Science that explains why we hear differences in cables?


Here are some excerpts from a review of the Silversmith Audio Fidelium speaker cables by Greg Weaver at Enjoy The Music.com. Jeff Smith is their designer. I have not heard these cables, so I don’t have any relevant opinion on their merit. What I find very interesting is the discussion of the scientific model widely used to design cables, and why it may not be adequate to explain what we hear. Yes it’s long, so, to cut to the chase, I pulled out the key paragraph at the top:


“He points out that the waveguide physics model explains very nicely why interconnect, loudspeaker, digital, and power cables do affect sound quality. And further, it can also be used to describe and understand other sonic cable mysteries, like why cables can sound distinctly different after they have been cryogenically treated, or when they are raised off the floor and carpet.”


“One of the first things that stand out in conversation with Jeff about his cables is that he eschews the standard inductance/capacitance/resistance/impedance dance and talks about wave propagation; his designs are based solely upon the physics model of electricity as electromagnetic wave energy instead of electron flow.


While Jeff modestly suggests that he is one of only "a few" cable designers to base his designs upon the physics model of electricity as electromagnetic wave energy instead of the movement, or "flow," of electrons, I can tell you that he is the only one I’ve spoken with in my over four decades exploring audio cables and their design to even mention, let alone champion, this philosophy.


Cable manufacturers tend to focus on what Jeff sees as the more simplified engineering concepts of electron flow, impedance matching, and optimizing inductance and capacitance. By manipulating their physical geometry to control LCR (inductance, capacitance, and resistance) values, they try to achieve what they believe to be the most ideal relationship between those parameters and, therefore, deliver an optimized electron flow. Jeff goes as far as to state that, within the realm of normal cable design, the LRC characteristics of cables will not have any effect on the frequency response.


As this is the very argument that all the cable flat-Earther’s out there use to support their contention that cables can’t possibly affect the sound, it seriously complicates things, almost to the point of impossibility, when trying to explain how and why interconnect, speaker, digital, and power cables have a demonstrably audible effect on a systems resultant sonic tapestry.


He points out that the waveguide physics model explains very nicely why interconnect, loudspeaker, digital, and power cables do affect sound quality. And further, it can also be used to describe and understand other sonic cable mysteries, like why cables can sound distinctly different after they have been cryogenically treated, or when they are raised off the floor and carpet.


As such, his design goal is to control the interaction between the electromagnetic wave and the conductor, effectively minimizing the phase errors caused by that interaction. Jeff states that physics says that the larger the conductor, the greater the phase error, and that error increases as both the number of conductors increase (assuming the same conductor size), and as the radial speed of the electromagnetic wave within the conductor decreases. Following this theory, the optimum cable would have the smallest or thinnest conductors possible, as a single, solid core conductor per polarity, and should be made of metal with the fastest waveform transmission speed possible.


Jeff stresses that it is not important to understand the math so much as it is to understand the concept of electrical energy flow that the math describes. The energy flow in cables is not electrons through the wire, regardless of the more common analogy of water coursing through a pipe. Instead, the energy is transmitted in the dielectric material (air, Teflon, etc.) between the positive and negative conductors as electromagnetic energy, with the wires acting as waveguides. The math shows that it is the dielectric material that determines the speed of that transmission, so the better the dielectric, the closer the transmission speed is to the speed of light.


Though electromagnetic energy also penetrates into and through the metal conductor material, the radial penetration speed is not a high percentage of the speed of light. Rather, it only ranges from about 3 to 60 meters per second over the frequency range of human hearing. That is exceptionally slow!


Jeff adds, "That secondary energy wave is now an error, or memory, wave. The thicker the conductor, the higher the error, as it takes longer for the energy to penetrate. We interpret (hear) the contribution of this error wave (now combined with the original signal) as more bloated and boomy bass, bright and harsh treble, with the loss of dynamics, poor imaging and soundstage, and a lack of transparency and detail.


Perhaps a useful analogy is a listening room with hard, reflective walls, ceilings, and floors and no acoustic treatment. While we hear the primary sound directly from the speakers, we also hear the reflected sound that bounces off all the hard room surfaces before it arrives at our ears. That second soundwave confuses our brains and degrades the overall sound quality, yielding harsh treble and boomy bass, especially if you’re near a wall.


That secondary or error signal produced by the cable (basically) has the same effect. Any thick metal in the chain, including transformers, most binding posts, RCA / XLR connectors, sockets, wire wound inductors, etc., will magnify these errors. However, as a conductor gets smaller, the penetration time decreases, as does the degree of phase error. The logic behind a ribbon or foil conductor is that it is so thin that the penetration time is greatly reduced, yet it also maintains a large enough overall gauge to keep resistance low.”


For those interested, here is more info from the Silversmith site, with links to a highly technical explanation of the waveguide model and it’s relevance to audio cables:


https://silversmithaudio.com/cable-theory/


tommylion

Showing 4 responses by itsjustme

If anyone would really like to begin a journey into what **might** make some difference, i suggest you watch a series (or any one is probably sufficient) of talks that that Rick Hartley gave to the Altium user conference. Altium is probably the leading PCB layout program, and these users are dealing with how to achieve good grounding in complex PC boards, possibly in the gigahertz region.
he has a second one on differential pairs that has similar but complimentary information.

He goes into the science hand -waived about above - that the energy is really in the fields, and the fields are in the insulation. The conductors simply guide the wave (hence the term waveguide).

Several caveats:
  • they are long
  • the info you want is tangential and you need to dig for it
  • this stuff really matters at hgih frequencies, but may have some tiny impact at lower ones
  • He’s talking circuit boards, layers and ground pours, and you need to mentally translate to the physical configuration of wires


But its still really good stuff. I think the one of differential pairs builds on this nicely.
https://resources.altium.com/p/us-how-to-achieve-proper-grounding-rick-hartley-expert-live-training

I have always maintained that the insulation was the most important part of any interconnect or speaker cable. If you;d use polypropylene, or Teflon, or at least Mylar in capacitors, you probably ought to in your wires too.
G

the differences in capacitance alone between different makes should be enough to understand how sound may change
A fast look at spec sheets says mogami interconnect has about 70pF/meter. So a (very long) 2M interconnect has 140 pF. And a relatively high output impedance of th edriving stage is 500 ohms.  So the roughly -3dB point is >2 mHz. (if my mental math is correct).

So, is this true?

There's a lot more to it than that. Different dielectrics (insulators) have different properties.

I wasn't going there but thumbs up.  Anyone who doubts read a datasheet on capacitors and all the characteristics of them; most critically to us (IMO) dialectic absorption.

The video(s) i linked get into the why - its the basically physics of electromagnetic propagation, which is in the wave, in the dialectric, merely guided by the wires.

While the effect at low frequencies may be smallish, I strongly believe that at the very least it is best to use twisted pair (tight waveguide) with a dialectric that is linear - typically both a plastic film such as polypropylene, polystyrene, teflon, or mylar, and if possible low density (e.g.: expanded foam).

What do you know, hgih frequency radio communications demands the same thing.

G

I started to watch the video but the first statement in the video: "The square wave and the sine wave are the same thing only with distortion" is complete lunacy.


OK, i would not state it that way. But...., step back. A distortion is a "change or difference in an electrical signal". Well, its a big difference no doubt, but i think that’s his point. Maybe a stretch, but valid/true. Just sayin’