What You Need to Know About Loudspeaker Cables
If you read audio magazines or cruise
audio websites, you will have probably noticed reviews and discussions of speaker cable.
This almost always confuses non-audiophiles. After all, they think, what's to
discuss? As long as the wire reaches from the amplifier to the speakers, what more could
you need? The topic is actually quite complex and is subject to a great deal of debate
within the audio community.
When you bought your speakers, you were probably given some
speaker wire -- most stores "throw in" some inexpensive "speaker
wire," with different colored conductors for the "plus" and
"minus" legs. This "gimme" cable will work -- sound comes out of the
speakers, obviously -- but it actually doesn't work well. It changes the sound of the
music it carries. Exchanging it for a better-designed audio cable can improve your sound.
Putting an End to It! Speaker cables are
"terminated" by having connectors fastened to their ends. These connectors
protect the wire from oxidizing and allow a more convenient and better connection to be
made with speakers and the amplifier. The type of connector your speaker wire will require
is dependent upon the types of terminals your amplifier and speakers possess.
Common terminal types:
Spring clips consist of an opening with a
spring-loaded clip that presses against the wire to provide an electrical contact while
also holding it in place with pressure from the spring mechanism. Spring clips accept pins
and bare wire, and, although we do not recommend this, some banana plugs can be forced
(although rather awkwardly) to fit into the openings.
Binding posts are commonplace on many components.
This is typically a threaded hollow-metal post with another hole drilled transversely
through it and either a plastic or metal nut covering the entire length of the post. The
nut can be tightened against bare wire or a spade lug.
A five-way binding post accepts spade lugs, banana plugs,
dual banana plugs, pins, and bare wire (i.e., just about any type of speaker wire
termination available). However, many binding posts do not qualify as five-way, and may
not accept banana plugs, dual banana plugs or spades. These binding posts may not have the
necessary openings for banana plugs to be inserted into them, or they may be spaced so
they don't accept dual banana plugs. Some binding posts have a raised lip around the base
of the post (most frequently found on Japanese receivers) that will not accommodate
spades.
BFA terminations are relative newcomers to the
field. The British Federation of Audio (BFA) developed the design because of new European
safety standards, which ban the use of the 4mm banana plug because it can be inserted into
a European AC socket -- with potentially deadly consequences. The BFA connector employs an
insulated recessed female plug and an insulated recessed male socket.
Common termination methods:
 Spade
lugs, so called because they resemble small split shovels, are a popular speaker-wire
termination because their flat surfaces provide a lot of contact area between the
connector and the connection. They come in several sizes and are made to fit between the
nut on a binding post and its base. If a binding post is too wide, some smaller spades may
not be able to fit around it.
 Banana plugs are basically
cylindrical springs that flex to fit into the opening of a binding post. Most banana plugs
only make contact with the inside of the binding post at a few points along their length,
so the connection is not as secure, nor is there as much contact area, as with spade lugs.
However, rolled banana plugs (consisting of solid copper sheeting) make much more
contact and provide a more secure connection than conventional banana plugs, since they
exert pressure -- and thus make contact with the binding post -- over their entire length.
The greatest benefit of banana plugs is their convenience, which allows for quick-and-easy
connections. There is also something called a dual banana plug, which simply consists of
two banana plugs (the positive and negative) connected together by a plastic housing.
These are falling into disuse since the spacing and 4mm diameter of the bananas is
identical to that of some European AC plugs. Banana plugs can work with spring clips, but
they're more commonly used with binding posts.
 Pins are narrow, solid connectors,
which do not provide much contact area, but are more convenient to use than bare wire
since they can easily be inserted into spring clips or the transverse holes of binding
posts. Their main advantage is that they are compatible with just about any kind of
speaker terminal imaginable.
 BFAs are used primarily on
components that come from the UK and Europe. Since BFAs are designed to be incompatible
with other common terminations, your speaker wires will need a BFA termination if your
amplifier has BFA connectors. Some audiophiles report that rolled banana plugs can be made
to fit into their sockets, but we at GoodSound! urge you never to force any
connection carrying an electric signal. We'd like to keep all of our readers!
|
|
|
But what constitutes a "properly designed" audio
cable? Ahh, that's where all the arguments start.
The musical signal travels from the power amplifier in the
form of an electromagnetic signal -- a combination of electric and magnetic fields, both
of which interact with one another and with the wire carrying them. The electric field
interacts with the wire's capacitance and dielectric; meanwhile the wire's
natural resistance to changing currents creates inductance, which generates a
magnetic field around it. And resistance truncates the musical signal’s amplitude.
It gets worse. Resistance, inductance and capacitance are
interrelated in one of the most basic laws of electronics: Ohm's law, which states that
the direct current flowing in an electrical circuit is directly proportional to the
voltage applied to the circuit. (V=RI -- in which V equals voltage and I equals current --
if you want to get technical about it.)
This sounds complex -- and is -- but it's not all that
difficult to understand.
When an electric current moves through a wire, it meets resistance,
or the tendency of a conductive material to oppose current flow (the wire's molecules resist
the current). When we say that resistance truncates a signal’s amplitude, we mean
that the signal's bandwidth (or frequency response -- the complete sound from the
lowest to highest frequencies) is reduced by the wire's tendency to oppose current flow.
We can reduce this resistance several ways. We can make the wire thicker (lower its gauge)
or we can make it shorter.
But changing one element in the equation changes the other
elements as well. Making the wire thicker changes its capacitance. (Capacitance
refers to the ability -- and tendency -- of a component to store electrical energy.)
A capacitor is a device for storing electrical energy made
from conductive foil surrounded by a dielectric. One way of thinking about speaker
cable is that it's like a capacitor rolled-out flat. The wire is analogous to the
conductive foil and the insulation surrounding it is the dielectric. As an electrical
signal passes through a wire, it interacts with the wire's insulation, which absorbs a
small amount (or sometimes even a large amount) of the energy traveling through the wire.
It can't store that energy forever, so the dielectric releases the stored energy back into
the wire, sometimes long after the original signal has passed through it. This
uncontrolled release of stored energy (capacitance) adds distortion -- a time and
frequency anomaly that "smears" details of the musical signal.
In addition, musical signals are constantly changing --
just as music constantly changes in time -- musical signals are complex combinations of
low and high frequencies. Higher frequencies tend to move faster and create more of an
opposing current, than low frequencies. This means that, with any length of cable, the
highs tend to be more rolled off than the low frequencies. This is a cable's self-inductance.
There's an additional interaction known as skin effect.
The core of a wire conducts electricity best. As current increases, resistance increases.
Low frequencies (low current) tend to penetrate the wire and travel through the core quite
efficiently. High frequencies (high current) tend to travel more easily along the surface
of the wire, where resistance is lower, rather than through the center.
This is only a partial litany of the obstacles confronting
the wire designer, but they should serve as examples of how complicated it can be to
design an "ideal" speaker cable. A successful designer has to juggle a great
number of factors without letting any of them overwhelm the others.
A simplistic way to explain all the different speaker wire
designs would be to say that different manufacturers put different emphasis on each
component of Ohm's Law. Some designers stress the reduction of resistance through
increasing capacitance. Some designers feel capacitance is a huge problem and that
resistance and inductance affect the sound less. Others emphasize the dielectric.
Some companies address these issues by utilizing special
cable geometries, while others tend to concentrate on the purity of the materials used.
Some even utilize special circuits added to the cables to compensate for one or several of
the wire's characteristics. As a result, the entire realm of audio cables can be confusing
-- and some cables can be staggeringly expensive.
At GoodSound! we've experienced the improvements
that well-designed cables can offer, so we encourage you to experience them too. You don't
have to spend a fortune for speaker cables, but you will end up paying for a company's
research and development costs, as well as its marketing and packaging efforts. Since
full-page ads and fancy packages don't add any sonic value to the cables, you might want
to seek out simply packaged wires from specialty companies you may not have seen
advertised in all the magazines.
How to choose the right wire for you? We encourage you to
audition wires at your local hi-fi shop. Many shops will arrange for you to procure
secured loaner cables, so you can audition them at home with your own system. This is
probably the best way to go.
Listen to speaker wires just as you listened to speakers or
amplifiers or CD players when you were shopping for them. Does the wire change the sound?
Is the change more musical or is it just different? If you can't hear a difference between
two wires, chose the less expensive one. If you can hear a difference, but you don't feel
it represents an improvement, keep looking. And always keep in mind that you don't have to
please anyone but yourself -- don't be misled by a brand's popularity or seemingly
impeccable credentials. This is about performance and your preference, nothing else.
No matter which speaker cable you buy, you should try to
buy equal lengths for each channel. This sometimes means that one speaker cable ends up
longer than it needs to be. That's okay, as long as you don't coil the extra cable. A
coiled wire is an electrical component called an inductor and -- you guessed it! --
it affects the sound of the signal passing through it.
|
