So I have had my M50s for about 3 weeks now. I spent a week and a half or so playing them on and off during the day and overnight whenever my computer was sitting still. While I have read that some argue against burn in and consider more of a psychological trick than actual fact, I would have to place myself in the opposite camp. There is a noticeable difference in the phones. The instruments are more crisp and seem to have better separation. The bass has also really opened up. After reading that they were a "bassy" set when compared to others that are considered natural or flat overall, I was a bit worried at first. Over time, the bass has definitely come forward some and is much more crisp and pronounced with the EQ set flat. Playing through Audirvana or Decibel also makes a very noticeable difference over iTunes. Next will be a DAC.
And after that....maybe another set of cans? I only wanted one set of good phones to roll with, but dear Lord help me, the bug has bitten. I gotta get off this forum.
if you are looking for another headphone set i think you should buy a HD598 headphones :D I have the M50 and HD598 and i think they are very compatible, because they are different sounding headphones and very good in many generes. For acoustic, vocal, jazz... i use HD598 and for electronic... the M50. I-m very happy with both :D