Checking microphone polarity

[Seeker]

I just picked up a cricket polarity/ continuity tester to make my life a little easier... However when I checked some mics using its built in speaker It is telling me that the polarity is backwards even on unmodded mics like md421 sm57, etc. 

Can this be correct?  I have checked the testing unit with itself, using the built in mic and speaker, and it appears to be working as it should....  I am fairly baffled by this at the moment.

 

[pucho812]

depending on the year made you may have sm57's that are pin 3 hot.

 

[gyraf]

yup. that's what makes them nice for under-snare-duties...


Jakob E.

 

[Seeker]

Hmm... So you're saying I should trust my  polarity checker.... Sm57, beta 57, md421, bk5, a new d112, all show a positive signal on pin 3...

I was wondering what the margin for error would be when checking a mic.... Since this setup uses a speaker to produce a (I'm guessing only positive going) waveform.... But I've thoroughly checked the unit and it seems 100% consistent

I'm pretty shocked at these results.  I thought everything had been pin 2 hot for a very long time...

 

[Matt Nolan]

I was wondering what the margin for error would be when checking a mic.... Since this setup uses a speaker to produce a (I'm guessing only positive going) waveform.... But I've thoroughly checked the unit and it seems 100% consistent

There's no such thing as an only positive going waveform in audio. They may use an asymmetric waveform if they're being really clever, but there's probably no need.

The margin for error will be somewhere around half a wavelength in distance between mic and speaker.

 

[zebra50]

In my experience the new Shures are pretty consistent, as are the md421s. And I would expect your d112 to be correct too. I think you have cause to question the test's validity.

Matt makes a good point. At what frequency does your polarity tester operate?

 

[Seeker]

The spec sheet doesn't tell me the freq used... I could record it and use an analyzer... Kinda hard to guess because it's a kinda chirpy sounding pulse.

I did do the tests from about .5" away from the mics so there souldnt be too much room for error I would think...

 

[Seeker]

After recording some drum hits with these mics, the polarity tester seems to be correct.... The leading edge of the hits is going negative.

Also, just to be clear I have checked cables and preamps, etc, So there are no silly errors.

 

[pucho812]

are they new mics?

 

[zebra50]

> The leading edge of the hits is going negative.

Pointing at the top of the drum or the bottom?  Remember that the drum hit pushes the skin away from you, so one expects the leading edge to be negative when micing from stick-side.

A good way to check a cardioid or fig-8 mic's polarity is to speak into it and listen on headphones at a moderate volume. Flip the phase back and forth.

One way will  cancel with the sound of your own voice in your head, the other will reinforce it.

Stewart

 

[PRR]

> cancel with the sound of your own voice in your head

Doesn't this also depend on headphone polarity? And indeed the whole signal chain?

 

[Seeker]

Thanks for all the replies, I've gitten slammed with work so it'll be a little bit till I can get back in the studio and sort this all out...

As for the age of the mics they vary... the 421 is old, bk5  was refurb by  enak, the d112 is brand new.... The beta 57 is about 12 years old....

 

[Seeker]

So after going through things again, I am now suspecting the tester, the electronics are fine (plugged in) but the speaker or waveform being used seems to be the issue.... And possibly the mic (on the tester)?

I came to this thought after doing the hum test... Though I am wondering about headphone polarity, as my tester shows my hd600s and my beyer dynamic dd770s as being inverted.... But I'd be surprised if that was true.

Now, back to the mics...  If instead of using the testers speaker the stimulate the mics, I make a plosive "p" sound with my mouth the receiving unit shows the mics as being in correct polarity.  Are there any problems with this idea?

Thank you guys for all the help!

 

[pucho812]

a 12 year old mic would be pin 2 hot, as would a d112. The 421 is how old?    I honestly think it doesn't matter until you hear it as a problem, then you can hit the polarity button on whatever mic pre or console channel you are using. Done deal.  If you do it enough times and are convinced that one of the mics mentioned is pin 3 hot can easily rewire the xlr jack in the mic. 

 

[Seeker]

You are totally right pucho, and this isn't stopping me from making music... I just got a little far down the rabbit hole when I found things not looking like I expected, and I wanted to know if this tester is valid on acoustic sources....

The 421 is a craigslist find so no idea of the age on that one.... 

 

[pucho812]

right on. As ray charles would say "the name of the game is how does it sound?"