Its not wise to run lamp cord type wire if that is what you used. The reason there is a code for in wall speaker wire has to do with possible breakdown of the insulating cover over time and the increased fire hazard from overheating or shorts. We are likely talking years before anything happens but it makes sense to use the proper insulated wire wire. Home Depot sells various guages of inwall grey coloured insulated CL rated wire and its fairly cheap.

John