Want more bass, clearer voices or corrected headphones for every app on your PC at once? Equalizer APO is a free, open-source system-wide equalizer for Windows that runs with very low CPU and latency and applies its filters to everything you hear.
Filters shape specific parts of the sound
Equalizer APO processes audio through a configurable chain of filters. A parametric equalizer targets selected frequency ranges, while high-pass and low-pass filters set frequency cutoffs; band-pass filters isolate a range between them. These controls let listeners adjust bass, midrange, or treble without relying only on broad sound presets.
The available processing also includes compressors and limiters. Those tools control changes in audio level, alongside tonal adjustments made with equalization. Settings take effect during playback, so changes can be heard across applications that use a device configured for APO processing.
Configurator selects the playback devices to process
Equalizer APO includes Configurator for assigning its audio processing to playback devices. Select the endpoint that should receive the equalizer settings; a separate device may need its own selection. This setup is important when a computer switches between built-in speakers, a headset, or an external audio device.
The Configuration Editor provides a graphical way to build and adjust a processing configuration. Changes there control the filters applied by Equalizer APO, while Configurator determines which playback devices use that processing.
Channel settings support stereo and surround layouts
Multichannel configurations let users tune channels individually, which is relevant for surround speaker arrangements as well as stereo output. Channel-level adjustments can address an imbalance between left and right or tailor the sound of particular speakers without treating the entire setup as one undifferentiated output.
- Load VST plugins for effects that go beyond the built-in filters.
- Use filtering and dynamics controls in the same processing chain.
- Import ready-made headphone correction curves, such as those from the AutoEQ project, or use the popular Peace interface for a friendlier front end.
Pros
- Applies processing across apps through Windows audio devices
- Includes parametric, high-pass, low-pass, and band-pass filters
- Supports multichannel adjustment and channel-specific tuning
- Offers compressor and limiter processing
Cons
- Configuration is text-based without an add-on GUI
- Some audio drivers with their own enhancements block APO
System requirements: Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11 · 32-bit and 64-bit · ARM64 supported on Windows 10/11
Does Equalizer APO affect audio from multiple apps?
Yes. It works at the Windows audio level, so every app playing through a configured device is processed.
Is there an easier interface?
Yes. The free Peace add-on puts sliders and presets on top of Equalizer APO.
Is Equalizer APO free?
Yes. It is open-source software under the GPL, hosted on SourceForge.
Why is there no sound change after installing?
Select your playback device in the Configurator during setup, then restart the PC so processing is applied.