It is often the first component to be blamed if there is a problem with the system during a failure, but too often it is the last ingredient thought about when the parts of the system are being put together. We all take cable for granted, and in the age of wireless technology where you can program all the elements of your show while sitting at Starbucks, it is understandable how it gets overlooked. But as any technician in the entertainment industry knows, cable is still the single element holding most of the system together. Since it is such an important element ED asked some of the experts to suggest a few things to think about before you choose cable.
First, you need to know the right questions to ask. There are a lot of considerations to take into account when looking for cable for your audio, video, and data needs. The primary consideration is what is your application? Will you need a cable that is going to stand up to a lot of abuse night after night? Will it get a lot of handling? Does it need to be flexible or will a stiffer cable be acceptable? From the rental house's perspective, they want a durable cable that will stand up to a lot of abuse and not need to be replaced for a few years. From the technician's perspective, it should be easy to handle and coil and uncoil as well as work each and every time. In order to achieve the right balance between durable and flexible and still maintain the proper performance quality that you need, here are a few suggestions.
All five cable companies we spoke to — Gepco International, Inc., Lex Products Corp., Link USA, Inc., TMB, and Wireworks Corporation — have been involved in the cable industry for decades. They all agree that the three main considerations are performance, durability, and flexibility.
“Performance has to be the number one criteria; the show has to work,” says Bruce Allen, president of Lex Products Corp. “Companies have spent a lot of time trying to achieve the best of all three things, performance, durability, and flexibility. That takes time and trial. You can have a compound that gives you flexibility but it may not last as long so you have to keep trying. It is all a tradeoff, but performance must always be number one. Durability is critical to the rental houses. They don't want to replace these things every six months; they want years of service out of them.”
Michele Yindrick, technical sales manager for TMB adds, “You also have to look at the long-term usage of the cable. If you want it to take abuse and be truly durable you might look at losing some flexibility. You always want to know how the cable is going to be used and where. If you need something to last longer and it is going to get more abuse, then you look at durability over flexibility. Durability includes the quality of assembly.”
Yindrick continues, “Assembly is one of the crucial points for long-term performance, assembly done properly so you don't have conductors pulling loose.” Jerry Krulewicz, president of Wireworks Corporation agrees. “You should look at the assembly; it should be expertly assembled so it will last,” he says. “The way it is terminated is very important; the connector that it is terminated to has to be carefully selected. If you are doing a road show, you want to plug it in and know it is going to work. It has to work out of the box the first time, every time.”
The road market not only demands reliability, but here is where technicians like flexibility. “Flexibility is important for storage: how well it coils and uncoils show after show,” says Yindrick. Flexibility is often most desired in audio cable, explains Krulewicz. “There are a lot of decisions to be made,” he says. “If you are looking for a microphone cable that a performer is going to be using in that situation, you want something that is ultra-flexible. However, some manufacturers of extremely flexible cables don't recommend them for road use because the internals can move. It is definitively a tradeoff with durability. What you are looking at is taking the best electrical characteristics that are required and then matching that with the best physical characteristics of the cable to do the job you are looking for.” Craig Bey-rooti, managing director for Link USA, Inc. concurs: “The biggest consideration for all cables, but especially for audio cable, is getting the right balance between flexibility and durability. Some cables will be very durable but will be very stiff and awkward to use and not lay flat on the stage. Too flexible and you lose some of the durability and it is too easily punctured or damaged. The balance is the key.”
The balance is found in the construction of the cable. The choice between stranded or solid conductors, filler materials, shielding construction, and jacket type all affect that balance. “Solid gives you better electrical performance where the stranded gives you better flex life and flexibility,” explains Scott Fehl, product development manager for Gepco International, Inc. “Flex life is how long the cable will withstand before it breaks due to flexing.” Besides just choosing stranded you should also consider the strand count according to Beyrooti. “A high strand count gives you good properties for audio use and makes it easier to work with as well,” he says. Once you know the conductor type, Fehl suggests that you look at the next element.
“Copper and the insulation is what the signal is affected by, and that is where a lot of the quality comes in. The next element in the cable would be the shielding. You have the choice between foil and braid shielding. Your best shielding is both. The braid shielding gives you better protection if there are power lines nearby; it has more copper mass and it will absorb EMI better, but the foil shield gives you more of a complete surface area coverage, so for straight RF it is better at that. So if you combine the two you have like broadband shielding; you get the low and the high end.
“Braiding is also more flexible,” Fehl continues, “so for portable cables out in the field, braid is better because it doesn't disintegrate and crack over time. Shielding is also there to keep the noise out. Your ear is very sensitive so even a small amount of noise that gets into a signal that is already low voltage, something at microphone level, for example. A very small amount of noise that gets into that cable makes a difference because the whole thing is going to be amplified by the preamp. The shielding is important in audio cable. DMX cable is shielded because it is a data cable. Power cables aren't really shielded because they are just passing power.”
Allen explains the importance of shielding in data cable. “Looking for a full braided shield in data cable will add performance and durability,” he explains. “With all the noise that is created now among all the moving fixtures and data lines, the density of noise in the entertainment environment has dramatically risen, so having a proper shield goes along way to keeping the performance high.” Allen goes on to explain the reason for twisted pairs in data cables. “The concept of a twisted pair is that should a stray voltage be picked up by that twisted pair — because of the geometry of the twist — when you reach the end of the cord they should cancel each other out. The quality of the cable manufacturer to keep that twist consistent is important. The shield is important but the twist is as well.”
Fehl agrees completely on quality. “One of the things that is not as well understood in cable is that the little things of quality are important and it can't be just about price,” he says. “When you get into anything that is high data rate, the electrical performance of the cable has to be more precise. Everything has to be consistent. You want to look for precision grade cables for networking. The thing that makes networking cable networking cable and not just generic control cable is the precision. Electrical performance and mechanical performance are directly related. Anything that mechanically changes affects the electrical performance; the consistency of the pairs has to be very precise.” Manufacturer quality is important in audio cable as well, according to Krulewicz. “For audio cable it has to be quality pairs,” he says. “You need a quality manufacturer, if you get someone who isn't watching the tolerances well, you get changes in the cable's characteristics, which colors the sound, and that's something you don't want.”
Finally the jacket holds it all together as Allen points out. “There is a wide range of very good compounds out there for jackets in data cables,” he says. “What I would stress in data cable is there is a fair amount of low end cable out there that does not use a braided shield and that is not compliant with the USITT spec for DMX cable. You want to look for a good braided cable with a polyurethane or PVC jacket and it should have a long life.”
The jacket is your first line of durability and should be chosen with this in mind. You also have control over durability depending on the care that you take with your cable according to Allen. “You can add life to your cable if you properly take care of it. You want to coil the cord correctly, you want to relieve termination stress, don't pull on cords, and always disconnect a cord at the plug,” he explains. “All of that care goes a long way. Also buy an inexpensive test set from people like Doug Fleenor and test your cable before you get to the show. When you have some downtime, don't just clean it up and coil it; test it as well. Also always have a spare — this is a critical component — it is surprising the times people don't have a spare.”
The cost today of both lighting and audio systems demands that you also plan your budget to include quality cable: without that crucial link your expensive system just looks pretty. Beyrooti feels that this is an often overlooked budget item. “The biggest thought about cable is that when people spend a whole lot of money on the latest array or the latest console, you have to resist the urge to not factor in adequate money for the cable,” he says. “Remember the saying ‘only as strong as the weakest link’ and of course the cable is the longest, biggest link so don't skimp on the cable. You want your system to perform to spec.”
The last thing that you want to worry about is your cable, so make it one of the first things that you carefully consider and you will reap years of service. “Some users have cable that is embarrassingly old, but that is reliability,” states Krulewicz. “Cable is an investment. It should work year after year.”