I have read that there's a problem to get the subwoofer working in these laptops. I tried this solution No sound from external subwoofer but I don't how to prove that the subwoofer is properly functioning. I use Pulseaudio equalizer and the bass sound seems to work fine, but when I go to the Sound Settings, I can't move the bar where it says 'Subwoofer' in my sound card option, so I don't know if everything is alright. If someone has a solution I would like to know, because there isn't much information regarding this. By the way, I'm using Ubuntu 12.04 64 bits.

Thanks beforehand, Dave

EDIT ----------- Possible Solution

Well, I will post a solution that worked for me and I think it will help a lot of users. I finally got the subwoofer working. Besides adding in /etc/modprobe.d/alsa-base.conf the line

options snd-hda-intel model=asus-mode4

I deleted the lines with load-module module-combine and module-combine-sink in /etc/pulse/default.pa (in the home folder there's also a ~/.pulse/default.pa file, I don't know if it has the lines too)

To assure all the channels are working, I think this command tells me that

speaker-test -c6 -l1 -twav

I use pulseaudio-equalizer and the bass sounds very well when properly adjusted. Also, all the channels seems to work fine and the sound is even better than in Windows (where I don't have an equalizer).

I pointed out before a module-combine and module-combine-sink problem, because one day I turned on my laptop and pulseaudio didn't work. So I deleted the lines with that names (don't know if they came by default, maybe I added them sometime when I was trying to fix my speakers).

After all this, I can now move the Subwoofer bar in the Sound configuration. Anyways, the Equalizer does a great job and it improves the sound a lot.