@David_Flores and @Sjoerd_Klarenbeek:
Interestingly, until now you are the firs and only people, how complaining about a too loud voice, as most people complain about too quite volume (for the normal FP2-speaker).
You don't have additionally a volume slider at the headset itself?
You could use "GravityBox" to "allow more volume levels", I guess also some more levels in the lower range are added.
@Friek: You really can't use it?? And with the maximum volume your can use your earphones as loudspeaker?
Your provided link have some help for the FP1 (mediatek chipset), here the FP2 is meant, right?