All we (and FMOD) do is build a sound based on the virtual location then hand it to Windows so Windows can figure out how to play it. We have no physical control over which speaker the audio is actually coming from.
Which speaker the sound is coming from is up to Windows.
If you do any kind of post processing of the audio, there is a good chance it will mess things up. If you do not set the Windows speaker configuration correctly, it will mess things up.