REW (Room EQ Wizard) is a Java application for measuring room responses and countering room modal resonances. It includes tools for generating test signals; measuring SPL; measuring frequency and impulse responses; generating phase, group delay, spectral decay plots, waterfalls, spectrograms and energy-time curves; generating real time analyser (RTA) plots; calculating reverberation times; displaying equaliser responses and automatically adjusting the settings of parametric equalisers to counter the effects of room modes and adjust responses to match a target.
REW uses a logarithmically swept sine signal for its measurements. This
is much faster than manual measurements, more accurate, less likely to suffer
from clipping at resonances, less sensitive to system non-linearity than MLS
and allows the impulse response of the room to be determined, which in turn
is the basis for many additional features. When using the Real Time Analyser
displays REW can generate Pink Periodic Noise sequences for much better
visibility of low frequency behaviour than obtained using random Pink Noise
without the need for lengthy averaging.
tccutil reset Microphonefrom a terminal before starting REW. You may need to use the mac's Privacy settings to grant REW access to the folders where measurements are to be saved, particularly if they are on the desktop.
When installing REW on Windows XP Pro x64, Vista, 7, 8 or 8.1 you may encounter a somewhat cryptic error message:
"The program can't start because api-ms-win-core-timezone-l1-1-0.dll is missing from your computer. Try reinstalling the program to fix this problem.".
This is caused by the Java runtime using components from the Windows Universal C Runtime which are not present on older Windows installations. To fix it see this Microsoft knowledge base article, KB2999226 at https://support.microsoft.com/en-us/help/2999226/update-for-universal-c-runtime-in-windows.
chmod u+x REW_linux_5_19.sh
sudo ./REW_linux_5_19.sh
roomeqwizard
REW saves diagnostic logs in the user's home directory in a folder called REW, the location is displayed in the Help → About REW window. The logs contain information from the last 10 startups, including any error messages or warnings that may have been generated. On macOS the logs are in an REW folder in the user library folder, which no longer appears in Finder by default. To display it either browse to ~/Library/Logs or open your Home folder in Finder (Shift Command + H), select View > Show View Options then select the checkbox to show the library folder.
REW saves a temporary copy of each measurement in a /temp sub-folder of the logs folder. Seven days of measurements are retained, any older than 7 days are deleted on shutdown. If REW did not shut down normally it will offer to load any measurements made since it last started up.
The roomeqwizard.vmoptions file in the REW program directory on Windows or REW.vmoptions in the REW Applications folder on mac contains settings for the Java Runtime Environment (JRE). The REW installer makes an entry in the file to define the amount of memory to request fore the JRE on startup using the -Xmx option, for example -Xmx1024m for 1 GB. The file could be edited to request a memory size larger than the installer offers, such as -Xmx4096m for 4 GB, but note that if the OS refuses the request for the memory size specified in the file REW will not start.
On Windows Admin privileges are required to change the roomeqwizard.vmoptions file: copy it to a user-accessible directory, make the edits, then copy it back using Admin privileges.
As an alternative to editing the roomeqwizard.vmoptions file
parameters can be passed to the runtime via the command line (e.g. by editing the Target
of a shortcut). To do that they must be preceded by -J, so to force REW to start
with 4 GB allocation (for example) regardless of the contents of the vmoptions file
the shortcut target on Windows could be
"C:\Program Files\REW\roomeqwizard.exe" -J-Xmx4096m
By default the preferences for REW on Windows systems are stored
in this registry key:
HKEY_CURRENT_USER\Software\JavaSoft\Prefs\room eq wizard
On macOS the preferences are stored under a key called room eq wizard in:
~/Library/Preferences/com.apple.java.util.prefs.plist
Linux preferences are typically stored in:
~/.java/.userPrefs/room eq wizard/prefs.xml
REW can alternatively use a file for its preferences. There are three ways to configure that, The easiest is to put a file in the REW log files folder with the name rewprefs.txt. If that file is found on startup REW will use it to store all preferences. To use a different file run REW with a -prefs argument or make a -Drew.preferences.file entry in the roomeqwizard.vmoptions file. The -prefs argument is checked first, then the -Drew.preferences.file entry and finally REW looks for rewprefs.txt. Switching to file-based preferences can be done quickly by saving preferences to rewprefs.txt in the log files folder using the entry in the Preferences menu and restarting REW. On Windows systems startup is faster with file-based preferences, on macOS shutdown is much faster with file-based preferences.
On Windows with the default REW installation a preferences file could be specified by launching REW using
C:\Program Files\REW\roomeqwizard.exe -prefs "C:\Users\johnm\Documents\myrewprefs.txt"
or editing the Target field of the properties of an REW Windows shortcut to add the prefs argument, so the target would look like
"C:\Program Files\REW\roomeqwizard.exe" -prefs "C:\Users\johnm\Documents\myrewprefs.txt"
On macOS it could be done from a terminal using
open -a REW.app --args -prefs "/Users/johnm/Documents/myrewprefs.txt"
To use the roomeqwizard.vmoptions file add an entry to specify the path to the file, for example:
-Drew.preferences.file=C:\Users\johnm\Documents\myrewprefs.txt
If a preferences file is being used the file name will be shown in the About REW dialog. If the specified file cannot be accessed, created or written to REW will instead use a file called rewprefs.txt in the REW log files folder and show a warning to that effect.
A preferences file can be created from an existing installation using the Preferences → Save preferences to file menu entry.
Preferences can be deleted with the Preferences → Delete preferences and shut down menu entry or by running the REW uninstaller.
REW can be made to always start with an initial set of preferences by specifying a file with those initial values. There are three ways to do that. The easiest is to put the file in the REW log files folder with the name initialprefs.txt. If that file is found on startup REW will use it to initialise all preferences. To force preferences to be initialised from a different file run REW with a -initialprefs argument specifying the file name for the starting preferences, or add a -Drew.initialpreferences.file entry in the roomeqwizard.vmoptions file. The -initialprefs argument is checked first, then the -Drew.initialpreferences.file entry and finally REW looks for initialprefs.txt. If a preferences file has also been specified REW will copy the initial preferences to that file, if not it will create a preferences file and copy the initial preferences into it. Any file specified as the initial preferences should be different to the file specified for the preferences. Note that the initial preferences file does not need to contain all preference settings. It can be edited to contain only those preferences which are to be initialised, any not included in the file will not be altered.
REW has support for English, French, German, Simplified Chinese and Traditional Chinese (Taiwan).
A "bundles" folder in the installation folder allows other languages to be supported by providing
a set of files for that language.
The bundles folder has a set of .properties files, which are text files with REW's user interface
text. The end of the file name indicates the language and country the file will be used for. As an
example, files for Korea would have names ending _ko_KR, e.g. apiprefs_ko_KR.properties. To create
translation files, first make copies of the bundles folder files, then change the names of the copies
to have the correct ending. After entering translated text the files can be copied back into the bundles
folder (keeping any existing files) and when REW is restarted it will pick up the new content if the
machine's default locale settings match the filename. The default locale can be seen in the About REW box:
The files contain entries in a KEY=text format, here are the first few lines of the apiprefs properties
file as an example:
# Copyright (c) 2025 John Mulcahy All Rights Reserved
# API preferences elements not already covered by prefboxlabels and prefhints
PORT_HINT_TEMPLATE=Enter a port number between {0} and {1}, default is {2}
START_SERVER_BUTTON=Start server
The key must not be altered, the translated text should appear after the =. Entries with _TEMPLATE in the name have values inserted by REW when using the contents, those values are indicated by the {0}, {1} etc parts of the text. Those must be retained by the translation, with the {0} etc. placeholders in the position they should occupy in the translation. Entries with _HINT are used for the tooltips that appear when hovering over a UI element. There is a lot of freedom when translating those. Other entries may be for buttons, labels or headings and that is generally indicated in the key. There may be layout issues in REW when translations are much longer or shorter than the English text. If you notice those, let me know where they occur and I will address them. Long lines of text in the properties files can be broken up by using a \ character, which indicates that the text continues on the next line. That is just a convenience for editing, it does not change how the text appears in REW. Some text has embedded html tags, e.g. <br> for a line break. Those should be preserved in translations, but placed appropriately. Do not add html tags in text that does not already have them.
Completed properties file translations can be sent to me to include in a future REW release to add support for more languages.
THIS SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE
Traditional Chinese (Taiwan) and Simplified Chinese translations by DC-Audio Lab 林佑叡
French translations by Eric Masssicotte de chez Maison Adam
German translations by Andreas Lartz, Automotive Consultant, office@audiosquare.de
Copyright © 2004-2026 John Mulcahy All Rights Reserved
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