The Electro-Voice Model 667A Broadcast Dynamic Cardioid — April, 1965
Description and Applications The Electro-Voice Model 667A is a dynamic cardioid microphone designed for boom mounting in broadcasting and recording. Not simply an improvisation on existing equipment, the 667A has been created specifically to overcome the problems encountered in boom applications. A specially designed shock mount provides effective isolation from mechanical noise, and the integral Acoustifoam windscreen virtually eliminates noise caused by motion of the microphone through the air. Unusually light in weight, the 667A is easily maneuverable. The shock isolation and windscreen systems are readily removable for service or replacement. Very low sensitivity to induced hum permits use close to lights, AC lines, etc.
An outstanding feature of the 667A is the self-contained computer-type programming board which permits a total of six different frequency response curves. The programming panel is part of a versatile passive equalizer which is completely self-contained; no external equipment or special connecting cables are required. The variations from flat response, thus made available, permit the 667A to overcome acoustical problems and background noise, make possible special effects, and enable its use mixed with existing microphones of differing responses.
The use of Continuously Variable-D, a highly developed version of the patented Electro-Voice Variable-D principle, makes possible extremely uniform rejection of unwanted background noise. The rejection pattern is unusually symmetrical in all planes. The CV-D principle, as employed in the 667A, uses a matched pair of slotted tubes coupled to the back of the diaphragm. The acoustic length of the tubes varies inversely with sound frequency, permitting them to phase out unwanted sound from all portions of the audible spectrum for maximum front-to-back ratio. The mic’s single moving element is a diaphragm of Electro-Voice Acoustalloy which is impervious to effects of temperature, humidity, and shock. CV-D permits optimum diaphragm damping, impossible with less sophisticated designs, for minimum wind and mechanical noise pickup and proximity effect.
Generating Element: Dynamic
Frequency Response: Uniform 40 to 10,000 Hz (See Figure 2)
Polar Pattern: Cardioid (See Figure 3)
Impedance: 50, 150, 250 ohms, selected at rear of case by moving one pin
Output Level: -51 dB on 250 or 150 ohm tap, -52 dB on 50 ohm tap