Mr. Geoffkait, I don't think it best to quote HowItWorks articles that poorly quote Wikipedia. The result can be less than coherent. Take this sentence,
The voice coil's electromagnet is placed within a permanent magnetic
field. The two magnets interact, and every time the electromagnet's
polarity changes, the interaction between the magnets changes.
The voice-coil is the electromagnetic, and the voice-coil's magnetic field interacts with the permanent magnet field. Perhaps that is what they meant, but you get the impression they didn't really understand it.
The signal energy travels down the cables in one direction
>>>> from the source to the load, (amp to speakers), in the
form of an electromagnetic wave.
That is not really true and is shown not to be true with a simple case, a DC voltage and a load. There is no continuous electromagnetic wave to transfer energy. What there is is an electromagnetic field that cause electron movement with causes a magnetic field. The product of those two (power) always points to the load which is the direction of power transfer.
In a transmission line, the changing e-field causes electrons to move which propagates down the cable as an electromagnetic wave, but technically, other than losses, no work is done. The "wave" sets up the fields, but does not define the transfer of energy ... at least using classical EM theory.
