What Makes a Flexible Cable “Flexible”?
Some AV installations – whether portable stage applications or temporary installations like music festivals and outdoor concerts – require flexible cables. This built-in flexibility makes the cables easier to route, coil up and pack away, and redeploy when necessary. Flexibility also ensures that the cable can withstand repeated pulling, flexing and bending.
So what makes up a flexible cable? There are three factors that can impact a cable’s flexibility.
The conductors in a flexible cable are often stranded (it’s easier to bend several small conductors instead of trying to bend one large one). Generally, the more strands in the cable, the more flexible the cable.
Cable specification sheets will show the number of strand used, If specification sheet says,” 26 AWG (19x40) stranded,” then this means you’re looking at a cable with an overall 26 AWG conductor made up of 19 strands of 40 AWG wires.
More strands typically lead to increased cost and production time. Stranding can also impact the electrical property of cable (such as attenuation, expressed in decibels), so it’s important to compare specification sheets to check performance against your project’s requirements. Higher-gauge conductors (which are thinner) have more insertion loss than lower-gauge conductors (thicker), so stranded cables exhibit more attenuation than solid copper conductors.
Ideally, a shielding on a cable should provide 100% coverage. Foil shields can offer this, but they can crack or unfold when flexed, leaving gaps or even leading to lost continuity when the foil completely breaks.
Braids—which are small strands of conductors woven into the sleeve around the cable—offer cables a flexible solution. Braid coverage is represented as a percentage. By nature, it has small gaps, so it’s considered impossible to get 100% coverage. To Increase coverage, you can use a cable with multiple layers of braid to achieve up to 98% coverage.
Cables are available with a combination of foil and braided designs. This can be a good choice if you want to take advantage of coverage of foil and the flexibility of braids (although you do lose a little flexibility). Belden makes several cables that offer these combination shields, which use both a foil and braid together.
Belden has also patented a flexible branding technique we call “French Braid”: two double spirals tied together by one weave, which offers better flexibility than traditional braid and extends flex life.
Some compounds used in cable construction for insulation and jacketing offer more flexibility than others. These rubbery-type compounds come with some downsides.
Rubbery jackets tend not to have same burn ratings found in traditional building cables. Because of this, they don’t pass the same safety ratings. If you are running them in a building, then you need to check local fire code for requirements.
The rubber material is also tacky and resists sliding, which can create problems if you try to install it within a conduit. You might have to use a large amount of lubricant and/or increase the conduit size.
Flexible cables often require special connectors as well; the soft jackets are often different dimensions and require connectors sized for them. Make sure the connectors you use are designed for stranded conductors (if your cable features stranded conductors). It might also be a good idea to choose a more robust connector design that can handle being installed and uninstalled repeatedly.
Belden offers a wide selection of flexible cables to meet the needs of any AV project. We make cables with more than 100 strands for extremely flexibility; we also offer a very flexible version of a braided shield on microphone cables (what we like to call “French braid,” mentioned earlier).
To find what you need, visit our online catalog and add the word “flexibility“ to your online search. Or, better yet, ask your Belden representative for the flexible version of your favorite cable. They’ll be able to help!