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The Electro-Voice Model 664A
Dual-Z dynamic supercardioid microphone

Electro-Voice 664A

Description and Applications
The Electro-Voice Model 664A is a rugged dynamic supercardioid micro­phone designed to provide reliable service in the many situations in which directional microphones are re­quired. Nearly all directional microphones exhibit proximity effect (a boost in low frequency response) when used near a sound source. The 664A does not, because it utilizes the Electro-Voice patented Variable-D principle. Therefore, the 664A will respond more accurately in those situations that demand the talker, singer, or instrument to be close to the microphone (see Figure 1).

Electro-Voice Model 664A typical frequency response

The principle underlying “close miking” is that the sound pressure level at the microphone increases 6 dB each time the distance from the sound source is halved. Obviously the output level of the microphone then increases proportionately, resulting in a louder sound system or a better signal-to-noise ratio on a recording. “Close miking” can also reduce the often undesirable effects of reverberation as well as provide an increased separation among competing sounds.

Polar response

As a supercardioid, the 664A provides maximum rejection at 150 degrees rather than the 180 degrees of a cardioid. This assures greatest rejection in the horizontal plane when the microphone is tilted in its most natural position, 30 degrees from the horizontal (as on a desk or floor stand). The polar response (sound source at varying angles to the microphone diaphragm) is exceptionally uniform with little or no off-axis coloration. This is important, because it means the microphone’s response in actual use will closely parallel the anechoic on-axis curve (see Figure 2). Many cardioids have good on-axis response, but radically different response at other angles, meaning the microphone’s published curve (undoubtedly on axis, anechoic) is of little practical use.

The 664A uses the mechanical nesting concept of design, providing a nearly solid mechanical structure that is highly resistant to damage from shock. The exclusive non-metallic Electro-Voice Acoustalloy diaphragm is virtually unaffected by extremes of atmospheric conditions. The case is made of pressure-cast zinc with chrome plating.

Impedance Change Instructions
The 664A features a new impedance selector combined with the on/off switch. Either balanced 150 ohms or unbalanced Hi-Z output may be selected and locked with the flip of a switch and the turn of a screw. No wires to change, and the selected impedance is plainly indicated.

On-off and impedance-changing switch

Look at the on/off switch located on the microphone stud (see Figure 3). Through the opening for the slider you will see either the word Hi or Lo indicating the present impedance. To change to the opposite impedance, remove the upper switch screw, the one nearer the microphone. Now push the switch button toward the indicated impedance (Hi or Lo). The switch button will slide the undesired impedance indication out of sight (push it all the way), and bring the desired impedance into view at the opposite end of the slot. Replace the switch screw and tighten. That’s all there is to it. The impedance has been switched to the condition indicated.

Changing impedance


  • Element: Dynamic

  • Frequency Response: 90 to 13,000 Hz (See Figure 1)

  • Polar Pattern: Supercardioid (See Figure 2)

  • Impedance: 150 ohms/Hi-Z, selectable

  • Impedance Change: Combined with on/off switch on stud (See instructions)

  • Output Level, 150 Ohm Impedance: -56 dB (0 dB=1 mW/10 dynes/square centimeter)
    High Impedance: -55.5 dB (0 dB=1 volt/dyne/square centimeter)

  • EIA Sensitivity Rating, 150 Ohm Impedance: -150 dB
    High Impedance: -150.5 dB

  • Diaphragm: Electro-Voice Acoustalloy

  • Case: Pressure-cast Zinc

  • Finish: Satin chrome

  • Dimensions: 181.0 mm (7.13 in.) maximum length,
    38.1 mm (1.50 in.) maximum diameter (tapered shank)

  • Net Weight: 520 g (18.5 oz.), not including cable

  • Cable: 4.6 m (15 ft.), two-conductor, shielded, vinyl-jacketed,
    with Switchcraft A3F connector

  • Optional Accessories:
    314E gray pop filter
    360 gray windscreen
    400 desk stand
    456 carrying case
    PLC-25X 25-foot cable with A3F and A3M connectors
    PLC-25P 25-foot cable with A3F and quarter-inch phone plug connectors
    PLC-25T 25-foot cable with A3F connector at one end and unterminated
    at the other end
Wiring diagram Electro-Voice 664A Dimensions

Quoted from Electro-Voice Model 664A Dynamic Supercardioid Microphone instructions,
Copyright 1983, Gulton Industries, Inc. Part Number 530289-322. Published in 1983.

Instructions cover page

Download the Instructions for this mic.

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