I found a manual online for it, it shows you how to hook up a console.
http://logitech-viva.navisite.net/web/ftp/pub/pdf/speakers/z680.pdf
check out page 7
Video game consoles
Digital Connection (PlayStation® 2 or Xbox™ only)
For optimal sound, use an optical cable to connect the video game console to the optical jack on the
Digital SoundTouch™ Control Center. If you are connecting the Z-680 system to an Xbox™, you will also
need to purchase an adapter (the Xbox™ Advanced AV Pack or the Xbox™ High Definition AV Pack) to
make this connection.
Analog Connection (all consoles)
The Z-680 system is compatible with all video game consoles that use red and white RCA audio cables.
If you want to connect the Z-680 system to your video game console using an analog connection, you
will need to buy an adapter that connects the red and white audio cables from your console to the
green analog input jack on the Digital SoundTouch™ Control Center. With this type of connection, the
audio signal will be directed to the front left and right speakers only.
After reading that, I think it's kind of strange how you can only get sound form the front left and right speakers. I was looking at the Z-640s manual and it looks like you can get sound out of all the speakers.
http://logitech-viva.navisite.net/web/ftp/pub/pdf/speakers/z640.pdf
If you have a video game console (PlayStation®, PlayStation®2, Xbox™, or
GameCube®):
• Connect the green and black plugs from the audio input cable to the 2 stereo
mini jacks on the included video game adapter. Connect the red and white RCA
audio cables from your video game console to the RCA audio jacks to the video
game adapter. To enable sound from the center channel speaker, depress the
Matrix button on the center speaker.
Thanks for bringing this up. I was thinking of how to get sound out of my dreamcast vga box to some speakers. I recently pulled my Dreamcast out and set it up in front of a VGA monitor, but didn't have any speakers to use. Forgot I had these speakers laying around.