Whenever I hear mono in headphones it sounds dreadful compared to stereo, even on a well recorded dedicated mono track. I use $200 in-ear headphones (Audiofly AF78) listening through an iPad and anything that's stereo sounds incredible. I don't know anything about audio or music, all I know is mono sounds bad to me, unless out of speakers in which case it sounds as great as stereo. I've also tried mono on other open cup headphones, although they're much cheaper and it sounds bad as well. Just for reference, I'm comparing Sgt. Pepper's 2009 stereo to 2009 mono and The Doors debut 50th remaster stereo and mono. Sgt Pepper's mono is FLAC whereas everything else is whatever Apple Music offers. I haven't found anyone who thinks the same to me where it's more of a sound quality thing instead of a subjective 'I prefer the more open space with stereo' thing or something like that. To the point, is it just me or does mono sound in the actual quality of the music worse than stereo or does it need better equipment to sound better or what?