bass-foundry/docs/quench/README.md

# Quench

Quench clips the top of the mix as hard as you like and lets the sub pass clean.
Current version **0.1.0**.

Riddim and dubstep masters are clipped hard. A plain clipper clips the sum of
the sub and everything above it. Near the sub's peaks only one side of the top
gets clipped, so the clipping takes energy out at the sub's rate: the sub loses
level, and the low end fills with products that were not in the mix. Quench
splits the signal at a frequency you set, never clips the sub, and clips only
the top, in the room the sub leaves under the ceiling.

![Quench](assets/editor.png)

## Install on Windows

Copy `Quench.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio
2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find
installed plugins. Load Quench last on the master or on the bass bus. Keep the
font license with redistributed packages.

## Work with it

1. Put Quench where you would put a clipper: last on the master, or last on
   the bass bus. Before a true-peak limiter is fine.
2. Set **Ceiling**, the highest output peak.
3. Set **Split** above the highest sub note, or at Anvil's Split when Anvil
   makes the sub. Everything below Split passes without clipping.
4. Raise **Drive** until the top clips as hard as you want. The panel shows
   how far the top is clipped.
5. Press **PLAIN** to hear a plain clipper at the same settings, then
   **QUENCH** again. **DELTA** plays only what Quench takes away. The listen
   choice is not saved and goes back to QUENCH when the editor closes.

The panel shows:

- **Low end changed by**: how much the band below Split differs from the
  input, against the sub's level, for Quench and for a plain clip of the same
  signal. Lower is cleaner. It reads "—" when no sub plays.
- **Top clipped by**: how far the top's loudest peak went past its room.
- **Sub peak · room left**: the sub's peak after Drive and the room it leaves
  the top under the ceiling.
- The scope: the output (grey), the sub band (blue), and the sub plus or minus
  the top's room (thin lines). The output stays between the thin lines.

Other controls:

- **Hold** keeps the room the sub's peak needs for this long. With a hold
  longer than half a period of the lowest note (17 ms at 30 Hz), the top's
  clip level stays steady through the sub's cycle and the top does not pump
  with the sub. Shorter holds give the top a little more room between sub
  peaks, and that room then changes at the sub's rate.
- **Soft** bends the top's clip: 0 % is a hard clip, 100 % a soft curve from
  the start. The ceiling stays a hard limit.
- **Bypass** crossfades to the input, delayed by the latency.

When the sub alone reaches the ceiling, the top has no room left. The panel
then warns: lower Drive or the sub. A safety clip still holds the ceiling, and
that clip does cut the sub.

### How it works

A Linkwitz–Riley crossover splits the signal at Split. The sub passes. The top
is clipped symmetrically at the ceiling minus the sub's held peak, so the sum
of sub and top never goes over the ceiling.

Clipping the top also makes products below Split, for example difference
tones between its partials. Quench high-passes what the clip removed at Split,
so those products do not reach the low band. High-passing lets a few peaks
overshoot. Two correction passes clip those again and high-pass the correction,
and a final hard clip at the ceiling takes the small rest. All of this runs at
4× oversampling. A safety clip after the downsampler catches the filters'
ringing; it reads "idle" or a few hundredths of a dB.

Measured on a 50 Hz sub at −10.5 dBFS under a top of five unrelated partials
peaking about 6 dB over the ceiling:

| | Sub level | Low-band products |
| --- | --- | --- |
| Plain clip | −2.2 dB | −16 dB |
| Quench | +0.04 dB | −35 dB |

Low-band products are everything below 110 Hz except the sub, against the
sub's level.

Quench pays for this in loudness. The top gets the room on the sub's quieter
side only, so at the same ceiling Quench measured 0.5–1.2 dB lower in RMS
than a plain clip. Add Drive to make up for it.

## Timing and limits

Latency is the oversampling filters: 37 samples (0.8 ms at 48 kHz), reported
to the host for delay compensation.

The split is a slope, not a wall. A top whose own fundamental lies near
Split, for example a distorted patch an octave above a 49 Hz sub, is partly in
the sub band. That part passes unclipped and takes up room, and Quench helps
less there: on a saw top at 98 Hz it changed the low end about as much as a
plain clip. Keep the top's lowest partial at least an octave above Split.

Quench keeps the ceiling on sample peaks. True peaks between samples can
still go a little over it: put a true-peak limiter after Quench if the master
needs one. Each channel is clipped on its own; Quench does not link the
channels or turn the sub to mono.