I'm using a Dell Vostro with integrated 7.1 audio. Speaker setup is Klipsch 4.1 system. Green from the klipsch is plugged into the green on computer. Purple from klipsch is plugged into the black (rear) on the computer. When doing the audio test tones, sound will come out of each speaker. However, when playing anything on the computer, I get no audio from the rear speakers. Netflix, Spotify, mp3's, or anything else, I get no audio from the rear speakers. What am I missing?