Loudspeaker tip

[pseudonym]

For a bit of increased speaker volume on the Xperia X Compact, do the following: Settings app/Sound/Audio settings/Sound effects (certain other options might have to be disabled in order to access Sound effects)/Equalizer/.
Set all 5 equalizer band controls to maximum. Back out of Settings app. This setting provides a small but noticeable increase in overall sound volume.

[pseudonym]

Other options for louder volume with certain types of media: A number of apps have a built-in pre-gain control, such as Music Folder Player and Podcast Addict. These provide a significant volume boost without a high risk of damaging speakers (as long as you're careful).