Spring Reverb Device
The reverb effect essentially represents a collection of delayed sound repetitions. Bell Labs company invented and patented the original spring reverb device. The reason for its creation was because they wanted to simulate the delays which were occurring over long telephone lines. Additionally, one of the first artificial reverbs is based on spring-based delay device. Spring reverbs provide a relatively simple method for creating reverberation effects. Furthermore, they add vintage character and grit to any audio track. Guitar amplifiers frequently incorporate spring reverbs due to their compact construction and low cost. Spring reverberators were once widely used in semi-professional recording due to their modest cost and small size.
History of Spring Reverb
The year 1939 marked a start of further development of the spring reverb. In that year Hammond company engineers wanted to add some “life”” into the dry sound of the organ instrument. Even Hammond company didn’t make spring reverb immensely commercially popular, they use it to enhance the sound of their instruments. Early versions used two 3`-long springs, with the addition of some of them being immersed in non-evaporative oil. They were minimally effective but a definitive improvement over no reverb at all.
As time passed, engineers and designers dispensed with the oil and discovered that 3 springs give a smoother response than only two. They have further improved the electrical components in a way of having a transducer on one end in order to introduce vibrations into the springs and a pickup at the other end to gather the strings vibration for amplification. Later on, spring reverb becomes more commercially exposed. This is because in early 1960`s Leo Fender added a Hammond spring reverb to his guitar combo. Afterwards, mass manufacturing by Marshall and Peavey followed.
Operation Principle
In its core spring reverb is an electromechanical device that uses a system of transducers and steel springs in order to simulate reflections. The operation principle is rather simple. An input transducer vibrates with respect to the input signal. Furthermore, a coiled spring is attached to the transducer and the vibrations transmit through it. When vibrations hit the output transducer on the other end of the spring, they are converted to the output signal. In addition, parts of vibrations bounce back onto the spring and then bounce back and forth between the ends. Such reflections are identical to those bouncing between “ surfaces in one-dimensional space”
Multiple Transmission Springs
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.
Spring Reverb Flaws
Besides having a certain readily recognizable artificial sound, in many cases, spring reverb units tend to be inflexible in adjusting the length of the reverb (decay ) and other characteristics that are important in varying the character of the reverb sound. Some of the high-quality spring reverb units used mechanical methods for varying the length of the decay, providing a relatively limited degree of flexibility. Other flaws include mechanical pickup of vibrations and a very limited ability to handle strong transients from percussive instruments.
Additional Resources & Source Texts
https://www.amplifiedparts.com/tech-corner/spring-reverb-tanks-explained-and-compared
