If you have a bunch of speaker cables that you need to sort through, the most difficult and time-consuming way is to untangle the cables one by one, following each length until you reach the speakers. When you factor in navigating all the power and connection cables to other equipment, this process can become an all-day chore.
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There’s an easier, smarter way to trace cables in a fraction of the time. All you need is a common household battery (preferably a new one), such as an AA, AAA, or 9-volt battery. Don’t wear anything bigger than this. While you’re at it, grab some tape and a pen so you can label the wires as you go. If you have speakers in other rooms (especially whole-house or multi-room audio systems), you may need an assistant to help you see or hear. Turn off all equipment before you begin.
Test speaker cables with a battery
Speakers, speaker cables, and batteries show positive and negative polarity. So you take a speaker wire and attach one end to a battery terminal (+ or -). Now take the other end of the cable and tap it repeatedly and disconnect it from the remaining battery terminal. This is best done with a gentle brushing motion. If the speaker is working and connected properly, you will hear static or a thumping sound from the speaker each time the wire rubs against the battery terminal. Battery current causes movement in the speaker drivers.
Check the polarity of the cables
Now that you know which speaker you’re working with, identify the correct cable polarities. Many speaker cables have color-coded covers or markings to show polarity. You want to make sure the speaker is “in phase,” a state where the positive and negative terminals match when connected to your stereo receiver/amplifier. Although out-of-phase connections will not damage your speakers, in-phase connections ensure the best performance.
If the wires don’t provide any clues to polarity, you can tell which is which by the way the speaker moves. Watch the cone each time you brush the cable against the battery. If the cone moves out, the polarity is correct. If the cone goes in and out, reverse the battery cables and try again. These movements can be subtle (particularly with small or high-frequency speakers), so good lighting and a sharp eye certainly help. Be especially careful if you bi-wire or bi-amp your speakers as you have to deal with twice as many connections.
Once you’ve identified the speaker and the polarity of the wires, use the tape and pencil to label it for future reference. You should also include the location (living room, bedroom, garage) and speaker channel (left, right, center, surround) on the label.
If you don’t hear anything from a speaker, check the cable connections on the back of the speaker to make sure they’re tight. Use a new battery and only briefly touch the battery cables when testing, otherwise the battery may run out quickly. If you still don’t hear anything, the problem may be a bad speaker or a bad cable between the amplifier and the speaker.
Connect a working speaker cable to the unresponsive speaker. If the battery trick still does not produce sound or movement of the speaker cones, the speaker may be faulty. You need to investigate further as if you were troubleshooting when a speaker channel is not working.
If the battery test works, the problem is likely with the original cable. You will need to carefully check the entire length of the cable in question, as even a small break can cause problems.
If it’s a subwoofer, you’ll need to take some extra troubleshooting steps when the subwoofer doesn’t work. Subwoofers are not always connected in the same way as typical stereo speakers.