A collection of anti-hifi [ripoff] information Reply #50 – 2003-09-19 22:06:13 Skin Effect Summary.The skin effect in a cylindrical conductor has two components :The resistance is increased because the usable section is reduced.The inductance is also changed.I calculated the effect on the resistance.Here is the formula giving the resistivity R' in IS units (ohms per meter). Note it, it is very difficult to find ! It comes from the "Traité d'éléctromagnétisme" de l'Ecole Polytechnique de Lausanne.R=1/(2*Pi*radius^2*gamma)*RE(k*radius*J0(k*radius)/J1(k*radius))Where Radius is the radius of the cable in metersGamma the conductivity of the metal in ohm^-1*Meters^-1RE (x) is the real part of xplus or minus k = (1-j)/dj is the imaginary number such as j^2=-1d is the penetration depht in meters defined asd= square root of (2/(omega*µ*gamma))omega is 2*Pi*f where f is the frequency in Hertzµ is the magnetic permeability in Henrys per meterJN(kr) (N integer from 0 to infinite) is the Bessel function of order N defined asJN(kr) = (kr/2)^N * [1/N!-1/(1!(N+1)!)(kr/2)^2+1/(2!(N+2)!)(kr/2)^4-1/(3!(N+3)!)(kr/2)^6+ ......]For a speaker cable of 3 meters (6 meters the two ways), this givesSection / R at 20 Hz / R at 20 kHz0.75 mm2 / 0.128 Ohm / 0.132 Ohm1.5 mm2 / 0.0640 Ohm / 0.0703 Ohm2.5 mm2 / 0.0384 Ohm / 0.0484 Ohm4 mm2 / 0.0239 Ohm / 0.0362 Ohm6 mm2 / 0.0160 Ohm / 0.0287 Ohm12 mm2 / 0.00804 Ohm / 0.0196 Ohm075 mm2 is your standard 1200 W zip cord2.5 mm2 is the big zip cord (must be rated around 3600 W)4 and 6 mm2 are common in audiophile speaker cables.I gave 12 mm2 a shot because I used some 12 mm2 cables in my tests (to be published after this), though it is quite impossible to find.I then computer the treble loss, between 20 Hz and 20 kHz, if the speaker is 8 Ohm at any frequency, and the ampli 0.08 Ohm. 0.75 mm2 : -0.0042 dB1.5 mm2 : -0.0067 dB2.5 mm2 : -0.011 dB4 mm2 : -0.013 dB6 mm2 : -0.014 dB12 mm2 : -0.012 dBThe loss is maximal at 6 mm2. Below, the skin effect is decreses because the cable is so small that the current fills its section completely even at 20 kHz. Above, the effect decreases, because the resistance of the cable becomes negligible at any frequency. This maximal loss, about on hundredth of a dB, is completely inaudible.This page came to a similar conclusion : http://www.audioholics.com/techtips/audiop...fect_Cables.htm, using different methods.