Connect second computer with 1/4" cables and route sound out to speakers? With outputs 5 and 6


I have an old iMac I’m using to watch tutorial videos while I do the tutorial work on my macbook. I’m wondering if I can get the iMac’s sound to route through my Steinberg UR44 and out to my speakers.

My Steinberg UR44 is connected via USB to my MacBook Pro and 1/4" cables are connecting the main outputs to my speakers, a stereo setup.

I have a cable which at one end is 1 1/8" jack and at the other 2 1/4" jacks. Before I had my interface, I connected my devices directly to my speakers and that worked fine. With this cable, I’m wondering if I can plug the 1/8" jack into my iMac and plug the 2 1/4" jacks into inputs 5 and 6 on my Steinberg UR44. And then have the iMac’s sound come out of my speakers.

System Preferences on the iMac shows the output option of Headphone port and it’s selected (it’s the only option, to mention).

Honestly, and really unfortunately, I don’t understand what the operation manual is telling me about outputs 5 and 6. Looks like the may be particular though.

Looking forward to any feedback. Thanks!