Please excuse me for this question if it is dumb. I'm trying to understand how music/sound moves down a wire. (I think) I understand how sound is transmitted through air and that an electrical signal is produced by the source (e.g., stylus in groove) which, after various amplification stages, then 'excites' electrons in the speaker cable.
However, I don't know if different notes (e.g., double bass versus flute) 'excite' the electrons in different ways. That is, do the electrons excited by bass notes move slower than those excited by flute notes? To add complication, music is comprised of many notes played at the same time. Do some electrons move with the bass notes and others with the flute notes, or is it a wave of electrons with various layers of frequency one atop the other?
Would electrons be moving similarly in each wire of a stranded cable (i.e., they would only be excited within the boundaries of that particular wire) as opposed to the electrons moving across the full diameter of the cable?
"But the signal all gets to the end of the wire at basically the same time"
This makes me think, how different would wire lengths have to be for the acute listener to notice a difference in the arrival time in a pair of a stereo signals at the speakers? Answers based on complex theoretical calulations, general principles or SWAGs all entertained here.
How different would wire lengths have to be for the acute listener to notice a difference in the arrival time in a pair of a stereo signals at the speakers?
Several miles or more, by which point timing differences would of course have long since been swamped by other effects (frequency-dependent signal losses caused by resistance, inductance, capacitance, among many other effects).
Electrical signals (as opposed to individual electrons, whose movement is irrelevant to the question) propagate through wires at roughly 60% to 90% of the speed of light in a vacuum, which in turn is about 186,000 miles per second. If we assume 75% as being typical (the actual number depends mainly on the dielectric constant of the cable's insulation), the corresponding propagation time is about 1.36 nanoseconds per foot of cable. 1.36 nanoseconds is 0.00000000136 seconds.
The speed of sound in room temperature dry air is approximately 1126 feet per second.
Based on the 1.36 ns/foot figure, a 20 foot difference in cable length between the two channels, for example, would result in an arrival time difference at the speakers of 27.2 ns.
Based on the 1126 ft/sec figure for the speed of sound in air, 27.2 ns corresponds to the arrival time difference at the listener's ears that would result from his or her head being 0.00037 inches closer to one speaker than to the other. In other words, not likely to be audible!
Thanks Elizabeth, that was a great explanation. From your explanation I would guess that connections (e.g., spades) also would affect the wave especially if the connector was a huge hunk of different material? I assume material "density" (or resistance) would impede some frequencies more than others?
Thanks Al, very cool logic. Your analysis would of course hold best in scenario of an anechoic chamber. In the average listening room, reflections and nodes etc. would further diminish any vanishing differences in sound imparted by differences in speaker wire length.
I have fretted about this in certain applications in the past and it has cost me in wasted lengths of speaker wire. I haven't ever noticed a difference in sound with differential lengths of wire, but since I was fretting about everything else, I thought I should worry about this too. Apparently not. Thanks again for your analysis.
I have fretted about this in certain applications in the past and it has cost me in wasted lengths of speaker wire. I haven't ever noticed a difference in sound with differential lengths of wire, but since I was fretting about everything else, I thought I should worry about this too. Apparently not. Thanks again for your analysis.
You're welcome! Keep in mind, though, that my comment only addressed the question of arrival time differences.
If other parameters, such as resistance, inductance, capacitance, and possibly skin effect, are not small enough to be negligible in the longer cable (all of those effects are proportional to length) a length disparity could conceivably have audible consequences.
And of course there is also the practical factor of resale value being less if lengths are unequal.
The likelihood of those effects being audible, btw, besides being dependent on the design and length of the cable, is also highly dependent on speaker impedance, and the variations of speaker impedance with frequency. Everything else being equal, higher speaker impedance can be expected to result in smaller cable effects.
Please, a follow-up question about signals "moving" through wire. I read that a signal takes the easiest path. If you pair two wires for, say, the positive run - one wire with fine strands, the other with large strands - will that create some difference in signal transfer, no difference, or will it provide more "bandwidth" for all frequencies?
In the case of dc, if two parallel paths are present the current will divide up between the two paths in inverse proportion to the resistance of each path.
In the case of ac, the current will divide up between the two paths in inverse proportion to the impedance of each path, "impedance" at audio frequencies essentially being the combined effects of resistance, inductance, capacitance, and to a slight degree skin effect, at each particular frequency component that is present in the signal.
Paralleling two wires for each leg of the run will have the net effect of reducing overall resistance and inductance, and increasing capacitance. Except in extreme cases, capacitance is usually unimportant in a speaker cable, while resistance and inductance can be important.
Whether two parallel conductors would perform better than, worse than, or the same as a single conductor having the same values for those parameters is IMO probably not technically predictable, and experimental comparisons would probably give results that are both system-dependent and listener-dependent.
Public A ha moment - pretty clear to me now why performance of speaker wire is contingent on impedance curve of speakers, amplifier capability and properties, and to a lesser (or greater) degree, the sensitivities and proclivity of the listener. Given all this difficult to see how anybody could recommend gear and wire combinations without first hand (or ear) experience with all in specific set up. I got that as a matter of common sense previously, but this series of lectures provides some theoretical and practical foundation. Nice.
You guys are obviously new to this forum thing. "Great Job!" "Excellent Answers, THANKS!!!" Sheesh!!
The whole point here is to attack the opinions of others and prove how intelligent you are, not some idealistic search for the truth. I think the last two administrations proved that the truth doesnt matter, so get with the program;)
Lplayer, thanks for providing the link to that paper, which is excellent IMO.
When I wrote my earlier comments, I hadn't thought of the fact that propagation velocity will slow at low frequencies. However, as can be seen in Figure 2 of the paper, it will still be about 5,000,000 meters per second at 20Hz, meaning that propagation times through cables at that worst case frequency are still utterly insignificant in a home audio system.
For those who don't want to bother with all the technical stuff, IMO the bottom line of the paper is expressed in its last two sentences:
Thus, at audio frequencies, a cable less than 2,000 ft long is no more complicated than its series resistance and parallel capacitance. As the cable becomes longer, or as frequency increases, the cable will BEGIN to behave as a transmission line.
I would add that in a speaker cable, in particular, inductance can also sometimes have audibly significant effects. The focus of the paper is mainly on transmission of line-level signals through coaxial or balanced cables.
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