I do have a speaker system but I can barely hear movie dialogue even after increasing the volume. Interestingly action scenes are really very loud. But I don't face this problem while watching cable TV. Is there any solution? Is there any app or something to adjust it? Thanks.
Turn off the surround audio settings. Also, some devices have bad Movie mode setting, so I recommend to reset the setting to default or User, or you can adjust them by yourself.
It would be useful if you give more details about the sound system, if it's stereo or 5.1 and number of channels in the file you are playing.
Sounds like a connection problem , try check your connection or even just try unplug and plug back
Check out any "downmixing" options you have.