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Zip cord for speaker test
Zip cord for speaker test
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Old 9th May 2021, 07:11 PM   #151
jneutron is offline jneutron  United States
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Ah, thank you, you are keeping me on my toes....

I will explain better.

The wire being used is I believe a 1kV rated twisted pair, so the insulation is fairly thick. This brings the impedance up, I am guessing roughly 150 ohms.

You are correct, I did mention 50 ohm coax. My intent at first was to use 5 paralleled 50 ohm coaxial cables with a effective impedance of 10 ohms. That would drop any wire settling time into a 1 or 2 ohm load (resistive) down into the single digit microsecond range.

900 runs of coax is a lot. So I researched triax, the intent is to use the two shield braids as the coaxial run. The inner core wire will not be used to carry current, it probably won't even be connected. It's the outer two braids that have an impedance of 10 ohms between them.

But thanks for picking that up. If I had been relying on the core impedance, I'd have been 50% off the mark...and totally sunk..

But now you have me thinking...If I use the inner shield as ground reference, the outer as the hot (+/- 20 volts), then I could use that 75 ohm core wire as a voltage readback from the magnet...hmmm. I'll be thinking about whether that buys me anything..

Thanks again,

John
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Old 9th May 2021, 07:44 PM   #152
RJM1 is offline RJM1  United States
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Thanks for clearing that up. I knew I must have been missing something.
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Old 11th May 2021, 04:28 PM   #153
Hans Polak is offline Hans Polak  Netherlands
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Here are resp. the Char. Imp, the Capacity open ended and Inductance with end shorted for a 3 meter 9222 Belden Triax cable measured between the two outer shielding layers.
Doesn't look like the ideal speaker connection to me in this form.
Hans
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Attached Images
File Type: jpg 9222 Zo.jpg (41.7 KB, 192 views)
File Type: jpg Cap 9222.jpg (471.5 KB, 181 views)
File Type: jpg Ind 9222.jpg (404.3 KB, 174 views)
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Old 11th May 2021, 06:55 PM   #154
jneutron is offline jneutron  United States
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I'm not exactly sure what an ideal speaker cable would look like in that form.

John

Oh, and thank you for that test result.
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Old 11th May 2021, 08:59 PM   #155
Hans Polak is offline Hans Polak  Netherlands
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John,
Neither did I, because so far I was never interested in the so called superior technical aspects of a speaker cable and only trusted my ears.
But after having recently measured my own LS cable, I was astonished how close the Char. Impedance matched the impedance of my speakers.
Perhaps I fool myself, but to my ears the sound of my cable is far superior to zip cord or whatever other simple type of connection.
So it could be that impedance matching is much more important than I ever thought.
In that case this triax cable does not have the right impedance form.

Hans
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Old 12th May 2021, 08:01 PM   #156
Hans Polak is offline Hans Polak  Netherlands
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As mentioned already to George, I found an error in the capacity calculation of the used software.
Will redo the measurements once corrected.

Hans
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Old 12th May 2021, 08:12 PM   #157
gpapag is offline gpapag  Greece
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Zip cord for speaker test
As mentioned already to Hans, this is the fate of pioneers


George
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Old 13th May 2021, 07:46 PM   #158
Hans Polak is offline Hans Polak  Netherlands
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Luckily I can confirm that the calculations I used for finding the Char. Impedance were correct after all because I used the impedance measurement of the used FRA Imp Viewer.
However the images showing capacitances are wrong most of the time, because of a simplified calculation that may give erroneous results in some cases.

But the impedance calculations are fully correct, so all the images relating to impedance and Char Impedance in this thread still hold.
Pfffff.....

Hans
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Old 14th May 2021, 07:05 AM   #159
gpapag is offline gpapag  Greece
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Zip cord for speaker test
Now you may enjoy a drink

George
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Old 14th May 2021, 02:39 PM   #160
Hans Polak is offline Hans Polak  Netherlands
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Still frustrating is that I couldnít convince the author of the program of his wrong calculation.
When Z = A + JB and you want to calculate the capacitance, then
1/jwC= A + jB

His aproach is in that case to say jwC = 1/jB or C = 1/wB

Because j are in the numerator and in the denominator, this is wrong.
Correct is: jwC = Im( 1/(A + jB)
Solving this gives jwC = jB/(A^2 + B^2)
or C = [B/(A^2 + B^2)] / w

When A is very small, both formulas give equal results with 1/Bw.
So sometimes the result is o.k. but most of the time itís not.

Hans
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