So, I'm in the market for custom iems in the near future, and I had the opportunity to demo a ton of customs. Hong Kong is awesome like that. Things I tried include UERR (obviously), UE4 pro, UE18 + pro, UM Miracle v2, UM Mason v2, Lime Ears Aether, QDC 8 driver (studio and live), EarSonics S-EM6, CA Andromeda, and a few others. My source was a demo version of the new Sony NW ZX-300 (highly recommended, by the way). I brought my own microSD card with music I'm familiar with.
To get a sense of where I'm coming from, I value naturalness and realistic portrayal of vocals/instruments above all else. Coherency and imaging are a close second (and highly related to naturalness). So, I tend to inherently prefer a very slightly darker/warmer approach to a neutral sound signature, which in my opinion, is the sound signature closest to my ideals. And it's a really delicate balance. Stray a little bit from my preferred sound signature, and it kicks me out of my immersion to the music.
For instance, I thought that the Andromeda was too bassy to be realistic, the S-EM6 waaaaaay too smooth and velvety, Miracle a tad too shrill and bright (some issues with sibilance here and there; cymbals too splashy to be lifelike).
But, the UERR. Man, these bad boys nail it. Violins, pianos, electric guitars, drums, saxophones, raw powerful vocals, refined elegant vocals, you name it. The UERR just gets it right. For my money, it's got spot on timbre and tonal accuracy for everything you throw at it. I even preferred the UERR to the UE18+ pro, despite the fact that the technicalities such as imaging, detail retrieval, and soundstage were better (marginally). I'm still not quite sure what it was, but the sound signature of the UE18+ pro wasn't quite as lifelike to me as the UERR. I intend to go demo both of these models again; this time more extensively.
Coherency was another big plus for me, and is another big factor in the realistic portrayal of music. For instance, I sometimes feel that, relative to my HD800s gigantic soundstage, the various instruments are stretched too far and too thin for me to consider the music to be lifelike. On the other hand, having the instruments sound too thick or having the soundstage be too small will lead to a wall of mushy sound. Again, its a delicate balance, and I think the UERR gets it just right. So, while the UERR only has an average soundstage size, it excels within its confines.
The only nitpick that I can think of is that its imaging can only be described as average (relative to the TOTL iems). But otherwise, I really do believe that this is the perfect iem for my needs.
Anyway, thanks for reading. I'll be joining this club soon enough, and I can't wait.