I have to defend
@B9Scrambler, he is very thorough in his reviews and appears to give each earphone plenty of playtime - and that over and over again. If 20 hours are not enough to characterize an earphone, then it is the earphone's fault. If the planar drivers really need 50 hours to be loosened up [says who?], they should be factory broken in (note: there is not such a thing as a "burn-in"). Did you document changes in frequency response through measurements or is your claim from memory - the second would be extremely unreliable.
Sennheiser explicitly claim that their stuff sounds great ootb. Mr. Grado thinks all mechanical items (membranes) may benefit from some break-in (3 min?), and innerfidelity measured break-in: no difference found.
I have "broken in" my
AKG-K550 in for 350 hours as demanded by a reviewer. Also no difference found. None! Zip! Zero!
As to break-in: how do the "changing" drivers know what the human ear likes? If break-in really has an audible effect, it should be perceived as negative in as many cases as it is perceived positive. Loosened-up drivers? I hope the bass doesn't
become boomy .
In my books "burn-in" is a faith-based procedure to eliminate disappointment on a first listening and to create an expectation
bias for the "optimistic" listener.
In summary, while there is empirical evidence of B9's quality of reviewing, there is also empirical evidence that "burn-in" is just a lame excuse.