Why can I not hear the sound from my Lg Blu ray surround sound?

I hooked up the optical cable from the blu ray to the tv which is a LG plasma. The Blu ray is also hooked up with a HDMI to the tv. My Direct Itv box which is not HD is connected with a regular coax cable to the tv. I have to go to Natural plus on the Blu ray to hear the sound come from all the speakers. If I put it on other sound effects it transfers the sound to different part of the speakers. Is this normal I thought I should hear the sound from all the speakers no matter which setting it is on.