Speaker Cable Basics: Length, Gauge and a Few Common Mistakes
First off, I am not going to venture into the controversial world of brands, designs, sound and such.
There are a thousand different opinions with millions of participants using all sorts of terms which, if spoken to a real musician or band, might leave them wondering what drug you were using when you either bought it or decided to avoid it.
Instead, I want to address some basic fundamentals.
In general, speaker cable runs should be kept reasonably short when practical. The longer the cable, the greater its electrical resistance. How important that becomes depends upon the length of the run, the gauge and material of the cable, and the impedance of the speaker.
There is no magical 10-foot point where suddenly everything goes wrong. A properly sized copper speaker cable can easily run farther than that without creating a meaningful problem.
The important number is the resistance of the entire circuit — out to the speaker and back again. A heavier-gauge cable has less resistance than a lighter-gauge cable of the same length.
Most loudspeakers are described with a nominal impedance such as 8 ohms or 4 ohms, although the actual impedance changes with frequency. The goal is simply to keep the resistance of the speaker cable small compared with the impedance of the speaker.
So, as the distance increases, it can make sense to increase the size of the cable.
That brings us to another common situation: excess cable.
For all sorts of reasons, people sometimes end up with more speaker cable than they actually need. The temptation is to neatly wind it into a tight coil and hide it behind the equipment.
With ordinary two-conductor speaker cable, the current flows in opposite directions through the two conductors, so the magnetic fields largely cancel one another. That means a normal coil of speaker wire is not likely to suddenly become some giant audio-destroying inductor.
Still, I generally prefer not to create a tightly wound pile of excess cable.
If you have extra length, simply lay it back and forth in a loose serpentine fashion and secure it with reusable cable ties or Velcro straps. It is neat, easy to service, and avoids creating an unnecessarily large coil.
And please — don’t cinch everything together so tightly that you damage the insulation.
“So, Lou, what about different cable lengths in stereo or home theater?”
Glad you asked.
This is where a little planning helps.
A short speaker run may work perfectly well with a smaller gauge cable, while a much longer run may benefit from a heavier gauge to keep resistance low.
That does not mean every speaker cable in the system has to be exactly the same length. What matters more is that each run is electrically appropriate for the distance and the speaker being driven.
In a typical home theater, the surround speakers may be 30 or 40 feet away while the front speakers are only several feet from the amplifier. There is nothing inherently wrong with that. You simply size the wire appropriately.
Another option in some higher-performance systems is to locate the power amplifier closer to the speakers and use a longer interconnect between the preamplifier and amplifier.
This can work very well, particularly with balanced XLR connections, which are designed to reject noise over longer cable runs.
With very long unbalanced RCA connections, however, capacitance and susceptibility to noise can become more important, so that arrangement needs to be considered system by system.
What About Splicing Speaker Cable?
Here's another one I see from time to time.
Can speaker cable be spliced?
Yes — if it is done properly.
A good splice using a secure mechanical connection, proper crimp connector, soldered connection, or another suitable low-resistance method can work perfectly well.
What I do not recommend is twisting two bare wires together, wrapping them with a little electrical tape and stuffing them behind the wall.
Poor connections can oxidize, loosen or create resistance. Worse, exposed strands from the positive and negative conductors can touch each other and create a short circuit.
Depending upon the amplifier, that may simply trigger its protection circuit. With less forgiving equipment, it can damage an output stage.
So the problem isn't that a splice exists.
The problem is a bad splice.
Whenever possible, I would still rather install a continuous cable from the amplifier to the speaker. But if a splice is necessary, make it properly and insulate it properly.
There truly is much more to discuss about speaker cables after more than 40 years of working with them, but the important lesson is actually fairly simple:
Use the proper cable gauge for the distance, make good connections, and don't make the installation more complicated than it needs to be.
Beyond that, the right answer can vary tremendously from one system to another.
And that's where having someone who has actually done this a few thousand times can still come in handy.
—Lou