I’ve been having this exact same problem. I used to have an xbox one s that was connected to a monitor and speakers as well. They were connected to the monitor via a headphone jack and my xbox via usb; sounded great. Now I have a series s and a new monitor that I’ve been trying to buy speakers for but they only go into the jack and dont have another cable for usb, which makes the sound just fuzzy and distorted. I tried buying a headphone to usb adaptor and plugging that into my xbox which produced no sound at all. Could just be a cheap adaptor, but I believe that you need speakers that have something plugged into both the xbox and the monitor for the most clear sound, but as I have not tested this yet with my series s I can not 100% confirm.