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The Electro-Voice Model 951
cardioid crystal microphone (1966)

The Electro-Voice Model 951

The Electro-Voice Model 951

Description and Applications
The Electro-Voice 951 is a crystal, Variable-D® microphone. The cardioid pattern is obtained through the use of two sound entrances located in the microphone case at different distances in back of the diaphragm. These sound entrances, each utilizing the proper acoustical impedance, combine to form one effective back entrance which varies acoustically in distance from the diaphragm, inversely with the frequency. The resulting phase and amplitude conditions produce a uniform cardioid pattern over a relatively wide frequency range. Patented Variable-D maintains frequency response characteristic virtually independent of working distance, thus eliminating proximity effect.

The Electro-Voice Model 951

The Electro-Voice Model 951

A high capacitance Bimorph type crystal, sealed against moisture, assures stable frequency response and long life. High output level (−55 dB) makes the Model 951 highly adaptable to all standard amplifier high-impedance inputs.

The Electro-Voice Model 951

The Electro-Voice Model 951

Mechanical construction of the Model 951 is such that maximum protection against mechanical shock damage is assured. The microphone case is die-cast zinc, with satin chrome finish. An On-Off switch is provided in the stand mounting stud. The microphone may be adjusted for desired position through an included angle of 75°. Standard 58''-27 threads are provided in the base of the stand mounting stud. The Model 951 is equipped with a pop-proof wire mesh grille to minimize wind and breath blasts. It can be used on a floor stand or desk stand, or hand-held.

The Electro-Voice Model 951

The Electro-Voice Model 951


  • Generating Element: Crystal

  • Frequency Response: 50 to 11,000 Hz

  • Polar Pattern: Cardioid

  • Impedance: Hi-Z only

  • Output Level: −55 dB

  • EIA Sensitivity Rating: −155 dB

  • Case: Die-cast zinc

  • Dimensions: 5716'' long × 12332'' diameter (6½'' long including stud)

  • Finish: Satin Chrome or Umber Gray

  • Net Weight: 1¼ pound (less cable)

  • Switch: On-Off; shorts microphone in Off position

  • Cable: 15-foot single-conductor, shielded

  • Cable Connector: Amphenol MC-1F

  • Stand Coupler: 58''-27 thread

Frequency response
Figure 1—Frequency Response

Figure 2—Dimensions

Polar response
Figure 3—Polar Response

Wiring diagram
Figure 4—Wiring Diagram

NOTE: Crystal and ceramic microphone elements function as voltage generators. The use of extremely long cables results in relatively severe attenuation of the signals generated by these devices. Generally, cables longer than 20 feet should not be used.

All text and illustrations on this page are taken from the Engineering Data sheet for this microphone, Part No. 532863, published by Electro-Voice, Inc., which is downloadable immediately below.

EDS cover
Download the data sheet for this mic.


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