The following Sound Samples were created by Ryan Fergon from the band Soulajar.
Signal path: Music Man Albert Lee with Dimarzio 36th Anniversary PAFs -> Spring Reverb 3-spring -> Siegmund Midnight Blues with 2x12 Tone Tubby Red Alnico cabinet.
The recording was done with one large diaphragm condenser mic with no EQ or compression and everything flat through a tube mic preamp.
I made these Sound Samples showing the difference between the 2 and 3 spring tanks.
The amp, reverb and guitar settings are the same on both sound clips. Only the tanks are switched.
The amp is the Sound King with 15" Field Coil speaker.
The guitar is the Suspense with P90 pickup and Volume and Tone up.
I upgraded a large diaphragm condenser tube mic with a Micro Tube, Neumann U47 replacement capsule and Jensen transformer plugged into the Simplex Mic Pre
2 Spring Tank
3 Spring Tank
Spring Reverb Tank Referrences
Historical use in Musical Instruments
Morrish, John; The Fender® Amp Book; pp. 25, 26 :
Laurens Hammond of Illinois popularized the use of artificial reverberation devices through his church organs in the 1940s and 1950s. The early (pre-B-3® ) Hammond® organs were sold to churches on the principle that organ music is greatly enhanced by reverberation, but the minister's speech in the church is hampered by reverberation. Therefore, churches were designed to be acoustically dead, and the Hammond® organ had to have its own artificial reverberation.
Reverberation made its debut in the Fender® line as a separate item, using a spring unit bought from Hammond® in 1961. It was first incorporated in a Fender® amplifier with the Vibroverb® of 1963 and then spread widely throughout the amp line, just as vibrato/tremolo had before it.
The Reverberation Effect
Scott, J. L. - Chief Engineer; Accutronics® document 126-00005 (February 1, 1978) :
A listener standing some distance from a sound source will perceive sound that is actually a combination of direct sound and indirect sound that has been reflected from the boundaries of the listening area. The reflections are referred to as reverberation. Reverb can enhance the perceived sound from a source by adding depth, color and liveliness. Reverb can be thought of as being composed of two parts:
1) Early reflections shape the listener's conception of room size
2) Cluttered reflections convey the liveliness of a room
The Significance of Multiple Transmission Springs
Imagine you are inside a large hall and you clap your hands once. The length of time required for the arrival of the very first reflections is called the delay time (usually on the order of tens of milliseconds, e.g. 33 ms) and is related to the volume of the room (or distance of the reflective surfaces from the listener). The number and density of reflections increases rapidly with time and they become cluttered while simultaneously decreasing in level until they are no longer audible. The length of time required for a sound to decrease in level by 60 dB is called the decay time (usually on the order of a few seconds, e.g. 3 s) and is related to the acoustical properties of the reflective surfaces in the listening area. For example, poured concrete walls will reflect more (absorb less) acoustic energy than drywall.
The use of multiple transmission springs helps to improve the reverb characteristics. A listener in a large hall with natural reverberation is not usually standing the same distance from each reflective surface. Naturally, there will be reflections from different surfaces having different delay times. The use of multiple transmission springs with different delay times serves to simulate a more natural ambiance, as well as improving the overall frequency response because one spring's response will fill voids or holes in the other spring's response. Vintage Accutronics® specs list the following delay times per spring:
Short 33 ms
Long 41 ms
Medium 37 ms
Decay time should be selected to suit the application. The same reverberation decay time that enhances and adds liveliness to the sound of the guitar can make speech unintelligible. General decay time suggestions traditionally used for specific instruments:
Guitar - Long (2.75 to 4.0s)
Organ - Medium (1.75 to 3.0s)
Vocals - Short (1.2 to 2.0s)