The History of Plate Reverb
Back in 1957 EMT, a pioneering German company invented and build the first plate reverb called EMT 140. This model had very large proportions (8ft * 4ft) and weighed more than a quarter of a ton. These original units were quite large and expensive but still cheaper than building a reverb chamber. You can hear the sound of this device on countless hit records from 1960’s and 1970`s.
While mobility of plate reverbs was not an asset, they had better sonic qualities than spring reverbs which came before them. Furthermore, the EMT 140 sound was still not resembling the true natural reverb. It sounded slightly metallic. However, it sounded extremely well blended with any instrument and especially the vocals. The bright, dense and smooth sound of plate reverbs also made them a likely choice for drums.
Sonic Complexity
Plate reverb is a type of audio processor that has a unique design. Comparing to reverb effects that came before plate reverb, it offers a sonic complexity. This means that plate reverb consists of a large plate of metal which vibrates in a two-dimensional way, down the length and across the width of the sheet of steel. An audio signal feeds a driver which is connected directly to the plate causing it to vibrate.
The presence of a plate reverb is unmistakable, but we can notice also that it doesn’t sound anything like the concert hall or cathedral. Plate reverbs have the distinct sonic coloration which modifies the timbre of the instruments. This mechanical system offers a unique strongly flavored sort of resonance. While its mechanical technology is hardly cutting-edge, like most of the modern reverb effects, its sound is still relevant and used in modern productions.
Plate’s Flexibility
Because the plate is excited with blending waves, not compression waves, the speed of propagation is determined by the elasticity and mass distribution of the plate and by the plate’s thickness and suspended tension. Plate reverbs can, therefore, slow the speed of the propagation down to one thousand of the speed of sound in air. A mechanical device much smaller than a hall can generate the reverberation similar in duration to that of a larger hall. Also, plate reverbs offer further advantages, like applying various means of damping. A good example would be placing liquids or porous materials against the plate. By applying these modifications, reverb time is adjustable across the useful range, offering the sound engineer highly desired production flexibility.
Conclusion
Lastly, when sound is transferred through metal, high frequencies tend to travel faster than low frequencies. This, more-less, happens in all mediums but especially when it comes to metal. In a plate, we hear the high frequencies arrive first and the lower frequencies arrive slightly later. This is very important when understanding why a plate reverb may be a better or worse choice than a natural space.
Additional Resources & Source Texts
https://books.google.rs/books?id=sfL7AwAAQBAJ&dq=plate%20reverb&source=gbs_navlinks_s
