Img source: wikipedia.com

XLR Cable 101: How Do They Work?

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XLR cables are important pieces of equipment for those in the professional audio field. These specialized cables provide a means of transit for an audio signal between hardware. While they may look simple on the outside, there is a lot going on behind the scenes that must be in place to ensure that the audio signal is transmitted flawlessly from one spot to another. In this article, you’ll learn all about XLR cables!

XLR Cable History

The first XLR connector was invented in the 1940s by a man named James H. Cannon. Back then, they were commonly called Cannon plugs or Cannon connectors after their original inventor. The formal connector name was the Cannon X series. After 1950, Cannon’s company added a locking mechanism, and the new connector was called the Cannon XL. With the addition of neoprene around the female parts of the connector, Cannon finalized the name to XLR, the “R” standing for “resilient” which is still used to this day.

Image Source: Soundfirst.com – The Cannon XL plug

XLR Cable Uses

XLR cables are manufactured with up to 10 pins! Each pin has a specific function. These special connectors have all kinds of applications, but mainly the XLR cables with higher pins are used for power and balancing. For example, on a 4-pin XLR cable, pins 1 and four are used for DC power. Some HD camcorders used to use 5-pin XLR cables, with extra pins for stereo audio. Neutrik, an industry leader in XLR connectors, recently released a 10-pin XLR connector. These can transmit four pairs of data along with 16 Amps at 50 V for high-performance audio applications.

  • XLR3 is the most common design and is used worldwide in professional audio. They are almost always used to connect microphones to audio interfaces in professional recording studios. They can also be used for stage lighting equipment.
  • XLR4 is used to connect intercom headsets as well as professional video equipment. These find their way into stage lighting as well.
  • XLR5 is very commonly used for DMX stage lighting, and also for stereo audio applications like we mentioned earlier.
  • XLR6 is used to achieve a balanced microphone signal in some headsets
  • XLR7 is used to connect specialized microphones to their power sources. They’re also used for fog machines.
Image Source: Sweetwater.com – This fog machine has two XLR inputs and two XLR outputs for DMX. One pair is 5-pin and one is 3-pin.

 

Designing the Best XLR Cable

According to synapticsound.com, the best XLR cable will have several design features that ensure they transmit the signal from point A to point B with as little distortion and added noise as possible. They are listed below.

Balancing

You may have heard the term “balanced” in the paragraphs above and wondered what that means. Balancing is a method that electrical engineers use to eliminate or reduce added noise caused by radio-frequency (RF) interference.

How It Works

A balanced cable usually has 3 or more conductors. In 3-pin balanced XLR cables, the cable contains two signal wires and one ground wire. The two signal wires carry the same signal waveform, except one of them that has its polarity reversed as it’s transmitted from point A to point B. While in transit, both signals will pick up the same levels and frequencies of added noise due to RF interference. Then, at point B, the inverted signal along with its additional noise is inverted once again and added to the other signal. What this then does is it cancels out the added noise while keeping the original audio signal intact!

Image Source: Aviom.com

The best XLR cables will always utilize this special design technique. Some cables, such as the Mogami Gold series, actually use two pairs of conductors for even more effective noise cancellation. For professional audio, balanced XLR cables are mandatory.

Shielding

The best XLR cable will always be shielded. Shielding is another technique used by electrical design engineers to reduce added noise from RF interference.

How It Works

A shield is usually a braided mat or spiral of many smaller-gauge copper wires that wrap around the conductors. Some shields are also made of aluminum Mylar foil, and some cables contain both a braid and a foil shield for maximum effectiveness

Radiation in all forms, including RF radiation that adds noise to our audio signals, is made up of coupled magnetic and electric fields. An electric field will create forces on the electrons of the atoms in the shield. When the shield is exposed to an electric field at the surface, it moves the charged electrons to create an electrical current. This movement, in turn, generates its own electric field which then cancels out the applied electric field and stops it from reaching the signal conductors. The induced current in the shield is then grounded. In this way, the shield absorbs the RF interference and diverts the energy away from the signal conductor.

Strain-Relief Connectors

The XLR cable’s connectors are very important for long term reliability. That is because many low-quality cables will break at the connectors. The best XLR cable will always utilize a connector design that eliminates stress on the soldiers that connect the conductors to the pins. Neutrik makes one of the best strain-relief connectors, called the Neutrik XX.

Image Source: Neutrik.com – Neutrik XX 3-pin Male XLR connector

Jacket & Contact Material

The best XLR cable will use a jacket material that is durable and resistant to abrasion and cuts. The jacket material will also be flexible to allow the cable to be oriented in many positions during live performances. For this application, PVC (polyvinyl chloride) is a great choice for the jacket material. Here is a rundown of common cable jacket materials:

  • PVC (polyvinyl chloride) – very common, low-cost, flexible and resists mild chemicals like oil and water. Also has flame-retardant properties
  • PE (polyethylene) – also common, but can be more rigid unless it is the low-density (LDPE) variant
  • PUR (polyurethane) – usually found in coiled cables, and is very flexible
  • TPE (thermoplastic elastomer) – flexible, abrasion resistant, and chemical resistant

The contacts (pins) are the parts of the XLR cable connector that connects directly to the hardware. They must be very conductive to effectively transfer the signal through the connector. They must also be able to resist corrosion. As the contact material corrodes, the signal transferring ability of the contacts degrades. This can lead to distortion of the audio signal. Gold and silver or silver-nickel alloy are the best choices for contact materials.

  • Gold – less conductive than silver or silver nickel-alloy, but more resistant to corrosion
  • Silver or silver-nickel – more conductive than gold, but less resistant to corrosion

Wrap Up

We covered a lot of information here on modern day XLR cables. They’ve come a long way since their distant relatives were invented by James H. Cannon in the 1940s. Some of the more important features of these specialized cables are shielding, jacket and contact material, balancing, and connector design. The best XLR cable manufacturers will always keep these in mind to best serve the consumers and professions that use them.

 



Peter is a freelance writer with more than eight years of experience covering topics in politics. He was one of the guys that were here when the foreignpolicyi.org started.