There is a way to normalise volume with several audio and video players; i.e. whatever is playing will have the same volume level and will not distort. I have used the feature in
vlc before, although I usually use
smplayer these days.
vlc screenshot where you can set the normalisation level in the effects tab to whatever is appropriate and then that will apply to everything played.
I have also used the option before in
smplayer (see screenshot 2) and found that it works well, although it will give you an overall higher fixed sound level, but one that will NOT distort and present unwanted frequencies for your speakers. It is particularly useful for DVDs which tend to have a lower volume level when you are not passing them through a preamp and large speakers.
There are other sound settings in
smplayer that you might be able to use to tweak the sound if this setting is not to your taste. You can also alter the overall volume, tweak the levels and perform quite a lot of useful fine tuning.