I don't know why, but to get my right loudspeaker sounding equally loud as the left one, I have to set the levels in alsamixer
like so:
http://s18.postimg.org/91nx9ojex/alsa.png
54/100 in Headphones column.
It is inconvenient for me, because when I habitually try to control overall sound level by Fn+Up/Down, it resets the left/right levels balance. So is there any way to permanently set stereo levels separately in some alsa/pulseaudio configuration files or utilities?