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In Reply to: Earth ground speaker cable shielding posted by Mark W. on December 19, 2006 at 18:23:00:
Rather than penjalize the speaker cables, whioch will not respond kindly to being put inside a copper pipe (it will dull the sound, and collapse the soundstage), shield the AC wiring, by putting it in steel conduit, and keeping all the other cables and wires away from this conduit as far as possible. Wrapping the steel conduit in a zipper-shield or equivalent ,that is grounded, will also help some more.
Follow Ups:
Jon How would shielding the cables via a copper tube be any different then any other shielded type of speaker cable? I am currently using Carol 1108 50ohm MINI 8 coax as my speaker cable. I wanted to change this to a Quad Star type but due to the 40 feet of cabling I didn't want to spend the money for a braided shield and then connect that to the ground conductor.So I wondered if a copper pipe grounded would work as well. what about being inside of a copper pipe would change the signal?
Well, a lot depends on how you have the coax wired.If you are using the center for the hot wire, and the outer braid for the ground wire of the speaker cable, then the coax is operating in a manner that was intended, with the braid carrying the signal current.
In fact, the so-called ground carries the signal just as much as the so-called hot. See:
About cable "ground":
http://www.AudioAsylum.com/audio/cables/messages/503.htmlIn this case, the braid is a part and parcel of the signal circuit, and since a coaxial cable has special properties with regard to the relationship of the center wire to the braid, the inductance is fairly low, and the EM field of the signal it carries is MOSTLY contained within the coaxial cable braid, with minor amounts of the magnetic field extending past the braid, and the electric field radiating out into space surrounding the coax braid.
BTW, if this is a mini coax, then the DCR could be fairly high, given that it is unlikely that the center wire is very big, and even if the braid is of a decent overall gauge, the round trip of the signal must go thru the center wire for half the trip.
So far, so good, your coax is probably going to be somewhat resistant to the intrusion of AC power line radiation.
However, once you ADD a copper pipe to a more conventional speaker cable, even a "star quad" style, the amount of EM field radiated is a LOT more than a coax, and the fields WILL end up encountering the copper pipe, which, if grounded, will literally SHORT OUT those fields, and generate a counter current within the pipe, severely distorting the original signal in the speaker wires. Yes, a "star quad" geometry does have somewhat better EM field retention than a simple zip cord (also refered to as a figure eight geometry), but it is NOT in the same league as a coax.
Finally, if you are not using the coax in the above manner, then it is likely that you are suffering various forms of signal distortion, loss of HF content due to excessive inductance, etc. If the coax is steel cored, or has tinning or other coatings, then there will also be losses of signal quality, of a more subtle nature.
Jon Risch
Jon the Coax is MINI 8 which is a twisted 16ga copper core and 95% copper braid. It is not a mini coax. I have no idea why they call it what they do Hams use it for lots of stuff.it is being used as a 2 conductor cable. I'm not currently haveing any problems as it is routed a different way then I want now. the new routing will shorten the lenght of the cable.
Use a spiral twisted star quad rather than the Mini-8 coax. While they offer the same appr impedance ( 50 ohms nominally ), the star quad should sound noticeably cleaner on the top end with improved bass definition. Make sure to stagger polarities on the star quad i.e. pos - neg - pos - neg, etc...As to resistance to radiated EM fields, the spiral twisted star quad will be superior to the coax at AC frequencies. As previously mentioned, spacing the AC conductors as far away from the signal carrying cables is recommended, regardless of the geometry of the cabling used.
So long as you are using at least a 4 x 16 gauge star quad, your series resistance will effectively be cut in half. This is for identical length runs as compared to the 16 gauge Mini-8 coax. If using something along the lines of a 4 x 14 gauge arrangement, series resistance would be about 30% - 35% as much as that of the 16 gauge Mini-8 cabling you were using.
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