The Physics of Electricity


Can anyone explain clearly in either common parlance or technical terms the difference between a $1,000.00 cable and/or speaker wire versus a $20.00 (or so) one? What does wire "do" in an expensive cable/wire that an inexpensive cable/wire does not? Does it conduct more or "better" electricity?
llanger

Showing 5 responses by johnnyb53

Can anyone explain clearly in either common parlance or technical terms the difference between a $1,000.00 cable and/or speaker wire versus a $20.00 (or so) one? What does wire "do" in an expensive cable/wire that an inexpensive cable/wire does not? Does it conduct more or "better" electricity?
Llanger
I'm surprised that with 39 responses, no one explained the difference between mains electricity and electronics. Power cords and power lines are built to transmit mains electricity. In the US, this is electrical current that alternates at 60 Hz, and is kept at a narrow range of voltage ideally from 110 to 120 VAC.

Electronics, on the other hand, is an elaborate system with the use of a combination of devices (e.g., diodes, triodes, resistors, capacitors, etc.) to amplify voltage fluctuations (which are known as *signals*) to perform tasks. In simple electronics rudimental signals trip a relay, close a switch, adjust temperature, etc. The task of signal transmission in audio is far more sophisticated. The musical performance is encoded to represent all the notes, all the frequencies of the instruments' and voices' overtones, the amplitude of each note, and the tempo at which these notes are played. There is a separate encoding and fluctuation for each of these.

Wire for electricity has very few requirements--it has to have low resistance, be able to transmit lots of current, and be insulated so it doesn't cause short circuits or electrocute the user.

Audio signal cables (interconnects and speaker cables) have a much more complicated job. Ideally they must convey all the various signals (which are minute voltage fluctuations) in time with one another (with the challenge that signal speed varies with frequency), keep the amplitude of each accurate, minimize (ideally prevent) signals from being absorbed by the dielectric to be released back into the signal path later, and have near perfect rise time (which requires frequency response somewhere past 1 GHz). High end audio cable is optimized for signal transfer of all frequencies. It is more challenging to optimize all audio frequencies to travel coherently for ultimate audio signal performance than it is to deliver up to 15 amperes at a constant 115 volts AC.

Even a power cord for an audio component has requirements that general power cord does not--you want to provide as consistent and noise-free power provided to the components as possible. To that end, high end power cords are wound, shielded, and/or woven to reject noise in the electrical lines that can degrade the sound quality of the component receiving the "dirty" sound.

So there's your basic answer. The primary job of electrical wire is to transmit a relatively narrow range of electrical power at a fixed voltage. The primary job of audio cables is to transmit an incredibly complex time-dependent array of electronic signals covering ten octaves of frequencies while rejecting electrical noise that can compromise the musical aspects of the signal quality when it reaches its destination--loudspeakers.
06-24-11: Almarg
Johnnyb53, while your well written post is, IMO, completely correct from a qualitative standpoint (i.e., if quantitative considerations are ignored), as I've mentioned in response to similar posts you've made in the past it is incorrect and misleading quantitatively.
Qualitative was the nature of the OP's original question. He was unaware of the qualitative functional difference between a refrigerator power cord and interconnects between a preamp and amplifier. You don't have to agree with how important the difference is, but the purpose and functions of the two kinds of wires is fundamentally different.

As for calling me "incorrect," that's rather presumptuous for what is a matter of opinion supported by research on both sides. Some very bright lights in audio base their designs on ultrawide bandwidth, including Soulution, Symphonic Line, Odyssey Audio, Spectral Audio, Kimber Cable, Zu Audio, and many others. If you disagree with them, write a letter and set them straight.

Test reports that chart frequency response and square wave response show that risetime is visibly slower on amps that start rolling off at about 20KHz. For example:

-1dB @ 20KHz, visibly very rounded risetime

wide bandwidth, fast (nearly vertical) risetime
So it would seem, but here is some food for thought. Audio is all about signal transfer. Is it cost-effective to spend crazy money on components and then lose signal speed and coherency to budget wires between the components? Could it be more cost-effective to get spend less on the components and then get better cables so that more signal arrives intact at your speakers?

06-24-11: Almarg
As I know you realize, bandwidth and risetime have an inverse relationship. Therefore a frequency rolloff that begins too close to the audible frequency range will result in risetimes that are visibly slow when viewed on a time scale that is meaningful with respect to the bandwidth and risetime of our hearing mechanisms.
The risetimes are visibly slower even when the component bandwidth stretches out to 100 Khz. Each component with such a bandwidth slows down the incoming signal by that much more.

I have four cables and three components between my turntable and my speakers, for 7 in all. Each component slows down the signal a little bit. By having > 1GHz bandwidth on the cables, I minimize the slowing of the rise times as the signal is passed from the source to the speakers. You may decide that 1 GHz is overkill, but it shouldn't hurt, and the cables (KImber Hero and Zu Wylde) are pretty affordable. The Kimber Heroes are rated out to 8 GHz and I got them at a pawn shop for $50/pair.
The difference between garden variety electrical cord and expensive signal cable is revealed in the OP's original question. His question is based on the presumption that electrical cables and signal cables have the same job--to conduct electricity. But that's not the case. Electrical cables only have to conduct electricity in the form of watts from point A to point B, while voltage remains relatively constant.

Audio signal cables (interconnects and speaker cables) are primarily designed to transmit the accurate values (in rise time, amplitude, and waveform) of voltage fluctuations--signals--that represent everything from the sharp transient attack and low fundamental of an orchestral bass drum thwack to the finest, subtlest timbre-defining overtones of the violin and cymbals in the 12-20Khz region. Electrical cord has no such mandate. You can use electrical cord for speaker cable and sound certainly comes out at the other end, but it's not optimized for accurate signal transfer.