I’m not too familiar with IEM tuning at all, but this portion completely addressed one of the biggest issues I’ve personally had with some of my IEMs. One of the first IEMs I got was the Dioko, with most describing it as mostly neutral but with some hotness in the treble.
I knew I was decent on handling treble, but when I got it, I found there to be some ear-piercing frequency that I couldn’t deal with at all. It sounded kinda like sibilance and I assumed the rather suspicious looking 8kHz (yes I am aware of the inaccuracy), but after eq-ing it just to check, found no improvement at all (no surprise there). However, after retuning it with some of the 5128/4620 measurements (in that 10-14kHz), I found it had significantly reduced that issue, putting the IEM back into my comfort levels.
I didn’t see many reviewers talking about a similar problem, so perhaps I am just extra sensitive to that region. Even tried swapped filters (I didn’t get an early batch), which of course made no difference. Honestly, I’m just glad to know I wasn’t crazy for hearing some weird peak, and saved me a lot of time trying even more mods.