SPRING REVERBS: The Mechanical Magic Behind the Boing

Spring reverbs are one of those audio technologies that never lose their charm. There’s something raw, unpredictable, and beautifully gritty about them. Maybe it’s their long-standing connection to Reggae and Dub. Maybe it’s the physicality of the springs resonating in a metal tank. Whatever it is, spring reverbs bring a unique character that digital emulations still chase after.

Let’s dive into the history, mechanics, and sound of these fascinating devices, and explore how you might use them creatively in your productions.

A BIT OF HISTORY

The spring reverb is an electro-mechanical reverberation device invented in the 1930s.

It first made its debut thanks to Laurens Hammond, the mind behind the legendary Hammond organs.

Originally, organs were designed for churches, where the natural acoustics of large cathedrals provided plenty of reverb. But as church architecture shifted towards more acoustically “dead” spaces (often designed to favour speech clarity over musical resonance) Hammond needed a way to add artificial space to the sound. That’s where the spring reverb came in.

The technology gained serious traction in the 1960s when Leo Fender (yes, the same guy who gave us the Stratocaster) integrated spring reverb tanks into his Vibroverb guitar amps. From there, spring verbs found their way into surf rock, psychedelic mixes, and of course, the echo-drenched landscapes of dub reggae.

HOW IT WORKS

At its core, a spring reverb is a physical simulation of reverb using (you guessed it) springs.

Here’s the breakdown:

• One or more springs are suspended inside a metal tank.

• An input transducer converts your audio signal into mechanical vibrations.

• These vibrations travel along the spring, bouncing, twisting, and overlapping.

• An output transducer picks up the resulting motion and converts it back into an audio signal.

  
  

This creates a reverb that’s resonant, gritty, and often chaotic in the most musical way.

Because spring reverb tanks are inherently mono, you’ll need two separate units to create a stereo image. But sometimes that mono, centered vibe is exactly what a mix needs, especially in genres that thrive on tension and movement.

WHAT DOES IT SOUND LIKE?

There’s a reason people describe spring verbs with words like metallic, boingy, gritty, and warm.

The reverb tail is full of character, often a little unpredictable, sometimes even borderline unstable, but in a way that adds life, depth, and texture.

Spring reverbs don’t try to mimic real spaces. Instead, they create their own artificial sonic environments. That makes them incredibly useful when you want to add vibe rather than realism.

KEY FACTORS AFFECTING THE SOUND:

• Tank size: Larger tanks generally have longer, smoother decay.

• Spring count & configuration: Two-spring tanks tend to sound vintage and gritty. Three-spring tanks are smoother and deeper.

• Spring material & tension: These change the tone and response.

• Transducers & circuit: The drive and recovery circuits heavily influence colouration. Inside most tanks, you’ll find two or three springs:

• Two springs: more flutter, more bite, classic vintage tone.

• Three springs: thicker, smoother tail, more low-end fullness.

A three springs reverb tends to generate a smoother, fuller, and bigger sound with more lows.

A two springs reverb has more grit and flutter and it sounds more vintage.

TYPES OF TANKS

Spring reverb tanks are standardised in size and configuration.

The most commonly found today are:

• Type 4 – 16.5 inches, usually 2 springs

• Type 8 – 9.5 inches, usually 3 springs

• Type 9 – 16.5 inches, usually 3 springs

  
  

(Older Type 1 units are now discontinued and have been replaced by Type 8.)

Tanks are also classified by their input and output impedances, which must match the reverb circuit.

For example:

Input impedance:

• A = 8Ω

• B = 150Ω

• C = 200Ω

• D = 250Ω

• E = 600Ω

• F = 1475Ω

  
  

Output impedance (recovery stage):

• A = 500Ω

• B = 2250Ω

• C = 10kΩ

Mismatched impedance can result in distorted or weak output, so if you’re building or repairing a unit, these values are essential.

TANK MOUNTING

Since spring verbs rely on mechanical vibrations, isolation is critical.

Any external rumble, like someone walking across the floor, can be picked up by the tank and ruin the sound.

That’s why tanks include rubber dampers or foam padding, and why manufacturers specify mounting orientation.

Here's how tanks are typically mounted:

• A – Horizontal, open side up

• B – Horizontal, open side down

• C – Vertical, connectors up

• D – Vertical, connectors down

• E – One end input up

• F – One end output up

If you're modding or building your own unit, following the correct orientation avoids unwanted mechanical noise.

REVERB DECAY TIME

Just like digital reverbs, spring tanks come with different decay times:

• Short (1) – 1.2 to 2 seconds

• Medium (2) – 1.75 to 3 seconds

• Long (3) – 2.75 to 4 seconds

  
  

Longer decay times are great for dub effects and psychedelic soundscapes, while shorter ones can subtly thicken a vocal or snare without cluttering the mix.

ANALOG vs PLUGINS vs CONVOLUTION

ANALOG UNITS:

There’s something special about the organic chaos of an analog spring verb.

That randomness, the way the springs resonate, collide, and feed back, can be hard to fake.

Analog units like the Fender Reverb Unit, Orban 111B are prized for this.

Downsides? They’re bulky, sensitive to movement, and require some maintenance.

PLUGINS EMULATIONS:

There are plenty of plugin options out there, from Waves Magma Springs to Arturia Rev Spring-636, and even DAW stock reverbs that offer spring-like presets. These are great for convenience and creative tweaking, but they often lack the tactile unpredictability of a real tank.

CONVOLUTION:

For the most realistic recreation, convolution reverbs with high-quality impulse responses (IRs) are your best bet. They capture the unique flavour of a specific spring unit, but they still lack of that random behaviour.

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SHOULD YOU USE ONE?

If you work in a mastering studio, spring reverbs aren’t usually the go-to tool.

But if you’re a mixing engineer or producer looking for a unique spatial effect, they can add tons of character to guitars, snares, vocals, or even synths.

They’re especially useful if you want to break out of the digital reverb “clean zone” and inject a bit of grime and nostalgia into your track. Whether you opt for an analog tank, a plugin, or convolution IRs, spring verbs can bring a sense of movement that algorithmic reverbs just can’t replicate.

IN SUMMARY

• Spring reverbs are mechanical devices using metal springs to create reverb.

• They offer a unique, boingy, metallic sound perfect for adding character.

• Tank size, spring count, and mounting orientation all affect the tone.

• Decay time is chosen via classification numbers: 1 = short, 3 = long.

• Analog units are organic but impractical for some; plugins offer flexibility.

• Convolution IRs are the best middle ground for realism in digital workflows.

  
  

Final Thoughts

In a world dominated by hyper-clean reverb plugins, spring verbs are a welcome dose of imperfection. Whether you're exploring vintage tones, building a custom unit, or diving into convolution reverb in your DAW, the spring verb remains a sonic playground full of character.

Curious how spring reverb could fit into your next project? Feel free to get in touch, I’m always up for a good gear chat or to help you shape your sound with a professional touch/feedback.

If your project instead is mastering-ready feel free to Get in touch we offers professional Online Mastering and Stem Mastering services to help you releasing your music confidentially on streaming platforms, vinyl and CD.