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Old 13th July 2007, 09:46 AM   #21
OzMikeH is offline OzMikeH  Australia
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to continue the vision analogy. a high power camera flash can produce pulses of light, some as narrow as 1/10,000th of a second. we see the flash very easily. We all know we no longer see flickering at 20Hz.

So why believe it's impossible for a person to detect certain acoustic effects that are clearly outside our normal timescales of detection?
You can't hear a 30kHz tone but you may still be able to detect an effect that is of similar duration such as a phase offset. You may not even be conscious of the effect.
Slam a door or trigger a strobe, which is more likely to startle a person?

the thing with the crossover is they roll off. you have multiple drivers producing the same frequencies, even multiple parts of the same driver when you add a whizzer cone. you have sound coming from 2 places at once with a slight distance difference and therefor phase offset. it's been made blurry. I can see how it's possible even if I know the timescales are microscopic.

Phase accurate: why do we accept such terrible speakers? No idea but 2 dimensional TVs are still being sold.
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Old 13th July 2007, 11:05 AM   #22
Pano is offline Pano  United States
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Quote:
Originally posted by OzMikeH
a high power camera flash can produce pulses of light, some as narrow as 1/10,000th of a second. we see the flash very easily. We all know we no longer see flickering at 20Hz.
A 1/1,000,000 has been done for years, I think Edgerton did it. You can see it. And at 20Hz you can see a flicker, for sure. If you are close to the light source, you need to be above ~70Hz.

Anyhow, you can sure see a flash that is much, much more brief than what the eye sees as continuous . I agree with you Mike. That's due to "persistence of vision." The chemicals in the retina decay slowly. But - do we have "persistence of hearing?" It's a good question.

The reason you can see an ultra brief flash of light has to do with the slow chemistry of the eye. Can/could the ear work in a similar manner?
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Old 13th July 2007, 11:26 AM   #23
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Quote:
Originally posted by OzMikeH

So why believe it's impossible for a person to detect certain acoustic effects that are clearly outside our normal timescales of detection?
You can't hear a 30kHz tone but you may still be able to detect an effect that is of similar duration such as a phase offset.
Well maybe we're just not asking the right questions?

For example, what might usually be involved in a stereo localization test? Multiple speakers arranged in an orb-shape surrounding a person? (Such as the picture in: http://www.aip.org/pt/nov99/locsound.html ) What about the sounds produced? Natural wildlife sounds?

If a test uses broad-spectrum pulses then the ears get a large amount of information all in one tiny fraction of a second. All of the necessary diffraction and shadowing information is given straight away.

I've heard of tests suggesting the existence of "virtual lobing", where one ear hears one frequency while the other ear is fed a slightly different frequency. A beat frequency is sensed despite the lack of physical interference between the sounds.

If a test uses long-lasting sinusoidal waves, similarly, the brain can statistically work out the coordinates of the sound source because the 'pulses' may repeat over a 1000 times in one second.

Perhaps it would be a good idea to test that "post processing" system by limiting both the time and frequency information that the brain receives and finding the point at which it starts to break down? For example, try to localize short "blips", low frequencies, or focus on peculiar combinations that form phase differences between our ears such as 360 degrees?

Rather than scientific flattery, why not ask how bad our hearing might be in some situations? See at what point human processing starts to make mistakes? After all, common sense suggests that if we want to fool the human ear we should start with the most obvious weak points.
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Old 13th July 2007, 12:36 PM   #24
Pano is offline Pano  United States
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Quote:
Originally posted by CeramicMan
Multiple speakers arranged in an orb-shape surrounding a person? (Such as the picture in: http://www.aip.org/pt/nov99/locsound.html )
Wow! Great link! Thanks. Reminds me of a "sonic tree" at Radio France that had over 200 individually addressable speakers. Crazy sound.

There seems to be a lot of good info in the link - I want to stay up and read it over a few times, but it's time for bed. ZZZzzzzzz
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Old 20th July 2007, 01:06 PM   #25
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Just a sidenote: I will most probably attaend an AES meeting in August with guest speaker John W. who will be demonstrating some of his constructions.

Regards

Charles
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Old 20th July 2007, 10:33 PM   #26
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Quote:
Originally posted by OzMikeH
to continue the vision analogy. a high power camera flash can produce pulses of light, some as narrow as 1/10,000th of a second. we see the flash very easily. We all know we no longer see flickering at 20Hz.

So why believe it's impossible for a person to detect certain acoustic effects that are clearly outside our normal timescales of detection?
You can't hear a 30kHz tone but you may still be able to detect an effect that is of similar duration such as a phase offset. You may not even be conscious of the effect.
Slam a door or trigger a strobe, which is more likely to startle a person?

the thing with the crossover is they roll off. you have multiple drivers producing the same frequencies, even multiple parts of the same driver when you add a whizzer cone. you have sound coming from 2 places at once with a slight distance difference and therefor phase offset. it's been made blurry. I can see how it's possible even if I know the timescales are microscopic.

Phase accurate: why do we accept such terrible speakers? No idea but 2 dimensional TVs are still being sold.

Iím pretty sure part of why we can see a flash of 1/10,000th of a second is not just because of persistence-of-vision, but also has to do with the amplitude of the light pulse. View the same 1/10,000 pulse with an LED limited to 100 mcd and see if itís detectable. Plus, and I really donít know much about camera flashes, but is there a thermal time-constant, and therefore decaying light output, to the cooling of the xenon bulb, or it the light output really -3dB at 1/10,000th of a second?

With the flash analogy, it would be like listening to a 30KHz tone at 170dB. Iíll bet you could hear it, or at least perceive it, albeit with some gnarly side-effects.
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Old 21st July 2008, 09:00 PM   #27
graaf is offline graaf  Poland
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Quote:
Originally posted by phase_accurate
Just a sidenote: I will most probably attaend an AES meeting in August with guest speaker John W. who will be demonstrating some of his constructions.

Regards

Charles
hello again!

what about this demostration? How was it?
Have You attended the meeting?
Has anybody?

best regards,
graaf
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Old 21st July 2008, 10:20 PM   #28
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Re. 'Putting the Science Back into Speakers', very interesting comment by the author regarding that ceramic magnet speakers cannot reach the 16 bit resolution of a CD.

This is not to say that a ceramic magnet speaker cannot resolve the full dynamic range of many recordings on CD which use significantly less than the full 16 bit resolution on average.

I post this just to be fair to ceramic magnet speakers, not because I like their sound very much. In fact, I just replaced the ceramic magnet woofers in a pair of my home built speakers with an alnico version of the same driver (the HF driver already was alnico) with a resultant dramatic improvement of the inner detail and soundstaging of good recordings.
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Old 22nd July 2008, 02:44 AM   #29
gedlee is offline gedlee  United States
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An interesting read. Not quite as "scientific" as I would like to see, but in general I can agree with his conclusions, even if I don't agree with all the data that he used to get there. His points about loudspeaker diffraction being a masker for artifacts is one that I have been saying for many many years now and a key reason why my loudspeakers are received so well. The room is also a diffraction source, which he fails to mention. I too could not hear MP3 and WMA artifacts until I built the Summas and then I found that I was bothered by these codecs. I only use lossless encoding now.

Everyone should read this paper, but don't assume that everything said is absolutely correct - at least the methodology for doing the subjective tests is not sufficient to draw conclusive results.

His psychoacoustics is a bit coarse and not exactly clear, but generally factual.

His points about magnets are a bit weak, and they ignore the fact that any good driver should have a shorting ring which dramatically reduces flux modulation. All of the drivers that I use have shorting rings - and ceramic magnets.

Graaf, thanks for the link.
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Old 22nd July 2008, 05:07 PM   #30
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what about this demostration? How was it? Have You attended the meeting? Has anybody?
The demo was fun and I could indeed get some insight into his constructions. Technically speaking most of the info could already be found within his papers - but it was funny to hear him life since he is very humorous and he makes funny comparisons like:

"The grill on a modern Rolls Royce doesn't have any function at all whereas in earlier days it had the function of the radiator but it is still there because people immediately recognise it as a Rolls. Speakers are most always rectangular and people easily recognise them as speakers - so we made a speaker that LOOKS rectangular but that actually isn't - just because people can recognise them as speakers"

It was his Legend Line of speakers that he was talking about in this case. They are actually built from cylindrical elements and they are omnidirectional by the use of deflectors. In their corners they have four poles over which a sock is pulled and that gives them the look of a fairly ordinary rectangular box.
He was taking two models of these with him but mostly used the smaller model for demoing. Although this has respectable performance for its size I assume that it would have been more fun if more demos had been done with the larger legend.

One thing that I missed was the Cabar studio monitor. But maybe there will be an opportunity to hear this one also one day.

There is another funny one that just jumped up: When he had finished his speech he was given a small cardboard box by the Swiss AES section vice president. He then asked if this was something that one isn't supposed to take on a plane in one's hand luggage. The vice president said yes. John W. then answered: "Well - that doesn't matter ! I don't fly anymore anyway - since I am always considered a terrorist by the security staff !"

Edit: forgot the link:

http://www.swissaes.org/nl/aes_newsletter_110.pdf

Regards

Charles
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