gaspower

Hello, I have a question about setting up my Klipsch surround system with Comcast. I just purchased a Klipsch system with a KSW-10 sub, but I notice that the green light on it is not always on when it should be. If I am informed correctly, the green light means that the sub is getting signal that the system is showing at least some sort of surround sound, but I notice when I view a DVD the light is green and it seems to be working, but when I view a HBO show in dolby 5.1 through the Comcast DVR box the light is red. I am using a Pioneer Elite VSX-54TX receiver. Can someone tell me where to diagnose the problem. Thanks JR