I know this isn’t a great solution, but I find that if 1) I set the speaker setup to 5.1 in realtek, 2) then start the engine/game, 3) then alt tab out (with the engine still running), 4) then unticking the center speaker in realtek, 5) then alt tab back into the engine has the effect of quadraphonic.You have to do this every time you want to start the game though.
