XLR Plugs Exposed and the Future of Pro Audio Connectors
The XLR connector is commonly used in professional audio and video applications. The plug itself is an electrical connector by design. Not unlike the more ubiquitous RCA plug , which used regularly with home audio and video electronics, the XLR connector is different in several important ways.
Originally designed and manufactured by James h. Cannon, the connector was originally called the “Cannon X,” and later the “Canon XL” and finally the “XLR” after the addition of the latch (XL) and rubber compound (XLR) which surrounds the connectors.
Most commonly found is the XLR 3-pin, which is used universally for high quality microphones and as a connector between equipment. Other widely used configurations of the XLR plug is the 4-pin XLR4, used with Clear-Com and Telex intercom headsets and as DC power connectors for video and film cameras. The XLR5 connector is the standard for DMX512 digital lighting control and also is used for dual element microphones and dual channel intercom headsets. XLR6 is widely used as a connection for dual channel intercom belt-packs.
There are several now obselete configurations with additonal pins including the XLR-LNE mains power connector, which was identified by its red insulation and shrouded pins, and has now been replace by the Neutrik PowerCon connector. XLR3 connectors were at one time also used extensively on 2-conductor loudspeaker cables, with either pin 2 or 3 as live (depending on the manufacturer) and pin 1 as the earthly return. However, this turned out to be dangerous to equipment and has since been replaced by the Neutrik Speakon connector.
Female XLR connectors are designed to first connect the ground pin before the other pins make contact as the male XLR connector is inserted. Because the ground connection is made first, before the signal lines make contact, XLR connectors can be inserted and removed without interference from external signals, a typical problem with RCA connections. There is some discrepancy between various manufacturers between swapping pin 2 (normal input) and pin 3 (inverting input), but this reflects nothing more than their own pre-existing standards before any standards existed. Pin 1 is always the ground, or earthly return pin, and is often connected to the internal shell or case.
Finally, the male XLRM connector is used for output and the female XLRF connector is used for input. So, for example vocal microphones will have a XLRM connector . Signal cables will have XLRM at one end and an XLRF connector at the other. Mixers and other multi-track recording equipment components will have XLRF inputs, and XLRM returns to stage, or out to other components.
XLR connectors have been the standard in the professional recording and audio industry. “Balanced” XLR cables help eliminate noise and interference, especially over long spans . Quality varies depending on the manufacturer, but for high end applications please can check out Canare, Mogami and Neutrik.
Recently, the advent of USB microphones that connect directly to a PC or MAC have gained popularity. So far, USB microphones are primarily intended to be used as studio microphones, and live stage vocal microphones continue to use the standard XLR connections.