Hopefully this will help.... FIRST... go into System Preference -> Sound and find the option to "Show volume in the menu bar" make sure it's checked.

Once you do that, Option+Click on the volume icon and you can select your output device for sound.. set it to the Eleven Rack and you should be good to go. Your setup is exactly the way I have mine (XLR to studio monitors) and that is how I do it to make it work.