dynamic EQ vs resonance suppressor

the same goal, different tools

a singer hits a loud phrase and a painful 3 kHz spike cuts through your monitors. you reach for a tool to fix it. but which tool? a dynamic EQ and a resonance suppressor both respond to the signal in real time. both reduce specific frequencies only when they become problematic. the difference is in resolution, automation, and trade-offs. a static EQ is an open window. a dynamic EQ is a thermostat. a resonance suppressor is climate control for the entire building.

picking the wrong one either cannot solve the problem or introduces artifacts that create new ones.

how dynamic EQ works

a dynamic EQ is an equalizer where each band has dynamics processing built in. instead of applying a fixed cut at 3 kHz, a dynamic EQ band sits idle until the signal energy at that frequency exceeds a threshold. when it does, the band engages and applies gain reduction. when the energy drops back below the threshold, the band releases and the gain returns to unity.

each band has the same controls you would find on a compressor: threshold, ratio, attack, and release. these determine when the band activates, how much it reduces, how quickly it responds, and how quickly it lets go.

most dynamic EQs give you 4-8 bands. you choose the centre frequency, Q (bandwidth), and dynamics settings for each one. you are making deliberate, manual decisions about which frequencies to target. (this is both the strength and the limitation.)

the strengths of dynamic EQ:

• near-zero latency: operates sample-by-sample, no FFT windowing. suitable for live sound and real-time monitoring
• familiar controls: threshold, ratio, attack, release. if you understand compression, you understand dynamic EQ
• precise manual control: you decide exactly which frequencies to target and how aggressively
• low CPU: typically less than 1% of a single core
• minimal artifacts: no spectral processing means no risk of “musical noise” or metallic artifacts

how a resonance suppressor works

a resonance suppressor takes a fundamentally different approach. instead of you placing bands on problem frequencies, it analyzes the entire spectrum automatically and identifies which frequencies are problematic.

the process uses spectral analysis, typically an FFT (fast fourier transform). the signal is decomposed into hundreds or thousands of frequency bins. the algorithm examines the spectral envelope of each analysis frame, identifies bins that protrude above the local average, and applies gain reduction to those specific bins. this happens every few milliseconds, with independent processing on every bin.[^1]

the key difference from dynamic EQ: there are no bands to place. the algorithm handles detection and correction automatically across the full spectrum. when a vocal formant shifts from 2.8 kHz on one vowel to 3.4 kHz on the next, the suppressor follows it without any manual adjustment. when a cymbal rings at a different frequency on each hit, every ring is caught.

more advanced resonance suppressors group FFT bins into perceptual bands (such as ERB bands) that model how your ears actually resolve frequency. this prevents the algorithm from processing frequencies at a resolution finer than human perception, which reduces artifacts and produces more natural-sounding results.[^2]

the strengths of a resonance suppressor:

• automatic detection: no manual frequency placement needed
• high resolution: acts on hundreds or thousands of frequencies simultaneously
• adapts to the signal: follows shifting resonances in real time
• handles complex sources: dense overtone patterns, moving formants, inharmonic content
• perceptual weighting: better implementations weight the processing to match human hearing sensitivity

the trade-offs

every tool has trade-offs. choosing between dynamic EQ and a resonance suppressor means understanding what each one gives up.

resolution

a dynamic EQ with 6 bands can act on 6 frequencies at once. a resonance suppressor based on a 4096-point FFT at 44.1 kHz analyzes 2049 frequency bins, each 10.8 Hz wide. that is roughly 340 times the resolution. for a source with one or two consistent resonances, 6 bands is more than enough. for a source with dozens of shifting resonances, 6 bands cannot keep up. it is not even close.

latency

dynamic EQ operates in the time domain with minimal delay, typically under 1 ms. a spectral resonance suppressor based on FFT processing adds latency equal to the FFT window size. a 4096-sample window at 44.1 kHz is approximately 93 ms. in mixing, your DAW compensates for this automatically. in live sound or real-time monitoring, 93 ms of latency is noticeable and problematic.

artifacts

dynamic EQ can cause gain pumping if the attack and release settings do not match the signal dynamics. a band that engages and releases too quickly on a sustained note produces audible gain modulation.

resonance suppressors risk “musical noise”: metallic, watery artifacts caused by isolated frequency bins being boosted or cut independently of their neighbors. good implementations mitigate this with temporal smoothing (independent attack/release per bin) and perceptual band grouping (ERB), but the risk exists at aggressive settings.[^3]

transparency

at gentle settings, both tools are transparent. at aggressive settings, dynamic EQ tends to sound like a compressor (gain pumping, breathing). a resonance suppressor tends to sound like a phaser or chorus (spectral colouring, thinning). the failure modes are different, and knowing what each one sounds like when it breaks helps you diagnose problems quickly.

when to use dynamic EQ

dynamic EQ is the right tool when:

• the problem frequencies are known and consistent: a room mode at 340 Hz that colors every take. a microphone with a presence peak at 4.5 kHz. a synth patch with a static resonance. if you can identify the frequency once and it stays there, a dynamic EQ band handles it efficiently
• you need low latency: live sound, real-time monitoring, tracking with near-zero delay. spectral processing cannot match dynamic EQ’s latency
• the source is simple: one or two resonances on a single instrument. the problem is narrow enough that 4-8 bands cover it
• you want explicit control: you want to set the exact threshold, ratio, and timing for each problem frequency. some engineers prefer this level of manual control over trusting an algorithm

when to use a resonance suppressor

a resonance suppressor is the right tool when:

• the problem frequencies shift: vocals changing vowels, guitars bending notes, string sections with vibrato. the resonances move with the performance and fixed bands cannot follow
• there are many simultaneous resonances: cymbals with dozens of inharmonic overtones. a dense mix with harshness from multiple overlapping sources. 4-8 bands are not enough to cover the problem
• you want automatic operation: you do not want to manually sweep for problem frequencies, set thresholds, and adjust parameters per band. a resonance suppressor handles detection and correction in one step
• mastering: you are working with a finished stereo mix where multiple sources contribute to the harshness. you cannot address individual tracks anymore. a resonance suppressor’s broad, adaptive approach handles the combined resonances more effectively than placing manual bands on a summed signal

the decision framework

three questions will get you to the right tool:

1. can you identify the problem frequencies by ear? if yes, and there are 1-3 of them, start with dynamic EQ. if you cannot pin them down, or there are more than you can count, try a resonance suppressor.

2. do the problems shift across the performance? if the same frequencies are always the problem, dynamic EQ. if the harshness moves with the pitch, vowel, or playing technique, resonance suppressor.

3. do you need real-time monitoring? if latency matters (live sound, tracking), dynamic EQ is the only practical choice. if you are mixing offline, latency is irrelevant and you should choose based on the problem.

frequently asked questions

frequently asked questions

what is the difference between dynamic EQ and a resonance suppressor?

a dynamic EQ gives you 4-8 bands that you place manually on problem frequencies. each band has its own threshold, ratio, and attack/release. a resonance suppressor analyzes hundreds or thousands of frequency points simultaneously using spectral processing and automatically identifies and reduces peaks that protrude above the surrounding spectrum. the key difference is resolution and automation: manual placement vs automatic detection.

when should you use dynamic EQ instead of a resonance suppressor?

use dynamic EQ when you can identify 1-3 specific problem frequencies that stay consistent. it is the better choice for fixed room resonances, microphone presence peaks, or synth patches with static spectral character. dynamic EQ also has near-zero latency, making it suitable for live sound and real-time monitoring. if the problem is predictable and narrow, dynamic EQ is simpler and more transparent.

when is a resonance suppressor the better tool?

use a resonance suppressor when harshness shifts across the spectrum. vocals changing vowels, guitars bending notes, cymbals ringing at different frequencies on each hit. these problems cannot be solved with 4-8 fixed bands because the resonances move. a spectral processor analyzes every frame independently and follows the problem automatically. it is also better for dense sources with many simultaneous resonances.

does a resonance suppressor add more latency than dynamic EQ?

yes. a resonance suppressor based on FFT processing typically adds 50-100 ms of latency depending on the window size, because it needs to collect a full frame of audio before analysis. a dynamic EQ operates sample-by-sample or with very small buffers, typically under 1 ms. in mixing, the DAW compensates for plugin latency automatically. in live performance or real-time monitoring, the latency of spectral processing can be a problem.

can you use dynamic EQ and a resonance suppressor together?

yes, and this is often the best approach. use a resonance suppressor first for broad, automatic control of shifting resonances. then follow with a dynamic EQ targeting 1-2 specific frequencies the suppressor missed or that need more aggressive treatment. the suppressor handles the complex, moving problems. the dynamic EQ handles the stubborn, fixed ones.

references

a note from the developer

“why not just use dynamic EQ?” is the question i got most when showing SMOOTH to people. and honestly, it is a good question. the answer is: you should use dynamic EQ. for a lot of things. i use it all the time.

SMOOTH exists for the moments where dynamic EQ runs out of bands and you run out of patience. a vocal that shifts formants on every syllable. a cymbal wash with dozens of ringing overtones. a mastering session where you cannot go back to individual tracks. those are spectral problems, and they need spectral tools. but for a room mode at 340 Hz that never moves? a single dynamic EQ band. simpler, cheaper, zero-latency.

the honest version of this guide would be: use the tool that matches the problem, even if it is not mine. if you have a workflow that combines both in a way i have not thought of, jonas@kernaudio.io. i want to hear it.