A Terminated Interconnect: The Right Type of Cable?

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A Terminated Interconnect: The Right Type of Cable?

High quality cables are essential to a stereo system’s performance. Upgrading to higher quality cables is a relatively affordable way to improve sound production. Speaker cables transmit electrical signals from amplifier to speaker, and good ones can carry optimal levels of these signals with a minimum of interference and distortion.

Terminated interconnects are speaker cables whose ends have connectors attached to the wire, usually by soldering or crimping. These connectors then fit into the input and output terminals of the speaker and amplifier. Termination is convenient for connecting system components, and helps reduce oxidation and fraying, two common problems with bare, unterminated wires.

When choosing a speaker wire, the options can be overwhelming. Consumers trying to find their way through various specifications and terminology may find it useful to inform themselves ahead of time about the most important things to look for in a speaker cable.

Understanding Impedance

Impedance is the cable’s resistance to the electrical current that passes through it. Measured in ohms (Ω), a lower impedance means less resistance.

Impedance or resistance is the most important specification for speaker wires. A speaker wire’s job is to transmit electrical signals from the amplifier to the speaker; these electrical signals are then converted by the speaker into vibrations, which make sound. Ideally, a speaker wire should not offer any resistance to the current from the amplifier, allowing a maximum amount of energy to reach the speaker’s coil for optimal sound.

It is very important that a cable’s impedance be less than five percent of the speaker’s rated impedance. This issue is related to the wire’s length and gauge, as discussed below.

Capacitance and Inductance

In addition to resistance, there are two more components of a cable’s impedance: capacitance and inductance.

Capacitance refers to the losses of charge between the two conductors; this can occur through absorption into the insulator, or can occur with nearby conductive objects. Capacitance is measured in farads (F). To keep audible capacitance losses below one percent, the total capacitance of the length of the wire should be under 2,700 pF (picofarads). Usually this is the case; however, some premium cables may have a capacitance of 300-900 pF per metre, meaning that one-and-a-half metres of the cable (three metres of conductor) would have more than one-percent audible loss.

Inductance is the resistance to changes in electric current. Since speaker wires run on alternating current, the sound is affected by inductive resistance. This is particularly true for high frequencies, which involve quick alterations to the current. Inductance is measured in henrys; to keep audible losses under one percent, look for cables with inductance of less than 2 μH. 0.06-0.15μH per metre is typical for premium cables.

Some high-end cables are designed to have greater capacitance in order to reduce induction.

Wire Length, Wire Gauge, and Resistance

The ideal speaker cable would have zero resistance. Since resistance is a function of length, the shorter the cable, the lower its resistance, and the closer it approaches ideal conditions.

Longer wires are needed to connect speakers and amplifiers that are farther apart, or possibly in separate rooms. Before shopping for a speaker wire, consumers should measure the exact distance between the amplifier outputs and each of the speaker inputs using a piece. Opt for the shortest wire possible to connect them safely and in a way that is aesthetically desirable, i.e., along the floor, hidden by moulding, or in-wall, as discussed below.

Wire Gauge

Gauge measures the thickness of the wire’s conductive material. It may be measured in American Wire Gauge (AWG) or in millimetres, or, less commonly, in Standard Wire Gauge (SWG). The optimal gauge is intimately connected with the cable length and speaker impedance. This is because the longer the cable, the higher its resistance. A larger gauge helps lower the resistance.

The following chart outlines the recommended gauges based on the factors. Remember that the higher the speaker’s impedance, the higher its resistance.

Wire Gauge

2 Ω load

4 Ω load

6 Ω load

8 Ω load

22 AWG (0.326 mm2)

3 ft (0.9 m)

6 ft (1.8 m)

9 ft (2.7 m)

12 ft (3.6 m)

20 AWG (0.518 mm2)

5 ft (1.5 m)

10 ft (3 m)

15 ft (4.5 m)

20 ft (6 m)

18 AWG (0.823 mm2)

8 ft (2.4 m)

16 ft (4.9 m)

24 ft (7.3 m)

32 ft (9.7 m)

16 AWG (1.31 mm2)

12 ft (3.6 m)

24 ft (7.3 m)

36 ft (11 m)

48 ft (15 m)

14 AWG (2.08 mm2)

20 ft (6.1 m)

40 ft (12 m)

60 ft (18 m)

80 ft (24 m)

12 AWG (3.31 mm2)

30 ft (9.1 m)

60 ft (18 m)

90 ft (27 m)

120 ft (36 m)

10 AWG (5.26 mm2)

50 ft (15 m)

100 ft (30 m)

150 ft (46 m)

200 ft (61 m)

 

Keep in mind that as the AWG gauge gets smaller, the cable gets larger.

Buyers should also note that 50 feet, or 15.24 metres, is the maximum length recommended for household installation; however, this length should be sufficient for most home sound systems.

Advantages of Terminating Cables

Buying speaker cables that are factory terminated is a convenient way to ensure a secure and durable connection. As opposed to bare wires, terminated cables have a device at the end that connects to the output and input of the amplifier and speaker.

Some audiophiles may prefer bare wires, since terminated ends are yet another point where an error in signal transmission can occur. However, termination has a few major advantages when it comes to speaker wiring. First, it prevents corrosion due to oxidation of copper and silver wires. Since corrosion increases resistance, this can be viewed as a major advantage. The second advantage is convenience: it makes disconnecting and reconnecting cables much easier when moving stereo equipment or for hard-to-reach places. Finally, termination helps safeguard against short-circuiting, which can occur when stray wires accidentally come into contact with each other.

Speaker Cable Materials

The best materials for speaker cables is a hotly debated topic. Furthermore, manufacturers boast the advantages of certain materials over others and raise their prices accordingly. However, experts tend to agree that the listening difference between top materials is little-to-none. Copper and silver are the most common materials for speaker wire. Their high conductivity means minimal resistance.

Copper has long been the standard for electrical wiring, and the International Annealed Copper Standard (IACS) is used to compare the conductivity of other metals. C1100 is the most common type of copper for wiring; electrolytic-tough-pitch (ETP) is 99.9-percent pure and 100-percent IACS conductive. So-called oxygen-free copper, C10200, is now available on the market: it has an oxygen content of 0.001 percent and is 99.95-percent pure. Its conductivity, however, is the same as C1100’s, 100 percent. Purer still is C10100, or oxygen-free electronic copper. It is 99.99-percent pure, with a 0.0005-percent oxygen content, and must rate 101-percent IACS for conductivity. While C10200 and C10100 may be much costlier, some experts believe the nominal conductivity difference has no significant impact on sound production.

Silver is more conductive than copper, meaning that a thinner wire may be used for the same level of resistance. On the other hand, it is more expensive than copper, and, when the resistance is the same, there is no listening difference.

Rhodium is highly conductive and is resistant to corrosion; for that reason, it is another popular material in speaker wiring.

Gold has a higher resistance than copper or silver, but resists oxidation. For that reason, it is often used in termination endings.

In speaker wire, the conductor is wrapped in an insulator material; this is usually a plastic such as polyvinyl chloride (PVC), polyethylene (PE), or Teflon. There are two important aspects of insulation material. First, it should be high quality so that it does not chemically interact with the conductor, which may result in corrosion. Next, it should absorb as little energy as possible, since energy absorption results in distortion.

Termination Types

There are many different types of interconnector terminations. Deciding on a connector type depends partly on the terminal of the speaker and amplifier, which are usually spring clips or binding posts. The following chart outlines the most common types of connectors.

Connector Type

Description

Pin Connector

Wires are soldered or crimped into a thin pin which fits into spring clips or binding posts

Banana Plug, or 4 mm Connector

Very common connector type; fits directly into binding post for a secure, quality connection; gold- or silver-plated plugs resist oxidation

Spade Connectors

Fit behind the collar of most binding posts for a good connection

Dual-Banana Plugs

Connect positive and negative speaker leads; spaced so as to fit with five-way binding posts

Crimping is a process that welds the conductor with the connector. This connection, when performed well, is stronger and more durable than soldered connections. It has the resistance of a length of wire, and is airtight against oxidation.

Although crimping is superior, soldered joints can also provide an excellent connection that is strong and durable. Soldering involves filling the connection between the wire and connector with a metal alloy, often some combination of tin, silver, and copper.

In-Wall Interconnects

Speaker wire meant to be run through walls should be rated for in-wall installation: CL2 or CL3. These ratings, established by the Underwriters Laboratory, test the heat generated by a current running through the cable, the cable’s susceptibility to damage, and how quickly a fire can spread along it.

Where to Buy Terminated Interconnects

Terminated interconnects can be purchased at electronic shops, and online through Internet merchants and websites like eBay. Shoppers should determine the length they need, and what gauge is optimal for that length and their speakers’ impedance. Prior to purchase, it may be advisable to research particular cables in one’s price range, and customer and expert reviews for different models. Verifying a seller’s return policy is also a good idea, in case of a defective cable or disappointing performance.

Conclusion

Terminated interconnects are speaker cables that have connectors attached at the ends of the wires. Quality speaker cables, which run between the amplifier and the speakers, can make a big difference in the way a home audio system sounds. When upgrading speaker cables, buyers may find themselves overwhelmed with the range of choices in terms of materials, specifications, and more. Informing themselves ahead of time helps them find the right cables.

The most important specification for speaker cables is impedance, which measures its level of resistance to an electrical current. Zero impedance is ideal, though impossible; however, by selecting quality materials, construction, and the proper length and gauge, consumers can reduce resistance for optimal transmission. The type of connector is also important: it should be well-constructed and fit with the terminal on the speaker and amplifier.

Familiarising themselves with the meanings of various specifications, as well as the performance of different materials, helps consumers find a quality speaker cable within their price range.

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