Boost LG G4’s Volume With This Modification

This small guide posted by XDA Member Usraek walks you through editing your mixer_paths.xml file found in /system/etc to utilize higher values, thereby giving you a fair amount of volume gain on your LG G4 with earphones. Be careful to not set them too high, lest you wish to be greeted by unbearable sound distortion!

source: xdadevelopers