Ultimate Voxengo SPAN Guide: Master This Free Audio Analyzer

Ultimate Voxengo SPAN Guide: Master This Free Audio Analyzer

Voxengo SPAN is one of the most powerful free plugins in the audio industry. It is a real-time Fast Fourier Transform (FFT) audio spectrum analyzer. Producers, mixing engineers, and mastering engineers use it to visually inspect the frequency content of their audio.

While it looks intimidating at first glance, mastering SPAN will transform how you make decisions regarding your low end, track balance, and overall frequency spectrum. This guide will take you from a beginner setup to advanced configurations. Why Every Producer Needs SPAN

Your ears should always be the final judge of a mix. However, room acoustics, cheap monitoring setups, and ear fatigue can trick your brain. SPAN provides an objective, visual second opinion.

It helps you catch hidden problem areas that your monitors might not reproduce accurately. This is especially true for sub-bass frequencies below 40 Hz and harsh resinous spikes in the high-mids. Initial Setup and Essential Core Settings

When you first load SPAN into your Master Channel or Mix Bus, the default settings can be misleading. To get a representation that aligns with human hearing, you must adjust a few critical parameters. Click the Edit button at the top right of the plugin window to open the settings panel. Spectrum Mode Settings

Block Size: Set this to 4096 or 8192. Higher numbers increase low-frequency resolution, allowing you to see precise bass frequencies at the expense of a tiny amount of visual latency.

Overlap: Set this to 50%. This balances the visual refresh rate so the display updates smoothly. Window: Leave this on Normalized Rectangle or Hann. The Secret Weapon: Slope (Tilt)

The human ear does not perceive all frequencies at equal volume; we are much more sensitive to mid-range frequencies than bass. Set the Slope parameter to 4.5 or 3.0. A slope of 4.5 is the industry standard for modern music.

When your mix is perfectly balanced, a 4.5 slope will make the frequency curve look relatively flat across the screen. If you leave the slope at 0, a well-balanced mix will look like a steep, downward ski slope, which makes it incredibly difficult to read. Key Metering Displays to Monitor

Beyond the main frequency graph, SPAN offers critical data readouts at the bottom and sides of the interface.

RMS and Peak Meters: These track the absolute volume levels. Keep an eye on the digital ceiling to prevent clipping.

Crest Factor: This display shows the mathematical difference between your peak levels and your average (RMS) volume. It tells you how compressed or dynamic your track is. A crest factor around 10–12 dB is generally healthy for a dynamic mix, while a competitive master might push lower toward 6–8 dB.

Correlation Meter: Located at the bottom right, this meter ranges from -1 to +1. A reading between 0 and +1 means your mix is healthy and phase-coherent. If the meter dips into the negative zone, you have phase cancellation issues that will cause elements of your track to disappear when played back on mono systems (like phone speakers or club PAs). Advanced Workflows and Techniques Mid/Side Routing Detection

You can configure SPAN to show you what is happening in the center of your mix (Mid) versus what is happening out on the wide edges (Side). Click on the Routing button at the top. Change the routing preset from Stereo to Mid-Side.

Under the spectrum display groups, set Group 1 to Mid and Group 2 to Side.

This setup allows you to see if your sub-bass is leaking into the sides (which causes muddiness) or if your high-frequency delays are wide enough. Multi-Track Comparison

You can route multiple instruments into a single instance of SPAN using your DAW’s sidechain capabilities. This allows you to overlay the frequency curve of your kick drum directly on top of your bassline curve. By viewing them simultaneously in different colors, you can easily see exactly where they are fighting for space and apply surgical EQ cuts to separate them. The Perfect Mixing Reference Target

While every genre of music requires a slightly different tonal balance, a well-engineered modern mix analyzed with a 4.5 slope should follow a general visual template:

Sub-Bass (20 Hz – 60 Hz): Should form a clean, rounded bump that sits slightly higher than or equal to the mid-range.

Low-Mids (100 Hz – 300 Hz): Should be smooth. Avoid massive dips (which sound hollow) or massive peaks (which sound muddy).

Mids to High-Mids (1 kHz – 5 kHz): This area holds the presence of vocals and guitars. It should stay relatively flat and free of sharp, jagged spikes.

Highs (10 kHz – 20 kHz): Should gently taper downward to prevent a harsh, piercing listening experience.

If you want to take your audio analysis further, let me know: What genre of music you primarily work on Which DAW you are using

Whether you want a step-by-step guide for setting up sidechain inputs in your specific software

I can give you the exact steps and target parameters for your specific workflow.