I use an Antelope Orion 32+ as my audio interface. Never had an issue with it till trying to use it with FCPX.
FCPX will not play audio through my Orion interface. No matter what I do…it will not route through my interface. My System Preferences have the Output selected to run through the Orion and all Mac audio runs through it fine.
If I switch to “external headphones”, then FCPX will pass the audio through the headphone port … but it’s 100% distorted (that’s another issue in it of itself).
Interestingly enough, if I restart the computer, immediately open FCPX and start playback, it will play for a few seconds through the interface but then will stop. It’s as if somehow it’s recognizing there’s external audio hardware and then ceases to pass through.
I never had this issue when I was using MOTU (firewire) hardware. But now, with this new interface (it’s been a year or so since I’ve used FCPX), FCPX doesn’t seem to want to play nice.
It’s been a long time since I set this up when I had a similar issue. I think you need to use the Audio MIDI Setup app in the Utilities folder in the Applications folder. Open the app and look for your interface. Define the input & output. Also, you need to configure the speakers. There’s a button for that. Sorry I can’t be more specific. Hopefully this helps.