Topic on User talk:Vlad 54rus
Investigated further - this doesn't have anything to do with 3D audio capability, but with system timer resolution, which IndirectSound raises to 1 ms (the default is 15.625 ms) within the game' process. The game applies some additional logic when enabling Vsync (like calling a Sleep() or some other function which delays code execution). Using Special K and ticking Sleepless Render Thread option removes all such delays.