Headphone jack splitter

Hello! I have an iMac (Retina 5K, 27-inch, 2017) with a single headphone jack. I would like to add a splitter to plug in a set of headphones as well as a set of speakers. Would it be possible to leave them both plugged in and somehow switch between the two on my iMac? I know you can change the output from under the Sound preference, but I'm not sure how this works with the splitter. Just don't want to spend the money on the speakers and splitter to find out it doesn't work like I'd like. Thanks!