Yes, it is due to tuning and crossover. Numbers of BAs can be a lot but the tuning and how it is being implemented are the hardest one. Haha, i thought my journey of finding a closed iem for vocals ended after getting La Hire lolApparently vocals done by only 2 BA. Not EST. I had that feeling earlier. It04 sounded so open and airy, compared to Roland. Now it sounds glorious. My brain can adjust to the difference, that means it's relatively minor. Hmmm...
Edit: what makes me upset is the description of the La Hire. "Made for female voice".