Equalizer APO 1.4.2 & Peace Equalizer 1.6.8.10

Equalizer APO is a system-wide equalizer for Windows, which means it works on every sound your PC produces rather than inside one player.

It is worth being clear about one thing before you download it: Equalizer APO is not really an application.

It is an audio engine that Windows loads into the playback path, and on its own it is configured by editing a text file.

The application is Peace Equalizer, a free interface built on top of it, and both are on the same download page here. Almost nobody runs Equalizer APO bare, and the page treats them as one install for that reason.

What an APO Actually Is

The letters stand for Audio Processing Object, which is a Windows component type introduced with Vista for exactly this purpose. Windows loads it into the audio path for a chosen device, so everything heading to that device passes through it on the way out.

That is why the effect is system-wide with no per-application setup, and why the latency and CPU cost are as low as they are. It is not intercepting anything or sitting in front of your software - it is a stage in a pipeline Windows already runs.

Install Order Matters

This is where first attempts usually go wrong, and it is four steps rather than one.

1. Install Equalizer APO first. Peace will not work without it.
2. During installation, tick the playback device you want processed. Miss this and nothing will happen later.
3. Reboot. Windows only loads the new processing object when the audio service restarts.
4. Install Peace, and use that from then on.

If you add a new headset or sound card afterwards, run the Equalizer APO Configurator again and tick the new device. Devices are opted in individually rather than all at once.

What Equalizer APO Provides

The engine itself is genuinely capable, and its limits are unusually generous for free software. There is no cap on the number of filters worth speaking of, it works on any number of channels rather than stereo only, and the CPU cost stays low enough that it is used in interactive applications where latency matters.

It reads Room EQ Wizard filter files directly, so a room-correction measurement can be applied without retyping anything. It supports VST plugins, and it integrates with Voicemeeter if you are running a virtual mixing setup.

Both Equalizer APO and Peace are released under the GPL version 2, so this is free in both senses and there is no paid tier anywhere in it.

What Peace Adds on Top

Peace turns the configuration file into sliders. Up to 31 gain sliders per channel, with the frequency, gain and Q of each one adjustable, plus peak, shelf, band, notch, low and high pass and all-pass filter types.

It handles up to nine speakers, so stereo, 5.1, 7.1 or a custom arrangement all work, and each device can carry its own saved configuration. There is a graph window showing the response curve you have actually built.

Beyond equalization there is an effects panel: crossfeed, up and down mixing, channel routing, balance, delay, and plain bass and treble for when you do not want to think about filters at all.

Configurations save as presets and recall from a hotkey, the system tray or a desktop shortcut, and a preset can activate itself when a particular program starts or a particular device is selected. There is also hardware MIDI controller support, a hearing test that builds a correction from your own results, themes, and an interface translated into fifteen languages.

The AutoEQ Shortcut

If you own a reasonably well-known pair of headphones, you can skip the theory entirely. Peace includes an AutoEQ interface holding roughly ten thousand ready-made headphone corrections.

You find your model in the list, apply it, and the sliders fill themselves in with a curve measured against a target response. For most people this is the entire reason to install any of this, and it takes about a minute.

It is also the honest answer to the reputation this software has for being difficult. Building a parametric EQ by hand is difficult. Picking your headphones off a list is not.

When It Will Not Work

There is one real limitation and it is architectural rather than a bug. Applications are only processed if their audio goes through the Windows system effect infrastructure, so anything that deliberately bypasses it is untouchable.

In practice that means ASIO and WASAPI exclusive mode. If you use an audio interface with an ASIO driver, or a player configured for exclusive-mode bit-perfect output, Equalizer APO cannot process that stream and no amount of configuration will change it.

That is usually deliberate on the listener's part - exclusive mode exists precisely to keep Windows out of the signal path - so the two goals are in direct conflict. Switch the player to shared mode if you want the equalizer, and accept that you have chosen processing over a bit-perfect path.

The other common cause is more mundane: the device was never ticked during installation, or a driver update replaced the audio stack underneath. Reinstalling the Realtek Audio Codecs package or your own vendor's driver, then rerunning the Configurator, clears most of those.

Equalizer APO or FxSound

FxSound gets suggested as the easy alternative, which undersells both. They are different classes of tool rather than a hard one and an easy one.

Both are free, and nothing stops you trying one and then the other. They cannot run usefully at the same time, though, since each is processing the same output.

Who Should Look Elsewhere

The tell is what you are actually trying to fix. If the problem is that sound is coming out of the wrong device, an equalizer is not the answer - SoundSwitch or Audio Switcher handle switching.

If a Bluetooth device keeps dropping to the wrong output, AudioPlaybackConnector is the smaller tool for that, and the rest of the audio utilities cover the neighbouring jobs.

If a file will not play at all, that is a decoding problem rather than a processing one, and the audio codec downloads are where to start instead.

And if you want to permanently change how a file sounds rather than how it is played back, edit it - Audacity applies EQ to the audio itself and saves the result.

Compatibility

Windows Vista or later, with Windows 7 through 11 tested by the developer. Builds exist for x64, x86 and ARM64, the last of those on Windows 10 and 11 only.

Because the processing happens below the applications, every player follows automatically with nothing to configure - foobar2000, AIMP and everything else use the processed output by default.

The same applies to lighter players such as XMPlay and Dopamine, and to browsers, games and video calls alike.

The full media players list is here if you are still choosing one.

One warning for anyone recording: what OBS Studio or the rest of your capture tools record from a processed device is the processed sound, equalization included. That is either exactly what you wanted or a nasty surprise in the edit, so check before a long session.

Quick questions

Download Equalizer APO 1.4.2 with Peace and see what it does for your headphones, or tell us how you got on if you have used it before.