[Cutless009]

So I recently EQ'd my MacBook Pro to get better sound out of my ATH-M50s. I've noticed that while the sound is much clearer, my ears get very sensitive after listening for a while.  Turning off the EQ makes the sound worse but lets me listen for longer. Right now I can listen for about an hour to an hour and a half before it starts getting intolerable. I used to be able to listen for 5-6 hours at a time before I had an issue.
 
To be more clear, my ears/eardrums do not hurt and I do not get a headache.  It's like the clarity of the music gets to be signal overload for my ears and they get very sensitive to the sound and they start having a fingers-on-chalkboard response to the stimulus from the headphones and I have to stop listening for a while.
 
I've made sure to adjust to the extra volume due to the EQing by turning the volume down so the volume is the same DB as my previous listening. I can't really narrow it down to a band of sounds either (highs, mids, or lows). They all irritate my ears equally once it starts.  As soon as I take off the phones outside sound doesn't bother them, but it's a little while (15-30 mins) before I can listen comfortably again.
 
Are my ears just trying to adjust to the clarity or what? The sound is amazing but I'd really like to be able to listen for longer periods of time.
 
 
For those wondering, my EQ looks like this (pretty typical headphone EQ):

 
 
Thanks in advance to anyone who can help me figure this one out.

 

[Bugler]

I'm kind of new to using headphones much, and my listening is almost always analog based, but either way I would suspect that's a lot more treble boost than I could tolerate.  My experience with digital sources is a bit of harshness in the treble to start with and this would just exaggerate it.  Just my opinion of course.  

 

[Billheiser]

The equalizer is another link in the chain that can add its own distortions. Keeping the signal path as direct and pure as possible is an ideal. Despite what equalizers can do, they have their downsides, and introducing time-domain distortion and other problems to the signal path are why they are not used as much anymore. Listening fatigue is a symptom (I think) of subtle problems and distortions in a system. Remove the equalizer entirely and see if things get better.

 

[Mad Max]

The issue here is the treble boost.  Couple that with M50's big 10kHz peak, et voila: P A I N. 

 

[DJScope]

If you look at the M50 frequency response, what you want to do is equalize it by countering the graph to try to make it into a straight line through all the frequencies. This will give it a true flat sound. Once you've done this, you can go ahead and tweak it to your preference.
 

 
Or simply reduce the treble at 10k. I personally wouldn't raise the low end since the M50 already has some pretty bloated bass.