I need help on directionality of speaker cables

My understanding was that audio signals could be carried as DC, but that AC was required for speakers to allow them to vibrate in piston fashion.

They could be carried as DC but they are not (in fact the sound you hear is alternating compression and dilatation of the air in your room....there is no stream of particles reaching your ears...the air just jostles around and you pick up these vibrations).

DC is used in power supplies but 99.99% of everything that involves information flow uses either AC or EM waves. Digital signals are transmitted in much the same way as analog but at much much higher frequencies...some kind of an alternating waveform (modulated by digital information to create a set of clealry distingusihable digital states that can be decoded at the receiveing end into the same stream of mathematical bits).

In the transmission of the signal in digital cables, electron travels down the cable at the frequencies used by audio/video signals. The higher the frequency of the signal, the more this signal is pushed to the surface of the cable, and the skin of the conductor itself carries a considerable portion of the signal. This phenomena which is called skin effect is a tendency for AC current to flow mostly near the outer surface of the solid electrical conductor at frequencies above the audio range.

In skin effect, the effective resistance of a wire is increased for AC current at moderate to high frequencies compared to the resistance of the same wire at DC current and low AC frequencies. In other words, both AC and DC current exist in digital cables.

I think the issue we need to be certain of here is whether we can really correlate AC current, which is non-directional, to the debate of directionality of cables. There may be other variables that may be overlooked.

On a separate note, I have always followed manufacturer's recommendations and never reversed the directionality of interconnects all this while but have once reversed my speaker cables for the sake of experimenting. Frankly I'm not so sure. I thought it sounded little messy, but then maybe it's in my head.

I guess we can kill off this discussion now for what could be just a simple question to the poster.

"In the transmission of the signal in digital cables, electron travels down the cable at the frequencies used by audio/video signals. The higher the frequency of the signal, the more this signal is pushed to the surface of the cable, and the skin of the conductor itself carries a considerable portion of the signal."

Ryder, where is this info from? The reason I ask is that a digital signal, by it's very nature, doesn't have frequency in the way analog signals do. As I've quoted above from a reputable book on electronics, a digital waveform is a DC signal that varies between zero volts and a max volts, with no in-between.
Skin effect, whilst it exists in analog transmission (especially video), is not relevant in digital data. That's why HDMI and digital RCA cables don't need to be silver-plated copper. The bitstream of digital data is either 0's (zero volts DC) or 1's (eg. +5 volts DC). The quality of the cable will impact on how much data loss or errors occur, and can cause timing errors, but it isn't carrying any frequencies as such in terms of audio or video frequency.

The only time you really need to consider the 'skin' effect is when using analog video, such as S-video, component etc.

My last word on this subject, which might cause more discussion!!
Electrons don't travel down cables like water through a pipe. They are transferred from one atom in the conductor to another, somewhat like pressure in a hydraulic line is transferred. If one injects 10 electrons (applies a voltage at one end of a circuit) then the 10 electrons displace 10 electrons in the first conductor atoms and those electrons displace 10 electrons in the next atoms etc. The original 10 electrons don't appear at the end of the circuit as some would believe. Depending on how the electron transfer is 'impeded', a different quantity of electrons is transfered to the final element for the same voltage. Thus if the final element and conductor offer a high impedence the current can indeed be very small, but the voltage at the final element still be sufficient for that element to get the 'message' (signal) and do its thing, amplify for example.

Salut, Bob P.

Carl109,

If you would do a search there are abundance of details of skin effect that do occur in digital interconnects, be it SP/DIF or AES/EBU. This is just one out of the many references that describes this.

http://www.psaudio.com/products/xstream_digital_moreinfo.asp

You have to scroll down abit though. I didn't provide any links earlier as I thought nobody would be interested to have a look (since Bob didn't read the earlier link by Stereophile). And just if anyone wants to know more about skin effect, here is the description in Wikipedia.

http://en.wikipedia.org/wiki/Skin_effect

Probably your reference book doesn't mention anything on skin effect in digital cables? Anyways, the main question that remains is whether there is any direct correlation between AC(non-directional) and directionality in cables. There is no definite answer to that I would really like to know as well.