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Bob Quintal
 
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Default How to measure a dynamic mic's output impedance?

"Andy" wrote in
:

Hello,
I'm a total beginner. How do I measure a balanced or
unbalanced dynamic mic's impedance? Can I do it with a
multimeter and, if so, how?

Thank you,
Andy

Applying a multimeter to a microphone's output may damage it.
Besides, the multimeter would give a DC resistance value, not a
true impedance, which is the resistance plus reactance at a
particular frequency, usually 1KHz.

The easiest way is to face the microphone to a speaker, play a
tone to the speaker, measure the open circuit output voltage,
then terminate the output with a resistance of approximately the
expected output impedance, remeasure the output of the
microphone and calculate the true impedance from the change in
voltage and resistor. When the termination is equal to the
source impedance, the voltage will be half.

The question is WHY? all microphones (except externally powered
carbon microphones) are designed to work into a higher impedance
than their own output impedance. The actual impedance value is
not really important as long as it's less than a tenth of the
preamplifier's input impedance.

Microphones manufactured today are all fairly low impedance,
about 100 to 200 ohms. Typical mixer inputs are 2.4 to 3.3
Kohms.

--
Bob Quintal

PA is y I've altered my email address.