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Old 2nd January 2013, 03:28 AM   #1
deanxxx is offline deanxxx  United Kingdom
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Default Modelling Audio Cables

Hi,

I'm building some DIY speaker cables and have been reading about resistance, capacitance and inductance; R and L being more significant than C.

I have used Electronics Work Bench to approximate a cable model (click attached thumbnail for image) and was hoping to get some comments about how valid or useful this approach is.

It seems to confirm much of what is said about capacitance affecting high frequency performance less than inductance and resistance i.e. when I change C not much happens but when I chance R and/or L the upper cut-off point can encroach on the audio band.

Note: The speaker impedance (Z) is a crude constant in this model as I'm not sure how to model the reactance of a typical speaker without actually drawing it in complete and given speakers vary quite a bit, maybe there is little point. Also, It's easy to increment Z and re-run the simulation to see the effect of changes in speaker impedance.

Any comments much appreciated.

HNY,
Dean.
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File Type: jpg speaker model diyaudio.JPG (120.4 KB, 179 views)

Last edited by deanxxx; 2nd January 2013 at 03:37 AM.
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Old 2nd January 2013, 03:51 AM   #2
DUG is offline DUG  Canada
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Try a distributed L & C like in real speaker cables.

Lots of little L's and C's...0.8uH / foot and 30pF / foot

Say about 10 feet worth.

It would be interesting to see the results.
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Old 2nd January 2013, 04:23 AM   #3
deanxxx is offline deanxxx  United Kingdom
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Quote:
Originally Posted by DUG View Post
Try a distributed L & C like in real speaker cables.

Lots of little L's and C's...0.8uH / foot and 30pF / foot

Say about 10 feet worth.

It would be interesting to see the results.
Same -1dB point, different response. No real impact on audio band it seems.
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File Type: jpg speaker model distributed L C diyaudio.JPG (168.8 KB, 170 views)

Last edited by deanxxx; 2nd January 2013 at 04:26 AM.
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Old 2nd January 2013, 04:43 AM   #4
deanxxx is offline deanxxx  United Kingdom
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Quote:
Originally Posted by deanxxx View Post
Say about 10 feet worth.
For a 3m cable the -1dB point close to top of audio band!
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Old 2nd January 2013, 04:46 AM   #5
Art M is offline Art M  United States
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Instead of using a benign Sinusoid for the generator, try a Pulse/ Square wave and see what arrives at load end.
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Old 2nd January 2013, 04:59 AM   #6
deanxxx is offline deanxxx  United Kingdom
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Quote:
Originally Posted by Art M View Post
Instead of using a benign Sinusoid for the generator, try a Pulse/ Square wave and see what arrives at load end.
I used the function generator instrument. No real change from sine, square, triangle waves and for different voltages (1v to 10v) apart from the Inductors blew! EWB puts on a nice little animation to that effect.

I'll model some real world cables such as Goertz foils, Pear Anjou, Nordosts, DNM, Naim, Slinky Links to see how they perform for Z=4ohms (just to make it difficult).
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Old 2nd January 2013, 06:16 AM   #7
deanxxx is offline deanxxx  United Kingdom
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Originally Posted by deanxxx View Post
I'll model some real world cables such as Goertz foils, Pear Anjou, Nordosts, DNM, Naim, Slinky Links to see how they perform for Z=4ohms (just to make it difficult).
In conclusion: Don't but Nordost!
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Old 2nd January 2013, 07:14 AM   #8
jcx is offline jcx  United States
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a couple of posts with LTspice lumped cable model sims, with .asc source for the parameterized lumped TL model

http://www.diyaudio.com/forums/analo...ml#post3264506

http://www.diyaudio.com/forums/analo...ml#post3269070
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Old 2nd January 2013, 09:43 AM   #9
Elvee is offline Elvee  Belgium
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Lumped cable models are essentially useless: for example, here is the comparison between a real, distributed model of a 320m cut and its lumped equivalent (when measured with a network analyzer, the resulting curve is identical to the simulated one [distributed, of course]).

This example is for a 100 ohm cable, but results are applicable to any type.
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Old 2nd January 2013, 01:38 PM   #10
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Elvee, your lumped model is lossless. Adding finite loss to each segment works wonders for getting rid of the ripple artifacts
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