Oxygen free copper is a type of copper that has had much of its oxygen content removed in an effort to improve its conductivity. The name actually is a misnomer, because trace amounts of oxygen are still found in this metal. Many audiophiles prefer this type of wire for stereo systems, claiming that it improves sound and volume quality. There are others within this community, however, who claim that the wiring provides no better results than traditional copper.
Any copper that has its oxygen levels lowered to anything below 0.001% is considered oxygen free. There are two types: oxygen free electronic and oxygen free. Standard copper is called electrolytic-tough-pitch and has an oxygen content of 0.02 to 0.04%. Oxygen free electronic is classified as having 0.0005% oxygen content and was forged in an oxygen free environment. Oxygen free is classified as having 0.001% oxygen content, and its conductivity rating is slightly lower than oxygen free electronic.
Oxygen free copper has a different forging process than pure copper. All copper has oxygen added during the forging process, but oxygen free adds less and is smelted differently. During this different process, hot metal is cast into a crucible, and the bottom is allowed to cool while the top remains hot. The entire crucible is cooled slowly, which allows for the oxygen content to be lower.
This type of copper is found in many aspects of manufacturing, but its most common use is for electronics. Its higher conductivity rating has made it an extremely popular choice of stereo enthusiasts and their audio equipment. It is commonly found in high-end headphones, speakers, and video equipment. Its low oxygen content means there is little iron within the copper wire, and therefore the conductivity is good for low-frequency home listening devices.
Products made with this metal have a great deal of controversy attached, however. Some audio experts claim that the preference for such cables and equipment is misleading. Regular copper wires have the same conductivity specifications. This, skeptics claim, proves that there is no audiological advantage to the more expensive, oxygen free type of copper wire. A listener's preference between copper wire and oxygen free copper comes down to a matter of personal taste, because these claims conflict so greatly.