I have a no brand speaker which I have been told to be 8 ohms. A VOM measures DC resistance which is a factor of wire thickness. A typical speaker may have an ohm rating (rating the speaker's resistance) of 4 to 8 ohms nominal impedance (impedance being resistance to current flow). Resistance in a speaker varies, however, from low ranges often as low as 2 or 3 ohms to high ranges as high as 30 or more ohms.

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It’s beenawhile since I last wrote a technical article on cables. Lately we’ve been getting hit with the commonquestion “what speaker wire gauge should I use” or 'what matters most in high performance speaker cables'? Is there a difference between 12AWG and 18AWG wire? The short answer is Yes. The higher the gauge, the more resistance. In this case, it's usually best to follow the advice of the Borg 'resistance is futile'. Audiophiles should always wish to minimize speaker cable resistance. Read on to learn why.

American wire gauge (AWG) is a system ofnumerical designations of wire diameters where the thicker and less resistivethe wire is, the lower the gauge number.More often than not, we’ve seen Audiophiles choose a higher gauge esotericwire over a lower gauge generic zip cord cable simply because they were soldsome marketing nonsense from the exotic cable vendor that their wire will yieldhigher dynamics and better Mojo from your system than standard genericcable. Don't believe me? Check out some of the 'midpriced' speaker cables from the likes of Audioquest and Nordost as example and you will see they are anywhere from 16-18AWG. This is much higher resistance than cheap 12AWG zip cord cables you can buy at a local hardware store. To see this graphically, note the resistance vs gauge table below.

Loop Resistance vs Gauge (AWG)

Only thetruth will set you free, so its time to clear your head of marketing slogansand get a good dose of reality about the single most important aspect ofspeaker cables – RESISTANCE. Anytime youare driving power into a low impedance load such as a loudspeaker, the dominantmetric of concern is DC resistance (measure of restriction of conductivity in acircuit). Certainly there are secondaryconcerns which are also important such as inductance, and capacitance. But, aswe’ve proven in our various cable articles and reviews, if you cannot firstselect a cable with low enough DC resistance, the losses will be so greatbetween the amplifier and loudspeaker that all other cable parameters will become a wash. This article willfocus solely on cable resistance and will serve as a guide for choosing theright wire gauge (AWG) for your installation to ensure you realize the maximumpotential of your setup.

Discussion on Choosing the Right Speaker Cables

The twoprimary things resistance affects in the amplifier-to-loudspeaker connectionare: insertion loss and damping factor, both of which are dependent upon cableresistance.

Insertion Loss

Insertionloss is the measure of the loss of load power at the speaker due to excessiveresistive losses of the cable or any additional component attached between theamplifier and the loudspeaker. We typically express this loss in decibels (dB)using the following formula:

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ILoss = 20* log [(Rload / (Rload + Rcable) ]

Note: Forsimplicity's sake, we will assume the output impedance of the amplifier is zerowhich represents an ideal amplifier.

What happens when you have too much insertionloss?

You willexperience power loss in the speaker cable resulting in the speaker not playingas loudly. But it takes a whole lot ofloss here to become audible. For example, it would take nearly 1 ohm ofcable resistance to drop the signal level down 1dB for an 8 ohm speaker. More importantly however, as the series resistancecaused by the speaker cable increases, it makes the amplifier look more like acurrent source which will in turn cause the speakers frequency response tofollow the rise and fall of its own impedance curve. This is particularly more prominent in some class D amplifiers whose response changes more significantly with varying load impedance.

In order tominimize the potential of audibility here, I have established a guideline ofthe maximum acceptable degree of insertion loss that a cable should present tothe system so that when a real world amplifier and loudspeaker are connected,the cable resistance will have a negligible contribution to the overall systemresponse. I plotted the Insertion Loss(dB) vs Distance (ft) for various cable gauges from 18AWG to 10AWG using an 8ohm speaker load.

If you aretruly concerned with top notch fidelity, then:

ILoss < -0.2 dB

(this is a very conservative estimate as the threshold of audibility is often cited at +-1dB)

Figure 1. InsertionLoss vs Distance for Various AWG Cables

As you cansee in the graph, once your distances exceed about 10 feet, you should considerspeaker wire 16AWG or lower. If you areusing a loudspeaker that is rated at 4 ohms, the critical distance becomesabout half that. It is really important touse thicker wire for long cable runs, especially when driving a lot of powerinto low impedance loudspeaker systems.

Damping Factor

Damping factoris a ratio of rated loudspeaker impedance (ZL) to the source impedance (Zs). In this case our source impedance is (Rcable+ Ramplifier). Since we set theamplifier impedance to zero, we will focus solely on the source impedance ofthe speaker cable and see how it affects the damping factor of the system.

Damping Factor = ZL /Zs

Dampingfactor is often an abused term in the industry much like contrast ratio is invideo. Beyond a certain number, itbecomes meaningless. The problem howeveris when the system damping factor is too low, it will have an effect on systemlinearity and again cause the same issues we noted with excessive insertionloss and speaker frequency response variation.If the source resistance is extremely high, it can be noticed audibly byboomy bass response.

In order tominimize the potential of audibility here, I have established a guideline ofthe minimum acceptable System Damping Factor between a cable and a loudspeakerso that when a real world amplifier and loudspeaker are connected, the cableresistance will have a negligible contribution to the overall systemresponse. I plotted the Damping Factor vs Distance (ft) for various cable gaugesfrom 18AWG to 10AWG using an 8 ohm speaker load and correlated the results withthe data we gathered on Insertion Loss in Figure 1.

If you aretruly concerned with top notch fidelity, then:

System Damping Factor> 50

Figure 2. DampingFactor vs Distance for Various AWG Cables

Asyou can see, lower the speaker cable resistance greatly improves the systemdamping factor and allows you to run longer lengths without being penalizedwith significant losses.

Tabulatedbelow are the recommended cable distances (+20%) one should use for variousspeaker cable gauges and speaker loads.

Table 1. Recommended Cable Distances vs Gauge

Read: What is Loudspeaker Impedance?for more information about this topic.

Realizeonce you attach a real world amplifier (non zero output impedance) and loudspeaker (reactive load), the overall systemlosses will be greater but the goal here is to ensure the speaker cable isas transparent as possible.

Cableinductance, AC resistance due to skin effect (to a much smaller extent), will further increase theselosses but they are secondary concerns to primary DC cable resistance. Although I have measured some exotic cablesto produce proportionally lower AC resistance than ordinary zip cord, most ofthese cables had such high DC resistance that even at the frequency extremes;standard 12AWG zip cord had lower overall resistance!

See: Speaker Cable Face Off IIfor further reading on this topic.

What About Braided Cables?

Braided cables utilize multiple individually insulated conductors (usually 22-26AWG) twisted in a pattern that helps to reduce series mutual inductance but usually at the expense of increased capacitance. Remember anytime you bring conductors closer together, the inductance gets reduced but capacitance goes up. I do appreciate these type of cable designs if they aren't overly blown out of proportion with high capacitance needing a zobel network termination to prevent amplifier oscillation for long runs. Braided cables are a fine choice provided that you aren't sacrificing resistance for the design. Some of my favorite braided cables are the mid priced cables like the 8PR or 8TC from Kimber Kable. However, some of their more expensive cables like the Bifocals exhibit lots of capacitance and are not something I'd recommend for very long runs especially because they are quite cost prohibitive and NOT worth the expense for no sonic benefit, in my opinion.

Cable Recommendations

Letme make it clear that the cable length guidelines I set forth here are done sofor audiophiles whom are particularly critical on system performance andtransparency. For casual listeners orinstallers setting up distribution whole house audio, you can certainly runcable lengths much longer than I recommend in Table 1. The degree of audibility of running cableslonger than these lengths depends on the quality of electronics andloudspeakers, neutrality of the room, and sensitivity of the listener.

Ipersonally run 10AWG speaker cable for all of my audio systems in theAudioholics Showcase home. The onlyissue here is this cable tends to be hard to work with and terminate. 14/4 cable is another good choice that iseasier to terminate and has an effective gauge of 11 AWG. Choosing quality cables from reputablesources such as Blue Jeans Cable and Monoprice isa good idea. I always recommend you avoid snake oil when purchasing cables. Otherwise you'll likely find yourself spending more money than you shouldon nebulous claims and fancy packaging. To add insult to injury, you may also end up compromising on the parameters that actually matter, such as wire gauge.

Usethe recommendations in this article as a guideline and NOT a biblicalsource. There is no magic number whenchoosing what gauge to use over a specific distance since the system dynamicsare often too complex. But, if you’rechoosing between two cable gauges, I usually recommend going for the lower one(all other things being equal) to ensure your cables won’t be the chink in youraudio chain for pursuing audiophile nirvana. Being an audiophile often means a bit of overkill on your part and that's ok.

Remember, never sacrifice low cable resistance for an elaborate exotic design that promises to solve a problem that doesn't exist. Many exotic cable vendors promise you the moon but deliver cheese.

My personal cable picksinclude:

• Kimber 8TC
  
• Monoprice 14/4 Speaker Cable