I'm using Moto G3 unrooted nd using Sony earphones of MDR series. Suddenly the left side of my earphone started producing lesser sound than the right one.How to balance them???
Android itself has a.f.a.i.k. no balance setting (which is a shame!).
But you can try in Googles Appstore "Bass Booster and Equalizer" - which installs itself as MusicPlayer and allows - amongst many other audio settings - to adjust the balance.
The only disadvantage is that the settings are limited to the application itself (the music player), and not system-wide effective.