Room EQ Wizard (REW) is free measurement software for Windows, Mac and Linux. With a USB measurement mic it shows you what your room is doing to the sound, and whether your room correction actually fixed it. Work through these seven guides in order.
Guide 1
Something not working? See REW troubleshooting for fixes to the most common errors and problems.
Measurement Kit
The mic, stand and cables you need, and what they cost.
Guide 6
Is My Result Good?
Numbers to judge your graphs against, from listening-room standards and research.
REW works alongside any system: Dirac Live, Audyssey, YPAO, Anthem ARC or RoomPerfect.