I started over from scratch today after taking a one week vacation from modding these. I was about ready to throw them out the other day because I was so sick of modding them. Almost ZERO of the mod techniques on here worked exactly as they should for my pair. I tried nearly every one of them and took my time.
Tonight I used some of the things I've learned while modding my DJ100. I've found out tonight that for me and MY pair, both felt and Akasa foam did squat for me. It made such minor changes that I got rid of it entirely. On my DJ100 it didn't do a thing either (but that's a totally different headphone, I know).
Here are the best results I've found yet..remember I tried it all. To the point I got sick and tired of this thing...almost.
Staring with a bare headphone with the blu-tack still on the baffle:
1) Added a super thin layer of Blu-Tack to the cup (instead of the Akasa Foam, which I found worthless for me).
2) Made sure none of the blu-tack was flat and made lots of indentations in it, even in the cup.
At this point I tested the sound and it wasn't that good. So I made the next updates:
3) I opened up a car wash sponge (kind covered with fabric) and cut the internal foam pieces into long thin strips. It's the type of foam found in cheap (fake) memory foam pillows.
With this configuration:
Two on the sides, one on the middle "post" and another on the top of that. Two smaller pieces around the vent.
I tested this again and it was much improved. Mids felt neutral and fairly clear, but not good enough. So I did more updates:
4) Completely covered the vent with foam and even taped it off. Any super tiny spots that are exposed I added foam to.
The change? Everything was now super clear! How I don't understand why, but adding lots of extra foam EVERYWHERE increased the sound clarity and seemed to make the mids a bit more forward.
I have this reference song from Utada Hikaru I listen to on my DJ100 that's just goose bump inducing on that headphone. On this it's close to how it sounds on the DJ100, but the mids on this song feel about 5% less forward. I did mod my DJ100 to make the mids more forward though. On this song, my modded DJ100 sounds slightly more clear, but most instruments on the T50RP sound more life-like and accurate. I don't want to bother comparing them since they're both so different. I would like to compare female vocals on each. The mids are now similar though and perhaps my modding technique changes them to something everyone else's T50RP doesn't sound like (worse or better? Who knows. I don't!). Mine feels slightly more forward than neutral, but that's fine with me and how I like it.
One thing I should point out is that I never got any good results with the vent open. At one point I did, but it was an awkward configuration. I also was kind of surprised and confused how the more material I loaded up under the earpads, the more clear the sound was?! Right now I'm using felt AND a super thin piece of foam (from my K240).
It's so amusing how the more I load up on this magical foam, the more clear and forward the mids are! At this point I won't change them for awhile since they sound good enough for me now. I'll get some better impressions soon.