Yeah, we all have a techno-ignorant past that we have to bear, especially when it comes to speaker cables. I remember when speaker cable for the P.A. system was that clear plastic stuff with copper and nickel/copper wires inside that we bought innocently at some retail store. Eventually, we realized that cheap is as cheap does, and better speaker wire leads to a listenable improvement in sound quality. This column is intended to dispel some myths about speaker cabling and to help you think about the right way to choose high-power handling cables.
We all have seen the coils of speaker cables on hooks at retail music stores (with good, better and best mentioned) and glibly assumed that we had options like 16-gauge, 14-gauge and 12-gauge. Then we saw the hyperbole on oxygen-free copper (OFHC), cable polarity and other techno-gibberish hyping up the offerings. Then there are the connectors: from guitar plugs (phone plugs), dual banana plugs, stripped leads and, finally, Speakon connectors.
Sins of the Past
As much as I tried to be a saint when choosing speaker cables, I fell into gigs that forced me to do almost unimaginable things with wire. I started out with 16-gauge Radio Shack speaker wire because that was the beefyest stuff they sold. And, of course, not thinking that there were other sources of heavy-duty speaker wire, I just went with the usual practice and terminated the cable with banana plugs and guitar plugs because that’s what the amps and speakers had for jacks
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When I first started doing hired-gun gigs in the mid-1980s, I fell into using a typical club P.A. system that most rock ‘n’ roll bands toted around. Of course, I knew something was amiss when I was handed coils of 14-gauge Romex (house wiring), complete with banana plugs on the ends for both the Perkins Bins and the amplifiers. Yes, it was a pain in the ass to straighten out the solid conductor wire for the speaker runs, and coiling up at the end of the night was no thrill either, but it did get the job done.
Forward Progress
Eventually, I found the right suppliers like Full Compass Systems and others that sold two-conductor stranded speaker wire in heavy gauges and nice black rubber jackets. Today, my speaker cable trunk has cable brands like Royal, Carol and Coleman, and every cable is 12-gauge, 4-conductor, with Speakon NL4s on the ends. Yeah, I keep some Speakon to banana plug and Speakon to phone jack adapters just in case I have to mate up with someone else’s wiring. But 12-gauge is not necessarily the end choice; you may need some 10-gauge wiring, should you need super-high-power subwoofers to drive from a distance. More on this later.
Calculations
When choosing the right speaker cables for the application, the first criterion is getting the correct wire gauge. When I discussed speaker damping factor a couple of years ago, I mentioned a typical number of 20 or higher as acceptable. Typically, damping factor is expressed as a ratio of im-pedances with the load impedance of the speaker as the numerator and the source impedances as the denominator. Since most amplifiers have small milli-Ohm source impedances, the main source impedance remaining is the speaker cabling impedance. So, solving for a 20-damping factor with a 4-Ohm speaker load gives us a 200 milli-Ohm impedance loss budget for the cable and the connectors.
Since I highly recommend using Neutrik Speakon connectors for modern speakers and amplifiers, their three-milli-Ohm-per-contact loss has a very small effect on getting a good damping factor. But remember, you have eight contact losses, at least, if you think about two conductors, plugs and jacks at the amplifiers and speakers. Then there are the wire gauges and resistivity per choice. Twelve-gauge has 1.65 milli-Ohms per foot, and 14-gauge has 2.62 milli-Ohms per foot. I only use 16-gauge speaker wire for connecting my Marshall Stack amplifier and 16-Ohm speaker cabinet these days, but if you have to use it, it has 4.17 milli-Ohms per foot resistivity.
Now that you are armed with the specs, you can calculate the “goodness” of the speaker cables. For example, a 50-foot length of 12-gauge speaker cable with Speakon connectors has a total of 100 feet of wire for the circuit, or 165 milli-Ohms. Adding the four times three milli-Ohm contact losses brings the assembly up to 177 milli-Ohms. For four-Ohm loads, this is just under the 200 milli-Ohm budget, and is definitely not hitting the budget at two-Ohm loads (100 milli-Ohms). This is why I have a cow when I hear about two-Ohm loading, especially with longer cables feeding the load.
Desired Setups
To make the best of things with real-world speaker cables, Figure 1 and Figure 2 show real-world practices on running speaker cables. Sticking to simple ground stack speaker systems, Figure 1 shows the best practice of placing the amplifier racks directly behind the speakers. Then, cabling up with around four-meter (~15 feet) speaker cables keeps the wiring and contact losses negligible with 12-gauge cables. Quickly running the num-bers, 30 feet of 12-gauge is 49.5 milli-Ohms, and 12 more milli-Ohms of contact loss makes it 61.5 milli-Ohms of total cable loss.
Figure 2 describes the smaller soundco scenario with a single amp rack setup. With 15-foot speaker cable runs for the short side speakers, and 50-foot runs for the long side, it is important to watch the loading and keep the wire gauges beefy. I know from my experience that I can stock my speaker cable trunk with 15-foot, 30-foot and 50-foot speaker cables and cover almost all of the main speaker and monitor wedge runs without hav-ing too much excess speaker cable coiled up at the speakers. If possible, keep excess speaker cable length a bit on both the amplifier, and mostly at the speaker side, in case locations of speakers and amplifier racks have to change.
Techno Conclusions
Do not fall for the hype on speaker cables. All copper used in cabling is oxygen free, otherwise we would all be replacing cables from brown and green corrosion growing out the connections. There is no “direction” on speaker cabling, as the amplifier and the speaker (load) complete a circuit with electrons traveling both ways in each conductor as we are talking about alternating current signals (AC) of audio waveforms. You can buy your raw speaker cabling from electrical supply stores, not just music or pro-audio stores. And, in a pinch, you can snip off the ends of an extension cord and make a speaker cable. At least stay away from using Romex wiring.
