I've seen it in the decoder sections of some receivers, if the source was recorded in DTS, Dolby Prologic etc, sometimes the receiver will have a hard time deciphering the difference. Make sure your speaker selection is set up right, Left and Right channels, Center channel if your using one, and the left and right rear channels. Some receivers you can set the distance between the front and rear speakers and control the volume levels between each of the speakers to your listening position.