No extra drivers are required. With the CXA switched to USB Audio 1.0 the CXA will work with the native Mac OS-X 10.5 (Leopard) or above Audio 1.0 driver and accept audio up to 24-bit/96kHz.
With the CXA switched to USB Audio Class 2 the CXA works with the native Mac OS-X 10.5 (Leopard) or above Audio 2.0 driver and can accept audio up to 32-bit/384kHz.
You can do this by pressing the Bluetooth/USB button, which will toggle between the two inputs. The USB Audio is shown by the symbol being lit orange
Note: To ensure you are getting the highest quality play back possible, ensure that the maximum sample rate for the CXA is selected, up to 384 kHz.
This can be done via your Mac by selecting ‘Audio Midi Setup > ‘Sound’ > ‘Speaker Properties’ > ‘Advanced’ Tab, and selecting the maximum sample rate and bit depth from the drop down menu.