[KinGensai]

For a while now, I have been collecting tips to find a versatile collection to use for my IEM collection on the assumption that fitment is the most important consideration. Not long into this process, I noticed tips change the sound presentation somewhat based on the geometry of the core and design of the flange(s) due to the change in airflow, although it hasn't been very pronounced up until now.

The Maestro SE has introduced some thought provoking changes to my previous assumptions due to how difficult it has been to choose an optimal tip solution for it, and now I have some questions arising from this experience.

1: the MSE thread has commonly reported that switching from universal to custom has changed the presentation of the bass (muddy to cleaner is the prevailing notion) and an 8k resonance peak is tamed.
2: my time using the universal fit MSE so far comports with the anecdotal accounts conditionally. It does have some flub in the bass and a sharp peak at 8k, but only with some tips and shallow insertion depth.

This got me to thinking about what these two things mean. Custom fitting seals the IEM better, but it also removes the need to use a silicone tip, and certain tips seem to affect the sound in a beneficial way (cleaning up & slightly lightening up the midbass and reducing the 8k peak). What is the difference between the tips?

The primary difference I see in the offending tips and the good tips is the core. Most IEM tips have a core that extrudes from the nozzle opening a few millimeters, which funnels the air and concentrates the movement to create relatively higher SPL levels depending on how restrictive the core is. The tips I found were helping the MSE were tips that have a significantly truncated core and have a bore wider than the nozzle. For a reason I can't articulate, I also perceive a more diffuse sound presentation that presents spacial cues more "naturally", for lack of a better term.

What could the reasons be for this? The MSE features an elongated nozzle that probably has something to do with the MSE's elevated bass presentation, which is relatively uncommon amongst the IEMs I own, and I suspect that there is a correlation because IEMs I own with a shorter nozzle (Anole V14 amongst others) seem to benefit from the longer core vs the shorter core.

 

[redrol]

There are only 2 things that matter with tips, and keep in mind this is coming from tuning IEMs. I don't have any skin in the game as far as types/brands.
1. Internal Tip Diameter
2. Tip insertion depth as it works with your ear canals.

1. will cause treble roll off and then a peak or higher SPL above 10k
2. will affect ear gain (as measured) around 2500hz. Deeper will produce less gain, shallow more.

The materials don't matter, so Foam vs whatever. Foam might leak a hair more air allowing less pressure build up, but the greatest reason they change things is the foam at the end of the tip can 'bunch' up in the ear canal leading to less 2500hz ear gain by filling more of the canal itself.

 

[KinGensai]

@redrol
I no longer think it's that simple. Those two factors make sense, but they don't answer my question.

Here's my initial hypothesis on why I am experiencing what I am.
1: As bore diameter increases, bass is attenuated by reducing the relative SPL level as opposed to smaller bore diameter, thus drawing attention to the mids & highs which are less affected.
2: As the core length extending past the nozzle decreases, the amount of distortion induced by reflections off the silicone core also decreases.

I think it's #2 that is the primary thing I'm a bit puzzled about because I didn't really notice this effect with other IEMs that don't feature the very long nozzle the MSE has. It could be because most other IEMs don't push bass so high up, so when the relative distortion is reduced I don't notice because it's too quiet to hear readily, but I'm wondering if the sheer length and exponential curvature of the MSE's nozzle has something to do with this also. Most IEMs seem to be designed with some length of tip core integrated into the tuning decisions, whereas FatFreq is claiming the MSE/GM were designed primarily for the custom version which would naturally preclude any kind of silicone tip.

 

[MudEnjoyer]

There are only 2 things that matter with tips, and keep in mind this is coming from tuning IEMs. I don't have any skin in the game as far as types/brands.
1. Internal Tip Diameter
2. Tip insertion depth as it works with your ear canals.

1. will cause treble roll off and then a peak or higher SPL above 10k
2. will affect ear gain (as measured) around 2500hz. Deeper will produce less gain, shallow more.

The materials don't matter, so Foam vs whatever. Foam might leak a hair more air allowing less pressure build up, but the greatest reason they change things is the foam at the end of the tip can 'bunch' up in the ear canal leading to less 2500hz ear gain by filling more of the canal itself.

Excellent post. Matches my findings as well besides the ear gain claim which I haven't experienced much on every IEM.

Specially in terms of insertion depth and treble response. I mean, just look at this:

Pretty much the reason to ignore most of the treble response we see in graphs. It's a bit sad that people are missing out on great sets just because the brand is not carefully reverse engineering reviewer couplers to make it look good when aligned at 8kHz

Also reminder to tune your foam tips and remove the excess material. The Sony, Sennheiser and the new bullet Comply foams are great stock, but most of the cheap ones really benefit from a snip here and there.

 

[redrol]

Excellent post. Matches my findings as well besides the ear gain claim which I haven't experienced much on every IEM.

Specially in terms of insertion depth and treble response. I mean, just look at this:



Pretty much the reason to ignore most of the treble response we see in graphs. It's a bit sad that people are missing out on great sets just because the brand is not carefully reverse engineering reviewer couplers to make it look good when aligned at 8kHz

Also reminder to tune your foam tips and remove the excess material. The Sony, Sennheiser and the new bullet Comply foams are great stock, but most of the cheap ones really benefit from a snip here and there.

Good going my man!! This clearly shows the effects.

For the record tips do NOT change bass frequencies unless you just plain are not getting a good seal.

 

[castleofargh]

I agree with the gang, if the bass changes with tips, the answer has to be seal quality. Some leakage=bass rolling off. We could in theory have other variables, but it would need to so massively restrain the airflow that I don't expect it to matter much on the side getting into a closed ear canal. And the rest is simply too small to clearly impact seriously long wavelengths like bass.

For higher frequencies, it's mainly about internal volumes AFAIK. There is the ear canal's volume, but also the inner volume/s. So that makes more than one resonant frequency possibly shifting from swapping tips. We(OK, I) usually simplify to the extreme by considering just about everything as tubes, because it gives an almost intuitive concept of why a certain frequency becomes louder.
https://xmphysics.com/2023/01/02/10-8-3-pipe-resonance/

You can also consider cones for simple shapes, it will have different results from tubes, but the principle remains the same. It's always about the distance and which wavelengths end up boosting themselves. I only know the closed cone case, where the resonance is the same as that of an open tube of the same length. Not very useful, but a great anecdote for diners when you want somebody to leave you alone.

 

[KinGensai]

I agree with the gang, if the bass changes with tips, the answer has to be seal quality. Some leakage=bass rolling off. We could in theory have other variables, but it would need to so massively restrain the airflow that I don't expect it to matter much on the side getting into a closed ear canal. And the rest is simply too small to clearly impact seriously long wavelengths like bass.

For higher frequencies, it's mainly about internal volumes AFAIK. There is the ear canal's volume, but also the inner volume/s. So that makes more than one resonant frequency possibly shifting from swapping tips. We(OK, I) usually simplify to the extreme by considering just about everything as tubes, because it gives an almost intuitive concept of why a certain frequency becomes louder.
https://xmphysics.com/2023/01/02/10-8-3-pipe-resonance/

You can also consider cones for simple shapes, it will have different results from tubes, but the principle remains the same. It's always about the distance and which wavelengths end up boosting themselves. I only know the closed cone case, where the resonance is the same as that of an open tube of the same length. Not very useful, but a great anecdote for diners when you want somebody to leave you alone.

Ok, this is starting to get relevant.

Let's get specific with the tips I'm talking about. As a default, I'm using the Divinius Velvet tips to start, these have a straight cylinder silicone core that is quite thick relative to other silicone tips. Using these with the MSE results in a pronounced bass response due to what I presume is the thicker material and dome shape providing a very solid seal. Using these also narrows my perception of the sound field for whatever reason I still don't understand enough to articulate compared to the next set of tips.

The tips I'm settling on at the moment are the Tangzu Sancai Wide bore tips. I don't know what those little ridges at the muzzle of the tip are supposed to be doing, but these have a significantly truncated core that, as mentioned, extend far less from the nozzle of the MSE and don't obstruct the nozzle at all.

So directly comparing these two, there are four perceived effects:
1: slightly attenuated peak at 8k. side by side, the reduced amplitude is noticable.
2: bass volume is lower on the Sancai vs Velvet. This I expected given the Sancai is supposed to not be completely sealed to allow air pressure to equalize.
3: reduction in perceived bass muddiness in the Sancai vs Velvet.
4: Spatial perception is wider with the Sancai. Whether this is due to a reduction of the midbass or due to effectively changing the insertion depth by a minimum of 2mm (counting the flared muzzle of the wide bore that is, since it's so flared out I would posit that it could be discounted for an even shallower insertion) I'm not sure.

Listening to a log sweep to these side by side indicates to me that the Sancai is attenuating the bass and treble response vs the Velvet.

With all this context out of the way, I'm beginning to suspect that maybe my perception of cleaner bass is coming from a reduction of amplitude in the bass, not necessarily any qualitative change. Your argument makes sense given the tiny scale of differences in core length and bore diameter vs the physical length of the waveforms we're talking about here. Phase cancellation is probably much more relevant to treble when discussing the presence of a silicone core or lack thereof.

My remaining question is about spatial perception then. Is there something besides an FR adjustment happening here that could contribute to this perception? Maybe the reduction of the influence of the core is allowing more of my ear canal to affect the sound, thus making it sound more natural in ways just a low shelf and high shelf adjustment doesn't?

 

[castleofargh]

Sadly, I have no clear answer about spatial impressions. Different people respond differently to certain stimuli. FR is sure to matter, but other aspects can weight on the global interpretation created by the brain (it's basically the 'raison d'être' for Sound Science ^_^). To go back to bass perception, something that's somewhat simpler, maybe the changes in FR at higher frequency simply give a relative feeling of attenuated bass? Maybe one set of tips happen to shake (physically) more noticeably? Physical vibrations even at a frequency unrelated to the bass sounds has been said to help increase the perception of bass and bass quality. But taking that concept and running with it, we get the shakers that we put on ourselves or on the chair that vibrate strongly with the music for headphone users. Some people swear by it, many don't seem impressed at all, and some just can't stand using them more than 5mn.
Having to deal with different humans, we find very common points, and also some highly subjective (as in "per subject") responses.
I believe that the general sense of pinpoint location comes from mid/treble frequencies being generously present(again, it's a wavelength thing and what works best between our ability to discriminate phase shifts and the distance between both ear for direction). While the bass gives me a feeling of being in a bubble of sound when it's strong and deep enough to get me in the mood. But then again, I generally feel like I'm getting more of a bass feeling from flat headphones than from IEMs with rising frequency and objectively lower range. I'm satisfied with flat or even rolled off bass on headphones, but I want between 3 and 6dB increase relatively to maybe 500Hz on IEMs before I can consider it to have "deep" strong bass. So obviously, I'm tempted to say that there is more than FR going on in that example. But I also have to add that it's my personal feeling, not a proved thing like some of the other stuff I brought up.

 

[KinGensai]

Sadly, I have no clear answer about spatial impressions. Different people respond differently to certain stimuli. FR is sure to matter, but other aspects can weight on the global interpretation created by the brain (it's basically the 'raison d'être' for Sound Science ^_^). To go back to bass perception, something that's somewhat simpler, maybe the changes in FR at higher frequency simply give a relative feeling of attenuated bass? Maybe one set of tips happen to shake (physically) more noticeably? Physical vibrations even at a frequency unrelated to the bass sounds has been said to help increase the perception of bass and bass quality.

Oh... I guess the tips could be absorbing and resonating with the bass. I thought that, since the correlation between felt bass and tip design is thinner flange & core = less bass, the thick tips like the Velvet are reflecting the energy as opposed to absorbing it, kind of like how hardwood floors reflect noise vs acoustic foam or carpet.

But taking that concept and running with it, we get the shakers that we put on ourselves or on the chair that vibrate strongly with the music for headphone users. Some people swear by it, many don't seem impressed at all, and some just can't stand using them more than 5mn.

That sounds like the goal of bone conduction drivers, which I am evaluating at the moment. I think there is something to that, bass rumbles the whole body in a normal state, so BC drivers recreating the sensation of felt bass seems like a logical progression to me.

Having to deal with different humans, we find very common points, and also some highly subjective (as in "per subject") responses.
I believe that the general sense of pinpoint location comes from mid/treble frequencies being generously present(again, it's a wavelength thing and what works best between our ability to discriminate phase shifts and the distance between both ear for direction). While the bass gives me a feeling of being in a bubble of sound when it's strong and deep enough to get me in the mood.

I guess this would explain the improved sense of space. The Sancai tips are essentially correcting the FR of the MSE to fit my HRTF closer, so the sound presentation sounds more accurate to me.

But then again, I generally feel like I'm getting more of a bass feeling from flat headphones than from IEMs with rising frequency and objectively lower range. I'm satisfied with flat or even rolled off bass on headphones, but I want between 3 and 6dB increase relatively to maybe 500Hz on IEMs before I can consider it to have "deep" strong bass. So obviously, I'm tempted to say that there is more than FR going on in that example. But I also have to add that it's my personal feeling, not a proved thing like some of the other stuff I brought up.

You know, now that you bring that up, I think you're right. My DT 1990 pro has an adequate sense of bass response despite being tuned closely to the DF target, and IEMs that graph like that sound completely wrong. This is probably related to why BC drivers are the logical next step in development.

 

[redrol]

Excellent post. Matches my findings as well besides the ear gain claim which I haven't experienced much on every IEM.

Specially in terms of insertion depth and treble response. I mean, just look at this:



Pretty much the reason to ignore most of the treble response we see in graphs. It's a bit sad that people are missing out on great sets just because the brand is not carefully reverse engineering reviewer couplers to make it look good when aligned at 8kHz

Also reminder to tune your foam tips and remove the excess material. The Sony, Sennheiser and the new bullet Comply foams are great stock, but most of the cheap ones really benefit from a snip here and there.

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

 

[KinGensai]

@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.

 

[castleofargh]

@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.

Your options are to aim for a statistical average human and use one of the recognized and expensive dummy heads with all the standards set for it.
Or to aim for your own perception, in which case, do whatever you want, the best result is going to come from your own experience at your favored insertion and tips. But will it serve others well? Who knows? If you're near the average human, then chances are you'll end up close enough to the Harman target (be aware that the curve everybody uses was not referenced to be used on their gear and as such is typically wrong somewhere).
And if your HRTF and by extension your head are not near the average, then you'll get whatever, and it won't please a majority of listeners.

For all this I'm talking about frequency response as that's what we change most significantly with different ears, tips, measurement fixtures and insertion depth.

 

[KinGensai]

@castleofargh
Yeah, that matches up with what I thought before, but I'm thinking in this instance that there may be a principle that can be derived from the facts in evidence here.

Of course no aught can be derived from what is, people are going to do whatever they want to get whatever sound they wish to get. I'm assuming for the sake of this discussion that the goal is to achieve the most fidelity possible to the original audio signal. I also accept that some manufacturers will specifically design their iems with different ideal insertion depths in mind (Etymotic comes to mind for designing mega deep fit IEMs), but most IEMs I have or had at some point seem to be designed with shallow nozzles, which I think implies that the designers meant to compensate for the pinna only, not the ear canal at large.

I think we agree here, but I'll articulate for the record that I think the ideal conditions to aim for is the experience of speakers in a properly treated room, which means that none of our HRTF is being ignored. Given this ideal, the principle to achieving hi-fi is to allow for as much of our HRTF to influence the audio signal as possible when sizing down to HPs and subsequently IEMs. Elements of HRTF that are ignored then have to be guessed at and compensated for by designers to attempt to maintain sufficient fidelity, making HPs and especially IEMs finnicky in terms of tuning and fit.

Thus, my contention here is that it may be conducive to this goal to select and judge tips based on achieving a secure fit at the most shallow insertion depth safely possible to allow our ear canals to influence the sound as much as possible, and the helpful graph @MudEnjoyer posted seems to support this notion given that the resonance peak at 8k probably should not be there as it is an artifact of possible phase interference altering the sound by the time it hits the eardrums in an unintentional way.

 

[castleofargh]

@castleofargh
Yeah, that matches up with what I thought before, but I'm thinking in this instance that there may be a principle that can be derived from the facts in evidence here.

Of course no aught can be derived from what is, people are going to do whatever they want to get whatever sound they wish to get. I'm assuming for the sake of this discussion that the goal is to achieve the most fidelity possible to the original audio signal. I also accept that some manufacturers will specifically design their iems with different ideal insertion depths in mind (Etymotic comes to mind for designing mega deep fit IEMs), but most IEMs I have or had at some point seem to be designed with shallow nozzles, which I think implies that the designers meant to compensate for the pinna only, not the ear canal at large.

I think we agree here, but I'll articulate for the record that I think the ideal conditions to aim for is the experience of speakers in a properly treated room, which means that none of our HRTF is being ignored. Given this ideal, the principle to achieving hi-fi is to allow for as much of our HRTF to influence the audio signal as possible when sizing down to HPs and subsequently IEMs. Elements of HRTF that are ignored then have to be guessed at and compensated for by designers to attempt to maintain sufficient fidelity, making HPs and especially IEMs finnicky in terms of tuning and fit.

Thus, my contention here is that it may be conducive to this goal to select and judge tips based on achieving a secure fit at the most shallow insertion depth safely possible to allow our ear canals to influence the sound as much as possible, and the helpful graph @MudEnjoyer posted seems to support this notion given that the resonance peak at 8k probably should not be there as it is an artifact of possible phase interference altering the sound by the time it hits the eardrums in an unintentional way.

If you do want speakers as the reference for correct signal, you want your own HRTF factored in. Then you need more than tips and EQ. You need the left sound source reaching the right ear with the attenuation and delay your own head would create for a given sound source direction(let's say 30° to the left for the typical stereo speaker model). As for the correct frequency on the left ear, it is also what your own head and ears would modify for the direct sound incoming from 30° to the left. Once both ears get the proper sound for stereo(with speakers as reference), you get something a sound, and a frequency response in particular that are almost certainly going to be your favored and perceived neutral signature, but that is probably never going to be what you favor when getting classic IEM sound, where only your ear canal is involved and the left drivers only makes sound for the left ear(not strictly true as some sound goes to the other ear through the skull at something like -60dB or so of attenuation, but that's very far from enough).

You can try to find out where the resonances are for you and a given IEM. Fooling around with an Etymotic IEM allows trying different insertions and with a sine sweep you can clearly feel the shift in resonance(and for me, some very attenuated area around 7,5kHz in one ear and 8kHz in the other, my hearing then goes back up above that sort of notch and is fine up to about 14,5kHz).
Just ignoring speakers and pretending that normal IEM audio is fine, different people do have different ear canals. Men and Women have statistically different lengths already.

 

[gregorio]

I'm assuming for the sake of this discussion that the goal is to achieve the most fidelity possible to the original audio signal.
I think we agree here, but I'll articulate for the record that I think the ideal conditions to aim for is the experience of speakers in a properly treated room, which means that none of our HRTF is being ignored. Given this ideal, the principle to achieving hi-fi is to allow for as much of our HRTF to influence the audio signal as possible when sizing down to HPs and subsequently IEMs. Elements of HRTF that are ignored then have to be guessed at and compensated for by designers ….

That’s a relatively huge number of variables. Firstly there’s the “original audio signal”; what is that, is it a standard stereo, a binaural or some sort of hybrid like Dolby Atmos? Then there’s the “speakers in a properly treated room”; there’s very significant variation even between different mastering rooms and even bigger variations between other types of properly treated rooms such as recording studios and dubbing stages. There’s also very significant differences between different individuals’ HRTF and then there’s a sort of feedback loop to the “original audio signal” (the distribution copy/master), due to the HRTF/perception of the mastering engineer, who very likely at least checked and very possibly altered the mix according to their personal observations when monitoring with HPs/IEMs.

I don’t see how this can be “guessed at and compensated for by designers”, there are too many conflicting variables here. If a designer actually did attempt to “guess at and compensate” for them, the result would likely be HPs/IEMs that are inappropriate (and/or not preferable) for the majority/vast majority of their target demographic. Far better to just ignore the variables of “original audio signal”, “speakers in a properly treated room” and most of the HRTF, just apply some basic/generic FR and let each consumer deal with these variables individually (with some DSP before the signal is sent to the HPs/IEMs), which of course is what the designers already do.

G