Microphone Polarity / Vance Powell / Cricket Polarity Tester

[MJ]

I just saw this video of Vance Powell using the Cricket Polarity Tester;

https://www.puremix.net/blog/vance-powell-checking-polarity-on-the-mics.html
I'm trying to get my head around what he is doing here?

Without getting into an endless discussion of polarity vs. phase...I'm trying to figure out what he is doing practically?

Is he checking each mic separately, or both mics at once that are micing the same source?

And without spending $250.00 for one of these units, how is it different than (for instance) the speaker polarity testers like the IOS/Android Studio-Six speaker polarity test (if you used two iPhones or iPads, say an iPhone with it's speaker on producing the click next to the microphone, and another iPhone in the control room giving you a plus or minus indicator?

Or could you just put an iPhone with the speaker on producing the clicks by the mic or mics, and record the clicks into your DAW and zoom the waveforms to see if they are both positive or not?

Thanks!

 

[Khron]

How about this?

https://sound-au.com/project185.htm

 

[user 41968]

If you want to check the polarity of a microphone simply sing or speak "e" (the vowel not the note) look at the waveform and make sure the output voltage has positive asymmetry. "a", "e" and "i" are the best vowels for the test.

The glottal pulse produces a more asymmetric waveform with greater positive peak pressure than rarefaction.

Here's an older Article "Build an Audio Phase Detector" https://proaudiodesignforum.com/ima...tector_Charles_Kitchen_Audio_January_1978.pdf

The correct title should be "Audio Polarity Detector."

 

[MJ]

Thanks this is very helpful!

 

[Marik]

The cheapest polarity tester is …your ears. Take a microphone with a good known correct polarity (usually, all reputable manufacturers have it correct). Plug it along with the mic under test into mixer and pan to center. If the mics cancel each other then the test mic polarity is flipped.

Also, if you monitor the mic on open back headphones and talk into it (keep the mic in close proximity), if the mic’s polarity is wrong because of cancellations you will hear very weird low end.

Best, M

 

[JohnRoberts]

The cheapest polarity tester is …your ears. Take a microphone with a good known correct polarity (usually, all reputable manufacturers have it correct). Plug it along with the mic under test into mixer and pan to center. If the mics cancel each other then the test mic polarity is flipped.

look for cancellation mainly at low frequencies due to longer wavelength, high frequencies will just sound phasey from comb filtering.

Also, if you monitor the mic on open back headphones and talk into it (keep the mic in close proximity), if the mic’s polarity is wrong because of cancellations you will hear very weird low end.

Best, M

Listening with headphones while talking into a mic can get a little weird due to the bone conduction path inside your head. I wouldn't trust this for right /wrong, but perhaps for comparing two mics for same/reversed.

Modern commercial mics should all be conforming to pin 2 hot. Even the old IEC/IHF standard for mics was always pin 2 hot, which was confusing for console designers when pin 3 hot was informally used for line level XLR. This has been sorted for several decades now with mics and lines now both pin 2 hot.

JR

 

[Marik]

look for cancellation mainly at low frequencies due to longer wavelength, high frequencies will just sound phasey from comb filtering.

Really depends--if the mics have similar frequency response and level adjusted for equal gain then the cutoff frequency will be determined by the wavelength (i.e. distance between the mic capsules). Because of small size SDC's can be placed very close to each other and get cancelled up to quite high frequencies. Method of cancellation is what many manufacturers use to select matched pairs.

Listening with headphones while talking into a mic can get a little weird due to the bone conduction path inside your head. I wouldn't trust this for right /wrong, but perhaps for comparing two mics for same/reversed.

After some practicing and flipping polarity switch it can actually be quite reliable. Because of distance between the headphones and capsule and long wavelength it is important to talk on low end and keep the mic close to your mouth, so the proximity buildup helps having plenty of lows (obviously, for cardioid, or fig8 mics only)--that's where the cancellation will be happening. I remember David Bock stopped by our booth at NAMM to say hi and was checking our new mic through closed back (!) Beyer 770 cans. The very first thing he said--this mic is out of polarity. Surely enough--the polarity switch on the preamp was accidentally engaged.

Best, M

 

[Brian Roth]

Modern commercial mics should all be conforming to pin 2 hot. Even the old IEC/IHF standard for mics was always pin 2 hot, which was confusing for console designers when pin 3 hot was informally used for line level XLR. This has been sorted for several decades now with mics and lines now both pin 2 hot.

JR

Indeed, AES-14 standard (from 1992) attempted to sort out the pin 2/pin 3 confusion and newer equipment began complying. However, equipment (particularly USA products) dating back to the early 1950's is still in use and followed what began as the "Ampex wiring standard" with pin 3 hot.

Even as late as the early 1990's, a brand new Otari MTR-90iii 24 track was shipped with pin 3 hot convention.

FWIW, here is an interesting little article regarding the history of audio connectors:

https://www.aes-media.org/sections/pnw/pnwrecaps/2020/aug2020/xlr_history.pdf
Bri

 

[Brian Roth]

I have one of these "polarity selectors" buried in my piles o' stuff.

 

[bremusound]

Certainly not known by everyone:
Neumann M49 and M50 had a reversed polarity. See picture attached

 

[abbey road d enfer]

Is he checking each mic separately, or both mics at once that are micing the same source?

As far as I can tell, he's doing both, first checking that the pulses from each channel register the same on the receiving unit, then checking that raising both channels result in amplification, not cancellation.

And without spending $250.00 for one of these units, how is it different than (for instance) the speaker polarity testers like the IOS/Android Studio-Six speaker polarity test

It's not significantly different, the test signal may be slightly different but anyway relies on a quite asymmetricak waveform.
BTW $250 is just a fraction of the price of an iPhone...

Or could you just put an iPhone with the speaker on producing the clicks by the mic or mics, and record the clicks into your DAW and zoom the waveforms to see if they are both positive or not?

Sure you could do that, but your ears will give you a good answer more quickly.

 

[cyrano]

Sounds like it's a 555 with a small amp and speaker, a few jacks and a case. I'll bet I can diy that for a bit less. Even 250$ for a well built one isn't outrageous either.

Or am I forgetting something?

 

[abbey road d enfer]

Or am I forgetting something?

What about the receiver?
Indeed you can watch the waveform in the DAW or with an oscilloscope.
$250 is for both the sender AND receiver.
I think Beh.....r makes a set for less than $100.

 

[cyrano]

Ah, I hadn't even noticed there are two parts. Silly me.