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Checking polarity on a U47 Equalisers (HW)
Old 11th December 2014
  #1
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Checking polarity on a U47

does anyone know how to test this, thanks in advance
Old 11th December 2014
  #2
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frans's Avatar
Take a few of your mics - set them up an make a percussive sound right in front of each of them. Maybe a snap, maybe a "plop" with your lips. Look at the waveforms on your screen. Do all of them start perhaps on the upper half of the zero-line? Try the same with your U47. Did that help you? It's also handy to identify if any of your mics or rack gear switches polarity. For example, the dbx 242 EQ does it.
Old 11th December 2014
  #3
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Old 11th December 2014
  #4
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Cathedral Guitar's Avatar
Easiest way to check polarity on any mic: put up the mic in cardioid, and then put up another mic next to it that you are pretty confident is wired correctly. Flip the phase on one mic. If you lose about 20 dB of signal on the phase reverse, then you know they are wired correctly. If you gain dB on phase reverse of either mic, than one of them is wired wrong. You can do this with any mic, but best to get one that is ballpark close in design, like another LDC from Neumann, like a U87 would work fine.

Second way is probably easier: put both in omni and talk into both see if you lose volume when switching to the back side of one of the mics. If they tend to null when one is flipped, you are good. If they get louder, than one is wired wrong. The difference will not be subtle.

Hope this helps,
Old 12th December 2014
  #5
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Thanks everyone for the tips. Frans, is correct polarity when a snap waveform starts on the upper half or th lower half?

If it's the upper half I'm good if it's the lower half then this mic is wired incorrectly.



Quote:
Originally Posted by frans View Post
Take a few of your mics - set them up an make a percussive sound right in front of each of them. Maybe a snap, maybe a "plop" with your lips. Look at the waveforms on your screen. Do all of them start perhaps on the upper half of the zero-line? Try the same with your U47. Did that help you? It's also handy to identify if any of your mics or rack gear switches polarity. For example, the dbx 242 EQ does it.
Old 12th December 2014
  #6
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frans's Avatar
If the first piece of the waveform goes up or down depends on your signal, the noise you make. The idea behind it is to put up all your mics and compare them. First try to make a "pop" sound with your mouth that will consistently give you roughly the same signal, with the first half rising. Or.. falling - what matters is consistency. Then you can try it on all your mics and see if they all react in the same way to the same signal. Make sure to test your cables, sometimes one is wired wrong and has inverted polarity.
The important thing is that your mics behave the same, so than on the same signal the first half will be going into the same direction on every mic.
Old 13th December 2014
  #7
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Thanks Frans, I will try that

Quote:
Originally Posted by frans View Post
If the first piece of the waveform goes up or down depends on your signal, the noise you make. The idea behind it is to put up all your mics and compare them. First try to make a "pop" sound with your mouth that will consistently give you roughly the same signal, with the first half rising. Or.. falling - what matters is consistency. Then you can try it on all your mics and see if they all react in the same way to the same signal. Make sure to test your cables, sometimes one is wired wrong and has inverted polarity.
The important thing is that your mics behave the same, so than on the same signal the first half will be going into the same direction on every mic.
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