Default (Mod) Enable Dolby Digital and other presets on external speaker.

Pretty simple xml edit for stock Music player 4.4.2

This will allow you to use custom presets/ EQ when the headphones are not connected. Works quite well.

Using a file manager of your choice (ES gave me errors)
I used rom toolbox and rb text editor.

Navigate to system/etc/com.lge.music.xml

Open com.lge.music.xml with your text editor.

Scroll down to:

<!-- Support Audio Effect through Speaker.
Default value is false-->
<eq_through_speaker data="false" />

Change to:

<!-- Support Audio Effect through Speaker.
Default value is true-->
<eq_through_speaker data="true" />

Save the file and reboot.

On a side note, in the same xml file. You can also enable playback and pitch control from within the eq settings. I tried and it added the correct tab to the eq. However, when changing the settings, playback became very choppy.