Loudspeaker cable only where? Bose only red plug?

Hello, everybody.

I have a few questions where the speaker cables go. I took a photo of several plugs. Unfortunately, only the red and black connection is there. The brown one's missing. see photos.

more photos here
http://www.qv8.de/Radio/1.JPG
http://www.qv8.de/Radio/2.JPG
http://www.qv8.de/Radio/3.JPG
http://www.qv8.de/Radio/4.JPG
http://www.qv8.de/Radio/5.JPG
http://www.qv8.de/Radio/6.JPG

you can only hear the sound very quietly over the red plug.
I know it so that there is still a brown one?

Does the Bose sound system even have the Brown port? Or is there only the red and black ?

Adapter? Is that possible?
http://www.ebay.de/itm/Mini-ISO jack-pre-reinforced adapter-Cinch-Bose-Audi/350373922699?pt=LH_DefaultDomain_77&hash=item5193e9c78b