Ask Dr. A! Does Speaker Cable Gauge Matter?

It's been a while since Dr. A answered a reader question so we pulled him away from his 4 month karaoke binge and tossed a new question at him. Seems like Dr. A has an addictive personality so we'll need to keep him a bit more occupied in the future for his own good. This question, from philophobos via our forums, has to do with speaker cable gauge, but we expanded it a bit in our answer to address some other related situations.

philophobos: Does anyone know what happens if one uses different gauges for the speakers? Like 18 gauge for the front speakers and 16 for the rear ones?

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Dr. A: Hi philophobos,

I'll address your specific question, but first let's hit some basics for others reading this question. The general idea is that you should always try to stick with a good gauge of wire - typically 16 gauge or higher is best. Now when we say "higher" realize that we really mean "lower". Er, let me explain...

Speaker cable gauge is short for American Wire Gauge, or AWG. This is a expressed in numbers that get smaller as the wire gets thicker. So, smaller numbers mean a larger thickness of wire, and larger numbers mean a smaller thickness of wire. Most bulk speaker cable is between 16 and 12 gauge (AWG).

Your particular question seems to center around consistency, but at it's heart there is an underlying question of what happens to the audio as it travels through these cables? Consistency only comes into play once you exceed a particular distance. We could do the math, but let's just give you some basic, conservative guidelines to follow instead:

• Less than 30 feet: 16 gauge
• 30 - 50 feet: 14 gauge
• 50 - 100 feet: 12 gauge
• 100+ feet: 10 gauge (or us 14/4 cable which works out to 11 gauge)
  
• Audioholic: 10-12 gauge, regardless of distance

For more information, read: Speaker Cable Gauge Guidelines & Recommendations

I tend to run 10-12 gauge everywhere just for fun since in the scheme of things it doesn't seem to cost all that much more. If, however, you are wiring up a whole house I see no reason to spend the extra money if your longest distances from the amplifier to the speakers are less than 100 feet. Stick with 12- or 14-gauge unless you're really concerned with eeking out the absolute best performance.

What happens when you exceed these distances? Power loss and reduced damping factor to the speaker (the ratio of the rated speaker impedance to the output impedance of the amplifier) occurs over the distance of the cable. This means reduced sound quality. To put it bluntly, a thinner gauge wire over an extended length will introduce its own significant amount of impedance (50 feet of 24 AWG wire calculates to be 2.62 ohms, for example). When you're dealing with an 8-ohm speaker, thats roughly 2.5dB of insertion loss!  You can see how this added impedance can dramatically affect the sound.

If you're in a typical theater room you'd have to have a very thin gauge of speaker wire for your surrounds (like 20-gauge) before you were able to tell the difference audibly in most cases - and even then you'd have to listen critically and compare the same source to the fronts. Add to this the fact that most people have different speakers for surrounds than they do for the fronts... Add to that room acoustics... Add to that the expected amount of use the surrounds get and the differing program material they receive than the fronts... and it becomes even more of a non-critical issue.

In your example I would doubt very much that there would be any audible difference between 18- and 16-gauge unless your surrounds utilized cable lengths of more than 30-40 feet. There would most certainly be a measurable difference - but that's not always as important.

I hope this helps - now for some more karaoke!