Instructions
Turn on your Xbox 360 and wait for the dashboard to load up.
Press the Xbox button on the center of your Xbox 360 controller. This will give you access to the "Xbox Guide."
Press right twice on your controller to go to the "Settings" tab
Select "Preferences" from the menu. Choose "Voice" from the second menu.
Select the "Play Through Speakers" option found underneath the "Voice Output" heading. Press the "B" button on your controller to save the settings.