In this article, Peter Awad describes the difference between an XLR cable and a DMX cable. Are XLR and DMX cables the same thing? Can they be used interchangeably?
It’s the classic “why use a hammer when the back of a screwdriver will do?” We’re often quick to grab the next best thing instead of the right thing. But what’s the real difference between an XLR cable and a DMX cable?
The Science of XLR vs. DMX Cables
On the surface, they look exactly alike (assuming your DMX cables have 3 pin connectors) and aside from the labelling on the jacket, who would really know the difference? It really has everything to do with the electrical properties of the wire. It’s easy to assume that three strings of wire wrapped in a jacket are the same as any other bundle of wire, but when you look at the science of it, there are important things about those wires. When data is sent down the wire, it doesn’t get sent as ones and zeros exactly, the method of communication is based on the voltage going up and down. (eg. +5 volts = 1 and 0 volts = 0). Therefore all the rules of electricity come into play. You may remember in science class something called Ohm’s Law or the formula V=IR. Well, it defines the basic rules for how the signal is sent down any kind of wire, and different kinds of wire have different electrical properties.
The Practical Side of XLR vs. DMX Cables
OK! Enough of the sciency stuff. Let’s just say that there is a slight difference between the electrical properties of microphone wire and DMX wire, enough that microphone wire is not the right wire to use because we are altering the electrical relationship of the circuit.
So why do so many people say they are the same thing? Many people will even say it’s a marketing ploy to make you buy more cables. If we start by asking who originally defined DMX512, you discover special groups that love to use acronyms for their names. Groups like IEEE, EIA, TIA and ANSI were formed to make sure that different manufacturers followed the same set of rules so their devices would work properly with other devices. These rules define things like: maximum wire length, speed in which the data is sent, maximum voltages, and even things like the size, shape, and number of pins in a connector. Understanding these rules, we discover that DMX is not supposed to be a 3 pin connector, but actually a 5 pin. The DMX512 standard actually goes so far as to state that 3 pin connectors are prohibited. However many manufacturers disregarded this rule because DMX doesn’t use the other two pins on the connector or the other two wires that are supposed to be in the DMX cable (yes, DMX cables are supposed to have 5 wires) and most importantly, using 3 pin connectors allows customers to use microphone cables when in a pinch.
So if the manufacturers say it’s okay and user experience shows that a microphone cable will do exactly the same job, why do we bother making or using DMX cables? Well it goes back to what I said at the start: Why use a hammer when then back of a screwdriver will do? If we are honest with ourselves, we have all cheated like that at some point in our life. I remember in my younger days watching my step-father use a chisel as a flathead screwdriver to remove a light switch. The chisel slipped into the electrical box and sparks flew.
We could go on for pages more explaining the science behind DMX and microphone signals, but at this point I think you get the general idea that there is a difference between these circuits. The question you have to ask yourself is, “If I know this cable is not exactly a DMX cable but it usually works, am I willing to take the chance that by using this cable the electrical properties of the circuit are going to change and something may stop working?”
I am going to let you all in on a secret here, I have cheated to the point of using networking cable as DMX cable. I’m not proud of that choice. If I could go back and do it over again, knowing what I know now, I would only use DMX approved wire.
So if you are lighting for a church service, and the lights are low while the worship leader is wrapping up the worship set with prayer, and you can feel the Spirit moving; how much of a schmuck would you feel like if suddenly one or all of the lights started to strobe because you chose to cheat and use a microphone cable?
It’s the respect for the whole art of lighting that will always influence my choice to use the correct cable. I hope you will too.
Peter Awad is a husband to Trisha, Foster parent to many, Tech Guy for The Church and a lover of fine coffees. @ChurchTechGuy