An RCA plug is used for connecting speaker wire to many name-brand stereo receivers. In some cases the speaker connectors on the backs of speaker cabinets each have an RCA jack. Cables are sold with the necessary plugs for a stereo speaker, but it's less expensive and more fun to wire the plugs yourself.
Strip 1/4 inch off the insulation on both ends of two short lengths of speaker wire with wire cutters. Wrap one end of each wire around one of the speaker input terminals on the back of a speaker cabinet if the terminals are not marked with plus and minus signs. One will be connected to the positive terminal, and the other to the negative terminal.
Check the polarity of the unmarked speaker inputs by connecting the other ends of the wires to a 9-volt battery. Twist one of the wire ends around negative terminal cap on the battery. Hold the other wire end against the positive terminal plug of the battery and observe the speaker cone. The positive battery terminal is touching the wire from the positive speaker input if the cone moves forward. The negative battery wire is touching the positive speaker input if the speaker cone recoils toward the rear of the cabinet.
Remove the plastic or metal shield from the back of the RCA plug by twisting it counterclockwise until it comes off the threads, or by removing the hex nut that holds some metal insulator shields with a hex key wrench. Push the speaker wire to be connected up through the bottom hole of the insulator shield.
Plug in a soldering iron and allow three to five minutes for the tip to heat. Separate the two seamed speaker wires by pinching one in each hand and pulling the thin seam two inches apart. Strip 1/8 inch off the insulation of both the speaker wires with wire cutter blades.
Hold the speaker wire from the positive speaker input against the short tip terminal of the RCA plug. Place solder against the wire and hold the hot tip of the soldering iron on the solder until it melts. Cover the bare wire and terminal with melted solder. Solder will cool and dry in less than one minute.
Hold the negative wire from the stereo speaker against the longer sleeve terminal of the RCA plug. Melt solder over the wire and terminal. Pull the insulator shield up the wire and secure it by twisting it onto the threads, or tightening the hex nut. Plug the wired stereo speaker plug into an "audio out" RCA jack in back of the receiver. Use steps 1 through 5 to attach RCA speaker connectors to all speakers in the audio system.