4 star is for bass and a thumping quality sound kind of a woofer sound that you can only get in boat stone 190f and that the only thing which lead me to boat rather than mivi despite of mivis killer battery backup build quality and a cool designif you are a bass lover like me put a stone on your heart go for boat stone 190f yes boat has lesser battery backup and not a good looking design but trust me boat has thumping bass that the only thing mivi lack ofyes you will get decent bass r