Introduction: How to Connect an External Microphone to an IMac
You will not find any microphone input on new iMac. Dont panic, buy yourself a "Apple-In-Ear Headhones with Remote and Mic". Another choice is to buy a USB audio adapter like "Griffin iMic." With USB you will get STEREO input. I just used some stuff laying around. If you can handle a soldering iron, have a go!