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-   -   Zip cord for speaker test (https://www.diyaudio.com/forums/everything-else/371099-zip-cord-speaker-test.html)

jneutron 6th May 2021 02:45 AM

Waitaminute..... the cables are touching the rug????

Where are your lifters???

I was quite surprised at the split impedance.

Jn
Measure the L and C.....to verify consistency with RFZ.

Hans Polak 6th May 2021 02:57 AM

I thougt the idea was to split the cables for one side only and leave the the zips for the other side intact.
On the picture it looks as if both sides were split ?

Hans

gpapag 6th May 2021 06:30 AM

1 Attachment(s)
Quote:

Originally Posted by jneutron (https://www.diyaudio.com/forums/everything-else/371099-zip-cord-speaker-test-post6644110.html#post6644110)
Waitaminute.....

And don’t you ever again call my wife’s precious (*) carpet a ‘rug’
Persian carpets are well known for their vibration damping and antitriboelectric properties, the perfect Hi-End cable lifter.

Then the 3 inch spacers are made from a space-age material, direct out from secret labs. I painted it yellow for not to attract attention from the intelligence community.

Hans, the other bundle is 4 zip cords unsplit

George
(*) it smells wool when it comes in contact with the soldering iron

Hans Polak 6th May 2021 07:49 PM

1 Attachment(s)
I tried to determine the char. impedance Zo for the zip cord that George used.
Results below are for 5 meter 4 parallel zipped- and unzipped cords.
Doesn't look like the best solution to connect your speakers.

Hans
.

gpapag 6th May 2021 10:45 PM

Quote:

Originally Posted by jneutron (https://www.diyaudio.com/forums/everything-else/371099-zip-cord-speaker-test-post6644110.html#post6644110)
I was quite surprised at the split impedance.
Measure the L and C.....to verify consistency with RFZ.

I used the LCR meter DER5000. The measurements at 100kHz are the most consistent.
L measured with far end of the cable shorted.
C measured with far end of the cable open
RFZ= SQRT(Ls/Cs)
Single zip: 132 Ohm
4 zips paralleled: 35 Ohm
4 zips split and spaced 3 inches: 447 Ohm
At 100kHz even using any of the Ls, Lp, Cs, Cp readings, ends in an RFZ very close (+/- 5%) to the Ls/Cs value.

RFZ using the TDR method (less time consuming)
Single zip: 155 Ohm
4 zips paralleled: 38 Ohm
4 zips split and spaced 3 inches: 443 Ohm
Tomorrow I’ll review and post the REW impedance sweeps

Hans, how did you produce these Zo traces? They look a bit strange

George

jneutron 7th May 2021 12:07 AM

Those numbers are far more consistent with my understandings. The 100 ohm you earlier stated for the unzipped was not feeling "right". The 443 value is much better.

Would you perchance have the impedance plot of the speaker?

John

gpapag 7th May 2021 09:38 AM

The 100 ohm was with the split wires unconstrained as seen at post 84. Zip cord for speaker test
The impedance of the speaker is at post 82 Zip cord for speaker test

George

Hans Polak 7th May 2021 10:50 AM

4 Attachment(s)
Quote:

Originally Posted by gpapag (https://www.diyaudio.com/forums/everything-else/371099-zip-cord-speaker-test-post6645204.html#post6645204)
I used the LCR meter DER5000. The measurements at 100kHz are the most consistent.
L measured with far end of the cable shorted.
C measured with far end of the cable open
RFZ= SQRT(Ls/Cs)
Single zip: 132 Ohm
4 zips paralleled: 35 Ohm
4 zips split and spaced 3 inches: 447 Ohm
At 100kHz even using any of the Ls, Lp, Cs, Cp readings, ends in an RFZ very close (+/- 5%) to the Ls/Cs value.

RFZ using the TDR method (less time consuming)
Single zip: 155 Ohm
4 zips paralleled: 38 Ohm
4 zips split and spaced 3 inches: 443 Ohm
Tomorrow Iíll review and post the REW impedance sweeps

Hans, how did you produce these Zo traces? They look a bit strange

George

I agree that the traces are looking weird, but that's what my VNA setup returned.
Zipped at 100Khz: 4,3uH+275pF resulting in 31R for 4 zips, close to your result.
Unzipped at 100Kz and spaced far apart: 16uH+34pF resulting in 171R for 4 unzipped.
The 275pF and 34pF being already corrected for the 15pF probe.

But that is just for one single frequency, and taking Zo=sqrt(Zopen*Zshort) gives an exact result because it also takes into account the R and the G of Zo=Sqrt[(R+L)/(G+C)].

Hans
.

Hans Polak 7th May 2021 11:51 AM

George,

Looking at the above images:
At 12Khz for the zip version, L=4,3uH and C measures 0pF.
Same for unzip at 63kHz, L=16uH and C measures 0pF.

So taking Zo=sqrt(L/C) leads in both cases to infinity.
Only G is preventing this from happening, but still results in a high impedance, as can be seen here
Zip cord for speaker test

That your unzipped impedance is so much higher, means that you are closer to the point where C measures 0pF.

Hans

Hans Polak 7th May 2021 12:16 PM

I used a zip cord with 25*0.15mm strands, giving roughly the same total surface of 0.5 mm^2 as 15*0.18mm.
But in my case the cable was was made from tinned copper strands.
I donít know whether this could make a difference, but that was all I could get.

Hans


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