I've been round the block and back again. I just felt like doing a mini review and almost nostalgia session. As you can see in my Sig I have tried a decent amount of mid-fi headphones. I recently sold my k701's (my latest headphones) and did a downgrade because I was curious about the Audio Technica sound.
I actually find the m50 a more enjoyable and dare I say better headphone than the k701's. The k701's sound great with some music, but have an annoying quality where some things sound thin, tinny, almost hollow and echo. I hear the k701's touted as being neutral, however I would argue like I do so often that neutral is not natural, bass on some instruments have a certain resonance, sometimes I punch when intended, not all bass is intended to feel tight and precise, some is there to surprise you, some to calm you, some to change the mood altogether, the k701's could only portray one side of bass, I feel like so far the m50's can do so much more.
I also find the detail retrieval on the m50 to be better of that of say the hd650's or even the denons. The hd650's introduced to me to what I call texture (I don't know audiophile terms so I make up my own) with these phones I could really feel the texture of the bass instrument being played, my old k701's could not do this but the m50 has revived this part of the music for me.
I will review more as I listen more, but color me thoroughly impressed with Audio Technica, I look forward to experiencing their further down the line products (AD2000, W1000x, etc)
Hope you guys find this mini-review useful any questions and comments feel free to post.