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How to check speaker wire polarity

post #1 of 13
Thread Starter 

How do you check polarity of the speaker wires coming out of an amp?  I'm not looking to check the polarity of the speaker, I know how to do that.  I want to know the polarity of the wires coming out of the amp.


What I've been doing:

I turn my digital multimeter to DC


I attach a red cable to the red terminal on the amp

I attach the red terminal on my multimeter to the red cable


I attach a black cable to the black terminal on the amp

I attach the black terminal on my multimeter to the black cable.


When I do this I get a negative reading

If I reverse the terminals I get a positive reading


My conclusion was that the polarity of the amp is reversed.  


 Is this correct?  Am I using the multimeter properly to determine polarity?  If not, please provide step by step instructions for using a multimeter to determine polarity.  Thanks you!

post #2 of 13
You're doing this with nothing feeding the input of the amp? If so, you're likely to just be measuring the amp's output offset voltage, which may be positive or negative regardless of how the speaker terminals are wired.

post #3 of 13
Thread Starter 
I am feeding the input of the amp with music from my DAC
post #4 of 13
But music is AC and you're trying to read the voltage with the DC setting on your meter. That isn't going to work.

Do you happen to have a digital recorder?

post #5 of 13
Thread Starter 

I have an iPhone which can record audio.  What would you use it for?  There is no way to test for this with a multimeter? 

post #6 of 13
Not unless the multimeter has a built in oscilloscope. biggrin.gif

Can your iPhone record electronically? In other words, not using the microphone?

The idea is to send a bit of audio (something digitally sourced so you have a waveform to compare it to) to the amp, record it electronically at the speaker terminals and then compare the waveforms to see if the output from the amp matches it or it's inverted.

What amp exactly are we talking about and why do you suspect it's inverting polarity?

post #7 of 13

Can't you just... hook up some speakers, play a test tone, and verify phase by ear? Would there ever really be a situation in which polarity would matter vs. merely ensuring the speakers are in phase?

post #8 of 13
Thread Starter 

I have a Yamaha htr-5240 amp.  Speakers sound significantly in the mid-bass frequencies when I "invert the polarity".  I was wondering if the amp wasn't wired properly.  

post #9 of 13
And this is when you flip both speakers and not just one?

post #10 of 13
Thread Starter 

Yes, both are flipped.  Not just one.  I've tried this on two different speakers and both sound better better. 

post #11 of 13
Then why not just go with what sounds better? I mean, trying to preserve absolute polarity in the electronics is a bit of a fool's errand as absolute polarity is not always preserved in the recording and many recordings can include mixed polarities.

post #12 of 13
Thread Starter 

I am.  I just wanted to know if there was a way to test for it.

post #13 of 13
There is, just not with a simple multimeter.

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