Alright, so I have two TVs that have this problem; their speakers seem to transmit voices awkwardly and they can only get so loud until the speakers play the voices in an almost lower quality. I actually play my games with one speaker on one of my TVs because this gets outright irritating. However, I don't know how to put such a thing into words.
If REALLY needed, I can try recording the game playing with the bad speakers.

So it basically sounds like the speakers are damaged or their input is loose and they're not fully plugged in. If that's the case, you need to make sure they're properly plugged in and check that there's no significant damage to the speakers. If it suddenly just transmit the voice awkwardly with no damage or loose inputs, you may probably have to get a new pair of speakers or stick with the current ones you have.

If it's the speakers inside of the TV though, then you probably need to unscrew the back of the TV and see what's causing the problem and then contact the company in charge of the TV for direct support or you need to get a pair of speakers to be the replacement. Those are my suggestions but i'm sure there are plenty of better experts around this forum.

Why don't you get a recording deceive that plugs into your TV and directly get the audio from inside.