What’s the difference between XLR vs DMX?
Posted on: 26th September 2021
Whether you’re a gifted gaffer or fully into foley, chances are you’ve handled your fair share of power cables. However, if you’ve ever found yourself short of a cable or two you may have been tempted to sub an XLR cable into your lighting rig or vice versa. Putting aside the rivalry between audio and lighting, it’s generally considered a cardinal sin among the pros to mix XLR and DMX cables; but to misquote Dr William Pepper, “what’s the worst that could happen?” Both types of cable use the same connector (most of the time), have similar size cables and come in a variety of colours. So, what’s the actual difference, can you mix them, and should you? Let’s get into the nitty gritty, and bust some myths.
XLR and DMX
First off, XLR is technically short hand for ‘External Line Return’ and describes a type of connector found on audio and lighting equipment and cables. On the other hand, DMX is short for ‘Digital Multiplex’ – the standard protocol used to transmit information between a lighting desk and certain types of lighting and special effects machines. Neither XLR or DMX describe an actual type of cable; however, for simplicities sake most people (including this blog) refer to microphone cables as XLR and lighting cables as DMX. Sorry in advance.
3-Pin or 5-Pin
Since 1955, microphone cables have used 3-pin XLR connectors, with a 5-pin version introduced in 1986 for lighting equipment. Not only did this help distinguish lighting cables from audio cables, but introduced an extra pair of data wires for future developments. Few manufacturers have tried to take advantage of these extra wires which is why most modern equipment accepts 3-pin and 5-pin connectors, and many 5-pin cables only wire the first 3 pins. So, aside from the number or pins, there’s no real difference between the XLR connectors found on audio and lighting cables.
Two examples of all wires in a 5-pin cable being used include transmitting low voltage power to a small DMX controller from a light and transmitting a second DMX signal to a splitter, effectively providing 2 separate lines of DMX data.
It’s all in the cable
The key differences then between XLR and DMX cables really boils down to the cables themselves. The main things that affect how well information is transmitted are capacitance, impedance and shielding. Capacitance describes how much signal – or energy – is absorbed by the cable, varying levels of impedance along a cable can cause reflections and distortion, and shielding protects your signal from noise caused by outside radio or magnetic frequencies.
XLR cables are generally built with high capacitance, low impedance (40 – 110ohms) and robust shielding. This is ideal for analogue signals which are not greatly affected by varying levels of capacitance and impedance, but do require protection from external noise. Digital signals on the other hand are very sensitive to changes in voltage, which means any energy absorbed by the cable can affect the next line of information and corrupt the signal. Digital data is also susceptible to signal reflections from the end of cables, which just like ripples meeting in water can cancel out and distort the original signal.
While XLR cables will work for DMX data, there’s no guarantee that your signal will make it though in one piece; especially over longer distances. This is why genuine DMX cables are made with low capacitance materials and higher 120ohms impedance which better match the characteristics of DMX signals and eliminates the risk of data corruption. Visa versa, DMX cable will work for sending analogue signals but with the differences in capacitance, impedance and shielding, you may experience some inconsistent sound levels and increased noise.
The Price of Peace of Mind
Finally, only of the most important things that impacts which cables some people buy – price. Based on everything mentioned above, it’s easy to see why DMX cables are more expensive. They’re made to a specific, reliable standard with different materials and manufacturing, which naturally carries a higher price tag. That’s not to say that some XLR cables won’t cost just as much, or will even do as good a job as a DMX cable, but in general XLR cables are considerably cheaper, making them a more attractive choice for novices.
Do They Mix?
In case you hadn’t guessed, or you’ve just skipped to the end, the answer to the question “can I use XLR cables for DMX” is “yes, kind of.” DMX cables can be used to transmit audio. XLR cables can be used to transmit DMX. But if you’re being paid to put on a show, it’s not worth the risk. XLR cables can cause lighting to flicker or behave strangely and DMX cables can muddy your sound. What’s more, once you’ve started mixing up XLR and DMX cables, it can be very difficult to tell them apart without looking at each cable, and troubleshooting large rigs can be an absolute nightmare. Save yourself the hassle; pick the right cable for the job, because things can and will go wrong at worst possible moment.
