Our verdict: Equalizer APO is the most flexible free way to equalize all sound on a Windows PC. It works below every app, so one profile fixes headphones or speakers everywhere. The trade-off is setup: you pick devices during install and edit filters in a technical editor or text file.
About Equalizer APO
Equalizer APO is developed by Jonas Thedering and published on SourceForge, which is the project's only official download location. It installs as an Audio Processing Object (APO), a component that plugs into the Windows audio engine, so its filters apply to every program that uses the normal Windows audio path.
Filters are stored in a plain text file, config.txt, and changes apply as soon as the file is saved. The bundled Configuration Editor offers a graphical way to build the same filters and shows the resulting frequency response. Programs that bypass the Windows audio engine, such as those using ASIO or WASAPI exclusive mode, are not affected.
What it does well
- Parametric and graphic EQ. Peaking, shelving, high-pass, low-pass and notch filters, plus a GraphicEQ with any number of bands.
- Per-device and per-channel filters. Separate settings for each output or microphone, and for each channel such as left, right or LFE.
- Room EQ Wizard import. Reads the filter text files exported by Room EQ Wizard, a free measurement tool.
- VST plugins and convolution. Load VST effect plugins or apply an impulse response for room correction or reverb.
- Microphone processing. Can be installed on recording devices to equalize a microphone for all apps.
Who it is for
Good fit
Headphone and speaker owners who want one correction profile across games, browsers and music players, and people tuning a room with measurements.
Look elsewhere
Users who want a simple slider app with presets, or who play audio through ASIO or WASAPI exclusive mode.
Pros and cons
Pros
- Applies to every app at once
- Very low latency and CPU use
- Unlimited filters per device
- VST and convolution support
Cons
- Device selection at install can be confusing
- Configuration Editor is technical rather than friendly
- No effect on ASIO or exclusive-mode audio
How to install Equalizer APO
Download the x64 installer from the project's SourceForge files page; the 1.4 series also has x86 and ARM64 builds. During setup the Device Selector asks which playback and recording devices to install the APO to. Choose your actual output device, then let it restart the Windows audio service or reboot. Rerun the Device Selector later if you add a new headset.
Questions about Equalizer APO
Is Equalizer APO free?
Yes. It is open source under the GNU GPL v2 with no paid edition.
Why do I hear no difference after installing Equalizer APO?
Usually the APO was installed to a different device than the one you listen on. Run the Device Selector from the Start menu, tick your current output device, and restart the audio service when asked.
Is SourceForge the official download for Equalizer APO?
Yes. The developer publishes Equalizer APO releases and documentation on SourceForge.
