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Electro-Voice Model 644
Sound Spot Microphone

Electro-Voice 644

Description and Applications
The Model 644 is a highly directional dynamic microphone utilizing a com­bination of cardioid and distributed front opening designs. This gives greatly extended frontal pickup on the microphone axis, extending working dis­tance over 2.5 times compared to present non-directional type micro­phones. Above 700 cps cancellation of sound at the rear and sides exceeds 20 dB providing unequalled rejection of random noise, reverbera­tion and feed­back without sacrifice of frequency response. The Model 644 allows much greater latitude in loud­speaker place­ment and will solve many spe­cialized problems where mics cannot be placed near the source of sound.

A front acceptance angle at high frequencies of 45° each side of the micro­phone axis also allows best isolation of individual performers when desired. The Model 644 gives improved wind noise rejection compared with con­ven­tional microphones and is much less susceptible to generation of noise from mechanical shock.

Electro-Voice 644, rear The Fawn Beige version The Fawn Beige version


  • Type: Dynamic

  • Frequency Response: 40 to 12,000 cps. See Figure 1

  • Directional Characteristics: Cardioid to 700 cycles, 20 to 25 dB
    of rejection at the sides and rear above 700 cycles. See Figure 2

  • On-Off Switch: Sliding contact shorts microphone
    in “Off” position

  • Impedance: 150 ohms or High Impedance

  • Impedance Selection: Selection is made at cable connector.
    To change from High to 150-ohm impedance, move white lead from Terminal 2 to Terminal 3 on MC4M connector. 150 ohm impedance is balanced to ground

  • Output Level: High Impedance: –53 dB; EIA sensitivity rating: –149 dB
                        150-ohm Impedance: –53 dB; EIA sensitivity rating: –147 dB

  • Diaphragm: Electro-Voice Acoustalloy®

  • Case: Pressure-cast zinc and brass

  • Finish: Satin Chrome or Fawn Beige

  • Dimensions: Maximum diameter 2516". See Figure 3

  • Net Weight: 2 pounds, 9 ounces, less cable

  • Cable Connector: Amphenol MC4M
Frequency response Polar response Dimensions Impedance setting Wiring diagram

Text and illustrations are from Electro-Voice Engineering Data,
644 Sound Spot Microphone,
Part No. 533608, January, 1967.

The Electro-Voice 644 The Electro-Voice 644 The Electro-Voice 644 The Electro-Voice 644 The Electro-Voice 644 The Electro-Voice 644 The Electro-Voice 644 Two-page spread

Download this two-page spread for the 644.

EDS cover

Download the Engineering Data for the 644.

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