Not too different to the plate reverb, but instead of a metal sheet a metal spring coil is used and this is not fixed as rigidly as the plate. A transducer feeds the signal into the coil and a pickup is used to collect the output as the coil reflects and vibrates. Due to its nature the spring reverb can be quite metallic and dense as it behaves similarly to the plate reverb when it comes to the processing of early reflections.
A single transducer and pickup means the spring acts in mono but running two springs together would create a stereo effect and each side of the channel could be treated separately thus accounting for some interesting stereo effects. The spring can also be ‘pushed’ to create a twang type of effect if the input is driven heavily and this accounts for one of the characteristics of the reverb and because of this it is still being used by guitarists. The tension of the spring/s can be adjusted to create different effects and the springs can also be ‘shaken’ or ‘rocked’ which allows the springs to collide creating huge and thunderous effects. It was not uncommon to use up to three springs.
The sound of the spring reverb is quite distinct and the following examples should reflect this ‘colour’ even when used conservatively. Probably the best spring reverb emulation plugin I have used that is sensibly priced is the Softube Spring Reverb. This vst allows for using up to three springs, adjusting the tensions, the ability to ‘shake’ the springs and additional control over bass and treble.