I'm curious about any and all differences between early and recent production runs of the M4U 2s. Here's why:
I bought a pair of M4U2s that had three specific issues: first, the headband developed the tiny cracks on both the left and right sides. Second, the headband creaked terribly. Third, when I would use them in active mode near my Apple router or my cordless phone base station, I would get feedback/interference/buzzing in the left ear.
I was sent a brand new replacement set from the retailer and the pair I received, while I was able to get rid of the creaking and feedback/interference was greatly reduced (but still present), it was from an even EARLIER production run than the first pair.
Leary of the early production units (having had one that cracked) I requested a second replacement from a recent batch. The one I received is definitely newer, it doesn't creak, and - I THINK - there may be a tiny bit more bass or sub-bass (but perhaps at the expense of the original balance or clarity of the original/early production units). HOWEVER, the feedback/interference/buzzing issue is worse than the first replacement set and about on par with my original pair.
I read here that one person who received a replacement set from a recent production run definitely noticed a bump in bass or sub-bass. Has anyone else noticed this or are my ears playing tricks on me? Has anyone noticed any OTHER changes in balance, soundstage, etc., between early production units and recent ones? If so, what is the consensus? Is one preferred over the other? I'm stuck between picking the early unit that might have a touch less sub-bass and which pre-dates the QC fixes that addressed the cracking headbands, but which has less feedback/interference vs. the newer unit, which may have slightly more sub-bass, and may have an improved headband, but which has much more prominent feedback/interference issues. I was leaning towards the newer unit until I remembered to check the feedback issue. Now, I'm completely confused.
At this point, I've gone back and forth between the two so much that I can't even hear myself think anymore. Therefore, I could use some advice.
Many thanks.