Kurzweil K2500 Reference Manual page 27

FXAlg #14: Grand Plate
This algorithm emulates an EMT 140 steel plate reverberator. Plate reverberators were manufactured during the
1950s, 60s, 70s, and perhaps into the 80s. By the end of the 1980s, they had been supplanted in the marketplace by
digital reverberators, which first appeared in 1976. While a handful of companies made plate reverberators, EMT
(Germany) was the best known and most popular.
L Input
R Input
A plate reverberator is generally quite heavy and large, perhaps 4 feet high by 7 feet long, and a foot thick. They
were only slightly adjustable, with controls for high frequency damping and decay time. Some were stereo
in/stereo out, others mono in/mono out.
A plate reverb begins with a sheet of plate steel suspended by its edges, leaving the plate free to vibrate. At one (or
two) points on the plate, an electromagnetic driver (sort of a small loudspeaker without a cone) is arranged to couple
the dry signal into the plate, sending sound vibrations into the plate in all directions. At one or two other locations,
a pickup is placed, sort of like a dynamic microphone whose diaphragm is the plate itself, to pick up the
reverberation.
Since the sound waves travel very rapidly in steel (faster than they do in air), and since the dimensions of the plate
are not large, the sound quickly reaches the plate edges and reflects from them. This results in a very rapid build-
up of the reverberation, essentially free of early reflections and with no distinguishable gap before the onset of
reverb.
Plates offered a wonderful sound of their own, easily distinguished from other reverberators in the pre-digital
reverb era, such as springs or actual ÒechoÓ chambers. Plates were bright and diffused (built up echo density)
rapidly. Curiously, when we listen to a vintage plate today, we find that the much vaunted brightness is nothing
like what we can accomplish digitally; we actually have to deliberately reduce the brightness of a plate emulation
to match the sound of a real plate. Similarly, we find that we must throttle back on the low frequency content as well.
A plate reverberation algorithm
Allocation Units: 3
Dry
PreDelay
PreDelay
Dry
Diagram of Grand Plate reverb
Plate
Wet
Reverb
Algorithm Reference-27
FXAlg #14: Grand Plate
Out Gain