Etymotic ER4SR.
My job is sound engineering, i record and mix music and sound for movies, so headphones/IEMs are my tools, tho i love listening music on them, and do it a lot.
Etymotic are professionals in IEM, they’ve invented them, they do a lot of R&D, spare parts, and’ve been doing this for years with success. We all saw measurements and read their papers.
I use ER4SR when recording musicians in a studio and on a movie sets. I need to hear every detail to pay attention and record highest quality audio, and so far for my almost 20 years career i’ve have not used better tool for this task. I’ve heard the same from a very respectful engineers that record classical and jazz music too - that’s a good sign.
High isolation: you need less volume, so you have low distortions and no fatigue due to them and volume, and no frequency response bias due to high loudness (Fletcher-Munson).
Good frequency response: i really love that fact that what’ve heard on ER4SR during recording is the same what i hear on a big high quality monitors in a treated rooms. The bass they “lack” due to their DF-curve is not a problem, but when i need to use Harman (it is more useful for mixing), i just add nice little shelf to LF. They do “translates” well to big monitors, meaning i definitely can mix on them.
Low distortions: i can mix on them! They’re so good, it is much more easier to hear any distortions in sound on them comparing to regular near-field monitors, and you need a really good treated room with a very good speakers to get to the same level of quality.
The thing i like most when using Etymotics:
when i set mics in a studio live room for musicians, i use them to listen to the sound from the mics i place...and when i go back to a control room to big monitors - i hear exactly the same sound, no need to go back and correct the placement.
(BTW, I think “missing bass” is compensated in this situation with an actual bass acting on your body in a live room....)