APU Software

APU Loudness Compressor

Loudness compressor (LUFS, True Peak, RMS, Peak)

The APU Loudness Compressor is a compressor/expander designed to support modern loudness types (LUFS, True Peak). This means the gain envelope is a function of LUFS measurements instead of RMS or Peak. Since LUFS is a more accurate measure of loudness, the result is very transparent compression, making it particularly well suited for mastering and post-production workflows.

The compressor is also capable of operating in a more traditional way, using RMS or Peak units of measurement, so you can have your cake and eat it too.

Buy now   10 Day Free Trial


Loudness flavors

One of the key features of this compressor is its support for a variety of loudness types. The compressor’s detection circuitry can be configured to use either LUFS or traditional measurement units (RMS, Peak). You can also choose to split or link channels, which is particularly useful for multi-channel audio formats such as Dolby Atmos®.

The compressor’s detection circuitry can be configured to use any of the following loudness types:

Momentary

Momentary is a short duration LUFS measurement (400ms), which is useful for processing the audio’s moment-by-moment dynamics. This mode is responsive but also transparent, making it an appropriate default for the compressor. K-weighting and channel weighting are applied to the compressor’s detection circuitry, improving perceptual accuracy.

Momentary LUFS

Short-Term

Short-Term is a longer duration LUFS measurement (3 seconds), which is useful for processing the audio’s large scale dynamics. Given the longer duration, this mode is less responsive than momentary, but it can be useful for adjusting the bigger picture of the audio’s dynamics. K-weighting and channel weighting are applied as with momentary.

Short-Term LUFS

RMS

RMS loudness types use a rolling time interval of 300ms. RMS is a traditional loudness measurement, which is a good first-order approximation of perceived loudness. This mode doesn’t apply K-weighting or channel weighting to the compressor’s detection circuitry, giving it a more traditional character.

RMS

True Peak

True Peak loudness types are similar to traditional peak measurements, but they are more accurate as they take into consideration inter-sample peaks. These measurements use a time interval equal to the configured block size (1ms by default). This mode is extremely responsive, making it suitable for very fast attack and release times.

True Peak

Peak

Peak loudness types are a standard peak circuit, operating on a time interval equal to the configured block size (1ms by default). This is another traditional compressor style measurement. Technically, this mode is even slightly more responsive than True Peak, but it is less accurate as it doesn’t take into consideration inter-sample peaks.

True Peak

Source → Target mode

One of the other features of this compressor is the addition of a “Source → Target” mode (available in the drop-down menu above “Dry/Wet” dial). In this mode, all loudness measurements inside the source range are compressed or expanded into the target range. In this mode, you don’t need to worry as much about whether you’re compressing or expanding, you just need to set the source and target ranges to your liking. Compression and expansion are both handled automatically.

The video below demonstrates Source → Target mode being used to get similar results to the main demo video above. The source range is first set to match the source material, and the target range is then adjusted to achieve the desired result. Some find this mode to be more intuitive than the traditional compressor mode, as it allows you to focus on the loudness range you want to achieve, rather than the specific settings you need to get there.

In this mode with “learn” enabled, the compressor will automatically adjust the source range to match the source material. You can then quickly switch between different target range presets or make adjustments manually. Once you have the source range set to your liking, you can then adjust the target range while listening to the result in real-time. This lets you easily experiment with different amounts of dynamic range to dial in the settings you want.

This mode is particularly useful for mastering and post-production workflows, where you may want to adjust the dynamic range of the audio to match the target medium. For example, you might want to compress the dynamic range of a film to match the dynamic range of a television broadcast. Or you might want to expand the dynamic range of a song to match the dynamic range of a streaming service.

If you have any questions or feedback, you can reach me (Aaron) using the “Contact the Developer” beacon on this website.

License key purchase (w/free lifetime updates)

You can purchase a license key for the compressor using one of the payment buttons below. The license key will be emailed to you after payment confirmation. The license key can be entered in the About tab on the plug-in.

Don’t hesitate to reach out if you have any questions or feedback!



Download and install (free trial)

Choose your operating system to download the latest installer below.

MacOS Windows User Manual

The user manual above is also available on the live docs site.

System requirements: macOS 10.14 (x86, x64, ARM), Windows 10 (x86, x64), OpenGL 3.2.
Supported plug-in types: VST, AU, AAX (Pro Tools 11+).
Free trial: 10 days, no limitations.