jj@rabbit.UUCP (12/05/83)
Wrong, Keith, WRONG! You miss the point entirely. (Your comments, though, are quite correct, if a bit optimistic. ?perhaps for politeness?...) The person who was claiming that at least 100kHz bandwidth was necessary didn't consider any of the electronic problems, neither did I in my response. (Even though all the problems would certainly detract from their arguments, I don't have the energy to be precise, I only wanted to make the point.) Certainly the electronics will intermodulate like mad. Certainly the tweeter (if it lives at all) won't even SEE any current in its voice coil <a piezo might, but....> Even IF you manage to get it through the electronics, and into the voice coil (I'm assuming a dynamic tweeter of some sort, perhaps ribbon/leaf), you will STILL get a real mess from the Tweeter. (Intermodulation will be the LEAST of the problems.) Now then. Let's assume for a minute that we DO get the two signals into the air. Let's assume (for purposes of argument) that they get into the ear intact (fat chance, the atmospheric absorbtion will be tremendous, just like at a real performance, where the high frequencies would vanish without a trace). What will happen? Well, the EAR is quite non-linear itself. You will get AT LEAST the first order intermodulation tones. These intermodulation tones will be the detectible part of the signal. When I posted the article, I was trying to point out to the people complaining about digital reproduction the fallacies that they were espousing. Distortion in amplifiers, the lack of even electrical input into the tweeter, etc, are ALL items that they had ignored. Just trying to make such a test (with low levels, so as to be non-destructive, please) would point out a number of difficulties. What's the point? I don't know. Perhaps that the physical limits of acoustic propigation, electronics, etc, should be required reading. Have an overly precise day, Keith! (-: -- -Diogenes stopped here- (allegra,harpo,ulysses)!rabbit!jj
witters@fluke.UUCP (John Witters) (12/07/83)
Has anyone bothered to find out if the original source material has frequency components above 20 KHz? I'm talking about the original performance here, not your old audiofile disks or tapes. If the best electronics and speaker technology can't produce hypersonic frequencies, then somehow I doubt that a 300 year old violin can. Who cares if one can tell the difference between a 20 KHz square wave and a 20 KHz sine wave if the highest frequency component in a live performance is 15 KHz (sine wave)? I sure don't. I don't give a damn who I offend. - John Witters.
kissell@flairvax.UUCP (Kevin Kissell) (12/11/83)
"If the best electronics and speaker technology can't produce hypersonic
frequencies, then somehow I doubt that a 300 year old violin can."
It is relatively easy to produce hypersonic frequencies, and most musical
instruments produce hypersonic partials. Conventional wisdom has been that
harmonics above the audio range need not be reproduced to provide an accurate
recording or transmission. The validity of this assumption is being debated.
Kevin D. Kissell
Fairchild R&D Labs,
Advanced Processor Development
uucp:{ucbvax!sun decvax allegra}!decwrl!flairvax!kissellakhtar@uiuccsb.UUCP (12/12/83)
#R:vax1:-42200:uiuccsb:5700018:000:733 uiuccsb!akhtar Dec 11 16:04:00 1983 Hmmm... I haven't seen any measurements on various instruments, however, I would imagine that some instruments do indeed produce harmonics that are above 15kHz and probably even above 20khz. The instruments that come to mind are harpsichords, triangles, cymbals, and maybe some of the smaller woodwinds e.g. sopranino recorder, flute etc. Would anyone care to verify or deny that? ..pur_ee!uiucdcs!akhtar I do not think it fair to compare a violin with a stereo system. The performance, or lack thereof, of a stereo, surely cannot be taken to imply that instruments are incapable of producing tones above 15KHz. In a slightly facetious line..... Since we cannot build a star, for instance, does this mean the sun is an illusion?
peters@cubsvax.UUCP (12/12/83)
Comment about 300-yr old violins is wrong. Bats can produce sounds above 20kHz & they're a lot more than 300 yrs old. You can make lots of sounds at higher frequencies than 20kHz by robbing various things together; eg, wet finger on crystal. That has nothing to do with whether you can hear the sounds or whether sound systems can produce them. I'm sure even new violins produce such sounds. They may not be relevant to the music they make, which is the real issue.
granvold@tymix.UUCP (Tom Granvold) (12/12/83)
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'It is relativly easy to produce hypersonic frequencies'
How? Do hypersonic frequencies commonally occure is live performances?
Tom Granvold
Tymshare
Cupertino, California
decvax!ucbvax!oliveb!tymix!granvoldlmg@houxb.UUCP (12/13/83)
# Please folks, the term is ULTRAsonic, not HYPERsonic. Hypersonic == much faster than the speed of sound. That isn't what you mean at all. Larry Geary AT&T Information Systems Holmdel, NJ ...houxb!lmg
shep@avsdS.UUCP (12/16/83)
A crash cymbal and a snare drum hit are good examples of instruments that produce substantial partials above 20KHz; but 200KHz ??? -ss
jj@rabbit.UUCP (12/19/83)
OK. I think I helped start this sillyness, so.... THERE ARE MANY, MANY THINGS THAT GENERATE SIGNALS WITH FREQUENCY CONTENT WELL ABOVE 20kHz. IN FACT, THE 200 kHz 'LIMIT' IS EVEN EASILY EXCEEDED..... *****AT THE GENERATING SOURCE******. Please, please, PLEASE consider the effects of propigation through air. It's NOT getting to you in your concert hall, even in the front row. (Go look at the dispersive characteristics of air, humid air, etc. Please.) -- -Diogenes stopped here- (allegra,harpo,ulysses)!rabbit!jj