How do I extend an audio speaker cable?

“I have an RCA home theater system. The speaker cables for the rear speakers are too short. I would like to extend the speaker cables. How can I extend the length of the cables without removing the existing wires?”
The ideal solution would be to swap out the entire cable for a longer one. It sounds like this isn’t an option, so your next best bet is to get some extension speaker cable and cable crimp-on connectors from the wiring department at Radio Shack, Home Depot, Lowes or your local hardware store. The crimp connectors are generally rubber shielded metal tubes that you insert the wires from the speaker and the extension speaker wire. You then squeeze the crimp-on connector with pliers to secure the wires in place.
If you don’t have any extra speaker wire on hand, you can pick some up at a reasonable price at Radio Shack or any hardware store. While there are many theories about what gauge speaker cable are best, you’re likely starting with fairly thin wire coming from the back of the RCA home theater system, so crimping on a heavy gauge wire will do little to improve your signal quality. 18-guage speaker wire will likely do the trick in most cases. I would likely recommend a different solution if this were a component-based system with individually powered amps, but for an all-in-one system, 18-guage wire will be sufficient.
Crimp-on butt connectors come in a variety of sizes. Make sure the size you choose is appropriate for the wire you use to extend the length of your speaker cabling run. Here again, Radio Shack and the local hardware stores will sell the connectors you need for most of the common wire gauges.