Xbox One sound issue

Hi all, apologies if this has already been answered but I’ve looked around and can’t see it anywhere. I’m new to Plex, think it’s amazing so bought a pass, installed it on my windows laptop and my Xbox One. The video playback is great, and the sound is good, but when watching a film, music is much louder than speech, which can be an issue. I contacted Plex via Twitter and they said I might be “getting 5.1 sound when downmix to 2.0 is needed. Recommend checking device and app settings”

I’ve gone through the settings on the laptop and the Xbox One app and can’t find that option anywhere, can someone please help?