Ribbon Mic Free Air Resonance thread

[zebra50]

Hi!
Marik & I were discussing ways to measure the free air resonance of a ribbon mic and came up with a couple of ideas. The first one is the one I've been using for a couple of years, based on an idea kindly posted by Dave 'Grizz' Royer over at Ampage, IIRC. I sweep the signal generator from about 20Hz upwards and look for the minimum reading on the volmeter. The voltage divider after the generator is to keep the voltage seen by the mic below about 10 mV.

The second is the one that Marik has been using. I am assuming he is looking for tha maximum voltage across the mic.

We'd appreciate any thoughts on these methods - are they really equivalent (I think that they are) and is there anything else we should be looking out for.

Cheers!
Stewart

 

[Marik]

Bump!

 

[PRR]

The second drawing can potentially put huge voltage in the ribbon, blowing it out. I'd want a 1K+10 voltage divider on the signal generator output. (Yes, even on a sig gen that can be turned down to 10mV: it can be turned up to over a volt and Murphy's Law says that will happen while you forget you have a ribbon hanging on it.)

Whether you rig the ribbon series or shunt is probably unimportant, for the small range of impedances a ribbon mike can have.

 

[chops]

Bump! 

Sorry for dredging up an ancient thread, but does anyone still have these drawings?  Just looking to measure resonant frequency of a 44BX using Marik's method of oscillator - mic - preamp - meter looking for max voltage to determine resonant freq.  But I'd like to see where the resistor goes to protect the ribbon from excess voltage.  Is 10mv from the tone gen a good safe target for a 44bx?

Thanks!