If it's not tuning then it's distortion (there's really not much else that can affect sound quality on IEMs). I haven't seen any measurements of the T10, but considering how very low the distortion of the Zero 2 are my guess would be that the T10 have higher distortion that might "spice" it up in a way that you prefer, though objectively that would make them have less clarity.
Though I'm pretty sure the tonality of the the Zero 2 and T10 do differ as well, so then I guess it's a combination of both frequency response and distortion.
You make good points. Please hear me out.
1. Frequency Response is definitely important and the graphs of most of the devices, we discuss on ASR, are out there for us to compare. on Squig.link, if one of the reviewers has measured any two devices we wish to compare.
2. Distortion. Unfortunately, there has not been any really detailed measurements of the T10, and it would be instructive, if one could check the measurements of other similar planar magnetic IEM's that have been measured on ASR, or elsewhere, cos, if the anecdotes of many online reviewers, is to be believed, most of the Chinese designed and manufactured planar magnetic IEM's use very similar drivers, made by the same source. They add their own shells, and maybe customise the driver a bit differently, using vents, and nozzles, and the specific eartips supplied, but the fundamentally the drivers are very similar. So one may deduce the kind of distortion that the T10 is likely to have, by examining any available data, from its siblings. I'll try and find the time to trawl through ASR's archive to see what is there.
So here we are talking about Harmonic Distortion, i.e typically some kind of resonance, where certain frequencies are amplified abnormally. But the challenge with distortion as I understand it, from the world of speakers, is that the human ear is quite tolerant of a lot of distortion.
Furthermore distortion is usually worse, when audio is played back louder, so much of the distortion in the kinds of measurements published on ASR, are kind of theoretic, cos, at normal listening levels, most IEM's have negligible distortion. And its only when measured above like 100dB SPL, that any appreciable distortion is seen in the published data. So for IEM's predominantly distortion, is a bit of a non-issue, as some would say, academic. Nice for education discussion, but in reality, does not have an audible impact.
I bought the Zero 2, cos of its really low published distortion, expecting that to be a significant factor, but as my own listening has confirmed, this low distortion does NOT confer on the Zero 2, the superior transparent sound signature, that I had hoped for.
3. Time Domain. For some reason, I keep trying to narrow down the observation of a transducers (i.e something that converts electric energy to audio) behaviour in speakers, headphones, IEM's etc, etc, and something that keeps ringing in my mind is this - how come two different products, even when they have been tuned to the same target curve, using EQ, in my case, I use AutoEQ.app, how come they still sound different. So Frequency Response alone, and this is why all the attempts to EQ budget IEMs, cannot introduce the quality of higher value products, there has to be something more than just frequency response.
I am familiar, in the speaker world, with time domain measurements like the waterfall and impulse response, which provide additional information about two things.
3.1 The coherence of bass and treble - probably also better visualised via something known as the group delay. Poor group delay implies that the bass is kind of slow, and you hear it a little bit later than the treble. Good group delay, implies that the timing, i.e the start of the production of bass and treble sounds, is closer, ideally this delay should not exist, i.e bass sounds and treble sounds are produced instantaneously at the same time. I posit that the technology of some products, limits their ability to achieve this ideal, and that is what some of us are hearing in the Zero 2. What I would call a sluggish driver. So what we hear is NOT in sync. Our ear then has to work harder to reconstruct the cohesion of the bass and treble, cos of the time delay, and this affects how we hear the audio.
3.2 The waterfall show us if we have any ringing, also a kind of resonance, but this one is time based, in any frequencies, like an extension of the sound. I.e when a sound should have stopped, it does not, and what is known as the decay, is extended. It could be that many of us are too familiar with this over extension in the time domain, especially of bass frequencies, which is common in dynamic drivers. We hear this as MORE bass, but actually what this is, is MORE inaccurate bass. But if we are accustomed to this. when we hear more accurate bass from products like the T10, at first it sounds insufficient, cos the problem is - we have been listening to the wrong thing for many years, and we now need to relearn, what proper bass should sound like - quick attack, and also a quick decay. 3.1 above deals with the attack, and 3.2, this paragraph, deals with the decay.
I am pretty confident, if I, an untrained amateur audio sleuth, can think of this, the experts here and elsewhere are fully aware of what I am talking about, and it could be that this is one of the reasons the impulse response and waterfall are NOT published. They would immediately let the cat out of the bag.
In my experience, with speakers, simply looking at about 4 or 5 measurements, tells you everything you need to know. Frequency Response, Waterfall, Impulse Response, Group Delay, Harmonic Distortion, and Directivity, and without listening to a speaker, you can make a well informed decision to shortlist, which speakers are worth auditioning OR NOT, and probably make a purchase decision, without hearing the speaker, and NOT be disappointed. Cos these measurements strongly correlate to perceived audio quality.
I suspect - if we had these kinds of measurements for IEM's, its game over, we would have similar objective data, that explains, exactly why one should avoid or buy an IEM.
I am confident, we will get there soon. If enough of us badger people like AmirM, about this.
On a positive note, the kind of testing he has done, and others also have done, on DACS and Amps, has achieved a similar objective, we can purely on the basis of measurements, confidently pick what to buy, cos the measurements correlate to what we expect to hear. This has forced the manufacturers to stop playing around and focus on improving their products.
I am very confident, with savvy buyers like many here, and increasingly more savvy reviewers, like AmirM, the gang at Headphones.com, and others, over the next period, we will eventually arrive at a point where we do not need comments about how something sounds, just a look at the measurements, tells us what we need to know. No need for all that subjective mumbo jumbo, of many reviewers. Well their mumbo jumbo subjective opinions are good for entertainment. !!
The better sounding IEM's will also have better time domain behaviours, and I so look forward to reading and seeing these measurements., which will put to bed, all the arguments and differing opinions, in the same way that that has already occured with DACs and AMPs.
I look forward to when we have even more breakthroughs in personalised HRTF's. From those who have had the opportunity to have theirs measured, I understand that this takes headphone listening to another level, more. So maybe the IEM in future just has to be flat frequency, and with a personalised HRTF, via DSP(i.e EQ in DSP), we can conform this to what sounds best for us. Maybe the IEM is NOT the ideal place for simulating HRTF's which is what's taking place, at this time.
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