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Old 20th January 2010, 12:51 AM   #11
tresch is offline tresch  United States
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Okay, so, I'm reading through this article:

http://www.physics.sc.edu/kunchur/pa...---Kunchur.pdf

and I'm already having doubts. Granted, I haven't read the entire thing, and I will, because it's quite interesting regardless of how it applies to the topic at hand, but there seems to be a very large difference between what we are discussing and what he's trying to prove, than what he is actually testing.

What we are discussing is whether there are positive benefits to having a loudspeaker that has a larger bandwidth in the frequency spectrum than the limits of human hearing (specifically on the high frequency end of the spectrum)

Kunchur is attempting to prove that having a larger bandwidth IS helpful. His process is to test a human's ability to detect PHASE distortion by adjusting the relative distances between TWO loudspeakers playing the same signal.

This seems like judging apples by observing oranges, to me. If one is determining the audible affect of a SINGLE DRIVER's bandwidth in relation to human interpretation, one must do all testing using only a SINGLE DRIVER. The physics of a single transducer following a waveform are very different from the physics of two separate waveforms from separate sources combining at different times and producing a distorted signal due to the additive/subtractive nature of phase.

i.e. If you adjust the position of one speaker, the human detects an audible change not due to "time smearing," that occurs in a system above the audible frequency range, but because the audible frequencies are severely distorted through addition/subtraction in a way that has no comparison to the affects of a single driver system following a single waveform, at least as it applies to the ability of the human ear to detect it.

It is an interesting test that says a lot about driver placement and the like, but I fail to see how such a test would have any bearing on the discussion at hand.

Someone please chime in and let me know if I'm crazy or not.
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Old 20th January 2010, 12:59 AM   #12
tresch is offline tresch  United States
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To paraphrase myself, for potential clarity:

This test determines nothing about the applicability of a driver that performs above the human hearing range, it only determines the extent of the human's ability to detect phase addition/cancellation within the audible frequency range.
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Old 20th January 2010, 01:08 AM   #13
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What his papers do, using 2 different techniques, is that the human ear + brain can detect time differences of less than 5 uS.

How you interpret how that affects hifi reproduction is still open to interpretation & further study.

It does give solid experimental evidence that suggests that limits set based on the ear + brains FR detection capability need re-examing and gives credence to people reporting that, say, adding a supertweeter, can be detected/heard despite reproducing above the persons HFreq limit.

It does give solid experimental evidence that suggests that not only FR but time response is important to consider.

dave
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Old 20th January 2010, 02:24 AM   #14
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Hi Guys
Alas, I'm heavily committed for the next week or so but it's nice to have a quick read of the new posts.

I well remember having a conversation some years back with Susan Parker. She's an expert amp maker based in the UK. Susan suggested that the issue may be more to do with audio component's ability to deliver audio data. i.e, the greater the F range of the equipment, the better the quality of music reproduction within the human hearing range.

Sadly I've go to dash but just thought it may be interesting to ask if anyone has references to any research done with this aspect in mind.

Cheers
Mark.
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Old 20th January 2010, 02:49 AM   #15
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Quote:
Originally Posted by planet10 View Post
It does give solid experimental evidence that suggests that limits set based on the ear + brains FR detection capability need re-examing and gives credence to people reporting that, say, adding a supertweeter, can be detected/heard despite reproducing above the persons HFreq limit.
I really don't understand your statement. There have been hundreds of thousands (and more?) of audiometry tests showing that humans can't hear above 20kHz.

You can easily test this: go to any competent audiologist and ask them to play tones (sine, square, triangle or whatever) through their calibrated headphones, starting at say 21kHz. There is absolutely no doubt - you will not be able to hear them.

How can adding a transducer that reproduces tones above 20kHz be of any audible benefit to a loudspeaker system?
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Old 20th January 2010, 03:36 AM   #16
tresch is offline tresch  United States
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Originally Posted by markaudio View Post
Susan suggested that the issue may be more to do with audio component's ability to deliver audio data. i.e, the greater the F range of the equipment, the better the quality of music reproduction within the human hearing range.
It makes sense to me that this is where the biggest changes would come into play. Something along the lines of "the characteristics that help a tweeter play to 30khz are also helpful in other parts of audio reproduction"

But then, I dunno. Does making a woofer play to 5,000 help it more accurately produce a 1,000hz tone? In that case that seems like an obvious fallacy, or at least a huge oversimplification.
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Old 20th January 2010, 03:39 AM   #17
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@boconnor : Because, according to that research, it's concievable that we can percieve two impulses which occur less than 5 microseconds apart, even if we can't actually "hear" them as a tone. To reproduce such impulses would require a transducer capable of 40khz+ in frequency terms, but I don't think anyone is suggesting that we'd actually be percieving melodic or harmonic tones, just some sort of additional timing data.
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Old 20th January 2010, 03:50 AM   #18
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From Kunchurs paper there are 2 different mechanisms for detecting signal (he describes the nature of each in the paper). The 1st (and familiar) is what we measure as you described... FR. I'm good to 12-14k max. The 2nd measures time differences (and ages more slowly than the FR mechanism), and is the one that allows us to discriminate <5uS.

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Old 20th January 2010, 03:58 AM   #19
jcx is offline jcx  United States
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Quote:
Originally Posted by planet10 View Post
What his papers do, using 2 different techniques, is that the human ear + brain can detect time differences of less than 5 uS.

How you interpret how that affects hifi reproduction is still open to interpretation & further study.

It does give solid experimental evidence that suggests that limits set based on the ear + brains FR detection capability need re-examing and gives credence to people reporting that, say, adding a supertweeter, can be detected/heard despite reproducing above the persons HFreq limit.

It does give solid experimental evidence that suggests that not only FR but time response is important to consider.

dave
people not understanding correlation keep confusing group delay resolution with bandwidth - they are not the same or even simply related


S/N dynamic range and observation/integration time are also required to estimate group delay resolution in addition to bandwidth - greater S/N and observation time can extend group delay resolution to far below 1/bandwidth


so the uS intra-aural delay results do not require any extended frequency response beyond the accepted 20-24 KHz limits to explain
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Old 20th January 2010, 04:00 AM   #20
tresch is offline tresch  United States
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Originally Posted by TheSeekerr View Post
@boconnor : Because, according to that research, it's concievable that we can percieve two impulses which occur less than 5 microseconds apart, even if we can't actually "hear" them as a tone. To reproduce such impulses would require a transducer capable of 40khz+ in frequency terms, but I don't think anyone is suggesting that we'd actually be percieving melodic or harmonic tones, just some sort of additional timing data.
Except when we're dealing with a single transducer, two impulses 5microsecds apart simply turn into a single wave of sound which contains sonic and supersonic information just like any other sound wave.

Given a single transducer, such timing issues seem irrelevant, because all sound produced by that transducer is relative to everything else the transducer is doing. A single transducer doesn't produce multiple waveforms that are offset at different timings, it just produces a single waveform which contains audio data, some of which may be above the range of human hearing.

The timing with which the driver creates the wave has nothing to do with it's ability to play high frequency waves. A driver is an analog device and will play an audio signal with whatever timing that it was fed to the driver, offset by a certain amount due to the driver's particular phase delays.

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.

I should note I'm not trying to be inflammatory, I'm just trying to piece together the correlation between timing and frequency response in my head, and it's not happening, so I'm stating my thought process in hopes of either being clarified or to see if I'm thinking correctly.
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