What You Should Know About Snake Cables and When to Use Them
Different Types of Snake Cables
The AV market in particular finds lots of value in using snake cables. (The first time I saw the term used years ago was in an AV application referencing an analog audio cable.) Imagine a concert stage with cables running from every on-stage mic to a back-of-house mixer: That could be messy and dangerous! Rather than running individual cables, these cables can be bundled together to create a cleaner, easier-to-manage solution. (The length of the cable is coiled up and fed out from component to component, so it ends up looking kind of like a snake.)
Analog snake cables are still used often in the AV world. They range in size, starting with two cables grouped under one jacket. In Belden’s case, they can go up to 32 pairs as a standard in a snake cable – with the ability to go up to 52 pairs within a few different product families. Typically speaking, in a snake cable, each individual cable maintains its own jacket in addition to being covered by the outer jacket. This allows the cables to be separated at the end of the snake so they can run to different equipment or connectors.
To meet burn requirements in plenum spaces, some manufacturers shield each set of conductors instead of jacketing them. This approach requires an extra termination step during installation; you have to apply heat-shrink tubing to protect each pair of conductors.
In many AV applications, audio signals have converted to digital signals, which require 100 Ohm cables. This has made digital audio snake cables popular as well. They mirror the purpose of analog snake cables (but handle digital signals, obviously).
Video snake cables are another option frequently used in AV applications. By bundling HD-SDI video coaxes, they work great for dual- and quad-link requirements while keeping environments neat and tidy.
As AV applications move toward IP convergence, category multicore cables are being used as well—especially in situations where broadcast crews are on the move.
For example, Belden manufactures CatSnake Cables, which are made up of highly flexible, 4-pair category cables designed for situations that call for frequent deployment and redeployment. Their jacket is soft like a microphone cable, so they work great in stage environments.
We often hear this question when it comes to category cables: If it only contains one cable with four pairs, is that really a snake cable? By definition, it’s not; however, AV technology sends multiple signals down a single cable so, in this situation, it’s more like a “virtual” snake cable.
The Manufacturing Process Behind Snake Cables
The simplest way to join individual cables together is through a manufacturing process called “zip cord” or “lamp cord,” which is where cable jackets are extruded next to each other; they’re bonded together with a small piece of plastic between them. The cables are separated by this small piece of plastic, leaving two individually jacketed cables.
It can take some talent to set up these machines correctly; the more cable you bundle, the more difficult the process can be. As they are bundled together, or as an overall jacket is applied, cables should be helical twisted. This involves very large equipment as spools of individual legs twist around each other.
To make them easier to drop, cable snakes are sometimes offered in “speed pulls.” Instead of using an overall jacket, one or two strands of aramid yarn are wrapped around individual cables in a spiral every two to three inches. This wrap holds the cables together while they’re installed. These cables are designed for permanent installations (not for repeated flexing). Installation should also be avoided in situations where wrapped aramid yarn could snag on rough edges.
With speed pulls, you can add different types of cable to bundles; if you use the same cable types, then you either need to color code the jackets or use custom-printed legends for each run.
Patented by Belden, Banana Peel® construction is also available on some snake cables that will be deployed in permanent installations. This construction groups three to six cables together to a center spline, eliminating the need for an overall jacket. The cables can be peeled away from this spline almost like peeling a banana. Each cable maintains its own jacket after it’s peeled away from the center.
An Important Consideration: Fire Ratings
When dealing with snake cables, fire ratings should be top of mind.
By nature, snake cables are made up of more flammable materials (all of the internal cables plus an outside jacket). To overcome this challenge, Belden developed a new line of audio snake cables called Indoor/Outdoor Stadium Cables, which have a riser rating and utilize waterblocking material.
Want to make your next project easier and more manageable? Think about using snake cables for runs that involve multiple cables going to the same location. If you don’t see what you need in our catalog, give us a call. Depending on your project, we may be able to create a custom snake cable.