The Unthingable

OS X system-wide EQ with Soundflower and AU Lab

Entirely free. Requires XCode.

1. Download and install Soundflower.

2. Open Audio MIDI Setup.

3. Create Aggregate Device (Audio -> Open aggregate device editor), constisting of:

   1. Built-in output (or whatever output you need)
   2. Soundflower

4. Set default output to Soundflower.

5. Start audio. At this point you should hear nothing.

6. Open AU Lab (/Developer/Applications/Audio/AU Lab.app).

7. Add 1 stereo input track, set Audio Device to "Aggregate device". Click "Done".

8. Now you should hear sound and see level meters move.

9. In either Audio 1 or Output 1 strip, click Effects drop-down and select Apple Graphic EQ, or whatever else you want!

Voila.