close to that target, but you can't entirely ignore the purely subjective and situational aspects.

On top of this is the matter of personal taste. The purpose of a home audio system is to provide an enjoyable listening experience for music. In fact, that is probably the primary goal, trumping any retentive compulsions to achieve some sort of absolute calibration setting. In a high quality restaurant, they still put salt and pepper on the table. You taste the food as it is presented, but you are free to adjust to your own palette. When human beings listen to music, I'm afraid science has to take a back seat to pleasure, because pleasure is the whole point of listening to music.

Fwiw, I agree that there may never be an absolute answer to the question of what is a neutral response. Because there are simply too many variables involved. That doesn't necessarily mean we give up looking for some better answers though.

And I'd also agree that people's personal preferences can potentially have alot to do with their enjoyment of their audio systems. And they might also provide some additional insights into the above question of a neutral response when considered as a large group from a statistical standpoint, as they did in the Harman studies.

 

[ADUHF]

Well, you can feel free to debate it until someone points out that it just isn't intended to serve that purpose! I don't see any point at all in debating misconceptions.

Correct me if I'm wrong on this, but it seems to me that you're also using the Harman curve as a (more or less) neutral point of reference when you suggest to others that it's a good starting point for adjusting the frequency response of their headphones, like many others do. Is this not so?

 

[ADUHF]

I don't hear that from him at all. Quite the opposite, I feel he believes DACs don't matter much at all.

I'll have to re-listen to the last two streams again to get a better read on Resolve's opinions on DACs.

Whenever he's asked whether or not someone should upgrade their amp, or their headphones though, he usually seems to come down more in favor of the new headphones. So I don't think he believes there's as much to be gained in the way of sound quality and what have from a variety of different amps. There are always some caveats that seem to go with those opinions though, about impedances, synergistic combos, specialized equipment and so forth. So he seems to have some flexibility on the subject... Which is probably a good thing, if you're reviewing headphone equipment for a living. Those are some of the impressions I've gotten anyway.

 

[ADUHF]

I don’t think it’s intended to be a model for a neutral speaker system and room. That was just a general baseline to start with, since most people prefer the sound of speakers to headphones. It shifted to match the input of the test respondents.

After thinking about this a bit more, I think I may possibly understand a little better what you were driving at on the above. And also with your remarks about misconceptions about the Harman curve.

Creating a new standard model for the frequency response of headphones was, I believe, one of Sean Olive's goals for the Harman target. And I believe there were also some modifications made to that model after they did some more thorough testing of listener's subjective preferences. And the model was subsequently adjusted to compensate for that, so it deviated a bit from their in-ear measurements of speakers in a room. So yes, I believe that you are correct on all of this, bigshot. And also correct that the Harman headphone target, in its later form, was not intended to accurately represent the in-ear response of a neutral loudspeaker in a room.

The reason this distinction didn't register for me (and why I wasn't really understanding what you were driving at with the "misconception" business) is because I believe that the two should measure the same at the eardrum. Imo, a headphone with a neutral response should, for all intents and purposes, measure essentially the same at the eardrum as a neutral loudspeaker in a semi-reflective room. Because to me that is actually the definition of a neutral response.

For awhile, I also believed that there could be other factors that potentially needed to be taken into account in a headphone's response to maybe better approximate some of the other perceptual or visceral aspects of a neutral loudspeaker in room. Resolve also touched a bit on this idea in his last live stream. And I'm also still partially open to it, if there is some more concrete and convincing evidence to support it. But I'm unconvinced by the currently available evidence on this from Harman's subjective tests. And think there could be some other equally plausible explanations for some of the variations that they found on this in their testing.

As Floyd Toole remarked in the video I posted above, human beings are remarkable measuring instruments. But they certainly aren't perfect measuring instruments. And I think one needs to look at the subjective tests that Harman performed from both of these perspectives. And perhaps lean a little more towards some skepticism on some of the conclusions that have so far been drawn from them. At least until there is some better confirmation on some of this.

Until then, I'm basically operating on the theory that a neutral headphone and a neutral loudspeaker in room should measure more or less the same at the eardrum. With perhaps only some minor (and largely meaningless) insignificant variations between the two, if any.

 

[ADUHF]

One other potentially plausible explanation for the variation in their subjective tests and in-room measurements is that the latter was not conducted with a sufficiently broad sampling of speakers and room conditions to really give a precise enough picture of the typical response of a neutral loudspeaker in a room. If this were the case, then it's possible that the subjective results could have the more accurate of the two. And the errors could have been more on the measurement side of the equation. Or the differences between the two could maybe have been less pronounced than the original results might have suggested.

I think these kinds of things should at least be looked at and maybe considered anyway.

 

[bigshot]

The reason there is variation in rooms is timing. You can calibrate the response, but the room determines the timing. A large room sounds different than a small one, even if the response measures the same. That's because of reflections, delay, decay, primary distance cues, etc... A good listening room isn't dead. It's live in a good way. And that varies widely between your living room and the Vienna Musikverein. The thing that makes speakers in a room sound like speakers in a room isn't the response. It's the effect of space on timing. The Harman Curve just addresses people's preferences for the response. It doesn't make headphones sound like speakers in a room.

 

[sander99]

Until then, I'm basically operating on the theory that a neutral headphone and a neutral loudspeaker in room should measure more or less the same at the eardrum. With perhaps only some minor (and largely meaningless) insignificant variations between the two, if any.

There still is the problem:
The difference between the transfer function from speakers to eardrum and the transfer function from headphones to eardrum is different for every individual.
Because of that any universal headphone curve can never be more than an average, maybe a perfect fit for one or a hand full of people and an approximation for the rest. No matter how much you try to improve it. So at the end of the day: the only way to get it perfect (whatever that is) for a randomly chosen individual is to use EQ tailored to that individual.

 

[ADUHF]

There still is the problem:
The difference between the transfer function from speakers to eardrum and the transfer function from headphones to eardrum is different for every individual.
Because of that any universal headphone curve can never be more than an average, maybe a perfect fit for one or a hand full of people and an approximation for the rest. No matter how much you try to improve it. So at the end of the day: the only way to get it perfect (whatever that is) for a randomly chosen individual is to use EQ tailored to that individual.

A good point, sander99. With over-ear headphones though, I think the variations in HRTF would mostly be head and torso-related, rather than ear-related. And how noticeable those differences might be from individual to individual (away from the original HATS rig where the measurements were made) is hard to say.

If you had the ability to measure both the neutral loudspeakers, and the headphones at the DRP for each individual though, then I think my theory about them measuring the same could still apply. This would not be practical for most people though.

 

[bigshot]

Measured at the eardrum, it would measure the same. But you'd have to simulate through a DSP all of the myriad of modifications that speakers in a room make on the source signal due to the room, the distance, and the physiognomy of the listener. There are a whole lot of variables in speaker sound that affect the response that you aren't taking into account.

For instance... A tweeter at 20 feet is entirely different than a tweeter at 20cm. You would have to calculate the amount of high end roll off that is created by traveling over a longer distance and incorporate that into your EQ curve. And that would be the simplest part of the simulation. Room reflections and timing differences are massive. I think your theory is like trying to figure out how to cut an apple to make it into an orange.