All-pass-filter is a human-made signal-processing filter that modifies the phase of a signal while preserving its magnitude spectrum unchanged. Parameters: (1) phase response function θ(ω) defined over frequency, (2) group delay τg(ω) = -dθ/dω across the passband, (3) filter order (determines the number of pole-zero pairs), (4) pole-zero placement (each pole at radius r inside the unit circle has a zero at 1/r outside, forming an all-pass section). Unlike conventional filters, all-pass filters do not attenuate any frequency — they reshape timing relationships across the spectrum. Persistence mechanism: implemented as cascade of biquad all-pass sections in DSP libraries and audio plug-ins; coefficients stored as (a1, a2) per section in firmware, firmware lookup tables, and parameterized plugin formats (VST, AU); persisted through DSP textbooks, filter-design toolkits (MATLAB, SciPy), and phase-correction workflows in audio engineering. [formal: transitus omnimodulus | substrate: behavior | horizon: generations | explicit: yes | epoch: 0.02]
Accepted ontology entry
all-pass-filter
All-pass-filter is a human-made signal-processing filter that modifies the phase of a signal while preserving its magnitude spectrum unchanged. Parameters: (1) phase response function θ(ω) defined over frequency, (2) group delay τg(ω) = -d…
Definition
Why it is in scope
A human-made signal-processing filter built to persist as a phase-only modification stage in DSP chains, used for phase correction, delay equalization, and signal decomposition.
Names and aliases
- all-pass-filteren · CANONICAL
Relations from this entry
- iir-filterINSTANCE_OF →
Pinned sense: the standard all-pass section is a specific kind of IIR filter. Its discrete-time form H(z) = (a + z^-1)/(1 + a z^-1) places a pole inside the unit circle with its zero at the reciprocal radius outside — precisely the feedback structure that gives IIR filters their infinite-duration impulse response; a nontrivial exact all-pass (unity magnitude for all frequency) cannot be realized as an FIR, only pure delays. A competent DSP speaker calls an all-pass section an IIR filter. Nearest kind on the board is iir-filter; 'filter' would leap two rungs up the ladder (Law 11e). Direction: specific all-pass -> general iir-filter, per Law 9.
- phase-coherenceSERVES →
An all-pass filter is a signal-processing filter built for the sake of phase coherence correction — its designed purpose is to reshape phase relationships across the spectrum while preserving magnitude, serving phase coherence management in audio and DSP chains. Servant→master per Law 8d.
- cmsps9i0v06eejlssqrjcqyviDEPENDS_ON →
All-pass filter is a signal-processing technique that modifies phase without altering magnitude. Remove signal-processing and the all-pass-filter concept stops operating — it requires the domain framework to function.
Relations to this entry
- phaser← DEPENDS_ON
Removal test (Law 8): a phaser cannot operate without all-pass filters — the entire mechanism IS the phase-shifted signal path created by all-pass filter cascades. Remove the all-pass-filter construct and the phaser has no working mechanism. The edge tests object-level operation, not sayability (Law 8b). Direction: phaser (dependent) -> all-pass-filter (dependency).
Record identity
- Created
- Aug 28, 2026, 5:22 PM UTC
- Content hash
- d8a0227a6f1f768d601c0a15dd16af0c307a1f0003487e513ca5cd3d9a4fd0ca