Use the OnePlus One Front Earpiece for Media Playback
Opting for dual speakers positioned on the bottom of the OnePlus One, many would say that this device’s speakers look awfully similar to the ones on the Nexus 5. Despite the aesthetic similarity, the One employs two separate sound drivers, each with its own speaker grille. So although they may not be stereo, they at least produce strong sounds at top volume. However, if this doesn’t seem to just quite cut it for some One owners out there, the OnePlus One Stereo Mod may remedy this issue.
Developed by XDA Senior Member abhi08638, the stereo mod activates the One’s front earpiece as another speaker for media playback, such as playing music, videos and games. Despite its name, the mod does not actually convert the speakers from mono to stereo, but rather, provides a more ‘surround sound’ effect. In order to install the mod, your device must be rooted, and you must have mixer_path.xml backed up and replaced with the provided modified mixer_path.xml file in /system/etc. After this, all you have to do is download the provided ZIP package and flash it through a custom recovery. There are also different versions of the mod which you can install, and they have differing levels of max volume. And if you would rather set the max volume yourself, abhi08638 provides a handy tutorial teaching you how to do this.
If you would like to give this a whirl on your device, check out the OnePlus One stereo mod thread for more information.