"Spring2 uses conventional signal processing techniques to model the well-known spring reverb effect. While significantly more cpu power would be required to achieve closer emulation using this method, especially to model the dispersive characteristics more accurately, this version is intended as a compromise between what is possible and what is sensible. The impulse response of this effect is generally similar to that of a physical spring.
Spring2 allows the length and dispersive frequency of up to three springs to be configured and includes a model of the amplification transformer."
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Source via Music Informatory