Wow, this is a very nicely-tuned stage monitor. The bass is a very nice, natural-sounding, balance between mid-bass and sub-bass.The mids have a nicely euphonic warmth and fullness without getting anywhere near wallow-in-mud territory. Amazingly, the treble isn't recessed or overly bright. No weirdly artificially hyper-instrument separation, no odd incoherence, no weirdly off BA-tinny timbre, none of the things that usually put me off a BA custom. There's a stage monitor lift in the vocals but they used a light touch here too and it sounds absolutely great.
Just using a two-way crossover and then tuning it really well turns out to be a very good way to make a custom iem.
The 2MAX only needs 2-BAs. The 3MAX adds another armature to give a little more warmth and bass presence, which I appreciate since they did it so well (and didn't over do it).
The silicone shell is fantastic. I've tried two other custom silicone tips, one terrible and one which is very good. Sensaphonics is a step above the latter. My 3MAX is just as easy to insert as an acrylic shell, but isolates far better and is very comfortable.
I'll write a more in-depth review on hf after a solid week or two of listening, but so far, I'm impressed. They hit a sweet spot and there seem to be no downsides.