I finally sold them a couple of days ago (at a loss but it is what it is). After trying to make them work for me and my music, I couldn't. I like how well built they are, and they are beautiful. I like many things about their sound (clear, resolution, speed, microdynamics, neutrality of the frequency range), but three things are wrong (again, for my music). And one is a killer.
1. Soundstage is narrow, side to side, bad for classical. And it depends on sound level/loudness/pressure, not only frequency. I will explain it below. Front to back is another problem I will try to explain.
2. In your face presentation, no lay back. Bad for classical. They are shouty and loud. But you can tame it with sound pressure/loudness level. But then you have the third problem.
3. Third one, and this one was the killer for me: not layering, no distance, not music/dynamic range, not macrodynamics or similar. Impossible for classical.
I can work around the first two but not the third.
Yes, there are many things that are wonderful, many. But let me explain how they react to sound pressure/loudness/musical softness. Imagine a triangle in front of you. One vortex in your face, the base of the triangle a bit far away in the distance, and it is not a fat base triangle but narrow-ish.. The sounds come from two layers/two distances only: the vortex (in your face) or along the base of the triangle, afar. Sounds in the distance, softer, quieter, has room left to right (not very wide but enough). But at a fixed distance from you and in the same level of softness, the same, fixed again. Sounds from the vortex are in your face, shouty, very loud, with no room for any soundstage at all.
This is more or less my experience. It was before from the beginning but I was trying and trying. And then I brought the Beyer to my office and tried the new recording (FLAC, 16/44.1) of the Per Nørgård 3rd Symphony (BBC Radio 3, Proms 2018, Recording available for free to download in Simon's page, 5 against 4). Yes, the lady at the end showed a lot of sibilance even in the soft 'mode' (putting down the sound level), and, yes, it was beautiful as well: the chorus, the piano, the harp, the tone, the timbre. But it wasn't as spectacular as this piece is, no space, only either shouty or afar, soft, detailed but without layers or dynamic range. And this music is very very detailed and very very soft! You need to play it loud and let the music raise and fall naturally. And the Beyer couldn't. This lack of dynamics or music range (pianissimo to fortissimo and back) surprised me, a lot, and it was the main point of disappointment for me as it was one of the main traits that a Beyer 770Pro-250 has: you can play very quiet music that suddenly raises without losing any other sound feature (long time owner here). Also there is something related to frequency: the soundstage collapse with frequency as well. This 'mental' triangle in front of you is also frequency related, not only loudness related. And it won't be that bad if the sound can travel from the front to the back smoothly, but it can't. It is only two levels or layers, two loudness settings, that's all. If you put the sound level down it collapses to the distance, if you put the level up most things -sounds- will crush you in your face.
Something of this is related to the semi-closed nature of the cups, more airy in the top and closed sounding at the bottom (frequency). But it acts as a dynamic compressor, a natural, mechanical dynamic compressor (in a weird way because it can show two layers at the same time, but only two).
I don't know how it can be useful for mastering/mixing/etc., at least with acoustic/natural timbre/instruments. Yes, a solo will work wonderfully. But against a background of players like in a concerto... And it is a pity, I really tried hard to like it. The nuances, the manipulation of the tempi from the players, emotion and drama, are all there but there are these weird qualities I can't stand.
Tested with a Linn Akurate source and a Lehmann Audio linear if you have doubts about the capacity of my playback chain.