Axiom Home Page Forums General Discussion Technical Questions Question about unmatched speaker wire length

I know for me it won't matter much because my longest run is no more than 40'. But it got me thinking.

When running speaker wires such as the rears, I can see that the delta in length between wires can sometimes be 10' to 20'. (I'm talking non-in wall here.) At what delta in length does the difference become audible?

That's an interesting question. I see it in two parts--what's the speed of propagation of the signal along the wire, and how much time differential in audio can a human detect? Got no answer for you, other than that the speed of propagation is close to the speed of light, so I imagine the difference in length would have to be fairly dramatic. Possibly so dramatic that you'd notice a drop off in sound quality (from the resistance in the extraordinarly long wire) before you'd notice the difference between the channels.

Good answer!

Yup, along the lines of what I was thinking too.

For some reason, your answer reminds of something funny I read in a magazine a while back. I had a Maxim article that tried to explain Einstein's theory of relativity and used the example of a baby flying through space at the speed of light. My wife (who is arguably much more book smart than me) read the article a few times and still said "I don't get it." I gave her a hard time because she didn't understand a Maxim article.

Cesar, for a timing difference to become audible, the difference in length would be miles. Of course, before that point was reached the greater loss in the longer wire would cause that speaker to be lower in volume, so the volume would have to be equalized, but at the differences that might actually exist in the home, such as you mention, even volume difference wouldn't be significant.

JohnK is right. Timing is not the issue. And for general home use, length never becomes an issue.

But to answer your question, for 12 gauge wire in use with 4 Ohm speakers like M80s, the maximum length should be no more than about 460 feet.

A 460 foot run results in a total cable length of 920 feet and yields a cable resistance of 1.7 Ohms. This will reduce the power to the speaker by 50% resulting in a 3dB SPL loss. 3dB is considered the minimum detectable SPL change for most people.

For 14, 16, 18, 20, 22 & 24 gauge, the maximum runs are limited to 290, 182, 115, 72, 45 & 28 feet respectively for a 3dB loss. For wires buried in the wall, use larger than 22 gauge to prevent over-heating. Also, small wire like this can get damaged easily during installation and that's why many prefer the larger gauges.

I personally would want no more than a half dB loss. These lengths would have to be decreased significantly (or wire size increased) to meet the half dB requirement.