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Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys. |
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Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys. |
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In Reply to: The physics of the third millennium posted by ro-s on October 3, 2002 at 01:28:28:
As Steve has pointed out, the electric fields and magnetic fields extending from the speaker cable will interact with their surroundings.This is a repost of a post at another message board from December of 2000:
First, ANY wire that carries an electrical signal generates an electric field. This e-field spreads out from the wire and radiates into the surrounding space. The wire insulation is the first thing it encounters, and so the insulation has it's effect on the cable's electric field, and can add it's own signature to the signal. I realize that some dispute this, but many others do not.
However, the field does not stop at the outer edge of the insulation, it continues on outward.
Hence, nearby objects can affect the electric field.
Even though the cable might have some magnetic field cancellation (and the more esoteric geometries are much better at this than zip cords), there is still some radiated magnetic field from the cable. See the EMF pages at my web site:
http://www.geocities.com/jonrisch/emf1.htm
and subsequent pages.Let's look at what a typical speaker cable might be near on it's way to the speaker: carpet, bare wood floor, concrete, metal rack legs, hardboard rack rear covers, and vinyl flooring, etc.
None of these things are very good dielectrics.
Carpet typically uses a polyester or nylon, or some other plastic that is not one of the best dielectrics, the carpet base is usually a weave of fibers impregnated with binders and glue, the carpet mat underneath may be foam of unknown composition, or a felt or fiber mat, etc.Wood floors will undoubtedly have nails in them, and the varnish or wax may not be a very good dielectric. Wood and certain waxes are diamagnetic, and this will slightly repel and distort the magnetic field.
Concrete is slightly conductive, and as such will partially, and probably non-linearly, short out the e-field. The composition and characteristics will vary greatly, but it is probably going to be a less than ideal dielectric medium.
As for vinyl flooring, I have posted many times about how poor a dielectric vinyl (PVC) is.
Rack legs are usually steel, and since steel is a conductor, it will tend to short out the e-field. In terms of magnetic fields, steel will have hysterysis distortions, eddy currents, and in general, be a non-linear magnetic "core" to the cable.
Anything that distorts either the e-field or the magnetic field of the cable as it carries an audio signal will be reflected in a distortion of the signal itself, one can not be affected without that effect being shown in the other.
So if we raise the speaker cable off the floor, and keep it away from less than wonderful dielectrics, and away from conductive and magnetic materials, it will alter (and hopefully reduce) what possible distortions of the EM fields may occur.
Some folks have a mistaken impression that speaker cables fo not radiate any EM fields, that the close proximity of the two conductors cancels out any radiated fields, but is this were true for the magnetic portion, then the mutual inductance would totally cancel opu the self-inductance, and the total net inductance would be zero. Since this is notthe case, obviously, there is magnetic field extension out from the conductor pair.
As for the electric field, this will extend out from a parallel pair of conductors, and this will spread out quite a bit, into the carpet, the floor, the nearby objects such as racks and other cables, etc.
Some scathing comments about the level of these effects have been made, with reagrd to waving hands,a nd the phase of the moon, but a piece of carpet, or a nail head or a rack leg right next othe speaker cabe is going to have a LOT morte effect than an object far away. Cube law for magnetics, square law for electric fields.
Jon Risch
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- Re: The physics of the third millennium - Jon Risch 16:41:21 10/03/02 (0)
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