What is the black box with the silver knob on the left side in front of the monitor?
That’s a Mackie Big Knob Studio, a monitor controller that listens to my “slantRant” mix and my main mix from my big mixer, then routes one or both (plus the sound of my Mac) to either or both of my two speakers and two sets of headphones. Very handy box, pretty good quality, and quite affordable. I wish I could afford a Drawmer or something classier, but this one does the job just fine.