I know years ago, like back in the 70's, a lot of stereos used to connect the speakers this way. If the speakers have wires leading to a male RCA plug, you could cut the plug off. If I recall correctly, the pin in the center should be the + and the outside should be the -. If the speakers just have a female RCA jack, like what is on the back of your receiver for the analog input of a CD player, tape deck, etc, then you would need a male RCA plug that you can solder speaker wires to. Radio Shack may still carry what you need but it's hard to tell anymore. They also used to sell male RCA plugs that had the speaker wires already connected to them. I would recommend using wire no smaller than 18 gauge. If not, a local electronics supply store may have what you need. If not you can always check ebay for a vintage electronics supplier. I don't think you will damage anything as long as you don't short any of the wires together. The sub should connect with a standard RCA male to RCA male cord. Just don't turn it up too loud as you may damage the speakers if your receiver is rated for more power than the speakers can handle. I hope this helps.