How to make Siri activate when you say ‘Hey Siri’ to your Mac with macOS Sierra

On iOS, I activate Siri by saying “Hey Siri.” Vocal activation isn’t available on the macOS Sierra Public Beta through the Siri system preferences, but as Jdcampbell on Reddit points out, it can be done through Sierra’s Accessibility system preference.
Essentially, you use dictation to activate the keyboard shortcut for Siri. The default Siri keyboard command in the Sierra Public Beta is to hold down the Command and Space buttons. You need to change this, because the Acc