Home Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

[ Follow Ups ] Thread: [ Display  All  Email ] [ Propeller Head Plaza ]
[ Alert Moderator ]

Re: Why Wires Sound Different or Objectivists Got It All Wrong...

Hi

I know your serious as can be but you toss a very large net when you include power cords, phono cables and such into one basket.

For one thing, unless you had a problem with a given power cord, your not going to hear any repeatable difference "if" you don’t also know which cord is which.
At power line frequencies, that last 6 feet of cable is truly insignificant in the chain.
It is insignificant because of the magnitude of the things you mentioned, like its parallel capacitance, resistance’s and such.
Here, when you carefully compare the signals at each end of the wire, one concludes they are the same or consistent with the R,L and C.

At the other end of the scale you have interconnects and phono cables.
Here one might have a high source impedance in which case excessive parallel capacitance can have a large impact on the response /phase.
Conversely on equipment with a low source impedance, that same cable may have no audible effect.
A phono cartridge is a tiny motor/generator like a speaker or dynamic microphone, it is also a complex mechanical system which is reflected into its impedance as a network of R’s, L’s and C’s. When loaded by the pre-amps impedance (which varies from one preamp to another) there is usually an optimum shunt capacitance which gives the best response shape. Many old preamps had a selector for this shunt C.
Here, the lead wire is also part of the parallel C.

For speaker cable, this is somewhere in between.
A modern amplifier is assumed to have a very low source impedance, damping factor is the ratio of the load to source fwiw (and anything over about 20-50 is inaudible).

A bare wire going in a straight line from A to B, has series resistance per length (set by the cross section area and conductivity).
It has series inductance per length set by the permitivity of space and it has parallel capacitance set by its area per length and permitivity of space.
These quantities are such that when a wire is long enough (around 1 / 2 electrical wavelength) for the frequency in question, that it becomes a transmission line with a specific impedance. At 20KHz, that is a wire about 4 1 /2 miles long, not the length of a typical speaker cable. At audio frequencies, speaker cables are never transmission lines, they are lumped parameters networks..

That same single bare wire also shows skin effect when its dimension and conductivity and frequency are sufficient.
From the "skin effect" one might conclude that a 3 inch solid copper rod would be a poor (yet expensive and heavy) speaker cable as it begins to exhibit skin effect at audio frequencies. Yet, if one looks at the overall resistance, it is still far less than say a 16 ga wire which has no appreciable skin effect in the audio range.

In a speaker system one has two wires, with equal currents traveling in opposite directions. Being a "loop" inductor, the inductance is proportional to the area within the loop. Twisting one conductor around another (as in a twisted pair) minimizes the loop area and removes any preferential induction direction so far as an external field.
When you place the conductors closer together, you decrease the series L per foot, when you substitute something other than air for the space between the wires, you increase the capacitance per foot by dielectric constant of that insulator.

If one deals with this stuff regularly (like crossovers etc), one finds some tools are useful for quantifying these properties.
In the photo in the blurb here, the stuff to the left is for electrical properties and the stuff to the left for acoustic properties.
http://systemscontractor.com/articles/publish/article_977.shtml
The thing to the left of my head is a network analyzer which is used for measuring cables and systems (electrical networks), the unit below is for measuring L’s and C’s while also measuring the stray components of them at the same time.

If one measures real speaker cables, one finds a LARGE variation in the properties, some have resistance’s which are not negligible, many have relatively high parallel capacitance’s and plain Jane cable like extension cord has enough series L to be an issue if more than say 20 or 30 feet long.
If one had an amplifier that had marginal stability or a high source impedance up high, then parallel C may really cause problems.

I would be really interested to hear your impressions of a cheap and easy to make speaker cable that "if" one goes by the numbers beats just about everything I looked at.
This will sound impossible but try some RG-8 coax (or the more modern derivatives like 9913). This is .45 inch in diameter cable so it is not "thin" but it has the lowest R, L and C of any of the wires I looked at. Do not substitute thin coax, it has to be RG-8 or equiv).
Anyway, if your inspired to look for a Ham radio shop or Ham flee market, try it and let me know what you think relative to "normal" cables.
Best,

Tom Danley


This post is made possible by the generous support of people like you and our sponsors:
  Atma-Sphere Music Systems, Inc.  

Follow Ups Full Thread
Follow Ups
You can not post to an archived thread.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]