pavolumeset pasink chan=vol-in-db chan=vol-in-db ...
For example:
pavolumeset alsa_output.usb-0d8c_USB_Sound_Device-00-Device.analog-surround-51 \
front-left=-5.5 \
front-right=-3 \
rear-left=0 \
rear-right=-0.7 \
front-center=-15 \
subwoofer=-6
Simon Schubert 2@0x2c.org