Here are the frequency response of the M50 pitched against my standard of neutrality, the hd600. As you can tell from this the starting around 1.5K - 5k are quiet recessed, this is what you are hearing. My recommendation is to buy a new headphone, I don't like EQ'ing parts of a headphone up, however you can try it, you'll probably want to push those frequencies about 5-7 dB's.
I noticed the same thing when I had the m50's. Also..
Why does this come up whenever someone says something bad about a headphone you own?
He's hearing what I heard, I didn't like my m50 with vocals either, and sold them shortly after buying them (bought them used so don't tell me about supposed burn in).
Edit: Also this quote from another thread is quiet applicable and well said:
In recording school they taught us that EQ, while integral and important, should always be the last resort. You should strive to get your audio sounding as perfect as it can without EQ, and then EQ the bare minimum amount and not any more in order to sculpt the sound the way you see fit.
I see a lot of judicial EQing going on, which may be fine if you are stuck with one particular setup, but it would seem to me from a purity standpoint you would want to change something in your signal chain before resorting to EQ to fix it. For instance if your signal is too bright, switching to a darker pair of headphones or a darker amp would yield richer results as opposed to EQing the crap out of it.
In photography (which is my profession now) its the same way. When you take a photo you want it to be as perfect as possible right out of the camera. Any post Photoshop work should be subtle and minimal. Photographers who go overboard with Photoshop editing are trying to cover up a bad photo. It's the same with audio.
Edited by TakashiMiike - 7/5/11 at 1:10pm