Sony - XBA-Z5

That treble spike you speak of is an issue of cone break up. I never denied the weakness of a single driver dynamic, nor did I advocate a single driver as the ideal solution. What I believe is that a simpler solution is needed and we already have them. A dynamic driver with treble support is all we need, and that requires only a 2-way crossover with as little as 2 or 3 drivers. That being said, spiky treble is not a character that is exclusive to single driver dynamics. The JHA JH16 has that spike despite being an 8-driver BA. In fact many multi-driver BAs do. Here's a non-exhaustive list of IEMs with minimal driver counts (no more than 3) that have the technical prowess that reveals the potential of simpler solutions: 1. Sony XBA-Z5. 1000 dollars cheaper than Z1R for the same technical prowess. As you know, only 3 drivers. This was a time when Sony actually innovated. Similar high end frequency response to the DUNU Luna, but produced by the magnesium BA drivers. 2. Radius HP-TWF11. Incredibly flat response, incredibly low distortion. All from only two dynamic drivers. Most of my IEMs were tuned for U or V shape. The Radius IEM had a refreshingly full midrange because of the flat tuning all the way to the treble. The dynamic tweeter driver had no treble spike that you spoke of. 3. Kiwi Ears Cadenza. Single driver IEM with a Beryllium coated diaphragm. Slightly overdone V-tuning but on a technical level they have done excellent design choices. Its "treble spike" is very tame as the diaphragm is still mainly plastic to avoid ringing. There's plenty more. You can take measurements of those IEMs and compare them to "TOTL" IEMs with ridiculous amounts of drivers and you will see they're not that different to each other. They could have almost identical frequency response and similar distortion profiles. Nothing stands out from a technical stand point that says these simpler solutions are better or worse than ridiculously complex 4-way 10-driver IEMs. They simply achieve the same target in a different way, and some of them were able to do it for cheaper. The HP-TWF11 and its other generational upgrades for example. But of course, proponents of the more complex solution would dismiss these technical achievements. Other industries are aiming for reduced mechanical components and simplified electrical circuitry. Only in the audio industry is excessive complexity seen as an advancement. Just putting in more and more drivers is enough to get people throwing money at them.

These are classics. Had the EX600, EX800ST and MDR-7550. Recommend the MDR XBA-Z5 - it is the culmination of that driver technology along with very high quality Sony BAs. My friend now has it and I miss them. Maybe will get a Sony again one day like the XBA-N3

A bit of a Sony fan here, but I like my XBA-Z5s for digital sources. They’re good for classical music, pop, and everything in between. I use a pair of Grado RS1s for analogue sources like vinyl and reel to reel tape. They’re my cans for jazz, especially mono. They’re paired with my Sony TA-A1ES integrated amplifier which has a dedicated output with impedance matching. I use a pair of Sennheiser HD-25s for casual listening. Went from MDR-7506s to those purely as the Sennheiser mids are less dry and slightly more resolving. I do miss the comfort of the 7506s though!

Oh yeah, without a doubt. The thing about the z1r is that it has been the best for so long, and in the conversation even till this day(especially desirable 2nd hand), also it is a Sony - they have a tendency of either making terribly unforgettable product or industry changing hallmark. Example of this would be xba z5, and the legendary mdr r10 (because of this brand reputation, it also effect their future product)