Connecting speakers with AUX cable

If the speakers are active and have their own amp built in then you would want to use standard RCA interconnect cables.
If the speakers are passive (no power cord) then even though they may have RCA jacks on them they still need to be connected to an amp. Cheap speakers save money by using the wrong connector. You don't want to use a coax RCA cable with them. You can get speaker wire with RCA plugs on the ends. If you have some speaker wire you could cut the cut off the RCA plug and maybe 6 inches of wire from an interconnect cable and splice the speaker wire. The center pin of the RCA is the plus conductor.