Amp / Cable / Speaker interaction....why?

This is a tough one. There is no clear-cut answer because there are too many variables (the human one being the most difficult to harness). Best is to just try them out. Do you want something warmer, cooler, brighter, clearer? This could be a first step since many of them have general sonic signatures.

Physics or perception?

First case: Ribbon cables like Magnan Signature and Nordost Valhalla are very popular with electrostats. The argument is that they minimize skin effect and, therefore, maintain signal coherence more effectively. The attributes generally ascribed to this bit of physics are neutrality, speed and accuracy. So, first question is, is the physical effect measurable? Second question, can the sonic attributes be linked to the measurable physical effect. I believe the answer to the second question is where the difficulty resides. It is difficult to connect a sonic impression to the physical observable with any reliability.

Case 2: People are generally very sensitive to the sense that something is warm vs bright. Absence of warm or bright is commonly thought neutral. I know of no claims where a cable that sounds bright with some equipment will sound warm with other equipment. What is actually physically responsible for this perceived spectral tilt? Is it a measurable?

Case 3: Transparent cable describes their cable as having a bandwidth limited to the audible range, resulting in a shift of the cable resonance frequency downward, with a corresponding increase in bass frequency transmission. Many people claim this to be audible. This is the ONLY case I know of in cable design where a predicted physical effect lines up with an observed sonic benefit.

Case 4: The most interesting observation about cable matching I have ever heard has to do with the notion that signal reflected at an impedance boundary will show up as noise after multiple reflections up and down a connecting cable, resulting in distortion and a loss of SNR, and a muddy sounding cable. Good physics. But sonic benefits? I hate this word "revealing", but it certainly is likely to apply here.

My own preferences? I would rather have neutral, accurate cables than play master chef of sonic blending.

One reason, and IMO the most likely, is that most gear is voiced with specific cables, speakers, amps, etc. For example, Avalon speakers are voiced with MIT cables - so there is a consensus (not unanimity) among those who prefer the sound af Avalon that MIT's sound better with these speakers. Whether the laws of physics can tell us why or not is irrelevant IMO if we like the product. This in not an absolute - different cables mean different things to different people...no matter what the physics says.

Judit - I agree wholeheartedly with your concluding sentiment, but I'm not sure such a thing is indeed achievable in practice. I'm also not so sure about some of the assumptions put forth on the physics side, but undoubtedly the EE's will come along to expound. :-)

Benthar, you and I will probably never totally comprehend this in depth, and I'm not sure that it is possible for even the cable designers themselves to completely understand everything that goes on. As to the "Why?", and omitting the obvious "What?" and "How?", I think the simplest fundamentally true explanation is that different cables are just that - physically different from one another. No condutor or circuit is perfect, and the same input passed through different ones will result in different outputs. What I am saying, in other words, is this: It wouldn't make sense if different cables sounded the *same*. They *sound* different because they *are* different. While we may struggle with the issues of prediction or explanation, there is really no more mystery as to why dissimilar wires should sound unlike each other than there is about the fact that dissimilar components don't sound the same. For some reason, people just tend to be less disturbed by the latter proposition, but the underlying reality is the same. They sound different because they pass the signal differently (and different signals differently as well), and also because they electrically interact with the other components they're connected to differently, which themselves vary just as much or more. The variables are unlimited in theory (including the whole system with its environment, the source material, and the listener), so the sonic differences are too. Which is why, as we all know, there can never be one 'right' or 'best' choice based on anything other than what you hear and prefer.

P.S. - A while ago when I was comparing some cables, the ultimate ramification of the situation fully hit me: If we were really to attempt to do this cable thing the whole way, then we would have to audition and reselect the best cables to use with *every recording* we listened to. And that's why I say I sympathize with Judit's closing statement - in the final analysis, all you can really do is try to choose the wires that best accomplish her stated goals of neutrality and accuracy (as best you can judge them) in one's system with the majority of well-recorded material, and then let the chips fall where they may after that.