Factory Equalization And De-Equalization
Canonical Definition
Factory de-equalization is the measured compensation of repeatable OEM transfer-function shaping so an aftermarket system receives a defined reference response. It may include magnitude, level, delay, or all-pass correction, but it must not be treated as a blind inverse of position-dependent cancellation, dynamic processing, clipping, or missing bandwidth.
Classify The Processing First
| Observed behavior | Possible class | Correction implication |
|---|---|---|
| Same magnitude curve at every volume | static EQ or crossover | may be a candidate for limited inverse correction |
| response changes with volume | dynamic EQ, bass rolloff, limiting, or compression | requires level-dependent strategy or another source point |
| magnitude similar but phase changes | delay or all-pass processing | requires stable timing reference and phase-aware decision |
| deep dip moves with channel, load, or measurement condition | interference, noise, missing content, or invalid measurement | do not blindly invert |
| output stops increasing or distorts | limiting or clipping | move the operating point or integration layer; EQ cannot restore lost information |
Measure Across The Operating Range
- Use a repeatable electrical measurement at the selected integration point.
- Capture low, middle, and high source-volume settings.
- Repeat for every source mode, tone-control state, surround mode, and relevant vehicle state.
- Record magnitude, phase or impulse delay where valid, noise, clipping, limiting, and available bandwidth.
- Compare left, right, center, surround, and band-limited channels separately.
Define The Correction Contract
Before generating an inverse, record:
- the desired electrical reference response
- frequency range and smoothing or resolution
- maximum positive and negative correction
- whether delay and all-pass behavior will be preserved or countered
- which volume and source modes the correction covers
- source noise, clipping, and minimum usable signal
- DSP and analog headroom after correction
What Not To Invert
- a frequency region absent because of a steep crossover or source limitation
- a deep cancellation created by incompatible contributors
- noise-floor structure or measurement artefacts
- clipped or heavily limited source output
- dynamic behavior represented by only one volume setting
- factory delay or all-pass processing that is intentionally supporting a multi-seat design unless the new design replaces it deliberately
Electrical De-EQ Is Not Final Acoustic EQ
The de-equalized source should be measured independently at line level. Once its response, headroom, noise, and stability are verified, the aftermarket system still needs separate acoustic crossover, level, timing, target-curve, and EQ work.
Keep an uncorrected comparison preset. If a source mode changes its processing, the correct response may be a different preset, a different integration point, or no inverse correction.