Knowing the Difference Between Positive and Negative Speaker Wire
Speakers will always have two connection terminals, positive and negative, and a wire attached to each terminal. However, when connecting your speakers, it's very easy to forget which wire goes to which connection. When wiring speakers, it's very important that the polarity is respected at both ends of the wiring; where they plug in at the audio system and where they're connected at the speakers. If the polarity on one or a few speakers should be reversed from the system's polarity, it would create a phase difference where the sound from the speakers connected one way would cancel out the sound from speakers connected the other way, an effect more noticeable at lower frequencies. There are fortunately a number of ways to determine the difference between positive and negative when dealing with speaker wires.
These specific methods will only apply if there has been no tampering with the connections to the speaker's terminals. Speaker wiring can actually be changed at any time and either wire connected to either terminal; however, these rules generally hold true in cases where the wiring is original.
Visual Inspection of the Connection Points
Every speaker is labeled at the connection point to delineate which terminal is positive and which is negative. If you can still access the back of the speaker easily at this point in your installation, a quick glance at the terminals should tell you exactly what you need to know.
Also, if you can look at either the owner’s manual or the top of most decks, you will be able to look up the polarity of the wires from the head unit.
The important thing when connecting speaker wires to the speaker terminals is to have all speakers polarized the same. This means matching the speaker wires to the same polarization of the source.
Look at the Wire Itself
Every speaker wire will have an indicator to tell them apart, such as color. In some high-end speaker wires, the insulation is transparent, or see-through, enough to see the bare wires. When this is the case, usually the silver wire will be the positive polarity and the copper wire will be negative.
Look at the Insulation
If the insulation isn’t transparent, you can still determine polarity by looking for the wire with the stripe. When installed professionally, the wire with the stripe (of whatever color) will be connected to the negative terminal. There will always be one striped wire and one solid colored wire in any speaker wire set.
Re-wire the Polarity
In the event that you discover your wiring has been changed from these common standards, there is nothing stopping you from reassigning the wires as you see fit. If it's easier to remember the striped wire as negative, you can change the striped wire back to the negative position. Just be sure when you've finished that both ends of each wire connect to the same polarities for all speakers.