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In Reply to: 20khz to 50khz upgrade? posted by twhaase on July 27, 2002 at 08:45:03:
The ear is indeed sensitive to the effects of sounds well above its normal hearing range, even if it can't hear those signals directly.For example, trumpets produce very rich and loud harmonic overtone structures up to and above 50 kHz. Let's look at two hypothetical overtones, at 32 kHz and 34 kHz. These two overtones actually produce four distinct sounds - a 32 kHz signal, a 34 kHz signal, a 66 kHz "sum" signal, and a 2 kHz "difference" signal. The latter two are considerably down in volume as compared to the original signals, but they are indeed present. The difference signal is called a "beat".
Beat signals are present in all harmonic structures, and add richness to the timbre. So in our exmaple above, even though we cannot possibly hear the 32 kHz or 34 kHz harmonics, the 2 kHz beat they produce (albeit at lower volume) does contribute to the harmonic structure that is within our range of hearing.
One subjective effect of very extended high frequency response is greater harmonic richness and airiness because of the beat signals generated within the audible range.
Okay, all that being said, very few tweeters will take you up to 50 kHz. It's not just a matter of changing tweeters - it's more a matter of adding a supertweeter. Changing tweeters is not a simple matter, because the crossover would have to be re-designed, and a tweeter that goes up to 50 K is probably not going to go down as low as a tweeter that only has to go up to 20 K. Adding a dedicated supertweet would be much simpler.
I believe Tannoy makes a high quality add-on supertweeter, and Radio Shack used to market some inexpensive piezo units, but I never liked them much.
Getting back to your overall upgrade strategy, I'd say go with an SACD player before you start adding 50 kHz response to your speaker system. SACD is a clear audible improvement even on lowly 20 kHz speakers.
Follow Ups:
As a horn player a trumpet hitting 34Khz, I don't know about that. There must be some harmonic ossicllations within the brass of the instument or a recording artifact causing that. If not that dude has a magic set of chops.
Charles
A number of other instruments have harmonic spectrums that extend well into ultrasonics.Quoting from "There's Life Above 20 Kilohertz! A Survey of Musical Instrument Spectra to 102.4 KHz" by James Boyk of the California Institute of Technology:
"Harmonics of French horn can extend to above 90 kHz; trumpet, to above 80; violin and oboe, to above 40; and a cymbal crash shows no sign of running out of energy at 100 kHz."
Below is a link to Mr. Boyk's paper, which you might find interesting.
I don't think it's any news that the sound of some instruments have ultrasonic components although the detailed measurements are interesting. But, since no one can hear that high, what difference does it make?Kaoru and Shogo measured what appears to be intermodulation distortion in the loudspeaker between ultrasonic frequencies and frequencies in the audible range. They eliminated this by having the ultrasonic frequencies reproduced by separate speakers, at which point the audible effects disappeared. So, we have a ready explanation for the audible effects of ultra high frequency content: deficiencies in the reproducing equipment, not the recording.
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"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
How about trying a comparison between a 20k-stone-walled recording with a 'no-holds-barred' one? (same performance of course).I haven't tried it before but it would be interesting to note on the magnitude of the sonic difference with and without the ultrasonic (convienently defined as > 20k) content, and how much it matters to the music that we are listening to. of course, terms like 'sonic difference' and 'how much it matters to the music' need to be very carefully/comprehensively defined.
Again my earlier comment: Some claim to be able to hear thru their teeth.. perhaps they can but the levels are REALLY low, perhaps even indistinguishable. Nice try.
I'm confused, Bare."BFD"?
"Nice try"??
And while we're on the subject, I never said anything about hearing through one's teeth.
Perhaps you don't buy my explanation of the phenomenon of "beats", so below I've posted a link to a site endorsed by the National Science Teachers Associaton.
By the way, a few years back Bob Carver was working on a device that involved a rather unique application of beats to "beam" a tightly-focused column of sound, using a 200,000 Hz carrier signal. He was able to re-create sound well within the audible spectrum entirely from ultrasonics. I searched the web but failed to come up with any specific reference to Carver's involvement. All I could find was a rather simplistic news article describing this technology, here:
http://www.abcnews.go.com/sections/scitech/CuttingEdge/cuttingedge010831.html
Basically, what I'm saying is: a) the "beat" phenomeon is real; b) ultrasonic overtones are real; and c) that ultrasonic overtones can generate beat signals within the audible range.
On the subjective front, a comparison of analog or SACD to redbook CD's demonstrates that the ear is indeed sensitive to things happening (or not happening) at frequencies theoretically above the range of human hearing.
Cheers,
Duke
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