|Elliott Sound Products||Cables, Interconnects & Other Stuff - Part 2|
Speaker leads have been discussed extensively in my article on impedance, but I shall repeat some of this here for the sake of completeness. For the full text, see Impedance  and Amp Sound, an article discussing the influences that affect the sound of amplifiers.
This was pointed out to me by a reader, and was originally published in the New York Times (on-line edition) a while ago ...
Copyright 1999 The New York Times Company
December 23, 1999
A Spat Among Audiophiles Over High-End Speaker Wire
By ROY FURCHGOTT
In the last year, Lewis Lipnick has tested high-end audio cables from 28 manufacturers. As a professional musician with the National Symphony Orchestra and as an audio consultant, he counts on his exacting ear to tell him if changing cables affects the accuracy of the sound from his $25,000 Krell amplifiers.
His personal choice is a pair of speaker wires that cost $13,000. "Anyone would have to have cloth ears not to tell the difference between cables," he said.
"In my professional opinion that's baloney," said Alan P. Kefauver, a classically trained musician and director of the Recording Arts and Sciences program at the Peabody Institute of Johns Hopkins University. "Has the wire been cryogenically frozen? Is it flat or round? It makes no difference, unless it makes you feel better." His choice for speaker wire? Good-quality 16-gauge zip wire.
The disagreement would be unnotable except for one thing: experts are in agreement that most cables that claim to improve the sound of audio equipment don't. Even cables costing thousands of dollars per foot are often little more than sonic snake oil, experts say. Consumers trying to purchase audio cables often find themselves buying high-end replacements because the only cables in the store are expensive ones.
A purchaser of an entry-level $550 stereo system might be sent home with $55 worth of the least expensive middle-quality audio cables. While experts agree that most cables make exaggerated and unfounded claims about improving sound, they cannot agree on which cables actually do improve sound and which do not.
The scientific record is unclear. So far no research paper contending to prove or disprove the value of fancy wires has been accepted by the leading industry publication, The Journal of the Audio Engineering Society, said Patricia M. MacDonald, its executive editor. She said there were dozens of reasons a research paper might not meet her journal's standards.
"I don't think anyone should infer anything from it," she said.
The manufacturers and sellers of audio goods like to stay above the fray. Cables are a highly lucrative item that may account for a modest percentage of sales but a greater percentage of profit. Even audio manufacturers not directly involved in the cable business like to steer clear of the debate.
[Related Articles: Do It Yourself: A Little Soldering Goes a Long Way; (December 23, 1999) ]
Polk Audio, a well respected manufacturer of loudspeakers in Baltimore, no longer makes cables but declined an invitation to set up a listening test in its laboratories. One reason it gave was that the test could affect relationships with audio stores. "We would be hearing from every retailer in the country," said Paul Dicomo, communications director for Polk Audio. Kerry Moyer, staff director for the Consumer Electronics Association, which represents manufacturers, said accessories were usually the highest markup items, wires included. Sales of high-margin accessories have become critical in the current market, where prices of components like receivers, amplifiers and DVD players, have had profit margins squeezed by competition.
"It becomes a question of where are we going to make a little money?" he said. Mr. Moyer, whose $3,000 sound system uses about $300 worth of cables, said the technological superiority of a cable is not the issue -- it is the perceived value to the hobbyist.
"If someone feels good about buying it, whether it works or it doesn't, it makes them feel good," he said. "I don't think we should question."
John Dunlavy, who manufactures audiophile loudspeakers and wire to go with it, does think questioning is valid. A musician and engineer, Mr. Dunlavy said as an academic exercise he used principles of physics relating to transmission line and network theory to produce a high-end cable. "People ask if they will hear a difference, and I tell them no," he said.
Mr. Dunlavy has often gathered audio critics in his Colorado Springs lab for a demonstration.
"What we do is kind of dirty and stinky," he said. "We say we are starting with a 12 AWG zip cord, and we position a technician behind each speaker to change the cables out." The technicians hold up fancy-looking cables before they disappear behind the speakers. The critics debate the sound characteristics of each wire. "They describe huge changes and they say, 'Oh my God, John, tell me you can hear that difference,'" Mr. Dunlavy said. The trick is the technicians never actually change the cables, he said, adding, "It's the placebo effect."
This leads to disagreements based on competing science. Bruce Brisson, who owns Music Interface Technology, an ultrahigh-end wire manufacturer in Rockland, Calif., also wants to see cable charlatans revealed and may use his extensive laboratory to do it.
"I am getting ready to expose this in the year 2000," he said. "People are paying a lot of money and getting nothing for it." But he disagrees with Mr. Dunlavy on the effectiveness of wires, saying that the theory Mr. Dunlavy uses to design his cables is not the right theory and that is why listeners cannot hear a difference. **
Some scientists say it would be difficult to prove one way or another. Changing cables leaves a time lapse that makes comparison difficult. Putting several stereos side by side with the different wires would mean that the speakers would be different distances from the ear, which could have an effect. And while a switch could be made that would send a signal through each of several cables to a speaker from a single sound system, cable makers say the switch itself might spoil the advantages of their wires.
Part of the difficulty is that there are still unexplained acoustic phenomena. William Morris Hartmann, a professor of physics at Michigan State University in East Lansing, works on psycho-acoustic projects, which investigate the way sound is perceived, rather than the way it is produced. There are examples, he said, of sounds that measure beyond the range of human hearing, and yet some people seem to perceive them. That means the market is left open to wild claims and psuedoscience. "It's annoying, but it's hard to disprove," Professor Hartmann said.
Perhaps the closest thing to middle ground is the position taken by Russ Hamm, an electrical engineer whose New York company G Prime Ltd. installs digital processing equipment for studios. Mr. Hamm said that indeed, wires do make a perceivable difference, but very little, and then only to professionals, like the engineers at BMG Music. He lent them new high-grade cables for use on roughly $250,000 of equipment. On his system, Mr. Hamm uses a specialty cable manufactured in Vienna that costs $2 a foot.
"We are talking subtle differences, but that is what the high end is all about," he said.
It is a subtlety he describes as a 2 percent difference on a high-end system. "If you had a fine Bordeaux wine, how much does it matter if it's in a nice wineglass or a Riedel crystal glass?" His advice to audiophiles: "I would say that you want to put the first $10,000 into your equipment."
Copyright 1999 The New York Times Company
The above is reproduced verbatim, and I hope that this information is helpful to your understanding of the topics to follow. Remember that the purpose of this article is not to try to sell you something, but to inform and rationalise the many myths that abound regarding the audibility (or otherwise) of different cables.
** It is worth noting that the year 2000 has come and gone, and to my knowledge, neither Bruce Brisson nor anyone else has produced a scientifically sound explanation for the alledged superiority of any one cable over another. There is simply little or no validation available for the vast majority of the outlandish claims made.
We hear so much about damping factor, the effect of speaker leads (and how much better this lead sounds compared to an 'ordinary' lead), and how amplifiers should have output impedances of micro-Ohms to prevent 'flabby' bass and so on. But what does it all really mean?
Before an informed judgement can be made, we need to look at some of the real factors involved. There are a multitude of different impedances involved in a typical amplifier to loudspeaker connection, most of them having a vastly more profound effect than the impedance of the speaker lead alone.
For example, my own (tri-amped) hi-fi uses separate amps for the bass and mid with a designed output impedance of about 2 Ohms. This provides a useful extension of the bottom end (I'm using sealed enclosures), without excessive peaking at resonance. Much the same effect is found with most valve amplifiers, which typically have an output impedance of 1 to 6 Ohms.
Ignoring the losses in the speaker lead (which are usually very small), the impedance of the cable is very low compared to that of loudspeaker crossover networks and the like. While there is no denying that some speaker leads do sound different, the important thing is 'different' rather than 'better'
A double-blind test carried out by an Australian electronics magazine many years ago found that most listeners thought that the really thin figure-8 type speaker cable had better bass than all the more expensive ones. Treble response was generally thought better using a heavy duty 3-core mains cable. No-one thought that any of the high priced cables sounded better than anything else.
Other workers in the field, such as Douglas Self , have determined much the same, so even in the light of some convincing evidence to the contrary, we have reviewers still extolling the virtues of cables costing more than a decent set of loudspeakers.
Generally, resistance and inductance in the speaker lead can (and does) cause minor variations in level, especially with difficult loads. These deviations are likely to be less than 0.1dB for reasonable cable constructions, with inductance less than 4uH. The resistance of a typical twin cable (perhaps 0.1 Ohm) causes response variations across the band, following the loudspeaker impedance curve, but these are usually even less at around 0.05 dB. Neither variation is audible.
You will even find references in some cases to the cable's characteristic impedance - a value that is only useful if cables are used for radio frequencies, or are many kilometres in length. These are uncommon in audio listening rooms in my experience. The characteristic impedance of a cable has no effect whatsoever on signal frequencies that are low compared to cable length, however the normal physical attributes of the cable (resistance, capacitance and inductance) can still play havoc with the frequency response if the cable is not sensibly sized.
At the worst (using coaxial cable) a signal travels at 0.8 of the speed of light (3x10^8 m/s), although many RF cables are far lower (less than 0.7 is not uncommon).
Assume that for an adequate safety margin we want to be able to pass up to 100kHz through the speaker cable. The wavelength at this frequency is 3000 metres, or 2400 metres in a cable with a velocity factor of 0.8. A typical listening room may require up to 10 metres of cable, so at the very worst case, the cable is 1/240 to 1/200 times the wavelength of the (100kHz!) signal. The effect is utterly insignificant in all respects. The signal will be delayed by an amount that is less than that experienced if the listener were to move his/her head by 1mm towards or away from the loudspeaker. This is of course a common occurrence, and often by several millimetres, even while asleep.
While it is true that reasonable quality twin cables (figure eight or zip cord) are adequate for nominal 8 ohm loads over short distances, there are a number of popular loudspeakers that are anything but nominal at high frequencies.
Two that a reader advised me about are the AR11 and the Quad ESL (old model). Both of these drop below 2 ohms in the treble frequencies. The AR bottoming out at 5kHz and the Quad at 18Khz (although anything from 15kHz to 18kHz is common). The dips are fairly sharp and so the load impedance is highly capacitive on the way down and inductive on the way up. The frequencies are high enough to not worry good amplifiers but what about the response at these dip frequencies?
Twin wire cables all have significant inductance which increases in proportion to length. With 10 amp rated twin flex over only 5 metres the response was down by 2.5 dB into one Quad ESL at 18kHz, and 3.5 dB into the other speaker which had 8 metres. This was audible and unacceptable.
The only way to reduce cable linear inductance is to make the two wires talk to each other. Running in close parallel is a start, tight twisting is better but only by using multiple wires for each and interweaving can you really get the inductance down. Several cable makers have done this and sell them as low impedance cables, which is exactly what they are. There are several different cables that use this method, and twin coaxial cable is also used to achieve a similar result.
One construction uses two groups of 72 strands of enamelled wire plaited around a solid plastic core. Using these cables with difficult loads, the droop at either 5 or 18 kHz disappeared and the sound was distinctly better. There would be virtually no other way to solve the problem short of mono amplifiers sited next to each loudspeaker.
One (potentially major) drawback occurs if you own certain amplifiers that are unstable with capacitive loads. Typical multiple twisted pair cable has about 9nF per metre of capacitance with little resistance or inductance, which causes many amplifiers to go into parasitic oscillation. The fix is simple, wind twelve turns of wire around a pen and put it in series with the beginning of the cable. This tiny coil has far less inductance than even one metre of twin flex. The other alternative is to connect a 10 ohm resistor and 100nF capacitor in series, and connect this Zobel network at the speaker end of the cable. Wiring should be kept very short.
This possible issue with speaker cables is one of very few that makes some sense from a technical perspective. There is sufficient evidence from my own measurements and those of many writers that there are indeed some detectable (and measurable) differences. With this in mind, and wanting to provide all the information I can, I have included this information - and this is the one area where properly sized and well made cables really does make a difference. If you own speakers that present a highly capacitive load, or have deep 'notches' in the impedance curve, I would take this information seriously.
Another popular method of minimising inductance is to use a pair of coaxial leads (e.g. 75 Ohm TV/video coax or similar). The inner conductor of one and the outer conductor of the other are joined to make the +ve lead, and vice-versa for the negative. A good quality coax has a relatively low capacitance, and by interconnecting in this way, inductance is also reduced by a very worthwhile margin.
It is widely held that with difficult loudspeaker loads - as presented by many modern speaker systems with complex crossover networks - that reducing inductance can be very beneficial. This is especially true where the crossover causes significant drops in impedance at some frequencies. This also places unusually high demands on the amplifier - one of the reasons that some amplifiers just don't 'cut it' with some speakers.
These problems can be reduced or even eliminated entirely by biamping or triamping , allowing the use of good quality but not extravagant speaker leads.
Resistance, which is easy to eliminate, reduces the damping factor and wastes power. With even reasonably robust leads, this should not be an issue.
Be willing to experiment, using 3-core mains cable (not the types described above, either), and paralleling two of the conductors for the speaker negative connection (or the positive - the speaker will not care either way). Save yourself a fortune, so you can buy more music instead.
I have seen several references on the web regarding the use of Cat-5 network cable and specially wired coaxial cable for speakers. The idea with network cable is to parallel the wires (these cables are usually 4-pair), and it is claimed that the sonic performance is excellent. I haven't tried it, but Cat-5 is relatively inexpensive, and might work quite well. Try it if you want to. Wiring coaxial cables for speaker use is also not too hard, and it is claimed that this can beat most of the really expensive cables.
Before one even considers the alleged benefits of one cable over another, here is something to think about ...
"What does 'veiled' mean (in reference to high frequency reproduction), and how is it determined that the veiling effect is caused by anything specific, as opposed to everything in general? This includes state of mind (i.e. good day, kids acting up, wife annoyed about something), health (cold or flu, hay fever), position of listening chair (was it moved to vacuum the floor?), etc."
And, no, these are not trivial questions. They are every bit as important as anything else, and all the more so if we have only a subjective interpretation of the sound, without measured results that show the effect. Have a look at the article 'Amplifier Sound' for more info.
|Copyright Notice. This article, including but not limited to all text and diagrams, is the intellectual property of Rod Elliott, and is Copyright (c) 1999 - 2010. Reproduction or re-publication by any means whatsoever, whether electronic, mechanical or electro-mechanical, is strictly prohibited under International Copyright laws. The author (Rod Elliott) grants the reader the right to use this information for personal use only, and further allows that one (1) copy may be made for reference. Commercial use is prohibited without express written authorisation from Rod Elliott.|