Obviously?? 23+ pages and you finally start getting it
That circle is very confusing for some.
This is hardly a new question. We've discussed the problem of accuracy from many angles, many times here and this was one of the implications that I had in mind starting the thread. When I asked "are we done yet?" and "where can we go from here?" obviously part of answering the question involves: How do we know when we've actually reproduced all the detail in a recording???
However, though the question certainly is relevant, as I indicated, it should be obvious that it is not a question that makes the concept of accuracy in speakers (in terms of reproducing recorded content) moot, much less insurmountable. We needn't be throwing up hands and saying
"Ah well, I guess we can understand what it means to maintain an accurate signal from the perspective of A to D converting and D to A converting, and amplification all the way through the chain all the way up to speakers and then...gee who knows what could be accurate?" Do you really think we are in *that* position?
For instance, we have a good idea of how to maintain the signal accurately in our A to D conversion. And then in our D to A conversion. Then we have a good idea of what we want our amplifier to do, to maintain accuracy to the signal: Amplify the signal evenly across the relevant frequency spectrum, to maintain the balance encoded in the recorded signal. Well...that gives us a good idea of what we'd want to do when we get to speakers amplifying the signal: amplify the signal evenly across the relevant frequency spectrum. (As the Klippel paper says is the remit for good speaker design). This isn't some total mystery. If the skeptic wants to challenge this and say: "
Well...how do we know even a perfectly neutral/flat speaker is accurately amplifying the recorded detail?" the question is turned back on the skeptic:
Why WOULDN'T a speaker with flat amplitude/frequency response be accurately amplifying the signal? Especially given the logic of reproduction up to the point of the speaker?
As to why a speaker might not be accurately amplifying (via transducing) the information, well there we can appeal to various forms of distortion known...through testing...to obscure or change sonic information. Again...see the Klippel paper or countless other realms of information on this (and as an AES member, you should have some idea). And ask yourself the relevance of Toole suggesting standards from production to reproduction.
I'm not sure if we can end up with ultimate certainty we are hearing every detail possible in a recording. Perhaps there is an actual logical/physiological/technical answer to that question (which is one reason I've raised the subject to explore). But merely raising the question "how do we know we speakers are reproducing the recorded information?" doesn't actually keep us stuck in Plato's cave on the issue. It turns out we aren't actually stuck in purely circular reasoning. We can make practical/experimental inferences and predictions from a variety of angles - basically the stuff of audio engineering in the first place.