In case someone is curious about Philips Fidelio S2 as I were, they're quite great, if splashy.
However, it turns out it's all only in frequency response - relatively easy to follow even on a limited EQ.
Fixing this issue also vastly improves soundstage, opening it up.
The fit as with all half-in ear designs is tricky... oh, and they work the best in my experience with Sony MHC1 medium soft silicone tips, probably also other Sony Hybrid tips. These tame the tubby bass and reduce the splash somewhat - probably due to narrower nozzle.
Both of included Comply kill the air and plain don't fit well at the required shallow insertion depth for me - they can rotate and then the foam obstructs the nozzle.
I found that these very much want a good amplifier, or they get splashier and less controlled. Plus the lack of efficiency requires driving portable device outputs nearly to maximum.
The in-line microphone produces very nice quality sound, it is relatively directional, but could be slightly more efficient. Cable noise is well handled.
The most interesting thing I found is that these have some kind of minijack that produces a lot less channel crosstalk than most everything I tried. Crossfeed is highly recommended.
They can easily compete with the likes of Hifiman RE-400 and RE-600, unless you're allergic to fit - and I think win even without correction. With the right tips, the originally tubby bass becomes pretty controlled and not at all warm, just the right quantity. It's a bit rounder than what orthos produce, but otherwise very high quality. Detailing is precise and on point, no smoothing over flaws.
Here's a correction chart, remarkably simple:
