ATH M50 and Burn in

Sup guys. Just got ATH-M50's, Fiio L9, Fiio E11 from my GF as a present. I listened to them for about 2-3 weeks and they were brilliant. The last couple times I listened though they were too trebly and I felt that their bass response had become way weaker than when i started. I got the white box edition, and I dont know if there is any truth to the neutrality rumors of the white box version but I never once found the bass to be overpowering. there was maybe a couple of times when I was listening for it and almost heard it over power but then they didnt quite get that loud in the bass.

Anyways, i finally got around to properly burning them in using pink noise at slightly louder than normal listening levels out of my AMB Gamma 2 F++. Yesterday I could hear a few high treble tones leaking out. I'm nearing 24 hours and now there is no treble to speak of.

I'll keep updating with the progress. I plan to burn in till monday or tuesday.

I listened on/off for a couple weeks. I put maybe 1-2 hours a day. The out of box sound was very lacking in bass initially. I tried listening to a couple bassy albums and the bass picked right up. The last 2 times I listened to them, though (in the car as usual) I felt like I needed to "pop" my ears. It felt like the bass was there if I listened but it was very odd sounding. Furthermore, when i was listening to my audiobook, the narrator's voice was very "strained". every time he pronounced a "p" it would sound odd, and every time he pronounced his "s" it would be VERY loud. I felt the treble was overpowring things, if anything. At first I chalked it up to just the audiobook's crappy format, but then upon linstening to music I realized that all sounded too.

I took a pink noise wav and played it on repeat through Foobar 2000 via AMB Gamma 2 F++. I fed it directly into the headphones, rather than through my headphone amp. I put the cups together and put the headphones in "portable mode", where they fold in. This holds the cups together so i dont have to listen to the pink noise until I fall asleep.

At first there was a very high pitched noise easily audible. After a couple hours, it slowly went up in pitch and turned to 3 different high pitched tones. Eventually that turned into a single tone which was a higher frequency than the original. Now, after 24 hours+, there is no high pitched noise.

I will test them out tomorrow morning and see how they sound. I'll be listening to them all day, then burn them in all night again, probably. I'll be doing this till wednesday or so.