The World is Not Flat!

by Ben Stowe, CTS

The world is not flat, and mic cable is not the same as DMX cable. Both might seem to be profound revelations, but upon review of the facts it seems patently silly that we would regard either as a revelation. In our advanced age of understanding, it’s hard to believe that the world was ever thought to be anything but a spinning oblate spheroid that orbits the sun. With an adequate understanding of electronics and the transmission of digital signals it seems equally silly to think that one might consider mic cable to be the same as DMX cable.

Both arguments have been defended with a great deal of passion, although to my knowledge nobody has been burned at the stake for espousing the truth about DMX cable. I guess if it comes to that, I’ll go pick another fight. I want to help spread truth and understanding about DMX cable, but not at the cost of my life. In fact, I’m really not even willing to sacrifice much of my peace of mind or personal comfort. Usually you can tell when someone will defend a position in the face of irrefutable fact, and ultimately it really doesn’t matter to me what type of cable they use, as long as they aren’t connecting to my fixtures.

I’ve heard some gems supporting the case that DMX cable and mic cable are the same. Some of my favorites are, “Wire is wire”, “It’s fine”, and “I use it and it works”. The last one is my favorite because it follows the same logic that says if I can shoot a basket then I’m Larry Bird, or if my car has tires and a steering wheel it must be the same as a Bugatti. It also brings to mind the experiments some fellow nerds did while testing the use of metal coat-hangers as audio cables. Guess what… it worked! I don’t think anybody in their right mind would actually recommend the use of wire coat hangers as audio cables though.

At the end of the day, most of us “nerds” understand that the differences can be difficult for normal people to understand. Who really wants to dig into the nuts and bolts of capacitance, inductance, impedance and the other properties a cable has. If you do, bless you! You’re one of us and, you probably already knew the differences! If not, here’s the quick version of it.

DMX is a digital signal (Digital is it’s first name in fact). It’s transmitting of approximately 250,000 1s and 0s (bits) every second to the lights. This digital signal requires a cable with a higher impedance and a lower capacitance than audio cable (which is designed with a lower impedance and a higher capacitance to optimally carry an analog audio signal). Each cable is designed to suit a specific purpose. If they were truly interchangeable, why would wire companies go to the trouble of maintaining different sets of tooling, dies, inventory SKUs, etc. when they could enjoy the manufacturing benefits of simply running more of one product.

Further, DMX cables should have superior EMF and RFI shielding to protect these bits, and the data true (+) and data complement (-) conductors should be twisted, as found in a structured cable, to provide the additional protection afforded by common mode rejection.

If you’re not willing to take my word for it, how about the folks that brought us the DMX standard? Do some reading here: http://www.usitt.org/DMX512FAQ.aspx#a6 If that doesn’t convince you, consider joining the Flat Earth Society. They’ve been trying to set the record straight for 547 years.

Ben Stowe, CTS – Sound and Lighting Guru

Ben Stowe serves the AV industry as the President of NLFX Professional, an industry leading supplier of sound, lighting and video systems, a role he has maintained since founding the company in 1993.

Ben’s AV installs have been featured in almost every major industry trade magazine. He has assisted lighting manufacturers with product R&D, as well as contributing to the DJ industry through presentations at trade shows and articles for magazines in the U.S. and Europe.

Ben holds an electrical license as well as other certifications and accreditations, including the most widely recognized one in the AV industry, the InfoComm CTS.

Ben’s highly praised “Event Lighting” DVD is available at ProAcademySeries.com.

To watch a promotional video about it click here.

To contact him email ben@nlfxpro.com.

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