sound delay when playing a video

[goodwill67]

I find that when I play a video on my Mac Mini such as Youtube video that the video plays but the sound is delayed for as long as 15 or more seconds. I did recently purchase new external speakers that connect to the Mac mini itself by way of a 3 mm connector. I also upgraded to Catalina at around the same time. Not sure if that has anything to do with the problem. I was advised to go into the sound preferences and select "external speakers" as the output source but the only thing there to select is "headphones" and nothing else. Still, the videos do play. Its just that there is the annoying delay. Would a USB speaker connection instead of the 3 mm possibly solve the problem? If anyone has any suggestions I would be most appreciative. THANK YOU