Click New Session from the bottom left and choose New Blank Session.
Select System Audio from the Sources pane on the right of the window.
Drag in Output Device and choose your audio interface. This allows you to pass the audio back to your speakers.
On the right hand side of the window: scroll down to the Audio Unit Effects pane.
Drag MiniMetersServer into the audio graph inside Audio Hijack.
Select "MiniMeters Plugin" as your Audio Device within MiniMeters.
Option 2 (Loopback):
Using a loopback driver such as BlackHole, or Rogue Amoeba's Loopback in conjunction with Audio Hijack.
Install and launch Audio Hijack.
Click New Session from the bottom left and choose New Blank Session.
Select System Audio from the Sources pane on the right of the window.
Drag in Output Device and choose your audio interface. This allows you to pass the audio back to your speakers.
Insert a second output device and select the loopback driver of your choice.
Navigate to Applications/Utilities in Finder and open Audio Midi Setup.
If it is not shown: Click the Window menu and choose Audio Devices.
Ensure that the Input and Output volume of your chosen loopback device is set to
1. Otherwise, MiniMeters may not show an accurate display of the audio on your
system.
Select the loopback driver you chose as your Audio Device within MiniMeters.
For advanced users:
BlackHole - Follow the instructions
to "Record System Audio"
Loopback - Set Loopback as system output or choose your DAW
as the source.
Specific Audio Interfaces:
Many audio interface manufacturers support a creation of a loopback device.