Missing center audio channel on stereo speakers [SOLVED]

[Sauon]

I am playing on stereo speakers (off the onboard sound card) since my headset is broken.
However I am missing a lot of sounds, most importantly the "Commander under attack"-Announcement.
All my sound effect are turned up to 100 (except for music).

It appears that all Audio that would be on the center channel in 5.1-mode are missing.
Is there a way to force FA into Stereo mode (either in soundcard or some FA setting)? (Or any other way to solve that )

[E8400-CV]

Did you set it to stereo in your windows sound settings?

[Sauon]

I managed to fix it by clicking the "configure speaker" option in windows sound settings
what did the trick is to uncheck the option "Front Left and Front Right"
Doesnt make any difference in the actual sound you can hear but now FA gives me all sounds again