I use have the Logitech Z-5500 5.1 speakers and an X-Fi Extreme Music sound card. I use Zoomplayer to play all my media and the latest Nvidia Purevideo software for video decoding and deinterlacing. By default Purevideo audio settings are in stereo mode. If I go to speaker calibration and enable center, rear or sub speakers the voice audio becomes almost inaudiable. I tried turning up the volume on the center channel but that only help slightly and doesent sound normal. How can I fix this?