OSX

AU: [user]/Macintosh HD/Library/Audio/Plug-Ins/Components

VST: [user]/Macintosh HD/Library/Audio/Plug-Ins/VST

AAX: [user]/Macintosh HD/Library/Application Support/Avid/Audio/Plug-Ins/

WIN

VST: (specified by user at time of installation)**

By Default:

C:\Program Files\VstPlugins\KORG

AAX: C:\Program Files\Common Files\Avid\Audio\Plug-Ins