[KinGensai]

@castleofargh
I get that tips and EQ are insufficient as compensation for HRTF as a whole, that's what I'd presume crossfeeders are supposed to help with.

The argument I'm trying to make here is that IEMs by nature bypass HRTF almost entirely, so maybe it's preferable to involve at least as much of the ear canal as possible to get an accurate representation of the sound being reproduced.

@gregorio
What is your opinion on the diffuse field target response curve? Is that a valid tuning strategy?

I think a distinction has to be made here between HPs and IEMs due to the physical point at which sound is being reproduced. HPs have some leeway here because the tuning target is sound as it reaches a point an inch or two away from the pinna, which means the main HRTF variables being ignored are the dimensions & density of the skull & torso as well as height differential of the ears. This is the rationale of the DF target curve as I understand it, I think it's a valid tuning method. I'm just a layman though, maybe you think differently about that.

IEMs go one step further because the tuning target is now within the ear canal, adding the pinna gain response to the pile of HRTF factors being ignored. This then has to be compensated for as well, but as I've seen it these measurements vary so wildly that no single tuning target will suffice. Harman provides a rather rough estimate of an average of a small sample, but it's better than nothing IMO.

As I understand the measurement methodologies at work here, it's done either through a dummy head or through in-ear microphones that record at the entrance of the ear canal, thus I think choosing tips that facilitate placing the sound bore of the IEM just at or slightly beyond the entrance of the ear canal helps produce a sound that the brain will consider more natural as opposed to a deeper fit, where altered dimensions will alter the sound sufficiently to render it less natural in direct comparison.

 

[MudEnjoyer]

Which graph is correct? The nicer one has an 8k peak?

The IER-M9 is meant to be used with a shallow insert so it should be closer to the red line. Specially with how I use it which is with the largest comply tips, gently inserted without compressing the foam.

That’s not my graph btw that’s @freeryder05 ‘s but I also have a coupler and have replicated the same results.

 

[MudEnjoyer]

@redrol
That's an interesting question. What is the more "correct" insertion depth in relation to the goal of hi-fi? Is that 8k resonance peak natural? Is that flat treble response natural?

Maybe there is no substitute to judging for that by listening and allowing your subconscious to judge which is more correct sounding yet. My initial thought is that perhaps it's desirable for the IEM to be shallow so that our ear canals are affecting the sound more, resulting in that smooth inoffensive treble profile recorded in that graph.

There is of course no correct insertion depth.

I personally prefer deep insertion because it greatly improves the bass perception (you can feel the air pressure on your eardrum and the shell vibrations transferred from the driver) but some are designed to be deep inserted like the Z1R, or shallow inserted like the M9, or not designed at all and just made to look good on Crinacle’s rig and methodology like the Moonjank stuff.

 

[KinGensai]

There is of course no correct insertion depth.

I personally prefer deep insertion because it greatly improves the bass perception (you can feel the air pressure on your eardrum and the shell vibrations transferred from the driver) but some are designed to be deep inserted like the Z1R, or shallow inserted like the M9, or not designed at all and just made to look good on Crinacle’s rig and methodology like the Moonjank stuff.

I agree there isn't a correct depth per se, such a distinction can only be made per quod to an objective (like fidelity).

Using custom tips has changed my perception on shallow vs deep insertion, I used to prefer deep because of exactly what you are describing, but my brain interprets the sound of shallow IEMs as more accurate spatially speaking than deep IEMs, which I think has something to do with the drastic changes to the treble response.

 

[MudEnjoyer]

I agree there isn't a correct depth per se, such a distinction can only be made per quod to an objective (like fidelity).

Using custom tips has changed my perception on shallow vs deep insertion, I used to prefer deep because of exactly what you are describing, but my brain interprets the sound of shallow IEMs as more accurate spatially speaking than deep IEMs, which I think has something to do with the drastic changes to the treble response.

For sure, but at the end of the day sound will be a function of tuning, eartip, insertion depth and your own ear canal. Even stuff like cortisol levels or being sick can affect the sound and treble tolerance too.

What I’m trying to say is that, I want to trust the manufacturer in knowing what they’re doing, and if the shell is made to be deep inserted the tuning should be optimized for such insertion depth, and using a shallow insert won’t be optimal and not necessarily better, just because you have experienced smoother treble in other models.

 

[KinGensai]

For sure, but at the end of the day sound will be a function of tuning, eartip, insertion depth and your own ear canal. Even stuff like cortisol levels or being sick can affect the sound and treble tolerance too.

What I’m trying to say is that, I want to trust the manufacturer in knowing what they’re doing, and if the shell is made to be deep inserted the tuning should be optimized for such insertion depth, and using a shallow insert won’t be optimal and not necessarily better, just because you have experienced smoother treble in other models.

I trust a few manufacturers (etymotic, beyerdynamic, sennheiser, etc). Others... Not so much lol.

 

[freeryder05]

The IER-M9 is meant to be used with a shallow insert so it should be closer to the red line. Specially with how I use it which is with the largest comply tips, gently inserted without compressing the foam.

That’s not my graph btw that’s @freeryder05 ‘s but I also have a coupler and have replicated the same results.

Ughhhh the m9 was a rough one. I wasn’t able to get an 8k peak in my measurements so I did a deep fit and shallow fit and figured the most representative treble would be in the middle. I struggled for like an hour before I gave up.

 

[castleofargh]

I get that tips and EQ are insufficient as compensation for HRTF as a whole, that's what I'd presume crossfeeders are supposed to help with.

The argument I'm trying to make here is that IEMs by nature bypass HRTF almost entirely, so maybe it's preferable to involve at least as much of the ear canal as possible to get an accurate representation of the sound being reproduced.

I don't think there is a solution of involving less of the ear canal. It still happens, all you do is shorten the "tube" so the resonance happens at a higher frequency. The ideal solution might be to end up with a signature that matches/simulates the resonance of your unobstructed ear canal. And I suspect that many designers aim for that, it's just bad luck that different people have different ear canals.

 

[theveterans]

What I'm interested with is some measurements of solid metal core eartips such as the Pentaconn Corier Brass. Doesn't metal cylindrical housing induce more resonance than silicone and to more extent foam tips, all assuming perfect fit across three tips

 

[KinGensai]

I don't think there is a solution of involving less of the ear canal. It still happens, all you do is shorten the "tube" so the resonance happens at a higher frequency. The ideal solution might be to end up with a signature that matches/simulates the resonance of your unobstructed ear canal. And I suspect that many designers aim for that, it's just bad luck that different people have different ear canals.

I think you may have misunderstood my post, I'm talking about involving more of the ear canal so the unnatural resonance(s) are mitigated.

 

[gregorio]

What is your opinion on the diffuse field target response curve? Is that a valid tuning strategy?

We could easily dedicate a whole thread to just this question. It depends on exactly what you mean by “diffuse field” and indeed by ”valid”. For example, Sennheiser often use diffuse field measurements/targets and as they make some very good HPs, we therefore have to conclude that this measurement/target is at least somewhat “valid”. On the other hand, the method of creating the diffuse field measurement varies considerably between manufacturers, is also dependant on the HRTF of the dummy head used and necessarily misses (effectively averages out) certain aspects of how HRTFs affect what we perceive according to sound incidence/direction.

HPs have some leeway here because the tuning target is sound as it reaches a point an inch or two away from the pinna, which means the main HRTF variables being ignored are the dimensions & density of the skull & torso as well as height differential of the ears.

Firstly, the variables of “dimensions & density of the skull & torso as well as height differential of the ears” is already a considerable number of significant variables to ignore. You could test the significance of this for yourself with some software, change the corresponding HRTF variables and see for yourself what effect they have on your perception of soundstage, etc. Secondly, these are not the only variables “over the ear” HPs are ignoring anyway. In a diffuse field (room) our ears will receive direct sound and/or sound reflections from different directions and our pinnae will absorb freqs differently depending on what direction, thereby producing a somewhat different FR depending on direction. For example sounds/reflections from behind the head (anywhere from say roughly the 4 - 8 o’clock position) will have to travel through the back of the pinnae to get to the ear canal, while sounds/reflections from the side or front won’t. There’s also a difference between side and front incidence but “over the ear” HPs effectively ignore these pinnae effects too, as all the sound is just originating from the side.

The key word in your assertion, IMHO, is “leeway” because ultimately it will come down to how sensitive a particular individual is to those variables being ignored.

This is the rationale of the DF target curve as I understand it, I think it's a valid tuning method. I'm just a layman though, maybe you think differently about that.

Clearly it is a valid tuning method as some very good headphones exist as a result of it. The question isn’t really one of valid or not valid though, it’s more a question of whether it’s more valid than using a free field target. This isn’t a question with a simple or satisfactory answer IMHO, there are too many variables at play and responses/perception varies too much between different individuals to arrive at a conclusive answer that will apply to more than just “some” consumers. Of course though, manufacturers are generally not going to admit this though, they’re obviously going to push the tuning method they’ve used in their own HPs/IEMs.

G

 

[KinGensai]

We could easily dedicate a whole thread to just this question. It depends on exactly what you mean by “diffuse field” and indeed by ”valid”. For example, Sennheiser often use diffuse field measurements/targets and as they make some very good HPs, we therefore have to conclude that this measurement/target is at least somewhat “valid”. On the other hand, the method of creating the diffuse field measurement varies considerably between manufacturers, is also dependant on the HRTF of the dummy head used and necessarily misses (effectively averages out) certain aspects of how HRTFs affect what we perceive according to sound incidence/direction.

When I use the word valid, I mean it in the context of validity vs soundness, which denotes internal logical consistency vs accordance of the concept with observed facts.

I agree with everything you say here. Sennheiser and Beyerdynamic seem to have a very different sound despite both of them using diffuse field in their R&D.

Firstly, the variables of “dimensions & density of the skull & torso as well as height differential of the ears” is already a considerable number of significant variables to ignore. You could test the significance of this for yourself with some software, change the corresponding HRTF variables and see for yourself what effect they have on your perception of soundstage, etc. Secondly, these are not the only variables “over the ear” HPs are ignoring anyway. In a diffuse field (room) our ears will receive direct sound and/or sound reflections from different directions and our pinnae will absorb freqs differently depending on what direction, thereby producing a somewhat different FR depending on direction. For example sounds/reflections from behind the head (anywhere from say roughly the 4 - 8 o’clock position) will have to travel through the back of the pinnae to get to the ear canal, while sounds/reflections from the side or front won’t. There’s also a difference between side and front incidence but “over the ear” HPs effectively ignore these pinnae effects too, as all the sound is just originating from the side.

The key word in your assertion, IMHO, is “leeway” because ultimately it will come down to how sensitive a particular individual is to those variables being ignored.

Completely agreed. Target response is a static representation of what is a dynamic situation aurally speaking, so the idea as I understand it is to set a point of reference for audio engineers to work with to create the illusion of spatiality through psychoacoustic models.

I'm guessing we are on the precipice of this paradigm changing, but from what I understand about audio production (not much at all compared to you, so please be patient lol), generic HRTF models and the engineer's perception is used for expediency's sake, so reproduction of the digital signal on the consumer end will not end up being necessarily hi-fi because the consumer has to be savvy enough to account for as much of their personalized HRTF as possible, a crapshoot at best.

Clearly it is a valid tuning method as some very good headphones exist as a result of it. The question isn’t really one of valid or not valid though, it’s more a question of whether it’s more valid than using a free field target. This isn’t a question with a simple or satisfactory answer IMHO, there are too many variables at play and responses/perception varies too much between different individuals to arrive at a conclusive answer that will apply to more than just “some” consumers. Of course though, manufacturers are generally not going to admit this though, they’re obviously going to push the tuning method they’ve used in their own HPs/IEMs.

G

This is just a natural consequence of us being organic meatbags lol. Variance is inevitable, so too must the equipment we use. I get the feeling though that we are going to see a huge paradigm shift soon once AI starts getting involved in tuning audio equipment to individuals.

 

[castleofargh]

I think you may have misunderstood my post, I'm talking about involving more of the ear canal so the unnatural resonance(s) are mitigated.

Ooops. Same answer though. The occluded ear canal and open ear canal won't have the same resonance, even with the tip at the edge of the entrance, the frequency being boosted will be different. If we believe in the necessity of getting that right, wearing earbud that seat loosely on the ear and don't touch the ear canal entrance, might be the ideal option (but then the level of isolation is 0 ).

 

[KinGensai]

Something I haven't seen addressed yet is acoustic diffusion in the context of tips. The Sancai is claiming to use small ridges at the nozzle for controlling airflow and the spiraldot & Eletech baroque tips are using patterns as acoustic diffusers according to the companies that manufacture them. What's the assessment on these claims? Does diffusion work at such a small scale?

 

[redrol]

Something I haven't seen addressed yet is acoustic diffusion in the context of tips. The Sancai is claiming to use small ridges at the nozzle for controlling airflow and the spiraldot & Eletech baroque tips are using patterns as acoustic diffusers according to the companies that manufacture them. What's the assessment on these claims? Does diffusion work at such a small scale?

My thoughts are no, those tips have been recced by some of my friends as well for sealed iems. They don't seal well but apparently provide enough bass. If I introduce tiny .. random patterns in an IEM bore it has no effect on graph.

What I do notice is the tip of the IEM is a horn shape, so this might be influencing how the iem tuning hits the ear canal.