Did a bit more work on my previous mod (
link for details). I finally used some rubber cement to hold the felt behind the driver in place, as I was pretty satisfied with how it sounded. Previously it was held in place due with the cup stuffing. I also took the time to redo the cotton stuffing in the cups. I wanted to try something slightly different, so what I did was complete tease apart 5 regular sized cotton balls (per cup), place half of that in each of the cups, and then I took a bit of fiberloft (compressed to the size of a cotton ball per cup, though not as dense or thick) and put a layer of that on top of the cotton in each cup. I then took the remaining cotton and placed that over the fiberloft. So, 5 teased, regular sized cotton balls per cup with a thin layer of fiberloft in the middle of the cotton stuffing.
I'm not sure if it helped or hindered the sound. I couldn't really tell a difference! I did notice that I had more stuffing in the cups than before, so I must have taken quite a bit out over time while experimenting with varying amounts of cotton. I noticed that I now felt comfortable leaving the bottom vent completely open. I previously had been closing the vent about 50%.
Next, I tried using a layer of Dynamat on the ear-side baffle with a layer of Silverstone acoustic foam on top of that. I did notice a change in sound after that, but I can't describe how it was different. At first I thought maybe it sounded worse, but after I gave it a second, I really had no idea whether it was better or worse. I found that after applying Dynamat, I preferred closing up that bottom vent by about 50% again rather than leaving it open. I'm not sure if it brought out the bass more, sucked out some of the mids/treble, or what. No idea. I really wish I was able to measure them so I had some hard data to compare various mods.
Can't really say for sure whether or not I'd recommend Dynamat on the front side of the baffle. It's definitely a viable option that you can work with. I'm thinking some of the change in sound has to do with the earpads being raised slightly more than before (acoustic foam vs acoustic foam and Dynamat on baffle).
Either way, I'm still very satisfied with how these sound. Nice and detailed without being harsh. They pretty easily extend to down 40Hz, and while you can hear frequencies below that point down to around 30Hz, there is a pretty sharp roll off. Sounds like a pretty smooth, natural sound overall to my ears. I opened up SineGen and did some sweeps. I didn't notice much in the way of dips and peaks between 40Hz and 10KHz except for the peak around 10KHz (seems to be pretty standard with the T50RP).
I'd still like to be able to take some measurements on these, though. Anyone have any advice? Feel free to PM me if you want.