At my desk I have my iMac (with a second monitor), a laptop, and sometimes more computers–and these are my day-to-day computers. And I’ve had this issue hooking the computers to my speakers because they both have media on them I want to hear with via my good speakers and I finally found a solution: I bought a $2.97 Y-adapter for headphones. I have configured it as per the picture below: (Just know that my speakers’ plug is a male connector.)
My cheap configuration for multiple computers to single speakers