Unplugging and Disconnecting Speakers
First of all you should unplug the speakers from electrical switch or disconnect them from any electronic gadget. For example, if you are using a tape recorder or television and speakers are connected to them through amplifiers or directly, disconnect them before taking further step.
You should also remove wires that are connected directly to the amplifiers or through sub-woofer to the amplifier. Removing wire of a speaker or speakers is necessary before testing for polarity. Sometimes, the problem might not be just wires. Again, before removing the wires make sure you have unplugged the system from electrical switch and any electronic device.
9-Volt Battery for Testing
To do the testing for polarity of the wires, you will need a 9-volt battery. There is no other way that you can test the wires for polarity. If you do not have a battery you can either borrow it from someone or let a professional test the the wires or through a purposeful device, which you can buy from the market.
In case you have a 9-volt battery, start with connecting the unsheathed of the wire to any of the two coils on top of the battery.
Check for Ring Movement
When you connect the unsheathed of wire on the battery coil, see which direction the ring of sub-woofer moves in. If it moves inwards, this reflects that the polarity of the wire is incorrect. After it, remove the wire from coil of the battery and check for it again.
You can test for polarity again after reversing the wire and reconnecting it to the battery coil from other end. If the ring of sub-woofer moves outwards, it means the polarity of wire is correct. This makes your job done, and then connect the wire to the speakers through to amplifier and other devices correctly. In case the wire still moves inwards, their might be some other problem with the wire and you should get it replaced immediately.