Xbox One audio levels

I have noticed that audio for various things over Plex is quiet.

I am aware of things like dynamic range (which I hate with a passion, having to turn the volume up to hear people talk and then turn it down when the explostions start ¬_¬) but this problem does not seem to be that - yes I’m weird.

Certain things are, for some reason, just quiet. No fault of Plex, I think, and no fault of the Xbox. But a boost option would be nice.

Other things are fine. Games are loud and clear, Netflix is loud and clear blurays/dvds are loud and clear.

Also sometimes the audio seems to go really quiet for a few seconds and then go back up, as if it was being turned up.