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Pano 18th April 2021 12:30 AM

Zip cord for speaker test
This thread will document a test of speaker cable stored energy using four bundled pairs of zip cord, also known as lamp cord. In this case it's 18 AWG SP-1, which is the thin insulation version.

The test was proposed here by jneutron:

jneutron 18th April 2021 12:45 AM

Just excellent. If there is anything I can do to assist, ask.

If you decide you need to test a cable that is 8 ohm RFZ, I can make it and ship it free of charge, either coaxial or stripline.


Pano 18th April 2021 12:58 AM

5 Attachment(s)
OK JNeutron. I've cut and stacked the zip cords and joined the ends.
The are stacked as flat as is reasonable, but could be tightened up with some more work. I hope this is what you had in mind.

All the negative leads are twisted and all the positive leads are twisted together at each end.

My L/C meter says the stack is 1.1nF between positive and negative.

Here we see an impedance plot of a Bowers & Wilkens HTM62 center speaker.
First plot is the WT3 connected to the speaker terminals, the second plot is the same speaker thru the cable stack. All I can see is that the DCR is just a tiny but higher thru the cable. Otherwise I can't see a difference.

Pano 18th April 2021 01:02 AM

Forgot to mention. Cables are 5M long. Or about 16' 5"
Next up will be IMD tests.

jneutron 18th April 2021 01:58 AM

Don't tie the cables together. To achieve a RFZ consistant with 1/4 of a single cable, they cannot be coupled magnetically. An inch or two spacing is good enough to decouple, tying them together doesn't do that.


Pano 18th April 2021 02:27 AM

Well darn, that was not easy to do. :xeye: Un-bundling them won't be difficult. Keeping them away from each other will be.

The second half of the test is splitting all the pairs, right?

jneutron 18th April 2021 02:47 AM

Yes. just allowing the wires to do their own thing basically prevents communication. In essence, just let them lay wherever.
For the divide by with respect to RFZ to happen, the cables cannot be really close. Just letting them get from amp to speaker should be enough.
edit: if you really want to, just measure capacitance and inductance, Z is just math.


Pano 18th April 2021 04:18 AM

Would the wires simply need to make a loop to measure their inductance? I.E. connect then together at one end.

jneutron 18th April 2021 11:47 AM

Yes, all have to be tied in a short.

Oh, when you go to split the four zips, bundle the 4 positives together and the 4 negatives together, keep the bundles apart. That will maximize the inductance and minimize the capacitance.

To measure that in advance, you could simply take 4 zips and bundle two together as 4 positives, two as four negatives, same number of conductors but physically more like the split ones.

Or, wait until after you did the audibles..


Pano 18th April 2021 03:01 PM

The bundle is now separated into loose pairs. The connections scheme is still the same, each zip wire carries positive and negative and the pairs are joined to each other at the ends. Each pair is spaced approximately 2 inches (50sm) from the nearest neighbor running along the floor.

I was not able to measure inductance either bundled or spread. It seems to be below the threshold of my L-C meter. Capacitance went from 1.109 nF to 1.453 nF. Disregard the last digit, it's noise.

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