I've been religiously buying a new set of SoundMAGIC E-10s every 8 -9 months for the past 5 or so years, and so when my latest set gave up, I decided to try something different.
Reading the rave reviews online, I bought a set of RockJAW Alfa Genus V2s. While they are definitely great sounding in the low and mid range, the trebles are absolutely atrocious. Cymbals and 's' sounds are piercing to the point of painfulness unless I listen to them very quietly.
Should I return them while I still can or will this disappear as they get burned in?
You could try leaving the headphones playing something on a loop at reasonably high volume for 24 hours; if they still sound fizzy after that, return them.