Ubuntu – System-wide equalizer for Ubuntu 13.10

Rhythmbox is not a canonical product so I don't think canonical can do anything about it. If you need a feature may be you can request feature to rhythmbox developers. If you are talking about third party plugin called 10 Band Equalizer.

What you can do is create a folder called plugins in $HOME/.local/share/rhythmbox and download the plugin and extract the equalizer folder in the plugins folder you created.

OR

If you know how to use git and have git installed. Just goto $HOME/.local/share/rhythmbox and do:

git clone https://github.com/luqmana/rhythmbox-plugins.git plugins

and then you can update your plugin with git pull command from plugins directory

Then enable the plugin from rhythmbox.

It can also be installed via a PPA as described in the linked question.

Linked Question: - How do I install third-party rhythmbox plugins?

I also have an N56DP, the solution is actually simple (It works for me on Ubuntu 14.04, i don't know about other versions.) First undo all the other junk you did, No need of messing with any conf files. Download alsa-tools-gui, open hdajackretask, switch to the realtek card and select show unconnected pins. Override the following:- 14- line out center 15- line out center 16- internal speaker lfe 17- internal speaker lfe 18- line out center 1a- line out front 1b- line out back 1e- spdif out

Note this config enables subwoofer to play the low frequency from the right speaker (this is the standard in windows) By messing around you can try other configurations (I have not tried them all) One configuration i particularly liked turned my mic input into a second headphone jack.