Spectral Dynamics: Benefits, Drawbacks and Techniques using FabFilter Pro-Q 4

FabFilter Pro-Q 3 has long been a favorite tool for shaping sounds. It’s simple, powerful, and always finds a place in my Quick Access folder. When FabFilter teased the release of Pro-Q 4. with its new “Spectral Dynamics” feature—what they call Dynamic Resonance Suppression—it naturally created a buzz, especially with the growing popularity of similar tools like Soothe 2.

The first tease from FabFilter indicating Spectral Dynamics

But what does this feature really offer, and how useful is it in practice? Let’s break it down to understand both the technique and the tool.

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What is Spectral Dynamics?

Spectral dynamics refers to dynamic resonance suppression which focuses on controlling resonant frequencies—those specific frequencies that overpower a mix and make things sound harsh or unbalanced. These issues can be caused by room acoustics, instrument characteristics, or mic placement.

How it Works

1. It detects resonant peaks in real time.

2. It reduces their gain dynamically (only when they become problematic).

3. It preserves other frequencies, ensuring the overall tone stays natural.

   
   

FabFilter introduces this as 'Spectral Dynamics' under its already popular Dynamic EQ capabilities and it is not to be confused with Spectral Processing that tools like iZotope RX specialize in.

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THE BENEFITS

1. Taming Harsh Frequencies

Instruments or vocals sometimes have resonances that stick out and sound harsh. Spectral dynamics automatically identifies and controls these problem areas, making the audio smoother without you needing to manually hunt for frequencies.

2. Preserving Natural Sound

Unlike static EQ cuts, this technique only activates when the resonance becomes a problem. The rest of the time, the original tone remains intact, making it feel more natural and less processed.

3. Saving Time and Effort

Manually identifying resonances can be tedious and time-consuming. This feature does the heavy lifting, making the mixing process faster and more efficient.

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THE DRAWBACKS

1. Harmonic Suppression

"When an instrument or voice produces a note, along with the main note (called the fundamental frequency), there are additional frequencies, known as harmonics, that give every sound its unique flavor. They’re the reason why a violin sounds different from a guitar, even if both are playing the same note."

With dynamic resonance suppression, overprocessing can take out too much of these harmonics, resulting in a very artificial tone. It can often remove the natural energy and dynamics that make a track exciting.

2. Uniform Suppression Across the Spectrum

Compared to tools like Soothe 2, Pro-Q 4 applies suppression equally across the frequency range. This results in greater suppression of lower frequencies than higher frequencies, as that is how the spectrum typically exists in most musical content.

Lower frequencies are suppressed more than higher frequencies

If FabFilter had a simple Pink Noise Tilt or modeled the Spectral Processing after Equal Loudness Contour, this issue could have been avoided.

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THE EASTER EGG

Pro-Q 4 as a Vocoder

This came as an Easter egg in the official introduction video from FabFilter, where Dan Worrall demonstrates how Pro-Q 4 can be used as a vocoder by simply adding an instance on a basic sawtooth synth patch and sidechaining it with a vocal track.

Feel free to give it a try yourself! If you run into any issues, don’t hesitate to reach out—I’d be happy to help you get the best results.

PRO TIP: 1. Make sure you are boosting the resonances and not attenuating. (Positive Gain) 2. Use multiple bell curves with high slope (96dB/Oct) and low Q (0.250-0.500) across different frequency ranges. (Remember that Pro-Q 4 applies uniform suppression (or boosting) across the entire spectrum, so you’ll need to adjust the gains (or thresholds) for different frequency bands differently to get optimal results.)

Pro-Q 4 is such a versatile tool that it often sparks creativity and encourages innovative uses. If you have any unique ideas, I’d love to hear them! Be sure to check back on this blog later—I’ll keep updating it with more creative techniques as I come across them.

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Conclusion

Spectral Dynamics is a powerful way to automatically tame harsh, resonant frequencies without compromising the natural tone of your sound. While FabFilter Pro-Q 4 is a great tool for accessing spectral dynamics capabilities, understanding the benefits, drawbacks, and techniques is essential to ensure that using this plug-in enhances the track rather than making it worse.

I hope this breakdown has helped clarify how Spectral Dynamics works and how it can improve your mixes.

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