directional cable?

Recently, a hi-fi store loaned me a certain speaker cable and indicated that the cable should be installed in one direction only. When I mentioned this instruction to a friend of mine who is an electronics engineer he laughed for an uncharacteristically long time and then wondered aloud why someone would apply directional bias to a signal that should move equally in either direction. If that were not the case he said you would have some form of diode. Reversing the cable made no audible difference but I have no idea what sonic traits I should listen for. Can anyone shine some light on this?
witchdoctorism? Actually, I think some cable brands ground their cable only at one end. That may be the instructional reason, even if sonically it makes no diff for us sane people. pcanis
Some cables like MIT have rectangular boxes built into them, evidently for resistance matching or some other unspoken reasons. Makes sense that these things are directional. Other than that, there is no logical explanation for why a wire would sound any different in one direction or another. Diodes are directional in nature, allowing current flow in one direction and protecting against current on the other (specified as reverse voltage breakdown). A wire is a bidirectional conductor, not a diode. Plenty of 'philes would argue with me, but common sense dictates a wire is a wire is a wire....
I had a course in electrical engineering (advanced physics of conductive metals) that explained the difference in cable directionality... The change is at a metallurgical level it the stucture of the atoms of metal (grain) in the cable. It has to do with the direction in the grains of the metals in the wires, the drawing process, and a multitude of other things. Whether or not you can hear this in your system depends greatly on the ability of your system to resolve minute detail. My system has enough resolution to resolve this difference. It is subtle, but to prove this theory, I conducted a blind cable reversing experiment with some audiophiles and I was not the only one to hear this difference. Some may laugh, some may proclaim they can hear the difference -- but you asked, and here is the answer...
one additional comment, longer grain structures have a more dramatic effect on cable directionality.
Actually, the main reason for directionality is pseudo-shielding. Anyone familiar with balanced, shielded cables and how they work understands why you can't truly shield a cable that only has electricity running in one direction. Well, what some cable manufacturers do is pseudo-balance it, and that requires tying the shield to the negative side on one end, and having it hang loose at the other.
Their is a sonic difference. When a cable is "broken in" in one direction it should always be hooked up with the flow going that direction. Reversing the cable makes it sound IMO like a new, not yet broken in cable. I have experienced a difference in sound (due to the cable being reversed) with Harmonic Technology Truthlinks and also a pair of Homegrown Audio's Super Silver IC's. It was noticable right off the bat, since I am familiar with the "broken in" sound of both IC's. I would assume that if I had left them backwards for any length of time that the "break in" would have been destroyed and that I would have had to go through the process over again. I would not go as far as to say that I have a highly detailed system, however my Musical Fidelity amp amd Castle Isis speakers clearly showed the difference in sonic signature. The only thing that I hear that does not exist are voices, everything else that I hear is definatly a part of the real world.
Many of the above indicate different reasons why cables are directional, but in reality there are multiple reasons - and I have had experience of each. The metallurgy answer is correct and this occurs as the copper is drawn. If the cable manufacturer wraps its cables, taking into account how each was drawn, either deliberately or accidentally, then the end result is a directional cable. Some high-end cable companies even treat their cables by connecting them to a current source in order to form the cable, which imparts directionality. The process of running a cable in affects directionality also, but to greater and lesser degrees depending on the aforementioned issues. And, of course, with interconnects - but not speaker cables (which was the subject of the original post) - the shield is often connected to ground at only one end, causing it to sound different in one direction from another. Ditchrecords - your friend may even become apoplectic if you were to tell him that I (and all others I know that have high resolution systems and who have tried it) have found that the mains cable used between your breaker box and the wall outlet used by your stereo is quite profoundly directional. You should not be concerned if you did not hear your speaker cables to have a direction. Some cables do not exhibit much directionality until run-in, and some don't even after being run-in. I suspect this is mainly because there are individual conductors that are directional in the cable, but that they are run in different directions when they are put together - just speculation though. However I remember reading a tweak in the UK of taking a well-known brand of cable apart and reversing the direction of one conductor and then putting it back together again - presumably because the manufacturer had not given enough weight to cable directionality.
I've seen where some directional interconnect makers say you can try using them backward to see if it sounds better. Some systems do.
Yes Sugarbrie - it depends on where it is best to make the ground. Often it is best to make the ground at the preamp, but how do you then make an IC that is good between CD and pre, as well as good between pre and power - given conductor directionality?
I can attest to the fact that the mainline AC cable from the main breaker box to the stereo system is indeed directional as I learned from Redkiwi. When I installed a dedicated AC system last summer, I tried it. In one direction, with my extra heavy 6 gauge stranded wire, music was rather dull, flat, and uninvolving, but when swithed end for end, the music was much more natural, live and involving without being too bright. The effect was not subtle. If the wire were permanently wired in the "dull" direction, I don't know to what extent it may improve over time. Directionality of wire is "really real". Cheers. Craig.
I recently bought a set of silver interconnects with no arrow indicators for directionality.They are high performance 22 gauge 7 conductors with Neutrik RCA's. In this situation,The owner/manufacturer stated it didn't matter which way the power flowed in the cable. Guess I have to trust him.
7671: Once you break them in, keep track or mark which end is which. The direction in which they were broken in is then the direction in which they sound best.
Thanks DeKay... I will mark them prior to taking off.