Comment 4 for bug 1481913

The dconf key for this is "high-volume-level", it defaults to 0.75 and can be overridden in the device tarball so each OEM can adjust this value to specific devices.

Details are in the first branch attached to this bug:
https://code.launchpad.net/~unity-api-team/indicator-sound/lp-1481913-revised-ui-volume-warnings/+merge/267393#L8