Getting my speakers to work?

Hello,

I have a Logitech 5.1 surround sound system. Works great with a PC but not so with my iMac.

To connect it to my Mac I have 3 little jacks, all look like headphone jacks.

I have a black one, a green one and a pink one. If I put the green jack into the headphone slot then one speaker works. I see no where else to plug the other cables.

How do I get more than one speaker running? (Would be happy with 2 atm)

Is there any adapter that I need to purchase to properly hook up my surround sound to my Mac?

Thanks

My logitech came with a wire adapter that reduced all 3 connectors down into one single 1/8" plug. Check around online to see if the system you have should include this or not.

Thanks, I will look into that. Is there anyway to change the default mac sound setting from headphone to stereo?