@audio/filter-oberheim

Oberheim SEM state-variable filter (–12 dB/oct multimode)

npm install @audio/filter-oberheim

import oberheim from '@audio/filter-oberheim'

Oberheim SEM (1974) — 2-pole state-variable filter with four modes from one circuit.

Topology: 2 trapezoidal integrators with nonlinear feedback; multimode output (LP/HP/BP/notch) Response: $-12,\text{dB/oct}$; warm, musical resonance; continuous mode morphing Implementation: ZDF (zero-delay feedback) via trapezoidal integration — Zavalishin, The Art of VA Filter Design (2012), Ch. 4–5; $\tanh$ saturation on the integrator states (not on a separate drive input — unlike the ladder filters in this repo, oberheim takes no drive parameter)

oberheim(buffer, { fc: 1000, resonance: 0.5, type: 'lowpass',  fs: 44100 })
oberheim(buffer, { fc: 1000, resonance: 0.5, type: 'highpass', fs: 44100 })
oberheim(buffer, { fc: 1000, resonance: 0.5, type: 'bandpass', fs: 44100 })
oberheim(buffer, { fc: 1000, resonance: 0.5, type: 'notch',    fs: 44100 })

Circuit: Oberheim SEM (1974), Two Voice, Four Voice, Eight Voice vs Moog/Korg: 2-pole like Korg35 but true state-variable topology; LP/HP/BP/notch from one circuit; warmer resonance character

| Param | Default | | |---|---|---| | fc | 1000 | cutoff frequency, Hz | | resonance | 0 | 0–1; damping R = 1 − resonance (inverted — resonance=1 gives R=0, max resonance); bandpass peak gain is exactly 1/(2R) | | fs | 44100 | sample rate, Hz | | type | 'lowpass' | 'lowpass', 'highpass', 'bandpass', or 'notch' |

Pass the same params object on every call to persist the 2 integrator states across blocks.

Use when: multimode synth filter (LP/HP/BP/notch from one set of coefficients) with warm, musical resonance — mode-switch by changing type without recomputing coefficients.

Part of @audio/filter — the filter family umbrella. This README is generated from the umbrella docs.

MIT © audiojs