# How to test speaker wire for polarity.



## x047x (Mar 16, 2004)

I have a voltmeter but admittedly I'm not very competent with it. I'll be installing new speakers into a 1989 GMC S15 this afternoon and don't have speaker harnesses. I'm planning on snipping the factory harness from the end of the speaker wire and soldering the wire to the new speakers. How can I test which wire is positive though? I know how to do the test for the speakers with a battery, but how can I test the car side wires? (the harness plugs directly into the OEM speaker I believe and so there won't be and actual wires connected to the speaker to test and refer back)...


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## BassNotes (Mar 16, 2005)

What are the colors of the wires? Usually one leg, either the positive or the negative, on all of them will have something in common, like a stripe on the insulation.


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## 'dubber (Jun 15, 2004)

Use a volt meter set to DC millivolts and test the wires while playing some static. If it displays negative voltage, you have your common test wire on the positive output wire.


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## BassNotes (Mar 16, 2005)

'dubber said:


> Use a volt meter set to DC millivolts and test the wires while playing some static. If it displays negative voltage, you have your common test wire on the positive output wire.


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## 'dubber (Jun 15, 2004)

The display on the meter will (usually) indicate reverse polarity if the meter is hooked up backwards while a signal is present. A steady signal makes this easiest so use some pink noise or turn to a static channel on the radio. Either the needle will slam all the way left, or the digital display will show a negative symbol if you have the common test lead attached to the positive output wire and the positive test lead attached to the negative output wire (backwards). If they are not hooked up backwards, the opposite will be true. What is so  about that?


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## blazerpounds (Mar 19, 2008)

All gm up to like 04 ish have light colored and similar colors in front are positive and the dark colored and similar colors are positive in the rear.


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## BassNotes (Mar 16, 2005)

'dubber said:


> The display on the meter will (usually) indicate reverse polarity if the meter is hooked up backwards while a signal is present. A steady signal makes this easiest so use some pink noise or turn to a static channel on the radio. Either the needle will slam all the way left, or the digital display will show a negative symbol if you have the common test lead attached to the positive output wire and the positive test lead attached to the negative output wire (backwards). If they are not hooked up backwards, the opposite will be true. What is so  about that?


What you're describing isn't an indication of reverse polarity, but of a DC voltage. That's why it's . There shouldn't be a DC potential between the + (which actually means "in-polarity" instead of "positive", at least in a DC sense) and - (which actually means "opposite polarity").

In car audio, most amp outputs in recent history are bridged so that one leg swings positive while the other swings negative, and vice-versa. Even on older, low-power outputs where the - side is referenced to the chassis ground, presence of DC would indicate a bad blocking cap.


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## superskyliner (Mar 27, 2012)

Speakers operate on ac voltage don't they, I mean a sound signal is some sort of sine wave right??? Sine wave goes above and below zero right??

On another note, do you have the factory sepakers with the factory plug??? If so do a polarity test on the speaker with a battery as previously mentioned , once you determine speaker "+" "-" then plug the speaker I to the factory harnes and you should be able to tell what's what right ???
Assuming you have the factory speakers...


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## blazerpounds (Mar 19, 2008)

Yes speakers do operate on ac voltage which is why a speaker moves in and out.


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## 'dubber (Jun 15, 2004)

Right but aren't you able to see a difference in potential between the two sides or something? I seem to remember being able to test for output polarity at least on some equipment.


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## blazerpounds (Mar 19, 2008)

With an oscilloscope I am sure.


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## chris.duspiwa (Apr 9, 2012)

+/-
Front left Tan-gray
Front right Lt.green-dk.green
Rear left Brown-yellow
Rear right Dk.blue-lt.blue


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## lhunt (Aug 5, 2006)

*D battery man*

This is an old school method(ya I'm old). Take a D battery and hook up the terminals to it, speaker pops up you have the polarity correct. If the speaker sucks down you have it reversed. The battery can also be used to find the correct speaker wires. Touch 1 wire to a terminal on the bat and start touching wires to the other end until you get a click....I think I got that right as I don't have a D bat handy.


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## BassNotes (Mar 16, 2005)

lhunt said:


> This is an old school method(ya I'm old). Take a D battery and hook up the terminals to it, speaker pops up you have the polarity correct. If the speaker sucks down you have it reversed. The battery can also be used to find the correct speaker wires. Touch 1 wire to a terminal on the bat and start touching wires to the other end until you get a click....I think I got that right as I don't have a D bat handy.


 That won't help you get the wires sorted out.


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## lhunt (Aug 5, 2006)

*sorry wrong soluttion*

Nevermind, should have read the post better:banghead:


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