This shell script toggles system wide eq using AU Lab and Sound Siphon (see e.g. https://github.com/thintsa/aulab-soundflower-equalizer-toggle) on and off on a Mac. AudioSwitcher app can be found here: https://github.com/deweller/switchaudio-osx.

eqtoggle.sh

#!/bin/bash
number=$(ps aux | grep 'AU Lab' | wc -l)
if [ $number -gt 1 ]
    then
        ./AudioSwitcher -s 'Built-in Output'
        killall 'AU Lab'
        osascript -e 'display notification "System wide EQ disabled" with title "EQ Toggle"'
    else
        open /Applications/Utilities/AU\ Lab.app/
        ./AudioSwitcher -s 'Sound Siphon Out'
        osascript -e 'tell application "Finder"
                repeat
                    delay 0.1
                    if (count of windows) of process "AU Lab" is greater than 0 then exit repeat
                end repeat
                repeat until visible of process "AU Lab" is false
                    delay 0.1
                    set visible of process "AU Lab" to false
                end repeat
            end tell'
        osascript -e 'display notification "System wide EQ enabled" with title "EQ Toggle"'
fi

Works on El Capitan too whereas the original toggle script doesn't without signing.