# Three springs, because one spring would just ring

> A spring reverb tank drawn from above shows three springs of different gauges, and the reason there are three is that a single spring only makes one boing at one pitch.

August 19, 2026 · https://justog.club/stories/spring-reverb-tank

Three helixes stretched between two ends, drawn from directly above. Each one has a slightly
different coil pitch. A 1 is stamped at one end, a 3 at the other.

One spring, tightly coiled. One spring, loosely coiled. One in between. Nothing else is in the box.

## What is this shirt actually showing?

The inside of a spring reverb tank, seen from above with the lid removed — three springs of
different gauges stretched between a transducer at either end.

A signal goes into one end as a vibration, travels the length of the springs, and comes out the
other end delayed and smeared. The tank itself is a long, narrow box built to keep three loose
lengths of wire under a fixed amount of tension, which is most of what there is to see.

## Why does a single spring only make one boing?

Because a spring under tension has a natural rate it rings at, the way a struck bell has a pitch,
and one spring can only offer that one rate back.

Send a sharp signal down a single spring and it comes back as a recognisable, repeating boing at
one frequency — useful for an effect, but nothing like the sound of a real room, which reflects a
sound at every frequency at once. A single spring is a single note played back at you; a room isn't
a note, it's a chord.

## Why does having three springs of different gauges fix that?

Because three springs of different gauge each ring at a different rate, and the ear can't separate
three overlapping decays as three — it hears one smeared return.

Tighter coiling means a higher pitch of ring, looser coiling means a lower one, and stacking three
different pitches close together is the cheapest way anyone has found to fake the way a real space
returns a sound across a whole range at once rather than at a single note. No circuit does the
mixing. The three lengths of wire just sit there under tension and do it on their own.

## Can a real reverb tank's markings go on a shirt like this one?

A manufacturer's badge or model name on a real tank is theirs, licensable the ordinary way if a
particular unit is the point of the print.

The two numbers on this one, 1 and 3, aren't a maker's mark — they're position labels on the
transducer ends, the kind of thing stamped into metal on a factory floor rather than designed as
identity. Three springs under tension, a box, two transducers: that's a description of how the
mechanism works, and a mechanism belongs to nobody.

## Does this trick work anywhere other than a guitar amp?

Anywhere a real acoustic space is expensive or impossible to have, and a physical trick like this
one is what a person reached for instead.

[The inside of a valve amp with the lid off](/stories/valve-glowing-amp-guts) is the same
kind of object — a box most people only ever hear the output of, opened up so the mechanism is the
picture rather than the sound it makes. A spring tank earns its place on the same chest for the
same reason: it's a physical answer to a problem, still visible, long after most of that problem
got solved with a chip instead.

## Isn't three lengths of wire a strange thing to put on a shirt?

Only if the wire is read as decoration rather than as the part doing the work.

Most of what makes a sound convincing lives in parts nobody looks at — a resistor, a coating, a coil
of wire under just enough tension. This print is making the case that the wire is exactly as
interesting as anything with a light on it, because it's the part actually responsible for the
effect rather than the part with a knob on the front.

## Does it print well?

Yes — three long, regular helixes at different pitches are strong, repeatable line work.

Charcoal against a rust orange ground keeps every coil legible without needing a second ink for the
line itself; the differences in coil pitch read clearly at chest size as long as each spring is
drawn coarser than a literal wire diameter would be —
[fine detail below the weave's floor just fills in](/stories/microphone-grille-mesh), and a
tight coil is exactly the kind of detail that risks it.

## How do I get one made?

Describe the tank at [JustOG](/) — how many springs, how different the pitches should look, and
what the end labels should read. Pick a direction, drag the crop frame, see it composited on the
real garment, and it's made to order and shipped.

Designs other people have published are in the [shop](/shop).

Three lengths of wire under tension in a box, and between them they're doing the work of a room.