Intro
I recently upgraded my work desk with a 2.1 speaker setup and wanted to introduce you to a DSP tool for Windows called Equalizer APO. This software is both free and open-source, enabling you to apply a wide range of filters and effects to your audio output per channel. Equalizer APO is easy to set up, especially if you have experience with custom EQing, and it offers a bunch of features. I have been using it on three different systems for years and it has consistently delivered excellent results.
What is Equalizer APO
Equalizer APO is a system-wide parametric equalizer for your computer that uses a high-quality audio processing engine, meaning that you will be able to adjust the frequency response as if you have a dedicated audio processor.
It can process most audio signals that go through your system, regardless of the application or device playing them. While it does not work with USB or HDMI devices that use their own drivers, I have not had an issue where it was unable to detect an audio device.
Features
Equalizer APO offers a wide range of functions to adjust and customize the audio output of the computer. With its graphic equalizer feature, you can adjust the gain of various frequency bands using sliders or knobs. Additionally, it grants greater flexibility by allowing specific equalizer settings to be applied to different devices or applications, while enabling quick and easy switching between configurations. I rely on this feature a lot as I am constantly switching between my gaming and music listening profiles.
Example of Equalizer APO GUI with a custom EQ file with parametric filters.
For more advanced control, Equalizer APO includes the parametric equalizer function. This function allows you to input the center frequency, gain, and width of the frequency bands (called the Q Factor). You can further customize your audio experience by utilizing a variety of filter types including low-pass, high-pass, band-pass, and notch filters.
To fine-tune your audio even further, Equalizer APO provides additional functions such as a channel mixer, compressor, limiter, crossfade, and preamp. The software supports multiple channels, enabling you to adjust the sound for each speaker individually. This is very useful for home theater applications especially where you may need to calibrate a surround-sound system.
In addition to its equalization capabilities, Equalizer APO supports VST plugins. This feature allows you to leverage a vast array of third-party software modules ranging from basic reverb and delay effects to complex synthesizers and modulators. Notably, the Peace Equalizer plugin is widely used due to its different graphical user interface and special features.
One of the standout features of Equalizer APO is its low CPU usage and absence of latency or distortion. This ensures a smooth audio experience without compromising performance, as it uses less than a percentage point of your computer’s CPU
Installation
Equalizer APO is compatible with all Windows versions newer than Windows 7. You can download Equalizer APO from its official website.
To install Equalizer APO, you need to run the setup file and follow the instructions. Then, you will select the audio device that you want to apply Equalizer APO to and reboot your PC. Finally, you will need to configure it using the Configuration Editor.
To begin using Equalizer APO, a highly recommended approach is to combine it with the use of REW. With this method, you can utilize REW to measure your frequency response and leverage its auto EQ function to generate the necessary filters. Once the filters are created, they can be imported into Equalizer APO, completing the setup process swiftly and efficiently.
I have included some good YouTube tutorials at the end of this post.
Results
To amplify the two speakers and the subwoofer, I purchased a budget-friendly amplifier from Amazon. After wiring everything together, I proceeded to install Equalizer APO and conducted initial measurements using REW and Umik-1.
My first step was to adjust the crossover point, ensuring a seamless blend between the Left/Right speakers and the subwoofer. Then, I took a combined baseline measurement, represented in cyan on the graph below, to identify any problematic areas.
It became apparent that there were prominent peaks in the 300-550 Hz and 2.5 kHz regions. To address this, I utilized the EQ function in REW, which generated filters and allowed me to create a custom house curve. Given that I often listen at low volumes in work environments, the bass boost from the EQ helped to enhance the system’s sound, making it fuller even at lower volume levels.
Results from calibrating my own speakers at my work desk. The white line was the target, the cyan line was the baseline, and the green line was the final result.
After creating the filters in REW, I exported them to a text file and imported them into Equalizer APO. I then verified that the filters were applied correctly. The resulting response curve, indicated by the green line in the graph, displayed a much closer alignment with the desired target response represented by the white line.
While the improvement is not flawless, I am quite satisfied with the outcome considering the challenging environment I work in and the fact that it only took about 30 minutes to complete. Working above a manufacturing floor introduces significant and inconsistent background noise, making it difficult to achieve perfect results.
Closing Thoughts
Equalizer APO is a lightweight and user-friendly tool that helps improve sound quality on computers with sound systems. With its versatility, it allows for customized audio settings for multiple devices, whether it is used for different music genres or gaming. This tool is ideal for individuals who value sound and wish to personalize their audio experience.
Now in theory, you might be able to use this tool if you are running a home theater PC to do additional manual EQ or to add loudness compensation to a system that does not have it. Please feel free to comment below if you use Equalizer APO in this way.
Video Tutorials
Here are a couple of video tutorials to get you started with installation
We also have an introductory guide to REW that can help you with calibration, especially if you are just getting started.
Very well written article. Thank you Tyler