Audio node
Audio Equalizer
A full 5-band equalizer: a low shelf, three parametric mid bands, a high shelf, and a master gain — eleven tone controls, every one of them a port. Sweep a mid band's frequency from an LFO, ride the low shelf from audio analysis, or simply dial in a static tonal balance for a track before it reaches the Audio Output.
Inputs
| Port | Type | Default |
|---|---|---|
| AudioThe signal to shape. Cable it from Audio Player, another effect or a synth; microphone input outside the engine graph passes through untouched. | structure | — |
| EnableOff bypasses the whole EQ — the audio still passes through, unshaped. | bool | true |
| Low GainBoost or cut of the low shelf, in dB. Clamped to -24…24. | float | 0 |
| Low FreqWhere the low shelf starts working, in Hz. Clamped to 20…20000; anything below it is lifted or cut together. | float | 80 |
| Mid1 GainBoost or cut of the first mid bell, in dB. Clamped to -24…24. | float | 0 |
| Mid1 FreqCentre of the first mid bell, in Hz. Clamped to 20…20000. | float | 250 |
| Mid2 GainBoost or cut of the second mid bell, in dB. Clamped to -24…24. | float | 0 |
| Mid2 FreqCentre of the second mid bell, in Hz. Clamped to 20…20000. | float | 1000 |
| Mid3 GainBoost or cut of the third mid bell, in dB. Clamped to -24…24. | float | 0 |
| Mid3 FreqCentre of the third mid bell, in Hz. Clamped to 20…20000. | float | 4000 |
| High GainBoost or cut of the high shelf, in dB. Clamped to -24…24. | float | 0 |
| High FreqWhere the high shelf starts working, in Hz. Clamped to 20…20000; everything above it moves together. | float | 8000 |
| MasterOverall output level of the EQ, in dB. Clamped to -24…24 — pull it down when several bands are boosted. | float | 0 |
Outputs
| Port | Type |
|---|---|
| AudioThe signal to shape. Cable it from Audio Player, another effect or a synth; microphone input outside the engine graph passes through untouched. | structure |
| Level | float |
How It Works
Audio Equalizer sits anywhere in an audio chain: source → filters → Audio Output. Connecting the Audio input splices the node into the shared AVAudioEngine graph — cables are the engine wiring, one clock drives every player, filter, and output, and the EQ can be spliced in mid-playback without a glitch.
Internally the node hosts a five-band AVAudioUnitEQ with a fixed topology: band 1 is a low shelf (boosts/cuts everything below its frequency), bands 2–4 are parametric peaks with a fixed one-octave bandwidth (boost/cut a bell around their center frequency), and band 5 is a high shelf (everything above its frequency). Master drives the unit's global gain, trimming the overall level after the bands — useful for compensating a big boost or cut.
All gains are in decibels: 0 dB is neutral, positive boosts, negative cuts. All frequencies are in Hz. The defaults (80 / 250 / 1000 / 4000 / 8000 Hz) cover the classic mixing bands: sub/bass, low-mid mud, presence midrange, definition, and air.
The Audio output re-emits the equalized signal as a new engine-backed snapshot, so more filters can follow and an Audio FFT can tap the chain after the EQ — watch your EQ curve actually reshape the spectrum in real time. The Level output is a peak-decay RMS of the equalized signal. Enable = false engages the audio unit's clean bypass: audio passes through unprocessed, perfect for A/B comparison.
Parameters in Depth
| Port | Type | Default | Description |
|---|---|---|---|
| Audio | Structure | — | Engine audio signal to process. |
| Enable | Bool | true | When false, the EQ is cleanly bypassed — audio passes through unchanged. |
| Low Gain | Float | 0 | Low shelf boost/cut in dB, clamped to −24…+24. Affects everything below Low Freq. |
| Low Freq | Float | 80 | Low shelf corner frequency in Hz (20…20000). 60–120 Hz covers kick and bass fundamentals. |
| Mid1 Gain | Float | 0 | First parametric band boost/cut in dB (−24…+24), one-octave bell. |
| Mid1 Freq | Float | 250 | First mid center frequency in Hz. 200–400 Hz is the "mud" region. |
| Mid2 Gain | Float | 0 | Second parametric band boost/cut in dB (−24…+24). |
| Mid2 Freq | Float | 1000 | Second mid center frequency in Hz. ~1 kHz is body and presence. |
| Mid3 Gain | Float | 0 | Third parametric band boost/cut in dB (−24…+24). |
| Mid3 Freq | Float | 4000 | Third mid center frequency in Hz. 3–5 kHz is attack, edge, and vocal intelligibility. |
| High Gain | Float | 0 | High shelf boost/cut in dB (−24…+24). Affects everything above High Freq. |
| High Freq | Float | 8000 | High shelf corner frequency in Hz. 8–12 kHz is sheen and air. |
| Master | Float | 0 | Overall output trim in dB, clamped to −24…+24, applied after the bands. |
Outputs: Audio (the equalized signal, chainable) and Level (peak-decay RMS of the equalized signal).
All frequency ports clamp to 20…20000 Hz. The three mid bands are identical in behavior — only their default centers differ — so they can be repositioned anywhere in the spectrum.
Use Cases
- Tone-shape a music bed: Audio Player → Audio Equalizer → Audio Output — cut Mid1 (250 Hz) a few dB to clear mud, add +2–3 dB High Gain for air.
- Pre-analysis emphasis: Audio Player → Audio Equalizer (boost Low Gain +6 dB) → Audio Output, with an Audio FFT tapped after the EQ so beat detection sees an exaggerated kick.
- Dynamic EQ sweep as a performance effect: cable Mid2 Freq to an LFO scaled 300…5000 Hz with Mid2 Gain at +12 dB — a moving resonant peak, the phaser-like "EQ sweep" trick.
- Voice clarity for live input: Audio Input → Audio Equalizer (Low Gain −6 at 100 Hz, Mid3 Gain +4 at 3500 Hz) → Audio Compressor → Audio Output — classic broadcast voice chain.
- De-harsh a distorted branch: Audio Player → Audio Distortion → Audio Equalizer (Mid3 Gain −6 at 4000 Hz, High Gain −4) → Audio Output — tame the fizz a distortion preset adds.
- Reactive tone: drive Low Gain from an Audio Analysis band energy so the bass shelf blooms with the music — an EQ that plays itself.
Tips
- Cutting is usually cleaner than boosting: to make highs feel louder, try cutting the lows and raising Master rather than pushing High Gain to the ceiling.
- Big boosts eat headroom — if you add +10 dB anywhere, pull Master down a few dB (or follow with an Audio Compressor) to avoid a hot signal at the Audio Output.
- The three mids have a fixed one-octave bandwidth; for a narrower surgical cut, use an Audio Filter node in Notch mode in series with the EQ.
- Tap an Audio FFT both before and after the EQ (the source's output and this node's Audio output) and display both spectra — the fastest way to see what your curve is doing.
- Enable = false is a clean bypass on a single toggle — the honest way to check whether your EQ actually improves the sound.
- Order matters: EQ before a reverb shapes what enters the space; EQ after it shapes the space itself.
Open Audio Equalizer in the interactive catalog →
Audio Equalizer is one of 381 nodes in Grafit Pro.
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