Speaker Wire
A History
Copyright 1996-2003 by Roger Russell
All rights reserved
No portion of this site may be reproduced in whole or in part
without written permission of the author.
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"Iconoclast:
One who attacks established beliefs or institutions. And who created these
institutions? And who established these beliefs in place of the truth?" |
For many years, wires that were used to connect speaker systems were
often zip or line cord. The longer the run was, the heavier the wire that was
used. There were no special speaker wires--just plain old copper wire--solid or
stranded. The emergence of high tech speaker wire has raised some fundamental
questions about the benefits of these new and sometimes extremely expensive
wires.
Resistance in the speaker circuit is the key factor that determines
loudspeaker performance. The loudspeaker circuit includes the connecting wire
between the amplifier terminals and the speaker terminals, the amplifier
internal impedance and the impedance of the speaker system. There's also
contact resistance at the connecting terminals of the amplifier and speaker
system. (See my page about connecting
terminals.)
The contact resistance of clean connectors and the internal impedance of
good quality amplifiers is normally small. The controlling factors that remain
are the speaker system impedance and the speaker wire resistance.
The DC resistance of a typical 8-ohm speaker system is about 7 ohms. This
resistance is due to the wire in the woofer voice coil. It may be a total shock
to some people to know that a typical 8-ohm four layer woofer voice coil
contains about 120 feet of number 28 solid copper wire. This wire is all in the
circuit with the speaker system hookup wire. It's also much longer than a
normal run of hookup wire from the amplifier to the speaker. Even a mid range
speaker can have about 30 feet of number 33 solid copper wire and a tweeter can
have 20 feet of number 35 solid copper wire.
In the early speaker manuals, starting with the XR5, I included a chart
for estimating the maximum wire lengths for various sizes of copper wire needed
for 4 and 8 ohm loads. I have expanded it on this page to include 2 and 6 ohm
loads as well. It was based on the resistance of the speaker wire not exceeding
5% of the rated impedance of the system. The wire length is for TWO-CONDUCTOR
wire. This includes one wire out to the speaker and one wire back again.
Maximum Wire Lengths For TWO CONDUCTOR Copper Wire
|
Wire Size |
2 ohm load |
4 ohm load |
6 ohm load |
8 ohm load |
|
22 AWG |
3 feet max |
6 feet max |
9 feet max |
12 feet max |
|
20 AWG |
5 feet max |
10 feet max |
15 feet max |
20 feet max |
|
18 AWG |
8 feet max |
15 feet max |
23 feet max |
30 feet max |
|
16 AWG |
12 feet max |
25 feet max |
37 feet max |
50 feet max |
|
14 AWG |
20 feet max |
40 feet max |
---------- |
---------- |
|
12 AWG |
31 feet max |
---------- |
---------- |
---------- |
|
10 AWG |
50 feet max |
---------- |
---------- |
---------- |
For example: you can use#18 wire for a 25 foot run to a nominal 8 ohm
speaker, but if the run is increased to 35 feet, #16 wire must be used. 50 feet
is the maximum recommended length for normal line cord or Romex solid copper
wire. This length is more than adequate for most installations. An explanation
is further down on this page titled "What about Wires Longer Than 50
Feet?".
A wire resistance of less than 5% of the nominal speaker impedance is
chosen to work well with almost all speaker systems and can be considered
conservative. Even a resistance of less than 10% of the nominal value could be
used with some speakers and would not be audible. A further explanation can be
found in the next section.
What happens when the resistance gets too high? First, there is power
lost in the wire and the speaker will not play as loud. More important, as the
resistance in series with the speaker increases, it makes the amplifier look
more like a current source. This means the speaker frequency response will tend
to follow the rise and fall of its impedance curve.
The impedance of most speaker systems is not constant with frequency. A
speaker that is rated at 8 ohms may be exactly 8 ohms at only a few
frequencies. The rest of the time it may wander above and below this value
several times.
As the wire resistance increases, it becomes significant compared to the
speaker impedance. It will affect the areas of lower impedance values first and
eventually will be audible. Speakers with small impedance variations versus
frequency, and that don't dip below the nominal impedance, will be more
tolerant of higher resistance in the speaker wire. On the other hand, speakers
with large variations in impedance that dip below the nominal value will be
much easier to notice. If the speaker has constant impedance versus frequency,
the only change will be reduced output.
What if you use wire heavier than the minimum size recommended in the
table? There is no audible improvement but there can be a considerable increase
in cost. On the other hand, it would be a conservative choice, particularly for
in-the-wall installation where you might someday be using lower impedance
speakers and would need to replace the existing wire with heavier wire. Solid
copper house wiring is sometimes less expensive than multi-stranded wire.
Heavier solid wire is harder to work with, though, and that may require special
connectors to fit the amplifier and speaker terminals.
Oddly enough, it isn't the freedom of oxygen in copper wire that makes
any difference. The process of removing oxygen also removes the impurity of
iron and it's this impurity that can cause the resistance to be slightly
higher. The difference in resistance between copper wire and oxygen free copper
wire is too small to be significant for speaker wiring. It can be considered to
be ordinary copper wire as far as the recommended lengths of copper wire in the
table. Oxygen free copper wire can be more expensive than ordinary copper wire.
Silver wire has lower resistance compared to the same gauge of copper
wire. Smaller silver wire can be used for the same resistance. It may cost
more, though.
What About Wires Longer Than 50 Feet?
Besides losses due to cable resistance, longer cables begin to exhibit a
significant reactive component of capacitance and inductance regardless of the
wire size. Measurements I have made show that response in the 10 kHz to 20 kHz
region is affected by a small amount. Then why are differences in extended wire
lengths not heard? There are at least two reasons. Both are related to our
hearing ability.
An article was published in Audio, July 1994 titled "Speaker
cables: Measurements Vs Psycho-acoustic data" by Edgar Villchur. The
psycho-acoustic data shows that for pure tones at 16kHz the smallest average
detectable difference in level is 3.05 dB. He also indicates: "It can be
predicted that at a given level the just noticeable difference will be
increased by a significantly greater amount by the masking effect of musical
sound below 10 kHz." (See note 1). The findings were based on individuals
20 to 24 years old that had normal hearing to 20 kHz (See note 2). This is what
might be called the best of conditions for hearing differences.
However, as we age,
our sensitivity to high frequencies decreases dramatically. The chart is from Modern
Sound Reproduction by Harry F. Olson. It shows the average hearing loss Vs age
for men and women at frequencies from 250 Hz to 8000 Hz. This means that for a
man at age 35, sensitivity is down about 11 dB at 8000 Hz. For a woman at that
age, sensitivity is down only about 5 dB. We can infer that sensitivity is down
a whole lot more at 20kHz.
So for these two reasons this measurable high frequency wire loss in the
10 to 20kHz region is not audible for a moderately long wires like 50 feet.
Longer runs may still not be audible for some people, provided the wire
resistance is kept low enough.
(Note 1) An article was published in the Journal of the Audio Engineering
Society by Lipshitz and Vanderkooy titled "The Great Debate: Subjective
Evaluation" Volume 29, No. 7/8 July/August. They estimated that when level
differences occurred over a wide band, they were detectable down to 0.2 dB.
However, in a phone conversation with Villchur, Lipshitz agreed this figure is
not applicable to speaker cables where the level differences are all in the
highest audio octave.
(Note 2) Villchur gives a reference of Florentine, Buns and Mason
"Level Discrimination As a Function of Level for Tones from 0.25 to
16kHz" Journal of the Acoustical Society of America, Vol. 81, No. 5 (May
1987)
Gordon Gow's Speaker Wire Listening Test
I have read several magazine articles and papers expressing the findings
and opinions about the various kinds of speaker wire. Some engineers have
applied their expertise to make measurements to prove conclusively that there
ARE differences between wires. A few authors have devoted their entire paper to
the measurements and never mention whether they have actually made any
listening tests or if they could hear any difference. Despite all the
measurements and opinions, the final test is whether you can hear any
difference or not. Obviously this must be done under controlled conditions
where you don't know which wire is connected and there is no delay in
switching.
In the early 1980's,
special speaker wires were beginning to appear on the market. Some of the
claims were totally unbelievable and had prices to match. Realizing that wire
resistance was the critical factor in speaker wire, Gordon Gow, President of
McIntosh Laboratory, used a speaker cable demonstration to show there was no
listening difference between these wires and plain line cord. He delivered his
presentation about the truth in speaker wire using a reel of Monster cable to
stand on. Fifty-foot lengths of wire were used in the comparison. The setup
consisted of a master control relay box and two slave relay boxes. A
three-position switch was used to select one of three different speaker wires
of equal length. One was line cord. The other two wires were from popular
manufacturers. 8-ohm speakers were selected to be used in the test. The two
other brand name wires were heavier than the line cord.
A slave box was positioned
at each speaker. Power to drive the relays in each slave box was provided with
separate cables. The speaker wires were switched at both the power amplifier
and the speaker so that only one kind of wire was connected at a time. Short
pieces of heavy wire were run from the speakers and amplifier to the relay
boxes. No other devices were used in the speaker line. The relay contact
resistance was measured to be less than 0.1 ohms.
The test proved his point. When I took the test, I was unable to hear any
differences using several different 8-ohm speaker systems. BUT, when I
deliberately played one particular 4-ohm speaker and I switched to the line
cord position, I could hear differences. I knew this system dipped down to 2.6
ohms in one frequency range, and 3 ohms in another. It verified that
differences could be heard if the wire was too light for a lower impedance
system. A system this low in impedance required heavier wire. After replacing
the line cord with a heavier line cord of equal length, differences could no
longer be heard.
Normally, a system can run as low as 20% below rated impedance. Although
many speaker systems stay within this limit, or higher, a few systems can have
impedance values much lower, depending on the manufacturer. If you have doubts,
it's best to ask the manufacturer about the lowest impedance of the system that
you plan to use and select a connecting wire based on the lowest impedance
value.
The lowest impedance limit for McIntosh speaker designs was 6.4 ohms, for
a nominal 8-ohm system. The wire selection table was calculated with this in
mind. Another reason was that the 8-ohm tap on McIntosh amplifiers could safely
drive impedance as low as 6.4 ohms without requiring connection to the 4-ohm
tap. Direct-coupled amplifiers, of course, did not have this restriction.
THE KIND
OF WIRE MADE NO DIFFERENCE
It can be solid, stranded, copper, oxygen free copper, silver, etc.--or
even "magic" wire--as long as the resistance is kept to be less than
5% of the speaker impedance. There is no listening difference as long as the
wire is of adequate size.
Of course, we are not personally able to establish the truth of
everything for ourselves and it's not easy to set up a similar wire listening
test. Very few people are able to make speaker impedance measurements or wire
resistance measurements down to 0.1 ohms. Like many other things in life, we
rely on indirect sources of information, such as sales literature, reviews and
opinions. This is called Authority Belief, which is part of our belief system.
An interesting article about the belief system is described in ETC: A Review Of
General Semantics Sept. 1964 titled Images Of the Consumer's Mind by
Milton Rokeach.
Gordon Gow's cable demonstration provided a personal experience for
customers that could replace the Authority Beliefs they had relied on earlier.
The demonstration was controlled. It was an instant comparison and the
listeners did not know the wire identification. Gordon held many such
demonstrations in dealer showrooms and at shows.
Despite the effectiveness of Gordon's cable demonstration and the truth
about speaker wire, people visiting the McIntosh room at the shows, who had not
experienced the cable demonstration, were disturbed that we were using ordinary
heavy zip cord instead of one of the popular brands of speaker wire. Instead of
listening to the McIntosh speakers and electronics, they recalled
"bad" things they had been told about "common" speaker wire
and this promoted questions about the "inferior" wire being used.
When we changed the wire to a popular brand of wire, customers were happy with
the setup, and directed their attention to the McIntosh equipment.
The demand for high quality speaker wire was increasing and appeared to
be a new marketing area for several companies. McIntosh did not make or sell
speaker wire. The solution seemed very obvious--rather than spend time and
effort to create negative sales for McIntosh dealers who were beginning to sell
speaker wire, it seemed best to encourage the speaker owner/customer to consult
with the dealer about what speaker wire to use. Consequently, I no longer
recommended the kind of wire or wire sizes in the speaker manuals.
By 1988, McIntosh no longer supplied audio interconnects with the
electronics. Again, many kinds of special audio cables were available to the
customer/owner. The dealer could also be consulted about what cables to use.
I credit the success of the speaker wire industry to their expert sales
and marketing ability. However, it is my experience that ordinary copper wire,
as long as it's heavy enough, is just as good as name brands.
Stereo Review Dares to Tell the Truth (1983)
A 6-page article by Laurence Greenhill titled "Speaker Cables: Can
You Hear the Difference?" was published in Stereo Review magazine on
August 1983. It compared Monster cable, 16-gauge wire and 24-gauge wire. The
price at that time for a pair of 30-foot lengths of monster cables was $55.00.
The cost for 16 gauge heavy lamp cord was $.30/foot or $18.00 and the 24 gauge
"speaker wire" was $.03/foot or $1.80
"...So what do our fifty hours of testing, scoring and listening to
speaker cables amount to? Only that 16-gauge lamp cord and Monster cable are
indistinguishable from each other with music and seem to be superior to the 24
gauge wire commonly sold or given away as 'speaker cable.' Remember, however,
that it was a measurable characteristic--higher resistance per foot--that made
24 gauge sound different from the other cables. If the cable runs were only 6
instead of 30 feet, the overall cable resistances would have been lower and our
tests would probably have found no audible differences between the three
cables. This project was unable to validate the sonic benefits claimed for
exotic speaker cables over common 16-gauge zip cord. We can only conclude,
therefore, that there is little advantage besides pride of ownership in using
these thick, expensive wires"
Needless to say there was a strong letter to the editor in the October
Stereo Review from Noel Lee, President of Monster Cable. "...was not the
conclusion of nearly three thousand Monster Cable purchasers who participated
in a warranty/response card survey in 1981-1982. Among those responding, 56 per
cent indicated 'an overall significant improvement, '42 per cent attested to a
'noticeable improvement,' and only 2 per cent wrote back that they heard no
difference in system performance."...
Yes, some of this claim is believable but for the wrong reasons. If the
wire used previously had resistance that was too high, there would be an
audible difference. If the wire connections at the amplifier or speaker were
loose or corroded, installing the new cable tightly would make an audible
difference.
Then we get into the more subjective evaluation. Suppose you're already
using adequate size wire and have good connections at the speaker and
amplifier. If you're then told the new wire will make an improvement, you will
be looking for it and truly believe that you hear an improvement. Some people
might go as far as saying "If I spent all that money for these cables, you
can be sure I'm going to hear a difference." (rather than admit I wasted
my money or have bad hearing).
There are other factors as well. If you listen to the system with the old
wires and then replace them with the new ones, it could take 5 or 10 minutes to
do this. By then you will have forgotten what the old sound was like. How many
of the customers made an instant and more reliable comparison like what was
done in Gordon Gow's demonstration or in the Stereo Review test? I wonder how
these customers would fare in a test where they didn't know which wire was
being used.
Stereo Review Gets More Conservative (1990)
A 5 page article by Rich Warren titled "Getting Wired" was
published in Stereo Review in June 1990. It devotes 4 and a half pages to the
creative claims and descriptions by the various wire manufacturers. Near the
end of the article reference is made to an Audio Engineering Society paper by
R. A. Greiner published in the JAES in May 1980 and titled
"Amplifier-Loudspeaker Interfacing." The conclusion is that speaker
cables do not behave as transmission lines despite the theory subscribed to by
many, if not most, esoteric cable designers.
This time the conclusion in Stereo Review was extremely conservative.
Perhaps this was due to the influence of speaker wire advertisers who pay for
their magazine ads. As in Gordon Gow's wire demonstration, wire sales,
advertising and dealer profits were hurt by the truth about speaker wire.
"Are there real sonic differences between audio cables? We leave
that up to each individual to decide. What we can say is that there are some valid
reasons, described in the box on the facing page (cable pictures and
manufacturer descriptions), to use good cables in your hi-fi system. Which
theory you choose to subscribe to and how high a price you're willing to pay
for cable comfort is up to you."
An Honest Answer from Sound & Vision
(2001)
Here's an answer by Ian Masters in
the May 2001 issue of Sound & Vision, page 36 Q&A.
Note: I saw no speaker wire advertisements in this issue!
"Cheap Wire
Q. Would it be okay for me
to use single conductor wire as speaker cables running through the attic or
under the house? Does stranded wire provide some sonic benefit? It would be far
cheaper and easier for me to run 12-gauge wire to a plate with banana
receptacles and then use specialty cable at each end to patch to the amplifier
and speakers. Jon Schwendig, Santa Clara, CA
A. There are a lot of
myths about speaker wires, but in the end it's thickness that counts, and 12
gauge should be heavy enough for any reasonable domestic application. I've
taken several comparative listening sessions over the years, and the sort of
wire you want to use involves no sonic degradation that I (or anybody else in
the tests) could hear. You could even wire the whole distance from amp to
speakers using 12-gauge, but it would probably be more convenient to use
something more flexible for the actual connection to components. Specialty
audiophile cables would serve that purpose nicely, although more modest cables
would work just as well."
All Low Cost Wires Are Not the Same
Here's some typical
low cost wire that's available today. The wire at the left with the heavy
insulation is 12-gauge low voltage cable that's used for garden lighting
accessories. It's 1/2" wide and cost 28 cents/foot. The white lamp or
extension cord is 16-gauge and is about 1/4" wide. It cost 25 cents/foot.
The black wire at the right is 24-gauge" speaker wire" that came with
a receiver. It's only 1/8" wide. Although the 24-gauge wire is very small,
it is only 8 feet long. That works out to just 5% of the impedance for an 8-ohm
speaker or 0.4 ohms.
All of this wire is stranded and is easy to work with. All the wires are
coded so that you can maintain proper phasing of the speakers. The smaller wire
has a white stripe on the insulation of one of the conductors. The other two
have ridges molded in the insulation covering one of the conductors.
All inexpensive wires
are not the same, However. This wire at the right is sold as speaker wire by
such places as Home Depot and Lowes. It sells for 33 cents/foot. It has
transparent insulation and is 12-gauge. It is much less expensive than the
brand names. It does not have any coding to identify one of the wires for
proper phasing. I had some of this wire for about 6 months and noticed it was
turning color. Now it has turned a very pronounced green on the surface of the
copper wire indicating a chemical interaction with the insulation and the
copper. A new piece of wire is at the right for comparison. Although the wire
may not corrode further, it doesn't inspire confidence, particularly if the
insulation comes close to the connecting terminals.
Perhaps the transparent insulation is an attempt to mimic the more
expensive speaker wires. Without researching the chemical properties of the
insulation or the need to code one of the wires, it is not well thought out for
use as speaker wire. I have heard complaints by others about the same problems.
The normal lighting wires and wire supplied with the receiver shown above do
not have these problems.
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More text and pictures about McIntosh will be added as my research continues. Any comments, corrections, or additions are welcome. |
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Created by Roger Russell |
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