In my recent article "Crossovers and Cables: Are They Really Any Different?", I proposed that both crossovers and cables, because of the Resistance (R), Capacitance (C), and Inductance (L) that both intrinsically have, can both effect changes to the phase, frequency, and transient response of any signal sent through them, and that both are, therefore, except for the differences in the magnitude of their R,L, and C, components that result from the different intents of their designers, functionally and essentially the same thing.
I was pleased to see that one reader, Rūdolfs Putniņš, actually "got" it, and posted a comment saying that: "Every electrical system can be defined by capacitance, inductance and resistance", and went on to ask "What isn't a crossover then?" That's exactly the point, of course, and I wrote a comment back to him, "liking" what he had said and illustrating his point with my own statement that: "For years, while I owned XLO and even after, I (and every other cable designer in Hi-Fi and every other field of electronics, including military and aerospace) did everything I/(we) could to create cables that would -- as the critics insist -- do nothing at all to affect or alter the signal passed through them, and I, along with everybody else, was unsuccessful...The simple fact of it", I said "is that, at the present state of the art, and probably for all time to come, the ability to make cables that DON'T do anything at all is and will remain beyond our capability. It's neither magic nor the voodoo that the trolls are constantly accusing us of. It's just physics and basic electronics."
That exchange was obviously on the subject of cables, but it applies to every other aspect of electronics, as well. The designer of every electronic product (and most other products, too) has TWO sets of goals and problems that he must deal with: He needs to figure out how to get whatever he's designing or making to do what it's supposed to do, and at the same time he must also figure out how to get it NOT to do anything else.
With Hi-fi, those goals and problems are, for most designers, both obvious and easy to define: A true high fidelity audio product MUST transduce, amplify, pass, or reproduce recorded music exactly as it was recorded and, for everything other than source components, must do so exactly (other than for necessary amplification or attenuation), as the signal was conveyed to it by the previous component up the chain. What it must NOT do, EVER, is to add anything, subtract anything, modify anything, or distort the signal in any way.
In short, the task of the designer - at least those designers who agree with the foregoing definition -- is to create products that, other than performing their intended function, do absolutely nothing at all.
To do nothing at all, though, is much harder than it seems. In fact, as Mr. Putniņš so correctly pointed out, because every electrical system has resistance, capacitance, and inductance (and all kinds of other electrical and physical characteristics, too) in at least some measure, and because all of those things will, depending on their mix and magnitude, affect that system's performance in some way and to some degree, getting just about anything electrical, whether an "active" component like a CD player, an amplifier or a preamp, or a "passive" one like a cable, to do nothing at all other than exactly what you want it to makes Hercules' task of cleaning the Augean stables seem like child's play by comparison.
There are two different ways that designers can approach the problem of doing nothing: They can either actually design and build their products to do nothing other than just what they were created to do, or they can design and build them to do whatever they do, and then "fix them in the mix".
For the "High End", the more common solution is probably the first -- to design and build products that, either by simplicity of design and execution, or by creative innovation and/or the use of special or exotic components and materials, simply avoid as many unwanted side-effects as possible. In loudspeakers, the common High End preference for first order (6dB per octave) crossovers that introduce zero degrees of phase shift is a good example of this.
The "fabulous", mostly Japanese Hi-Fi electronics of the 1980s are the perfect example of the other approach to doing nothing: In these products, vast amounts of "global" negative feedback were commonly used to correct (by creating and inserting an identical or purposely altered out-of-phase signal) for any frequency-response or other aberrations and simply cancel-out any distortion. The "specs" on these things were spectacular, with a huge range of frequency response and posted distortion figures of as little as .00001% (!). Unfortunately, they almost never sounded as good as they measured and, today, global negative feedback is seldom encountered, even in "mid-fi" products.
Another example of this same kind of approach at the High End is the "magic boxes" used by some cable-makers to correct or prevent whatever evils their cables may produce in the process of passing signal. Personally, I always preferred to solve the problems in the design stage, rather than trying to cancel them in the finished product, but that's just me. If the boxes really work and people are pleased with them, that's all that matters.
As I said in my response to Mr. Putniņš, I and other designers have, for many years done "... everything I/(we) could to create cables that would -- as the critics insist -- do nothing at all to affect or alter the signal passed through them, and I, along with everybody else, was unsuccessful..." There are other designers, though, who don't agree with that philosophy, and, instead of just reproducing whatever has been recorded, actually set forth to "improve" the recorded sound.
To them, doing nothing is never the goal. Instead of the best possible presentation of the recorded information, they want to produce the most pleasing possible presentation, and that, just in itself, makes them musicians - creators of music - instead of the engineers they claim to be.
To engineers, and to audiophiles who want to listen to music instead of participating in the creation of it, doing nothing at all other than just play back what's there is an important achievement. Or at least it would be if it were possible. As I told Mr. Putniņš, though, I don't think anybody's ever actually done it.