Trying to change 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
Boot V1.00. Main V1.10. IEEE 1394 V1.02

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?

Try going to Apple’s Audio Midi application. In the Audio window, click on the MR816 and go to the Output tab. There you can choose the output channels you have plugged into on the MR.