That's how it goes.
Well, not sure whether it was burn-in, brain burn-in, or tip rolling, but using the medium R1 tips with a 1.5 octave midbass cut (-4.5 dB) and a few small cuts around 5 kHz, 6.5 kHz, and 7 kHz to take the edge off the sibiliance, and the CKN70 are my favorite again over the MH1C. The sub-bass goes allllll the way down in comparable quantity to the MH1C, with much more speed and impact. I had absolutely nothing to worry about bass-wise. However, the midbass bloat and sibilance makes some music just about unlistenable on my iPod when I can't do precision EQ to fix it.
So although I do love these, I might be in the market for another pair for portable listening. Can anyone suggest an IEM that would combine the efficiency, detail, speed, precision, impact, and treble level of the CKN70 with the more even bass response (by which I mean no overwhelming midbass, but strong sub bass) and lack of sibilance of the MH1C (but without its massive hole in the treble around 10 kHz)? I'm intrigued mainly by the XB90EX, XBA-3, and XBA-30. How do those compare to the MH1C and CKN70 in treble extension/smoothness/completeness, detail/speed, and bass extension/shape? Are there any others I should be looking at?