The demands placed on the driver are quite different, due to extra isolation granted by IEMs, a small enclosure encompassing the IEM housing and the listener's ear canals which increases bass pressure and extension, as well as the significantly shorter distance to the eardrums, which does not require as high SPL levels to be perceived as appropriate listening levels at the listener's position due to energy lost
I don't think it was necessarily due to the physical requirements of the driver diaphragm size, but it does seem that the accepted driver size is 10mm or larger for sub-bass to mids performance in a hybrid configuration and 8mm or smaller for mids to treble performance in a multi-DD configuration. High excursion drivers are challenging to maintain any significant agility in, as it can be difficult to design a magnet structure and voice coil in such a small package that can generate a strong enough flux to net you that excursion when you're using a driver with significant mechanical spring force, so you'd be looking to use a driver with a more flexible surround with less mechanical spring force and rely primarily on electrical spring force to pull the driver back to its nominal state. You tend to lose agility and "texture" when you go this route, but it can result in incredibly deep bass with a very "warm", "smooth", "honeyed" quality to it. When you opt for a driver with comparatively low mechanical spring force, then the role that the enclosure design plays is more pronounced, but still not as noticeable as in actual loudspeaker designs, since a lot of the theories and calculations don't scale accurately down to that form factor.
have you by chance heard the Dunu Titan 6? I think it's got a 14mm beryllium coated dynamic, but I don't think I've seen any reviews of it floating around.
I have heard the Titan 1 and Fiio EX1, EX1 gen 2 and F5, but not the Titan 6 although I was really interested in it. Reason was the graphs from this site https://reference-audio-analyzer.pro/en/report/hp/dunu-titan-6.php#gsc.tab=0 compared to other IEMs I was eyeing as well
It looks like @CK Moustache did a review of them a while back and didn't find their performance to be worthwhile, mostly because the driver wasn't ideally suited for treble performance or it just wasn't tuned properly for that application. It does look like a strong contender if the rear chamber is ported to act as a sub-bass and bass driver in a hybrid config. I think the Dunu EST112 uses a larger driver that they based off what they learned with the Titan 6. Though I have heard some complaints that the EST112 could stand to have more texture in its sub-bass and bass performance, so maybe they ended up making the driver too large or the diaphragm too heavy with the two-sided beryllium coating. I don't really know, and I can't fit them in my ears anyway, so there's no point in me considering purchasing them, even if their cable is excellent.
From experience, generally for IEMs there is little reason to look back unless you are after a specific, particular sound signature that you already know of and want. In the past few years they have improved so much, my IEMs which were considered good from around 2012 are mostly unlistenable now
That does certainly seem to be the case. The only ones that seem particularly worthwhile might be some of the Sony XBA series, but even then, the newer models are objectively superior and the old ones aren't so cheap on the resale market that it's worth choosing them instead.
By the XBA series, do you mean the XBA-1, 2, 3 and 4?
The H2 and H3 have decent graphs, but the A2 and A3, the A3 in particular, are just better. But then there's the N3, whose graph just looks more pleasant than any of them. I wish they were more affordable, because I may have purchased them before getting my GS Audio GD7B, and I'm hard pressed to want a side-grade.By the XBA series, do you mean the XBA-1, 2, 3 and 4?
the H3 was a bass cannon. The A3 was not a bass cannon (but still had amble bass without the veil) but the detail retrieval and resolution were just average. Quite underwhelming, and coming from the H3, I was so excited to get them for my birthday. I now have the XBA300, and with balanced output, they are very good, and they are quite good through 3.5mm, BUT I warn treble sensitives to avoid, as they do possess very BA type highs in extension and timbre.
