I did some testing ala your instructions.
I have to say I disagree. Strongly.
I was using my iPod, with my GR04 Flagships (about halfway between the GR06 and GR07 by all accounts), and also experimenting with my output transformer rig, which basically drops voltage but boosts current, anyway it does not work with the MH1C, because of the TRRS plug.
So, using my iPod headphone out, ball park volume matched, the MH1C is incredibly warm, with massive mid-bass emphasis. The GR04 may actually have more subbass, but no wehre near the mid-bass of the MH1. Regardless of position, the MH1 sounds incredibly warm. Admittedly, the warmth of the MH1 makes the mids quite enjoyable, but there is a considerable roll off at the top. When inserted deeply, the pressure is such that they clearly are not performing properly, and just sound plain bad.
I have a hunch about what is going on here. On my phone (which has a terrible headphone out), the MH1 sounds okay. The MH1 has a low impedance, something like 20z. What is your source? I have a hunch that it sounds good with my phone because the phone has a high output impedance, yielding a substantial bass roll off, if your device has high output impedance, you may get a similar result.