Table of Contents
Advertisement
APPENDIX
9. APPENDIX
Operation of the Fx 70 was designed in such a way that all functions and parameters are quickly and easily
accessible. The idea was based on various organ cabinets and the Simulator CLS 222.
For our simulation purposes we did, however, eliminate all the various noises connected with these "ancient
dinosaurs!"
The Fx 70 was equipped with MIDI control possibilities and additional programs to utilize the unique rotor effect
with more modem instruments (organs, keyboards, computers ...) more efficiently. Identifying all the parameters
hidden under Options and Sysex should really be a delight for sound sleuths!
As younger contemporaries are only familiar with these cabinets from records and CD's we have included a brief
description of the mechanics and sound properties thereof.
In the Sixties to the mid-Seventies, the heyday of cabinets, there was an enormous variety of types and
manufacturers. The pictures above correspond with the most common forms produced. The dimensions measured
approx. 80 x 60 cm, the height between 100 and 150 cm. The cabinets weighed anything between 40 and 100 kg.
A frequency crossover was used to supply the two loudspeakers, the bass rotor below and the treble rotor above
with organ signals via power amplifiers integrated in the cabinets. The rotors were partially located in two separate
housings to facilitate transportation.
Sound guide drums (low frequency) and horns were mounted in front of the loudspeaker membranes or
compression drivers. These were pivotable so that the sound could be reflected in all directions, driven by two
(sometimes four) motors. These rotating sound sources led to the unmistakeable sound of the rotor cabinets.
Important contributory physical effects included: Doppler effect (pitch jumps) when passing the listener, panorma
effect via direct and lateral sound emission and room effect due to the creation of a lot of reflections when the
rotors were facing towards the rear. Interference sounds resulted from the slightly varying speeds of the two rotors.
This effect is especially marked when the speed is switched over from stop - slow - fast, as the variety of varying
differences crop up due to the differing rotor masses.
The materials used for housing, loudspeakers and rotors, along with the finish of the materials, play an important
role in the characteristic sound effects produced. Rotors were made of wood, cardboard, polystyrene, aluminium
and plastic.
All the above-mentioned effects and peculiarities were examined and taken into consideration for simulation
purposes involving the Fx 70.
9-1
Advertisement
Table of Contents
