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 deanxxx 2nd January 2013 02:28 AM

Modelling Audio Cables

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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.

HNY,
Dean.

 DUG 2nd January 2013 02:51 AM

Try a distributed L & C like in real speaker cables.

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

It would be interesting to see the results.

 deanxxx 2nd January 2013 03:23 AM

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Quote:
 Originally Posted by DUG (http://www.diyaudio.com/forums/parts/226855-modelling-audio-cables-post3307446.html#post3307446) 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.

 deanxxx 2nd January 2013 03:43 AM

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Quote:
 Originally Posted by deanxxx (http://www.diyaudio.com/forums/parts/226855-modelling-audio-cables-post3307464.html#post3307464) Say about 10 feet worth.
For a 3m cable the -1dB point close to top of audio band!

 Art M 2nd January 2013 03:46 AM

Instead of using a benign Sinusoid for the generator, try a Pulse/ Square wave and see what arrives at load end.

 deanxxx 2nd January 2013 03:59 AM

Quote:
 Originally Posted by Art M (http://www.diyaudio.com/forums/parts/226855-modelling-audio-cables-post3307481.html#post3307481) 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).

 deanxxx 2nd January 2013 05:16 AM

Quote:
 Originally Posted by deanxxx (http://www.diyaudio.com/forums/parts/226855-modelling-audio-cables-post3307486.html#post3307486) 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!

 jcx 2nd January 2013 06:14 AM

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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

 Elvee 2nd January 2013 08:43 AM

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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.

 davidsrsb 2nd January 2013 12:38 PM

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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