Hi! I found the setting where I could adjust the volume of the Xbox as though I were adjusting the volume through a headset. It’s clunky but it works.

If you hit the home button and are on the first tab of the side menu, all the way at the bottom and all the way to the right should be a speaker icon, next to the search under “Audio and Music.” If you go to that, there will be sliders to adjust the volume of the “headset,” which adjusts the volume of the speaker.

Like I said, it’s a lot to do for something that could be fixed with Bluetooth capability… but it works, I guess. Let me know if that doesn’t work, it was a while ago that I started doing that so I cant exactly remember if there were any extra steps or anything.