Increased the external and internal volumes of the Sony Xperia Z, would be a possible remedy for those who may have had issues with its sound capabilities. Well, despite having a largely improved external speaker on the phone’s successor, the Xperia Z1, users longing for that extra ‘umph’ may be interested in a mod by XDA Senior Member auras76.
Auras76 created a similar mod to that previously covered called Volume Boost XZ1, which increases various volumes on the device. Provided in a single and simple flashable zip, the mod increases the volume of the: external speaker, headphone volume and calls.
As always, it is recommended to create a Nandroid backup before you proceed with the installation to guard against any software or hardware incompatibility issues.
However, one should also keep in mind that listening at high volumes for long periods of time is, in most cases, unhealthy both for yourself and possibly for the external speakers. Nevertheless, if you would still like to check out this mod, make your way over to the forum thread for more information and download.