Trying to with output channels


I have a 2017 macbook pro (High Sierra 10.13.3)with Logic 10.4.0 I use an OWC Thunderbolt 3 dock to connect the Firewire to the MR816csx
I get this odd swishy buzzing sound (in my speakers) from output 1 & 2
If I feed the speakers from a headphone out, then it is clean. (so I don’t think it is the speakers or the DAW)
I would like to try different output channels…

But I can’t seem to get them to work.
I tried plugging my speakers into output 3 & 4 on the back of the MR816 on the output bay
Then click the Out 3-4 tab on the Steinberg input mixer screen, but there is no signal in the DAW channel
The DAW channel only has signal when the Out 1-2 tab is selected.
I have also tested Out 5-6 and Out 7-8

What am I doing wrong?