Frequency Response of L.P's

Fine as the console may have been, that doesn't answer the monitor question. Again, I don't doubt that there may be a germ of basis in fact for this story, but no matter what Mr. Neve theorizes, I don't believe it's because Mr. Emerick can hear minor response variations *at* 54KHz, even if the audible problem did turn out to be *correlated with* or *caused by* something occurring at that frequecy. Mr. Neve may be in a position to know what the end result of episode was, but IMO can't be certain about the mechanism for its original detection. It makes for a nice story though...

JB: The presumed advantage of that diamond tweeter would have to include its performance in the audible range, not just its allegedly greater extension. The exact Hz figures I'm guessing are mostly 'specsmanship'. One of the real benefits of designing a tweeter diaphragm with the highest possible rigidity-to-mass ratio is the potential to move its fundamental resonance frequency out as far above the audioband as possible (allowing it to act most like a pure piston within the audioband), and I assume that's the reason for the "diamond" construction. There's nothing of musical value going on at 100KHz anyway, even if the software could capture it, the rest of the system could transmit it, and we could hear it (we can't). A CD and its player can only capture and transmit information up to between 20KHz and 22KHz due to the Red Book sampling frequency standard, but it's generally thought that the audioband side effects of the steep filtering above that frequency limit - rather than the loss of any higher frequencies per se - is mostly to blame for any audible artifacts that degrade CD HF reproduction. Human hearing is nominally considered to extend to 20KHz max., but while a few individuals (probably mostly young, and maybe mostly female) may be able to hear up to a somewhat higher frequency limit, most of us adult males actually get by with hearing response that begins rolling-off well before those heights, maybe between 12KHz and 16KHz, and a lot of us are completely deaf to info above 16KHz-18KHz or even lower.

Stefanl: I'm sorry, but to me that story is likely mostly apocryphal. There were no monitors Emerick could have been using that would reproduce 54KHz flat even if he could hear that high (which I don't believe), and I doubt the response of his board was extended flat beyond that frequency either. If the story has a germ of basis in fact, I would have to assume that whatever was the fault in the board (a ringing spike caused by incipient oscillation? - certainly not a -3dB dip), it must have been precipitating some audible artifacts affecting frequencies down much closer to the range of normal human hearing.

Eldartford: I can understand that smooth ultrasonic extension will aid in maintaining waveform linearity lower in the audioband, and that glitch-free gradual ultrasonic roll-off beginning well above the audioband is probably never a bad quality to cultivate everywhere throughout the recording/reproduction chain (even if a lot of what goes on up there is probably noise). But to me it seems that when it comes time for such a signal to exit a speaker, most conventional designs will be capable of only such limited dispersion that one would have to listen perfectly on-axis with their head in a vise to receive much of the theoretical benefit...

JB: The problem seems to have more to do with the CD standard's implementation of the steep ultrasonic filter so close to the audioband, rather than the loss of the ultrasonic frequencies per se. However, the solution takes care of both problems: Simply increasing the sampling frequency (in a PCM format) of the recording, storage media, and playback machine, as is done with hi-rez DVD-A, to at least double the 44KHz CD standard will both extend the ultrasonic response into LP territory, and move the anti-aliasing filter well above the audioband allowing for a much gentler and less problematic filter slope.