Engineering vs. Horsepucky - Skin Effect

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"Figure 3 shows the power loss in the cable as a function of frequency. The solid (blue) line shows the loss when the wire?s internal impedance is taken into account. The broken (red) line shows the loss that would occur if we ignored the internal impedance. Hence the difference between the two shows the results in this case of ?skin effect?. In principle, the broken line shows what we might expect when using wires of ?Litz? construction with a fill factor approaching unity. The solid line shows what we might expect from either a solid wire or a multistranded wire of closely packed thin strands.

For the example chosen, at low frequencies the bulk resistance of the copper wire causes a power loss of around 0?008dB. At 10kHz the loss rises to 0?009dB if the internal impedance were absent, and 0?016dB with the internal impedance taken into account. At 25kHz these values rise to 0?012dB and 0?028dB respectively. Hence the change in relative signal level from near-d.c. to 25kHz, with internal effects taken into account is around 0?020dB. This is quite a small change so it is not obvious that it would be noticed in a practical audio system."

See <http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/skineffect/page2.html>

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OOOPS! Lost the link -

http://www.st-andrews.ac.uk/~www_pa/...ect/page2.html

[AllanCT]

I didn't see a significant number on the whole page. Make that an audible number.

Then again I wouldn't be caught dead worrying about skin effect either.

[rolandr]

Come on guys if you disagree with a viewpoint at least have the decency to wait for a reply prior to ridiculing remarks.

Additionally although we are concerned with speaker response as 20-20K Hz, in reality many better experts than ourselves say harmonics above 20KHz carry additional info such as 3D clues etc.

Most importantly Hi End-Hi resolution equipment for example preamps are designed not for a 20-20K Hz wideband response, instead designers would like a 2Hz to 200,000 or even higher wideband response. At these freq levels the time based freq smearing associated with heavier gauge wire mentioned elsewhere does play a role! Old timers used relatively thin often solid cable for their connections... open up an old Altec speaker cabinet, crossovers, or preamp you will see a lot of solid core 24 gauge wire even to woofers. This "new" wave of grossly thick cables came about as the new gimmick for wire manufactures to be able to charge more money, also ditto for the overprized esoteric cables.

Prof Hawksford recommends about 0.5mm to 1mm wire thickness if bandwith is only 20-20Khz

In this field and especially in this forum all we are doing is looking for answers. Nobody has all the answers to all the questions. Believe me I
am very ignorant of much of audio, but at least it is honest ignorance.

[Steve Burger]

I agree with you Roland. I did not see the reply as overly abusive but the one thing I love about this site is that people are very respectful toward others despite varying degrees of expertise. I my self have gathered some info but am acutely aware of what I don't know. I have a few people I deal with on a regular basis who often go over my head and lose me in about 10 seconds. I would really hate to see this site take a turn toward something like the audio asylum where there are a lot of techsnobs (at least they pretend to know everything) who hurl abuse at each other. Get real! This is audio, though a great hobby and a profession for many, in the overall scheme of life it is not that important.

[StuWelwood]

Are there any Altec speakers that can reproduce much above 20 kHz?

[AllanCT]

Not without some help from a JBL 075.

I would think the audio range is off by at least a factor of 100 for skin effect to even be considered.

Thick heavy cables are rather good for power transferal but I wouldn't use something you can trip over.

[StuWelwood]

As an EE, I fully agree with your assessment of the lack of importance of skin effect at audio frequencies. To seriously consider such a trivial effect would be ludicrous. Just use some everyday 12 guage wire and forget about hocus pocus.

Also, the reason that so many preamps and amps can reproduce ultrasonic frequencies is because the devices available today easily perform at these frequencies, wide bandwidth decreases phase errors in the audio range... In fact, with some circuit topologies the designers would have to arbitrarily limit the bandwidth to yield a 20 kHz maximum.