No sound from external subwoofer "Sonic Master" on an Asus N76VM

to get the subwoofer I added on the file /etc/modprobe.d/alsa-base.conf this line:

options snd-hda-intel model=asus-mode4

then rebooted and selected 2.1 output in audio pref. It should work right away :) got this information from Keyboard backlight not working on an Asus N56V

hope it helped!

Which sound card are you using?

$ lspci | grep Audio
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05)

If so, I think you have a common problem with many new laptops: you are lacking the 2.1 surround mode enabled in your audio driver. Here a solution that worked for me: intel audio fix

Here are three things to do:

1. echo 'options snd-hda-intel model=asus-mode4' | sudo tee -a /etc/modprobe.d/alsa-base.conf

2. sudo -H gedit /usr/share/pulseaudio/alsa-mixer/profile-sets/extra-hdmi.conf

   [Mapping analog-surround-21]
   device-strings = surround40:%f 
   channel-map = front-left,front-right,lfe,lfe 
   paths-output = analog-output analog-output-speaker
   priority = 7
   direction = out
   

   Note: On Asus N76VB running on the newer kernel 3.8.0-30, change the last line to be this instead:

   direction = output
   

3. sudo -H gedit /etc/pulse/daemon.conf

   enable-lfe-remixing = yes
   

4. Reboot.

You should now be able to see your "analog surround 2.1" among your possible Hardware settings in the sound menu.

"Analog Surround 4.0" is also working but changes the loudness from Front to Rear.

Additionally you can install the GNOME alsa mixer to boot your basses.