Uhm... you replaced ribbon tweeters. This is a discussion about earbuds. Ribbon tweeters are their own exotic weirdness. Home-rolled ribbon tweeters are another thing altogether. To use an analogy, the discussion at hand is Briggs & Stratton flathead lawnmower engines ... ...and you're talking about your experiences with pneumatic valves in Formula 1. MP3s do not lose "detail." If you check 'em on a 'scope they got plenty of high frequency info. What they lose is accuracy. Articulation ain't never going to put that back, it's just going to more faithfully reflect the error.
With crappy MP3 files, the loss of detail resulting from compression is not noticeable under normal circumstances, but when accurate reproduction is possible the difference in quality may astound.