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Fall off my chair.....REALLY?
Ringing can't be heard for two reasons:
1. Nobody can hear 22.05 kHz.
2. A Dirac impulse that is used to give you an impulse response that is used to show the ringing is an illegal signal from sampling theory point of view, as it contains equal energy at FS/2 (22.05 kHz) when sampling requires bandwidth limiting, which means there is no energy at 22.05 kHz. No energy on the input means the filter will in practice not ring at all.
This basic and gross misunderstanding of simple digital sampling theory has been adopted by the whole audio business; indeed, the M scaler with it's huge tap length WTA filter, with a bandwidth limited analogue signal will actually reconstruct the original analogue signal to a better than 16 bit accuracy; with no added ringing at all.
It is pretty simple really.
@Rob Watts, do you sit back and watch us poorly informed mortals discussing your chosen profession to death. Only for you to jump in at the 11th hour and squash us.
Keep it up its very entertaining it really is.
Thanks for your explanation again,Jazz,
not the first time!
I derive at least some little comfort from the fact that the soon to be "ex editor" of Stereophile is obviously a bit ignorant of digital theory too?
It feels nice not to be completely alone in my ignorance.
And as I said I'm always keen and willing to learn!
But regarding the need for ultrasonics or not?
Isn't there still some debate around that in some quarters?
I know Rob definitely thinks those who believe ultrasonics are needed, are wrong.
That is also something he mentioned at his seminar in Singapore last year.
But there are instruments in a symphony orchestra that produce harmonics well into the 30khz range and even above.
I know most of us,me definitely included, don't hear those overtones as tones.Only bat,cats and dogs, and apparently some very exceptional young women seem to be able to hear any actual tones above 20khz.
But isn't there at least some small chance that they might still influence the final sound we hear even in recordings?
Some still claim that they do.
Or have those claims been refuted?
Straight from the horse's mouth!
Even more comforting for me in my ignorance, to hear that not only I and Atkinson at Stereophile have misunderstood things a bit,but also the whole audio business.
Cheers CC .
Actually I'm still hesitating to say ultrasonics do absolutely nothing, since there's some theoretical scenarios where they could come into play, despite being inaudible as such. On the other hand I tend to believe Rob in this respect. So definitely slightly undicided yet. However, even if they're audible under certain circumstances, they won't play a decisive role, that's what I think.
Rob, in this case John Atkinson used an impulse response as a criterion for showing the characteristic of the ringing, which indeed looks like an illegal signal. On the other hand, if he had used a square-wave response for the same purpose, I bet the result would look very similar if not identical. At least that's what usual measurements with both measuring criteria illustrate. And a square wave is definitely a legal signal.
[Edit:] Of course I'm talking of a bandwidth-limited square-wave signal – doing otherwise would be downright criminal.
It's always been my belief that any low-pass filter that's not infinitely sharp will be «excited» also by frequencies minimally below its own frequency, so in this context the ringing would be unavoidable in any case. Or where's my fallacy?
My limited understanding is even if we don't directly hear those high frequencies, the hetrodining between them can add a little colour to the timbre of a given instrument. Which may be one reason why some people find 44.1k digital a bit dry or lacking exactly because of the removal of partials above 20k. Wazzzzup made some through-the-nose snark remark last time I brought this up. But, I don't bother with bar-room smugness anyway. But, until someone refutes my naïve thoughts with some actual facts, I'm stickin' to what I think is the case.
Hell, we even talked about this back in engeneering school back in the '80s. The digital experts said things that add up to: Don't worry yer perdy little head about it; 20k is all you need. On the other hand, I talked to some actual sound engineers who felt that pushing the cutoff from 22.05 up to about 50K would have been better in the beginning. So we'd have had to live with perhaps 8" or 10" disks. Some whine about missing the 12" cover of an LP with all the pictures and album credits.
A little confused about point no. 2. Didn't Dirac postulate antimatter? If so, how does his work fit into sound?
This is a good book about Dirac, but I don't know if it is available in audiobook format.
Thanks, I'll find out. If not, I can OCR scan it.
In this context it must be the Dirac Delta function.
I also purchased a QED reference optical quartz, my cheap kabeldirekt was cutting out but was fine for a year. I didn't expect an improvement in sound but there was, initially i just wanted a higher qaulity and nice looking cable so that was a nice surprise. I will mention though i do not have it plugged in to an Mscaler but a Hugo2.
Let’s say it’s true that ultrasonic frequencies generated by an instrument color the audible spectrum. If so, the mic capturing that audible spectrum will pick that up and record it in the audible spectrum, to be played back as originally heard. Reproducing the ultrasonic component. Isn’t necessary.
Thanks for the link, since I haven't gone to the "hills" yet this week. I will visit the quite impressive really big and well stocked as they used to be,bookshop Kinokunya at KLCC today and see if I can find this title at the science section there.