XLR Connectors Exposed and the Future of Pro Audio Plugs

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 common 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. the connector was first called the "Cannon X," and after the addition of a latch the "Cannon XL" and finally the "XLR" after having a rubber compound added to the connectors.

The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections 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 the standard 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. Ultimately, this application turned out to be potentially harmful to equipment and the XLR has been replaced by the Neutrik Speakon connector.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 earthly return or ground pin, and often soldered to the internal shell or case.

Lastly, the XLRM male plug is used for output and the XLRF plug is used for input. So, a microphone for example will have the 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 are the standard in the professional audio and recording industry. XLR plugs are typically referred to as “balanced” and help reduce noise interference, especially over long spans. Quality in XLR cables varies greatly depending on the manufacturer, but for professional use please 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.