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Old 20th January 2010, 04:02 AM   #21
tresch is offline tresch  United States
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Originally Posted by jcx View Post
so the uS intra-aural delay results do not require any extended frequency response beyond the accepted 20-24 KHz limits to explain
yeah. what he said.
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Old 20th January 2010, 04:07 AM   #22
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My hearing goes to 16kHz on sine waves, still i can apreciate a tweeter that goes to 30kHz -3dB. I my measurements i found that "fast" tweeters perform better in the time domain. For example the "waterfall" looks cleaner even in band. Resonance higher up seem to "fold down" into the audible range. I also now about research done in Japan with older people that got exposed to high resolution audio with high sampling rate. When the response in the treble was truncated they heard a difference and the brain wave detector sampled a difference. One explanation is that higher frequency signals modulate down into the audible range, for example a 22kHz and 23kHz signal played simultanuisly over a nonlinear transduces like a loadspeaker makes an audible 1kHz intermodulation product 23kHz - 22KHz = 1kHz
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Old 20th January 2010, 08:01 AM   #23
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Originally Posted by tresch View Post
Another way to look at it is, say you have a subwoofer that only plays to 150hz, and you have it wired up through a digital sound processor. If you wanted to delay the output of the subwoofer by 5 microseconds in order to get it to match phase better with your woofers, would the subwoofer have to be capable of a 40khz signal in order to delay an extra 5ms? Absolutely not.
Yes, but if you wanted to produce two impulses of a given amplitude 5ms apart, you could consider that to be equivalent to a section of a square wave tone of 100hz. So you'd need a transducer capable of 100hz to give even a crude reproduction of such a pair of impulses, and a transducer capable of several times that to reproduce it as an accurate square wave.

Now, assuming it's true that we can percieve impulses at a 5us resolution, you need a transducer capable of frequences >> 100 KHz to produce such impulses.

Hopefully my square wave analogy illustrates why you don't need to think of it as a tone.
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Old 20th January 2010, 09:47 AM   #24
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Originally Posted by TheSeekerr View Post
Now, assuming it's true that we can percieve impulses at a 5us resolution, you need a transducer capable of frequences >> 100 KHz to produce such impulses.
OK, just trying to get my head around this.

Lets say you have a woofer that is reproducing a 30Hz tone. The tone ends, the signal goes to zero. Then 5 micro-seconds later a 40Hz tone is fed into the transducer. Is the theory that the woofer must be able to reproduce frequencies > 100kHz to be able to reproduce the transition from 30Hz to 40Hz correctly?

Can't say I get it. The signal going to zero means the transducer has nothing to do. So why does it have to be able to reproduce 100kHz to then handle the second (40Hz) signal? Maybe I'm missing something - happy for someone to steer me onto the right way of thinking about this.
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Old 20th January 2010, 10:19 AM   #25
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Because it needs to be capable of physically moving a certain distance (corresponding to the amplitude) in a particular time, ie. the rise time of the signal. In short, it needs to be fast, and that in turn corresponds with the ability to reproduce high frequencies.

(this is probably why subwoofers with extended high frequency response are thought to sound "faster" - they're better able to reproduce signals which aren't particularly sine-wavey. In the extreme case, a square wave can be seen to be made up of a fundamental frequency and the summation of an infinite series of harmonics)
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Old 20th January 2010, 11:43 AM   #26
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Originally Posted by TheSeekerr View Post
Because it needs to be capable of physically moving a certain distance (corresponding to the amplitude) in a particular time, ie. the rise time of the signal. In short, it needs to be fast, and that in turn corresponds with the ability to reproduce high frequencies.
Ok, so in this example the transducer needs to stop moving when the 30Hz signal goes to zero. Then start moving again on receipt of the leading edge of the 40Hz tone. And do both within 5 microseconds.

So what you are saying is (I think) that the ability to stop and start within such a time entails that the transducer could reproduce a 100kHz tone, if given one. Therefore, conversely, that if it can't reproduce such a 100kHz tone then it wouldn't be able to correctly reproduce signals with small time gaps.

I suppose its a bit of a moot point anyway, given that the analogue signals fed to speakers are continuous in time. And of course woofers by design aren't great at reproducing 100kHz signals.
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Old 20th January 2010, 12:06 PM   #27
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That's basically my argument, yeah. That said, I'm far from convinced that any such "time detection" mechanism:

a) Exists
b) Makes any difference to our perception of music

I do believe, as Mark does, that having tweeters extend into the 30khz range will, as a direct result of the improvements necessary to do so, result in greater fidelity in the audio range. This is for reasons similar to my "fast" subwoofer hypothesis above.
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Old 20th January 2010, 06:02 PM   #28
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Wince. Controvertial subject if ever there was one (shades of speaker / interconnect wires etc). Not being the brightest, my own observations have to be fairly clunky, & far from original, but FWIW:

1/ I'm in complete agreement with the idea that the work necessary to increase the HF bandwidth of a driver (higher quality materials, tighter manufacturing tolerences &c.) might result in improvements lower down. It may also push non-linearities up, out of the main audio-band. But

2/ This isn't a given; it depends on the quality of the engineering. Sadly, some companies do it purely in bout of 'numbers oneupmanship.' Mark doesn't, but the same doesn't necessarily hold true elsewhere.

3/ Not everyone actually benefits from massive HF extension; you might get an improvement in non-linearities lower down, but if it comes at the price of, say, more HF energy than you personally like / enjoy, then it's not really done you any favours.

4/ Massive HF extension has to be context dependent. If we're talking wide-band drivers here, a large one is going to be beaming something chronic in the extreme HF. You might get some of the potential benefits lower down, but assuming for the sake of argument (without in any way conceeding the point either way), there is some benefit purely to having, say, extension an octave above our notional HF limit, it's surely going to be extremely limited in that respect.

5/ Most of the dominant storage formats are BW limited to quite a low frequency, and if it's not on the recording, it's not going to be reproduced by the speaker. QED.

6/ Kunchur's papers make very interesting reading & it looks to me to be a field worth further exploration. I'll certainly be keeping an eye on future developments, but at present, they still appear to be largely theoretical initial studies with very small sample groups. Seem to indicate some interesting trends, but I'll probably reserve judgement until they've had chance to do a larger scale study.
YMMV of course.
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Last edited by Scottmoose; 20th January 2010 at 06:31 PM.
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Old 20th January 2010, 09:24 PM   #29
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Originally Posted by Scottmoose View Post
6/ Kunchur's papers make very interesting reading & it looks to me to be a field worth further exploration. I'll certainly be keeping an eye on future developments, but at present, they still appear to be largely theoretical initial studies with very small sample groups. Seem to indicate some interesting trends, but I'll probably reserve judgement until they've had chance to do a larger scale study.
YMMV of course.
Hi Guys,
Excellent debate going on. I'm up early ploughing through emails and just caught this contribution from Scott. I gather that the number of human test subjects was very small, mentioning a total number of 22 humans, spilt into 5 groups of varying size.

This is an unrepresentative trail size. The variability risk is very high and therefore specific outcomes made by Kunchur should be considered "Unreliable". Sorry to disappoint but Kunchur's papers aren't "authoritative". Considerable care should be taken when using his work to support the argument for extended human hearing beyond 20-kHz.

At least his papers are making a contributing to the general debate. I think this maybe Kunchur's intention although it would be nice to see him specifically state this.

Cheers

Mark.

Last edited by markaudio; 20th January 2010 at 09:25 PM. Reason: typo mending
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Old 20th January 2010, 09:36 PM   #30
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Considerable care should be taken when using his work to support the argument for extended human hearing beyond 20-kHz.
Finally, somebody is making sense.
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