Attaching external speakers-very basic question

[JDL51]

I have a set of Logitech speakers & sub-woof. They attached into my old Dell through 3 separate plugs (right, left & center). My iMac doesn't have the same configuration and I'm wondering if I need to purchase an external sound card so I can plug in the speakers. I know this is a very rudimentary question, but I'm pretty green to all of this. Thanks for your help and patience.

 

[MTI]

The iMac has, like most personal computers and laptops, a single 3.5mm mini-stereo jack that serves as headphone/audio out. On the later iMacs, the same jack also provides a digital (toslink) audio signal, which is compatible with home theater amps and other devices.

If your speaker connection is separate L, R and C (combination L&R or is it a discrete "center channel" for 3.1 audio?) . . . then you'll need to adapt your speakers' wiring via plug adapters.