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@audio/filter-oberheim

Status calibrated

npm1.2.1licenseMIT

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

Overview

Install
Updated
Family
filter, 16 packages under it
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shape
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 dB/oct-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⁡\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.

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