In a perfect world, every cable should be labelled, identifying which speaker they are connected to. However, that is often not the case. Perhaps you are helping a friend, or you have moved into a new house which has speakers in many rooms, or perhaps the kids have pulled the wires out for fun. Whatever the reason, you’ll be pleased to know there is a cheap and easy way to find what speaker each cable is connected to.
You will need two things: someone to help you, and a 1.5 volt battery.
Each cable going to a speaker has 2 wires. Make sure the wires are stripped (that is, the outer plastic is stripped off, allowing around 12mm (1/2″) of bare copper wire to be seen at the ends.
Hold one of the wires (doesn’t matter which one) on the bottom of the battery. With the other wire, tap it on and off the top of the battery (the +ve terminal). The connected speaker will make a scratching noise. Note: the speaker only makes a noise when the wire is tapped on or off the battery. So keep tapping the wire on and off the battery until your assistant finds the speaker which is making the noise.
Once identified, label the speaker cable.
Use an impedance meter: an impedance meter sends a tone (normally 1kHz) down the cable to measure the speaker impedance. Most meters also allow the tone to be held on continuously so you can test and/or identify what speakers are connected. This is a great way as the meter will also tell you the total load impedance.
Connect to amplifier: You can connect the cable under test to an amplifier playing some music at a low volume level. Just be careful not to short the wires when connecting the amplifier. Probably best to turn amp off when making each connection.