I thought the remote on an Apple TV would sort out the volume? Or the soundbar will have a remote?
The volume buttons on the Apple TV either send an infrared signal to your TV like a universal remote, or do some HDMI trickery to control the TV's volume control via the Apple TV. What they don't do is change the output volume of the Apple TV itself.
The volume buttons on the Apple TV either send an infrared signal to your TV like a universal remote, or do some HDMI trickery to control the TV's volume control via the Apple TV. What they don't do is change the output volume of the Apple TV itself.