After 3 days of using my JH16, I think I am experiencing the same dilemma as other CIEM users. I went back to my goto UIEM the H-200 and it now sounded very tinny. The bass really is night and day in contrast.
The bass truly, powerful and is emphasized when it's really supposed to be there. It does seem to overpower the mids and high a bit but doesn't really mask them.
Mids and highs are as clear as crystal with lots of detail. It's just the bass is the emphasis on tunes with lots of bass. But it does not get in the way of tunes which it is not the focus like soft melodies. Overall, for me it's pretty much a detailed and fun headphone.
I'm glad I chose this over JH13, which by the way is not an easy choice. I spent late nights doing research, reading reviews, forums, impressions after another.