Spectral Expander

Parameters

Threshold — Per-band level (in dB) below which expansion engages. Each band’s signal above its threshold passes; signal below gets attenuated. Range goes down to −92 dB (the noise floor of K2K’s spectral data) so you can target very quiet material. Set just above the per-band noise to clean up bleed and ambience without affecting program material.

Ratio — How aggressively each band’s signal below threshold is attenuated, 1:1 to 20:1. Spectral expansion at moderate ratios (2:1 to 4:1) cleans up noisy frequencies without sounding like a gate. High ratios approach per-band gating — useful for surgical noise reduction where only specific frequencies need silencing.

Attack — How fast each band recovers (returns to unity) when its level crosses above threshold, in ms. Affects how cleanly the start of notes/hits is preserved per-band.

Release — How fast each band attenuates when its level falls below threshold, in ms. Slower release creates smoother, more natural per-band pull-down; faster release tightens to a more gate-like feel.

Range — Maximum attenuation in dB applied per band, −96 to 0. The “floor” of the expansion — bands at this level can’t drop further. Shallow ranges (−10 to −20) for transparent leveling; deep ranges (−60 to −96) for surgical noise reduction approaching gating.

Additional controls

Knee — Soft-knee transition width in dB applied per-band. Smooths the engagement of expansion around threshold for a more transparent feel.

Bands — Number of frequency bands processed independently, 1–32. Many bands = surgical noise reduction (clean up only the frequencies that need it). Few bands = broader cleanup. 8–16 for balanced cleanup; 32 for hi-res repair work.

Detection Mode — Peak — instantaneous per-bin level. RMS — short-window average. RMS is generally smoother for tonal material; Peak more reactive.

About Spectral Expander

A spectral expander pushes down quiet frequencies per frame, rather than pushing down quiet moments. This is a fundamentally different operation than time-domain expansion — it can clean up tape hiss in just the high frequencies while leaving sustained low-mid material untouched, or pull down room tone in just the low-mid range during quiet vocal passages. It’s surgical in a way that no broadband expander can be. Pair with the Spectral Gate when you need full silence below threshold per-band.

Generated 2026-05-05 from K2K_Dev@96730bdc by scripts/gen_lexique.py. Edit _intros/ or _overrides/, not this file.