This is what I mean.
FOR XBOX 360
IDEAL SETUPS: The following examples divert the audio output separately, not through the HDTV.
HDMI CABLE + AUDIO ADAPTER TO EXTERNAL AUDIO
An HDMI OUT connector alongside an AV cable. The AV cable carries audio to the sound system, while the HDMI OUT connector carries video directly to the HDTV.
It’s important to avoid running the audio signal through the HDTV.
NOTE: This configuration may require an adjustment to your Xbox 360
COMPOMENT CABLE TO EXTERNAL AUDIO
This configuration uses a component AV cable only.
The audio part of the component AV cable is routed directly to the audio receiver, and does NOT go through the HDTV.
WARNING: Using the optical audio output method can add audio latency, and is not recommend.
COMPOMENT CABLE + HEADPHONES
This configuration uses a component AV cable with headphones, connected using a Y-cable adapter.
The audio portion of the component AV cable is routed directly to the headphones, and does NOT go through the HDTV.
NOTE: Outputting the system’s audio through standard headphones will likely require an audio adapter (sold separately).