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Technical and scientific discussion of amps, cables and other topics.

RE: You've supported Jon Risch's speaker cable idea I believe

Hi
I think John was an engineer at Peavey, I remember him from AES a good while ago, not familiar with his speaker cable idea.

I am not sure you got my meaning though, ALL of the “small things” like parallel C, series L, become the limiting factors much higher in frequency or in much longer wires. If one wants “low loss” dielectric, then looking at “ultra low loss coax” is logical.
Note some of them have a mostly air dielectric using a spiral web insulator, others have foam TFE etc. Hard line, the next step up from cable is like two copper tubes one inside the other or one tube with a solid center. This can be made with even lower losses but is not flexible or logical in light of the speakers electrical load and frequency range.

Orders of magnitude more work go into making these kinds of cables because the market is vastly larger AND the effects more critical.
At a reasonable distance, cable like the 400 would appear to be blameless based on what difference one would see at one end vs the other and it’s parallel C loading vs other choices.

Audio and loudspeaker design is my hobby, my love and for much of my life part of my job.
My background has been in making things, sometimes audio transducers, sometimes other things.
I would say the most useful things to have worked on in this area was in trying to improve output transformers a large (250W) tube amp and then being Principal investigator on a research contract in high frequency electromagnetic levitation.

A high frequency is used because a material like glass or ceramic has a large skin depth and so one can induce an eddy current through most of it’s volume. Once there is a current, then the material heats and becomes more conductive and easier to levitate (that eddy current produces an opposing magnetic field)
Anyway, picture how one would make a small one turn coil out of solid copper plated with heavy silver and pass 100 to 300 amps through it at 10 to 13Mhz. Then, set up six of those orthogonally and drive them 120 degrees apart in phase and the top opposite from the bottom and one has a way to average out the force so that melted material stay nearly spherical. The transformers and networks needed to match a one turn coil to the 300W, 50 ohm amplifiers were a real “learning experience” which if anyone says that about your job to you, it means run away..

http://adsabs.harvard.edu/abs/1991AdSpR..11...79D

http://ip.com/patent/US5150272

I have developed a number of other electromagnetic / acoustic things too, some of which are transducers, speakers or audio related a few which have not issued are the basis of the company’s products I work for now.

http://www.google.com/patents?tbs=bks%3A1&tbo=1&q="Thomas+j+danley"&btnG=Search+Patents

Twisted pair is a great configuration, the thin insulation and tight twist has an effect like shielding in that it is hard to induce a differential signal with an external field. The only possible down side would be the measured parallel C value relative to the driving impedance.
On the other hand, making the cable as short as practical minimizes any effect, all the undesirable stuff is “by the foot”.

For an interconnect, one might try Teflon wire wrap wire as a way to lower the C with a slightly larger spacing and lower dielectric constant (than the magnet wire insulation).
The other old days trick at short wave frequencies (before tfe was popular) was to wind a tight twisted pair and then unwind it a bit so there was a casual airspace between most of the conductors.
Seems to me there was a thumb rule for the optimum twist per foot relative to the wire diameter but i don't remember what is was.
Best,
Tom


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