Spring Reverb

A physical model of a vintage spring-tank reverb — the dripping, twanging, dub-friendly "boing" you hear on guitar amps and old dub records. It adds metallic, dispersive space to whatever you feed it, with a built-in dry/wet blend.

How it works

Real springs don't reflect sound cleanly; high frequencies travel faster than low ones, so a sharp transient smears into a descending chirp — the signature spring "boing." This module recreates that with a long cascade of dispersive allpass filters wrapped in a feedback loop, plus a slowly modulated delay that keeps the tail alive and shimmering. The result rings, chirps, and rattles like a real tank rather than smoothing into a polite hall.

Controls

  • Decay — how long the spring rings out, from a short splash to a long, sustained wash.
  • Tone — the color of the tail. Low settings are dark and chirpy, leaning into the dispersive spring character; high settings are brighter and cleaner.
  • Mix — dry/wet blend. At 100% you hear only the reverb (ideal for an effects send); lower it to sit the wet signal under the dry as an insert.
  • Size — the round-trip length of the spring tank, 20 ms-80 ms, which sets its size and tension. Short settings are tight, bright, and metallic; longer ones open into a bigger, slower, more spacious boing.
  • Disp — how many dispersion stages the signal passes through, from 20 to 100. Fewer stages flatten the chirp toward a metallic plate; more pile on the springy, dispersive twang that makes a tank sound like a tank.

Inputs & outputs

  • In L / In R — the stereo signal to drench; the two channels are summed into the mono spring engine.
  • Decay / Tone / Mix / Size / Disp CV — voltage control over each knob; patch an LFO or envelope to automate the space, sweep the spring's size, or modulate the tail.
  • Out L / Out R — the processed stereo result, widened by a decorrelated tail so the reverb spreads across the field.

Tips

  • Feed it short, percussive hits — a drum, a pluck, a stab — and crank Decay to hear the spring chirp and twang at its most characterful.
  • Roll Tone down for classic dub: dark, rubbery, and full of motion.
  • Patch an envelope or LFO into Mix CV to swell the reverb in and out under a part.