[ProAudio] Microphones question

Dan Lavry dan at lavryengineering.com
Sat Jun 12 09:15:05 PDT 2021

Hi Scott,

Yes, and we all know that speakers behave like 8 Ohm resistors :-)

I was hoping that someone would talk about how to measure the electronic 
part of the mic, without contributions from the membrane. I would assume 
that one could replace a variable capacitor membrane with a fixed cap. 
The old carbon mic could be replaced by a resistor. That or similar 
methods to remove the acoustic contributions can help characterize the 
circuit (flatness, noise, impedance...). There are at least 2 ways to 
measure the equivalent source impedance using the Audio Precision 
system. We (designers) measure all sorts of circuits. I don't intend to 
open my mics, remove the membrane and "put the circuit on neutral".

Ideally (or close to it), we need the proper acoustic and mechanical 
setup, with a clean acoustic source (frequency sweep or a chirp). That 
would include the acoustic part and measure it all. I know AP has test 
gear for speakers. I will look up to see what they do with mics.

Thank you all for your comments

Dan Lavry

On 6/12/2021 7:32 AM, Scott Dorsey wrote:
> Yes, 150 ohms -is- arbitrary, but as arbitrary constants go it seems a
> pretty fair one since it's about in the middle of the values you would
> expect from a wide range of typical microphones.
> --scott

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