Post by KeithL on Jun 21, 2016 9:31:56 GMT -5
Actually, though, when you understand the science, it doesn't always match up exactly with the way people interpret it...
The science, which I would agree is pretty well understood, and well substantiated, says that "most people cannot identify the presence or absence of frequencies above 20 kHz when listening to sine wave test tones at normal listening levels". Note that this covers very specific conditions. It does NOT claim to be true for all waveforms; it does NOT claim to be true for music; and, most importantly, while it talks about "detecting the presence of sound" it does NOT talk about things like the phase relationship between audible frequencies in the two channels. Therefore, the science does NOT "refute the difference"; instead, it suggests that, in a certain situation, when tested in a certain way, we shouldn't expect the difference to be audible.
(And, to answer the objection I hear to that statement pre-emptively... Yes, if you were to record a 5 kHz tone in each channel of a stereo recording, with a slight phase shift between them, at a 44 kHz sample rate, when the audio was reconstructed it could in fact accurately portray even phase differences of a few microseconds between the channels. HOWEVER, all of the math that supports that claim, and, in fact, most math involved in the Nyquist theorem, assumes that you're talking about a continuous sine wave; when, in fact, music is not at all a continuous sine wave. Likewise, most of the theoretical math about DACs assumes that a DAC is using a mathematically accurate SinC function to reconstruct the audio signal, while the process DACs actually use is only an APPROXIMATION of the correct function. NOTE that I'm not specifically suggesting what is or isn't audible, and under what circumstances; all I'm saying is that a lot of the "science" that is supposed to "conclusively refute" claims of audible differences is often misinterpreted or oversimplified.)
If you want a glaring example to refute the idea that "nothing above 20 kHz is audible or can produce an audible effect" - Google "Sonic Spotlight". This is one of several products that "projects" audio in the form of a specially modulated beam of ultrasonic sound in the 65 kHz range. The device is made up of an array of ultrasonic transducers, operating in the neighborhood of 65 kHz, yet produces audible sound by the interaction of that beam with the air. So if, for some strange reason, I were to employ one of these as a guitar speaker at one of my concerts, anyone it was pointed at would hear my performance, but, in order to record it accurately, you would need a microphone, a recorder, and speakers, which could accurately reproduce audio up to about 70 kHz. (This is a real commercial product that you can buy - it is what's known as "a parametric speaker".) Therefore, it's premature (or presumptuous) to assume that it's impossible that other, similar, things can't possibly be happening in recordings.
Of course, if we're talking about LPs, and comparing them to other formats, then you must also consider the various FLAWS in the vinyl reproduction process, which may be responsible for audible differences between records and recordings done in other formats. (To put it bluntly; don't assume that all the differences are things that, while they should be there, are missing from recordings in other formats. Some of the stuff missing from non-vinyl recordings could simply be various audible flaws.)
Agnostic amongst the religious? I would definitely 1000% agree on the incredible sound of the XMC-1, but my switchover from an Audyssey-Pro corrected Onkyo 5508 happened "within" my audio memory window after years of listening. But I was referring to 24/96 over 24/48 or, more specifically something missing when playing LP's. There is science that refutes it that there is a difference. Of course there is none to refute that you HEARD a differnce. 
But you are obviously passionate as well as experienced in this area, and have caveated the issue enough to cause me to slightly regret jousting at your windmill.
Jeff
The science, which I would agree is pretty well understood, and well substantiated, says that "most people cannot identify the presence or absence of frequencies above 20 kHz when listening to sine wave test tones at normal listening levels". Note that this covers very specific conditions. It does NOT claim to be true for all waveforms; it does NOT claim to be true for music; and, most importantly, while it talks about "detecting the presence of sound" it does NOT talk about things like the phase relationship between audible frequencies in the two channels. Therefore, the science does NOT "refute the difference"; instead, it suggests that, in a certain situation, when tested in a certain way, we shouldn't expect the difference to be audible.
(And, to answer the objection I hear to that statement pre-emptively... Yes, if you were to record a 5 kHz tone in each channel of a stereo recording, with a slight phase shift between them, at a 44 kHz sample rate, when the audio was reconstructed it could in fact accurately portray even phase differences of a few microseconds between the channels. HOWEVER, all of the math that supports that claim, and, in fact, most math involved in the Nyquist theorem, assumes that you're talking about a continuous sine wave; when, in fact, music is not at all a continuous sine wave. Likewise, most of the theoretical math about DACs assumes that a DAC is using a mathematically accurate SinC function to reconstruct the audio signal, while the process DACs actually use is only an APPROXIMATION of the correct function. NOTE that I'm not specifically suggesting what is or isn't audible, and under what circumstances; all I'm saying is that a lot of the "science" that is supposed to "conclusively refute" claims of audible differences is often misinterpreted or oversimplified.)
If you want a glaring example to refute the idea that "nothing above 20 kHz is audible or can produce an audible effect" - Google "Sonic Spotlight". This is one of several products that "projects" audio in the form of a specially modulated beam of ultrasonic sound in the 65 kHz range. The device is made up of an array of ultrasonic transducers, operating in the neighborhood of 65 kHz, yet produces audible sound by the interaction of that beam with the air. So if, for some strange reason, I were to employ one of these as a guitar speaker at one of my concerts, anyone it was pointed at would hear my performance, but, in order to record it accurately, you would need a microphone, a recorder, and speakers, which could accurately reproduce audio up to about 70 kHz. (This is a real commercial product that you can buy - it is what's known as "a parametric speaker".) Therefore, it's premature (or presumptuous) to assume that it's impossible that other, similar, things can't possibly be happening in recordings.
Of course, if we're talking about LPs, and comparing them to other formats, then you must also consider the various FLAWS in the vinyl reproduction process, which may be responsible for audible differences between records and recordings done in other formats. (To put it bluntly; don't assume that all the differences are things that, while they should be there, are missing from recordings in other formats. Some of the stuff missing from non-vinyl recordings could simply be various audible flaws.)
But you are obviously passionate as well as experienced in this area, and have caveated the issue enough to cause me to slightly regret jousting at your windmill.
Jeff
