Modelling Audio Cables - Page 4 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 3rd January 2013, 01:34 AM   #31
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by jcx View Post
multiple RLC sections are still called lumped element approximations - Spice also has a "continuous" transmission line model

some like to use just a single RLC section - may often be good enough for audio - but multi section RLC lumped TL can approach the continuous model in accuracy at increasingly higher frequency as the number of sections/cable length increase

and, as usual, audio frequency "transients" don't stress the accuracy of even single section RLC cable models for domestic <10m lengths compared to the continuous TL models - as long as both are ignoring skin/proximity effect
Hi,

From memory, the transmission line for Spice is based on a single conductor with the return path a perfect conductor - similar to a strip line analysis.

I think you can simulate a balanced transmission line by connecting two spice transmission lines together - about the ground plane conductor - or 0volts line with capacitances and inductors sized accordingly.

Regards,

Shadders
  Reply With Quote
Old 3rd January 2013, 01:40 AM   #32
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by davidsrsb View Post
Continuous models and lumped are identical as long as each lump is less the 10% of the electrical wavelength. It is unusual for either model to take into account changes of resistance due to skin depth or capacitance with dielectric constant over frequency.
Hi,

My original statement was that the speaker cable should be modelled as a balanced network - as stated by others distributed lumped elements can approximate a continuous model as the number of elements increase.

Also, as others have stated, for audio frequencies the lumped element approach and generally the single lumped elements are sufficient. What cannot be shown is why some people hear differences for cables that have similar electrical characteristics - differences have no impact over the audio spectrum.

Regards,

Shadders.

Last edited by shadders; 3rd January 2013 at 02:08 AM.
  Reply With Quote
Old 3rd January 2013, 04:27 AM   #33
deanxxx is offline deanxxx  United Kingdom
diyAudio Member
 
Join Date: Mar 2012
Location: brum
Quote:
Originally Posted by shadders View Post
Hi,

At the -1dB point, i obtain 600kHz for the distributed response and 700kHz approx for the lumped response.

I think the 1dB at 23kHz may mean you may be using too many elements - or the cable length is quite long ?

Regards,

Shadders.
I used the vales of 0.36uH/m, 4.6mOhms/metre, 295pF/m then multiplied each by 3 for a 3m cable which gave -1dB @ 28kHz (not 23k, my bad). I used a single component for R, C and L while Z(speaker)=4ohms.

I guess L should be even lower. In fact, halving L gave -1dB @ 64kHz. An improvement.
  Reply With Quote
Old 3rd January 2013, 04:51 AM   #34
deanxxx is offline deanxxx  United Kingdom
diyAudio Member
 
Join Date: Mar 2012
Location: brum
Quote:
Originally Posted by deanxxx View Post
I used the vales of 0.36uH/m, 4.6mOhms/metre, 295pF/m then multiplied each by 3 for a 3m cable which gave -1dB @ 28kHz (not 23k, my bad). I used a single component for R, C and L while Z(speaker)=4ohms.

I guess L should be even lower. In fact, halving L gave -1dB @ 64kHz. An improvement.
Actually, scrap the above. Maybe my EWB is playing up (it does sometimes). I'm now getting the same results shadders got for the "Hifi News cable".

For a 3m length i.e. multiply 0.36uH, 4.6mOhms and 295pF each by 3, I'm getting 700kHz into 8ohms and roughly 350kHz into 4ohms.
  Reply With Quote
Old 3rd January 2013, 05:01 AM   #35
deanxxx is offline deanxxx  United Kingdom
diyAudio Member
 
Join Date: Mar 2012
Location: brum
Quote:
Originally Posted by DUG View Post

0.36uH/m seems a bit low

295pF/m seems a bit high

Do you know what gauge and spacing were they using?
Low L is good though? Do you mean L seems low compared to inductances of typically cables on the market or too low to be any good?

I have noticed most commercial cables have L higher than 0.36uH/m and my sims so far have shown them to be very poor cables in terms of high frequency performance: Nordost Vahalla as an case in point with L=33uH/m!

Of course, I take the points made about hearing differences that aint seen in sims or on scopes. I'm trying to get the first-order stuff right before I build a set of cables. Btw, I fancy building copper foil cables wrapped in cotton.

Cheers.

Last edited by deanxxx; 3rd January 2013 at 05:06 AM.
  Reply With Quote
Old 3rd January 2013, 08:58 AM   #36
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
In my first sim, I made a factor of 10 error in the sections of the lumped line.

It doesn't change the gist of my argument though: here is the comparison, and with the resistance also spread between the lumps.

The two transfer functions begin to diverge as early as 20KHz, to reach ~1dB at 100KHz (for 10m sections).
The phase/time aspect is more accurately modelled though: this means that such artificial lines are suitable as delay lines, but not as cable simulators.
There are much better topologies for that, departing completely from the method consisting to attempt to duplicate the elementary L/C cells (which have no actual existence, since they are infinitesimal).
The impedance plots are also seriously divergent above the corner frequency:
Attached Images
File Type: png CableMod2.png (108.7 KB, 60 views)
File Type: png CablesImp.png (113.1 KB, 58 views)
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪
  Reply With Quote
Old 3rd January 2013, 09:31 AM   #37
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by deanxxx View Post
Low L is good though? Do you mean L seems low compared to inductances of typically cables on the market or too low to be any good?

I have noticed most commercial cables have L higher than 0.36uH/m and my sims so far have shown them to be very poor cables in terms of high frequency performance: Nordost Vahalla as an case in point with L=33uH/m!

Of course, I take the points made about hearing differences that aint seen in sims or on scopes. I'm trying to get the first-order stuff right before I build a set of cables. Btw, I fancy building copper foil cables wrapped in cotton.

Cheers.
Hi,

The inductance was as printed - th other cables had similar - some higher and some lower, but these values seem typical.

Regards,

Shadders.
  Reply With Quote
Old 3rd January 2013, 11:39 AM   #38
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by deanxxx
I'm trying to get the first-order stuff right before I build a set of cables. Btw, I fancy building copper foil cables wrapped in cotton.
In my view there is no point whatsoever in building a cable. If you can hear a difference between it and an appropriate normal commercial cable then that just means your DIY cable is particularly bad. (Bad at one or more of: high C, high L, high R, high RF pickup, high microphony).

If you want to DIY components (a cable is a component) then do this for those which could have a bigger effect on the sound, such as resistors, caps or transformers (or speakers?). You will find that in almost all cases it is easy to change the sound, but much harder to actually improve it. Reputable component/cable manufacturers do know what they are doing.

The aim of your current investigation should be to demonstrate to your own satisfaction that cables are not that important, provided a few electrical parameters are correct.
  Reply With Quote
Old 3rd January 2013, 09:42 PM   #39
deanxxx is offline deanxxx  United Kingdom
diyAudio Member
 
Join Date: Mar 2012
Location: brum
Quote:
Originally Posted by DF96 View Post
In my view there is no point whatsoever in building a cable. If you can hear a difference between it and an appropriate normal commercial cable then that just means your DIY cable is particularly bad. (Bad at one or more of: high C, high L, high R, high RF pickup, high microphony).

If you want to DIY components (a cable is a component) then do this for those which could have a bigger effect on the sound, such as resistors, caps or transformers (or speakers?). You will find that in almost all cases it is easy to change the sound, but much harder to actually improve it. Reputable component/cable manufacturers do know what they are doing.

The aim of your current investigation should be to demonstrate to your own satisfaction that cables are not that important, provided a few electrical parameters are correct.
You make a good point.

I think I have learned about those parameters.

Still, it's interesting. I have plans to build a few speakers also, just for the hell of it I guess

Cheers all.
  Reply With Quote
Old 3rd January 2013, 11:45 PM   #40
deanxxx is offline deanxxx  United Kingdom
diyAudio Member
 
Join Date: Mar 2012
Location: brum
Quote:
Originally Posted by shadders View Post
Hi,

The inductance was as printed - th other cables had similar - some higher and some lower, but these values seem typical.

Regards,

Shadders.
I'd be happy to try that cable. Cheers for your input Shadders.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Old power cables make good audio cables? paean Parts 9 2nd November 2010 09:21 AM
NAGYS AUDIO Best Audio Cables in the World!!! Guaranteed!!! NagysAudio Vendor's Bazaar 0 25th August 2010 04:17 AM
Pear Audio Cables - Only $7,250!! sdclc126 Everything Else 13 29th December 2007 07:09 PM
Oritek Audio X-1 Cables Spiritzly Swap Meet 0 6th August 2006 07:01 PM
Colors of Audio Cables Glen.Yule Car Audio 2 13th November 2004 10:47 AM


New To Site? Need Help?

All times are GMT. The time now is 01:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2