My house came with 2 wall speakers. There is wiring for both of them. The right and left speakers have 2 wires each.

I'm trying to hook them up to my amp but I have no idea which wire is positive or negative.

  • They are both copper
  • Neither wire has a stripe
  • The insulation for both wires is the same color (gray)
  • There is no + or - indicator on the insulation

I'm at a loss. I also tried hooking up one speaker and then swapping the wires to see if the sound quality was noticeably different one way or the other. I honestly can't tell, it sounds good either way.

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Sorry it's blurry but as you can see the wiring is identical. The insulation as Ecnerwal mentions in his answer is different - one is smooth and one ridged.

  • 3
    It looks like the wire on the right has ridges, which often is done to identify one of two wires. It doesn't matter which is "plus", as long as you're consistent. Jul 8, 2016 at 23:32
  • "I honestly can't tell, it sounds good either way." One way to tell if they're flipped is to play something monophonic (or just something with vocals) and stand in between the two speakers. You'll probably notice that nothing seems to be coming directly from the center, everything is diffused and vague. If wires are correct, the sound will appear to be coming from the center.
    – Duston
    Feb 28 at 16:03

4 Answers 4


Look closer at the insulation - there's nearly always a physical clue, such as tiny ridges on one wire, not on the other.

  • You are correct. One of the insulation is smooth, the other is ridged. But which is which?
    – ferret
    Jul 8, 2016 at 22:27
  • 1
    After a little research it sounds like the ridged one is negative. Thanks!
    – ferret
    Jul 8, 2016 at 22:33
  • 1
    Or you could point two speakers directly at one another and flip wires back and forth. When they're out of phase, they're quieter. Jul 8, 2016 at 23:58
  • 6
    Printing is often restricted to one of the two wires. Jul 9, 2016 at 18:06
  • Does them being opposite phase makes a difference for real ?? Always plugged them randomly, over multiple installation.
    – Jeffrey
    Sep 14, 2021 at 23:24

Note that the wire doesn't care which is positive and which is negative. Nor do the speakers, really; what matters is that both/all speakers be in phase with each other.

So if the same side of the speaker wire is always hooked to the same terminal at the signal source (amp), and the same side is always hooked to the same terminal of the speakers (even if all the speakers are backwards -- as long as it is all of them), everything will work properly.

(I usually adopt some mnemonic such as "ridged to red", to help remember which convention I've chosen.)

If there is no physical difference in the insulation or the conductor color, that isn't intended as speaker wire. You can certainly use it -- I used old unpolarized lamp cord for decades -- but then it's your problem to figure out which is which. (I checked using continuity testing, then tied a knot or colored one side so I didn't have to repeat that test until next time I cut the wire shorter.)

  • Agreed. The only way to be sure, is to check how the wires are connected to the speaker. Which is which will completely depend on the manufacturer's or installers preference.
    – Tester101
    Jul 9, 2016 at 13:13
  • 1
    Yes, I knew about that, but a) I couldn't discern any physical difference so I would have had to trace it with my finger, and probably would've gotten lost and b) the speakers were already wall mounted and I didn't want to have to get back there to look :) But thanks!
    – ferret
    Jul 10, 2016 at 17:31
  • Added a comment about dealing with unmarked cable.
    – keshlam
    Feb 28 at 15:52

That wire is distinguished by ridges on one side and writing on the other. It is up to you to decide for yourself how to allocate them.

And it really doesn't matter with speakers as long as you are consistent.

For what it's worth, in 120/230 mains wiring, there is a standard that the ridged wire is neutral. In a DC system, a common convention is to consider the - terminal to be near/at ground reference, which is analogous to neutral in mains power.

  • Yes, just to be clear, the wall speakers were already in the wall and I wouldn't easily be able to get back there to look. I know all the work done on this house is quality and would've followed standards so I wanted to know what the standard was. The ridged one is indeed the negative/ground. Thanks!
    – ferret
    Jul 11, 2016 at 0:53
  • 1
    Your best bet is to assume the installer was consistent. For speaker wire, that's all you need to know. Jul 11, 2016 at 5:26

Had the conductors been truly identical -- no discernable differences such as ribbing, jacket printing color of the conductors, etc -- use a battery and a battery tester or volt meter.

Disconnect both ends of the cable from the amp and speaker; get somebody to hold the conductors at one end onto the terminals of a battery; measure the voltage at the other end with a volt meter or a dollar-store battery tester. Try connecting it both ways. One way the meter will show negative volts or the batter tester needle will swing the wrong direction. The other way the meter will show positive volts or the battery tester needle will swing the right direction. When this happens, the conductor touching the + side of the battery is the same conductor as the one that's touching the red lead of the meter or the + side of the battery tester. Make a label and mark both ends as +. Done!

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