By Jack Sharkey, November 29, 2018
There are three things I never discuss in polite company: politics, religion and audio cables (I hang out with a lot of geeks). But, when it comes to cables, there is so much information, disinformation, lies and damned lies out there I thought a quick look at some of the specs was in order. The problem with doing a piece about cables is you can’t avoid the science: Once you leave the realm of just hooking up a piece of wire to your gear, you’ve got to drill down somewhat into the science of why one thing may be better than the other.
In 2014, New Scientist Magazine commented on the London Heathrow Hi Fi Show, saying that among the cables selling for up to £30,000 for 6 meters, they found [a KEF competitor] demonstrating – to great enthusiasm – their latest speakers with an oddly familiar looking orange cable. When asked about it, the engineer demonstrating them (who'd used the speakers as monitors while recording Saint-Saen's complete works for piano & orchestra, Gramophone's Record of the Year), said of the cables: "Yes, they would look familiar if you have a garden. Before the show opened we went over the road to the DIY superstore and bought one of those £20 extension leads that Black & Decker sells for electric hedge-cutters. They are made from good, thick copper wire, look nice and sound good to me. The show's been running for three days and no one in the audience has noticed..."
I agree with and disagree with this. There are so many variables involved, and sure, the average listener, in an average room with average gear is not going to hear much of a difference when it comes to cables. But cables do make a difference. Plus, in above case, you will never hear the subtle differences a cable can make in the horrible acoustic environment of a trade show!
There’s a lot of copper around, it’s inexpensive, easy to work with and is an excellent electrical conductor. Therefore, copper is the most common conductor you will find, so the scope of this piece will be limited to copper. The downside to copper is that it does oxidize when exposed to air (particularly humid air), so a good insulator is important, but what’s also important is the termination – the exposed part.
Silver is slightly more conductive than copper and it is somewhat less prone to oxidation that copper, but the extra cost outweighs the benefit. Gold is also a very good conductor and is also oxidation-resistant, but the reality is its just not a cost-feasible material for an audio cable. The differences between the three in terms of conductivity measure between 1.50 x10-8 to 2.44 x10-8 so for everyday audio use, those differences are all but immeasurable.
Terminations like banana and spade lugs are excellent, especially if you are going to disconnect and reconnect your components more than once. High quality, gold-plated termination ends are superior, mostly because of their resistance to oxidation and tarnish.
But the most important thing is a good electrical connection, with no stray strands of wire or intermittent connections. If you’re buying terminations, spend the money and buy high-quality ones – but make sure you have done the crimping or connecting as expertly as possible, otherwise you’ve wasted the money you’ve just spent and your music will likely be constantly interrupted with drop-outs and noise.
A simple tinned lead works as well as any other connector, but only if you’re adept with a soldering iron, otherwise just go grab some decent quality screw-type bindings. For line-level connections like RCA cables, a good solid termination with a heavy insulator surrounding the interface between cable and connector is recommended simply because of their strength and resilience.
Some purists will excoriate me, but I pretty much always use bare wire, slightly tinned, for my speaker connections. I like to put as little between me and my music as possible.
The short-take is purity is important, and it does affect the speed a cable will oxidize, but as far as conductivity goes, be careful when someone touts the enhanced conductivity of their “purified” copper.
Conductivity specifications for regular old C11000 ETP copper (Electrolytic-Tough-Pitch) like standard every day cable are exactly the same as the conductivity specs for more expensive C10200 Oxygen Free copper (OFC).
Super-expensive C10100 copper which is highly refined with virtually no impurities and an oxygen level of 0.0005% boasts a full 1% in increased conductivity, which is meaningless at the power and frequency levels we're talking about. This increased conductivity is only going to make a difference in super-precise navigation, aeronautic and medical systems, etc.
It is true that purer copper will take longer to corrode or pit, but in a stable environment like your home it’s going to take quite a while before reaching the point that it messes with your audio signal.
Without getting too involved, let's just say this: Theoretically, in a vacuum a signal such as a radio signal or electrical impulse moves at the speed of light, giving it a Velocity Factor of unity, or 100%. A typical VOP for a standard audio cable is around 80%. Eighty per cent of 186,000 miles per second is 148,800 miles per second which is still pretty fast. In fact, delay over a cable is inversely proportional to its VOP, so for our purposes a cable with a VOP of 80% introduces a signal delay of 20% from one end of the cable to another. In high-frequency applications where the wavelength approaches the propagation delay or in critical systems like navigation systems, a delay of 20% is unacceptable, especially if you don't want your battleship to bump into Hawai'i.
However, in the power cable going into your stereo, the signal is pretty much constant (60Hz) so the delay is meaningless and in an audio system if the delay is uniform and doesn't cause a shift in phase, it’s also not an issue. That being said, keep your cable pairs a uniform length relative to each other to absolutely avoid any issues with propagation delay.
There are three fundamental electrical components that affect analog signals – inductance, resistance and capacitance (all three combine to make Impedance). When speaking about audio cables, generally at audio frequency, inductance and resistance are too low to matter. That leaves capacitance as the primary concern. A spec of 1nF/meter (nanoFarad or one billionth of a Farad) of cable capacitance is acceptable, but anything in the pF (picofarad or one trillionth of a Farad) range should be the target.
At 1nF and an output impedance of 1k Ohm the attenuation is -3dB at 160kHz! If the output impedance, from your vacuum tube preamp for example, is 10k Ohm then the -3dB attenuation will be at 16kHz which is problematic in a quality audio system. So, cable capacitance is more important for the interconnects leading to and from a vacuum tube amp (generally) than a solid-state amp. For a speaker cable run, capacitance in the 1nF/meter range is not going to affect your sound. Of course, the longer the cable run the more concerned you need to be with capacitance, but your cable runs should never be more than 15m.
Maximum Speaker Cable Runs Per Gauge
The lower the impedance, the shorter the cable run. At 14AWG (the minimum recommended gauge for speaker cable) with an impedance of 8 Ohm you can get away with up to 24 meters (78 feet) before cable capacitance becomes a problem, but at the length insertion loss and delay gets introduced, so in reality, the recommended cable length at 8 Ohm is 15 meters (50 feet). In fact – regardless of your cable gauge or impedance, you should never exceed 15 meters.
At 4 Ohm, with a 14AWG cable, the maximum run should not exceed 12 meters (39 feet). With a 10AWG cable even down to 2 Ohm you can run 15 meters without a problem – of course 10AWG cable is pretty expensive, so plan accordingly.
A Quick Note On Power Cables
As with everything, quality counts but there are limits as to what a power cable can do for your sound.
Walk outside and look up at the utility pole outside of your house. See those steel cables up on the top? That's where your power comes from before it goes into your house and magically squirts out of the wall. If you think a good insulator and conductor alone is going to clean that power up, I've got some cable I'd like to sell you. Quality components all contain circuits to filter the power inside of the individual components in your system so spend your money on good components that are well-designed on the inside and you won't have to worry about how well your comparatively incredibly short power cable cleans up all of that mess acquired in a potentially thousand-plus mile outdoor cable run.
If you live in an area with particularly dirty or unstable power, a conditioner will definitely help.
Current Bunching, Or, Oval Cables Are Apparently Better Than Round Ones
Occasionally cable manufacturers will cite their product’s ability to minimize current bunching. They claim that due to things like cable resonance and current return flow, electrons "bunch up" or slow down while traveling along a conductor which degrades audio performance.
Current bunching is a thing but not with cables. Current bunching mostly occurs between the P and N layers of a semiconductor where the effect causes problems along the "standard c-direction of the nitride semiconductor lattice". In audio applications, not so much. If current bunching were really a problem those high-frequency hi-hats in your favorite P-Funk record would always by a tenth of a beat behind the groove.
The shape of a cable (round over oval) will not affect current bunching in a low-energy, low frequency audio cable.
A Quick Note On Cable Break-In
I haven’t yet found a company specializing in cable break-in, but I did come across a company that manufactures cables who allows you to pay an extra fee to break them in for you.
The claim is that the atomic elements of a piece of wire endure tremendous stress when forced through a die at thousands of pounds of pressure and then are suddenly cooled upon extrusion. This stress creates an impediment to the electrons as they begin their journey along the conductors when first put into service.
Even if this was a thing, you could just plug your cables in and let them play for a nanosecond and all of those stressed electrons would chill out.
But, if you’re convinced you don’t want stressed electrons in your house for any reason, for an extra five to 7 days and a measly $200 per cable, I know a company that will hook them up and run them in for you, so you don’t have to.
Skin Effect is the phenomenon where high frequency signals tend to travel on the outside of the cable – along the “skin” of the conductor. Skin Effect is most definitely a thing, even in the audio world as it manifests in any frequency above DC (0 Hz). However, it’s not until around 100kHz that any appreciable degradation begins because of it. The very best equipment will handle frequencies in the high 40k range, but your hearing stops at 20kHz.
At microwave frequencies, conductors that look like hollow pipes are used because the signal only travels on the outside. But at the very upper limit of the audio spectrum (20kHz) the skin effect is so small as to be negligible (assuming a normal cable run as found in a normal house).
At 20kHz a 22AWG cable "uses" 100% of the conductor while a 12AWG cable (common audio size) "uses" 75% of the cable. However, there is more "skin" or outside surface on a 12AWG cable then on a 22AWG cable, so the net effect is negligible.
The Cable Bridge
The claim is that cables resonate, and that resonance interferes with the audio signal running through them. Some cable bridge manufacturers purport to prevent mechanical vibrations from interfering with the music that is otherwise happily traveling along in your speaker cables – at close to the speed of light. Most specs suggest two per cable (they don’t however mention length of run or floor composition, which I would think would be important to the creation of resonances).
Cables are distributed elements and, therefore react like an infinite number of inductive elements, which in turn makes the resonant frequency of the cable go to infinity Hz. Simply put: Speaker cables don’t resonate in the audio range. As far as the speaker cable being susceptible to the plodding footsteps of your clod-like teenager who insists on walking to the refrigerator while you’re listening to Dark Side of the Moon, that's all in your head.
I love the way cable bridges look because I am a borderline OCD neat-freak when it comes to cables, but I have yet to hear an audible difference.
Claim: The Insulating Material Makes A Huge Difference
Yes, but not for the reasons I have read when researching the specs of some manufacturers who claim the insulation absorbs energy from the conductor when music is playing. I have read claims that this energy-absorption causes the dielectric's molecules to re-arrange themselves from a random order into a uniform order. When the molecules have been rearranged, the dielectric absorbs less energy and consequently causes less distortion. At the molecular level, there is no basis in fact for this claim.
Any re-arranging of molecules happens nearly instantaneously and not cumulatively. Molecules in a cable do not stand around in a specific order as per your amplifier’s demands. What you want is an insulator resilient to everyday wear and tear, and that has been designed to shield your audio signals from electromagnetic pollution like radio waves. RF will not directly affect your audio performance but can possibly affect the performance of circuits within your equipment.
I use the best cables I can afford based on the system I am setting up. We work with some excellent cable manufacturers who design cables and insulators that are tough, resilient, with low capacitance and resistance, and with terminations that are equally tough and tarnish- and corrosion-resistant. If you've got the money, you should buy them and keep your system filled with quality components.
Keep your cables as short as possible, but not shorter, and remember that the transducer (speaker) is the mechanical device affects your music the most. Spend your money on your speakers and your amps first. High-end cables look very cool and add a certain panache to your system, but you can enjoy your music plenty without them.
We audio enthusiasts often suffer from hearing what we want to hear, regardless of what we actually hear. So as always, if it sounds better to you, then it is in fact better. If $8500 speaker cables make your music sound better and you've got the $17,000 in your cable budget, go for it. If all you can afford is a spool of 12AWG from Home Depot but you love your music when you listen to it, that's what matters.