Check alsamixer (
alsamixer in terminal), to see that the subwoofer is not muted which sometimes may be happen.
/etc/modprobe.d/alsa-base.conf usually works
In terminal run
gksu gedit /etc/modprobe.d/alsa-base.conf
Add the following at the end then save:
options snd-hda-intel model=auto
options snd-hda-intel model=ref
Check alsamixer and sound settings again after each attempt.
/usr/share/doc/alsa-base/driver/HD-Audio-Models.txt.gz has a list of models to put instead of
auto/ref, I don't see your model in there, but maybe one of the others using the same codec will work.
cat /proc/asound/card0/codec* | grep Codec to discover your codec (mine is
92hd91), so not supported there either, but sometimes one of the others does the job.