REW Measurement Kit

Last updated

29 September 2026

Room EQ Wizard (REW) is free software for measuring what your speakers and room are really doing. It’s how you check that room correction has worked. Here’s what you need to get started.

Jump to: Beginner Advanced

What you need

Beginner

REW main window with the Measure button, Preferences, graph tabs, measurement list and legend marked — The REW main window: 1 Measure, 2 Preferences, 3 graph tabs, 4 your measurements, 5 smoothing and legend. (REW 5.40 beta.)

Item	Why	Notes
REW	Plays test signals and analyses the results	Free, for Windows, macOS and Linux
A USB measurement mic	Records the test signals at your seat	The miniDSP UMIK-1 is REW’s recommended mic. The one you use for Dirac Live works.
Your mic’s calibration file	Corrects for the mic’s own small errors	See Microphone Calibration
A mic stand or tripod	Holds the mic still at ear height	Essential. REW says small mic movements cause large changes in the results.
A laptop and an HDMI cable	Sends the test signals into your AV receiver	Connect the laptop’s HDMI output to a spare HDMI input on the receiver

You don’t need a separate sound level meter. A calibrated USB mic lets REW show sound levels directly.

Connecting to your AV receiver

Connect the laptop to the receiver by HDMI and select that input on the receiver.
In REW’s Preferences, choose the HDMI device as the output and your mic as the input. Pick the actual devices, not Default.
On Windows, REW’s standard driver only gives you stereo over HDMI. To reach the centre, surrounds and subwoofer, choose the WASAPI exclusive entry for the device, or use an ASIO driver such as FlexASIO.
On a Mac, miniDSP publishes its own HDMI setup guide.
Start with the receiver’s volume turned well down.

This follows REW’s own help and miniDSP’s setup notes. It applies to any AV receiver with an HDMI input.

REW Preferences Soundcard tab with sample rate, output and input device and channel marked — Preferences, Soundcard tab: pick the output device and channel feeding the receiver, and the UMIK as the input device. (REW 5.40 beta.)

Next step

Guide 2: Microphone Calibration

Got the kit? Load your mic’s calibration file so the readings are accurate.

Continue to Guide 2

Back: Measure with REW

Getting the details right

Advanced

Which REW version?

The current stable release is V5.31.3, from July 2024. Newer V5.40 beta versions are hosted at AV Nirvana and add features such as measurement groups and measuring with music or noise. Many experienced users run the betas. Either works for everything in this section.

Timing reference

To compare timing and phase between speakers, REW needs a timing reference. With a USB mic and an HDMI output, the input and output are separate devices, so a loopback cable isn’t possible. Use an acoustic reference instead: REW plays a short high-frequency sweep from one speaker, usually front left, before each measurement. A subwoofer can’t be the reference because it can’t play that sweep.

HDMI channel order with FlexASIO

REW output	Speaker
OUT0	Front left
OUT1	Front right
OUT2	Centre
OUT3	Subwoofer (LFE)
OUT4	Surround left
OUT5	Surround right
OUT6	Surround back left
OUT7	Surround back right

Channel order is from miniDSP’s Windows HDMI guide. Play a quick test on each output to confirm the right speaker plays before you measure.

Sample rate

The UMIK-1 only runs at 48 kHz, so set REW’s output to 48 kHz as well. The UMIK-2 supports 44.1 to 192 kHz, but the input and output rates must match.

The channel map applies to FlexASIO on Windows.