There are two ways to switch the audio back to your Sonos Arc, Beam (Gen 2) or Ray from your Sonos Ace headphones. You can use the Sonos app, or you can use the headphones themselves. In the Sonos app, there will be a yellow button called "Swap Back" when the audio is playing through your headphones. Tapping this button will send the audio back to your Sonos Arc, Best (Gen 2) or Ray, and a pop up will appear allowing you to adjust the soundbar volume. On the Sonos Ace headphones, there is a Content Key on the right ear cup. A long press of this button will also switch the audio back to your Sonos Arc, Beam (Gen 2) or Ray.