I have looked for answers to this but have not found anything. People have similar problems but mostly with getting the subwoofer to work at all.
I got the subwoofer to work by editing the /etc/modprobe.d/alsa-base.conf file and adding options snd-hda-intel model=ref.
When I plug in my headphones, the main speakers turn off but the subwoofer still has sound coming through it. The output is selected automatically in sound preferences and is set to headphones when they are plugged in. I also have tried muting the main speakers, which in turn mutes the subwoofer, before plugging in the headphones as they seem to have two different volume controls, but as soon as the headphones are plugged in, the subwoofer has sound coming out of it.
I am running Ubuntu 11.10 64 bit on HP dv7- 4285dx.
I am able to just not have the subwoofer on but since I have gotten it to work I would like to keep it around and not have to change a config file every time I want to plug in my headphones.
Any ideas or suggestions would be greatly appreciated.