Why Are Some Cables Sheathed?

We rely on various cables in audio production. These cables help connect equipment to other equipment and power sources.

It’s important to understand the logic behind some cables being a certain way as compared to others.

In this post I’m going to discuss why some cables are sheathed.

This post is important for people that work with and use equipment in audio production and other industries that rely on the use of cables.

Without wasting too much, let’s get right into this post.

So, why are some cables sheathed?

There are many reasons why cables are sheathed but the main one is to protect and provide insulation to conduction wires so that the electric flow is isolated and doesn’t come into contact with anything that obstruct or interfere with flow of electric signals or current.

Insulation and sheath are important in any situation where cables are being used to conduct electricity or signals.

Why sheath is important

Cables are sheathed for a number of reasons. Below are two of the most important reasons.

I’m a music producer and this is a music production website so I’m going to basically discuss the importance of cables with regard to the audio production.

Hold cables in place

Working with audio production equipment usually means working with a bunch of wires and cables.

For some equipment, cables come in pairs and sheathing is used to hold all the cables in place.

For example, a cable connection that is made up of two or more single cables that all serve distinct functions for one overall result will be sheathed to ensure that they’re all held in place.

 This makes it impossible for them to be accidentally stepped on or destroyed by anything in the space.

Therefore sheathing is something relied on in the use of many different cable connections.

For example your headphones are made up of the main pin that you plug into your phone and other small wire cables that run and connect the ear piece and the pin.

These small wire cables are protected by a layer of sheathing that holds them all in one place making it difficult for any wire to get pulled and unhooked from the pin.

There are many examples I can use but this one is perhaps the simplest because we all at one point or another have owned a pair of wired headphones.

Shields the cables

Cables inside a sheath are shielded from anything that could damage them.

In audio production, we relyon cables being sheathed to help us avoid any issues of electromagnetic interference which can make it difficult for us to carry out our work.

When dealing with any audio production, engineers or audio producers always want to ensure quality.

For example, in music production audio signal quality is the paramount thing we look at before we even start recording any vocals or instruments.

Cables being sheathed allows signals to be transferred without running into issues of signal interference that could lead to equipment like mics picking up unwanted electric noise such as hum and hiss.

Audio production cables

In audio production you’ll most likely be dealing with two main kinds of cables. Which are signal and electric cables.

Signal cables

Signal cables are cables that carry electronic signals such as analog signals. Analog signals are mostly in the form of any physical signals such as voices, instruments etc.

Signal cables have outer shielding other than insulation that is called sheathing which is usually made of plastic-rubber like material that pretty much protects the integrity of any signals sent through the cable.

When signals are sent through a cable that isn’t shielded, they can be interfered with by many things such as metal material and other electric signals near the cable which is why sheathing is of the utmost importance.

Electric cables

Audio equipment also utilizes electric cables that carry actual DC and AC power. These cables are usually what you hook into electric outlets.

They also have to be sheathed to ensure that there isn’t any issues that may make it difficult for electric cables to do what they’re meant to do.

Material

The choice of material that is used for insulation and sheath can have a significant impact on the performance of a cable.

Let’s look into an overview into some of the material

Polyethylene

Polyethylebe or PE is the material of choice for most external cable installations.

It can be stiff and very hard, however low density Polyethylene is more flexible.

High density PE sheaths or HDPE can offer a good option for external or direct burial applications.

LSF

LSF stands for Low Smoke & Fume which is simply a modified PVC compound which can produce less HCI gas and smoke compared to original PVC cables.

However, LSF is somewhat a misleading term, because it is PVC based and could still emit up to 22% Hydrogen Chloride gas when burnt and can give off black smoke.

LSHF

LSHF is also reffered to as LS0H, LSZH (Low Smoke Zero Halogen) or sometimes OHLS (Zero Halogen Low Smoke).

LSHF compounds are quite similar in appearance to PVC cables they differ however in their behaviour when exposed to fire.

They do not give off huge amounts of toxic fumes or smoke and often their fire retardance is a lot better.

LSHF cables are those which emit no more than 0.5% HCl when burned.

Whilst more expensive than PVC/LSF cables; LSHF provides improved building safety and are often specified for use in public buildings such as hospitals and airports etc. 

PTFE Also known as Polytetrafluoroethylene

PTFE, or commonly known as Teflon is a non-flammable, highly flexible, non-toxic and environmentally safe material that can be used in demanding conditions.

The good part is that It can operate at temperatures from -75°C to upwards of 200°C, or up to +250°C in the short term. It is also unaffected by most fuels, oils and fluids. Which makes it a great material for highly demanding conditions.

FEP

FEP or Fluorinated Ethylene Propylene is a Teflon variant which is a type of fluoropolymer that has many similar properties to Polytetrafluoroethylene such as the operational temperatures and its low-reactivity to chemicals.

Rubber

Natural rubber is another great material for cable insulation because it allows for flexibility, even at sub-zero temperatures.

Furthermore, Rubber is absolutely waterproof, chemical resistant, extremely flexible and retains it’s flexibility over varying temperatures.

Due to it’s high cost, synthetic rubber compounds are available and are more economical solutions which can offer a very similar performance. 

Neoprene

Neoprene is a synthetic rubber that provides good oil and chemical resistance, tensile strength, as well as flexibility, even at very low temperatures.

Silicone

Silicone is something you’ve probably heard of.

It is mainly used for high or low temperature applications.

Silicone operates from -50°C to +180°C and has excellent UV resistance.

When exposed to fire, it does not produce any smoke or toxic gases. The soft material is however prone to damage and must be installed with care to ensure that it gets the job done right.

PUR

PUR or Polyurethane offers a lot of good mechanical and chemical resistance properties. Its anti-kink characteristics make it ideal for high flexing automation applications.

Depending on the blend, Polyurethane can be halogen free and flame retardant although it is not ideally suited for use in extreme temperatures due to the operating temperature range, typically between -40°C and +125°C.