Glad you're enjoying these. I've owned EXT since the middle of November, and as of now with my current collection, it's the IEM I reach for the most with Odin following it very closely, two very different and complementary IEMs to me. Indigo and IE 900 I would rank at spots 3 and 4 respectively for my usage. IE 900 will likely shoot up in ranking again once I start working in the office more in the future since I'm mostly from home and IE 900 is my dedicated out of the house IEM for hiking/office use.
I don't find the upper midrange of EXT to be a problem for female vocals, and I say that as someone who doesn't mind the aggressive rise to a high peak that Odin has in that area (coupled with the leaner bass which can accentuate the upper midrange). I'd call EXT a light U shape for my hearing and music (FYI I can still hear up to ~17.5 kHZ when I got tested last year), and I agree with what
@aaf evo is saying below about a U shape, and I can hear the upper treble/air/sparkle a bit higher than the upper midrange. The U doesn't bother me, it's kind of a light U from what I can hear when I listen to a band that has female vocals + cymbal splashes/riding all happening at the same time. FYI I listen to a lot of female vocal bands, a few male vocal bands, and tons of electronic music. What I consider a "W shape" in my collection is the UM MEST Indigo FWIW.
Anyhow, I really love so many things about EXT such as the quality of the bass/mids/treble, and that the treble extends pretty high up. The bass quantity is an amount that I
really like, and I prefer the bass overall (quality + quantity) to even the IE 900. I also like that the size of musical notes on EXT is on the larger side (kind of like Odin). Listening to distorted electric guitars with EXT's thick sound
is so satisfying to me.
Can't wait for my PHöNIX to arrive sometime this month hopefully to see how I like it.