I'm sure there's an easy fix, but it's escaping me right now.
Is your computer connected to the internet when you game? Perhaps something is connecting in the background and causing hassles.
I don't think changing the speakers would do anything like that, although you could switch it back just to be doubly sure.
When was the last time you performed some maintenance on your computer? Windows Updates applied? Cleanout temporary files and defragment your hard drive? Applied patches and updates for each of your games?
Have you tried uninstalling and reinstalling the games?
There's a whole bunch of thoughts for you.
Let me know what you try, and how it's going.