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Old 17th January 2010, 05:34 PM   #1
tresch is offline tresch  United States
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Default Upper Limits of Human Hearing

I have a curiosity that I'd like to enter in on this discussion, because the whole "20khz vs 30khz" issue intrigues me.

The logical side of me tells me that making a tweeter go to 30khz is pointless, as we can't hear that high, and in general, harmonic distortion applied to frequencies at the high end of the spectrum shoes up as even higher frequency harmonics, which are outside of hearing. Thus, the ability to reproduce a complicated wave at 17khz is irrelevant as all we're going to hear is a sin wave anyway.

The reasonable side of my brain knows that audio is complicated and I certainly can't predict the whole situation. I imagine the biggest advantage would be that having a tweeter that extends to 30khz might make for much more accurate transients in the higher frequencies which could make for some very subtle, but audible differences in sound quality. Perhaps, also, the same characteristics that allow a tweeter to play flat to 30khz are also beneficial when it comes to preventing harmonic distortions and other negative effects.

So, what I want to know is this: Have you tested multiple tweeters that are as close to identical as possible while offering different high frequency extension? As in, do you have a 20khz tweeter and a 30khz tweeter and have listened to them both? This could be fairly irrelevent, as getting the tweeter to go to 30 might necessitate such a broad redesign that the two are no longer comperable, but I figure if there was a way to test, being a designer/builder, you'd be able to put together a closer comparison than anyone else
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Old 17th January 2010, 06:42 PM   #2
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Quote:
Originally Posted by tresch View Post
So, what I want to know is this: Have you tested multiple tweeters that are as close to identical as possible while offering different high frequency extension? As in, do you have a 20khz tweeter and a 30khz tweeter and have listened to them both? This could be fairly irrelevent, as getting the tweeter to go to 30 might necessitate such a broad redesign that the two are no longer comperable, but I figure if there was a way to test, being a designer/builder, you'd be able to put together a closer comparison than anyone else
Hi Tresch,
Very interesting points. Extending frequency range beyond the upper limits of human hearing has been a "hot" topic over the years and will no doubt continue. Take a look at some of the ribbon tweets that claim +40-kHz outputs!

Does extended range make any difference? Well, from my work on designing and making cones, the answer is yes to point. Extending the range of my cones has improved their resonance properties. Check out the various comments on the Alpair 7 and Alpair 12 and you'll pick up on the outcome of my work in this area. On the question of Tweet comparison, I end up making anything up to 12 pre-production variants (more sometimes) and test them before committing to production. I do compare them to other brands but I hope you'll appreciate my stand regarding not commenting on the performance of particular competitor products. More important, I'm involving more forum members into the testing process. This thread is part of this process.

However, I believe there is a limit beyond which it's more about "commercial hype" rather than genuine beneficial performance gain. Frankly speaking, taking any Full Range or tweets much beyond 30-kHz (ish) isn't likely to be beneficial. There's only so much data that can be extracted from an emitting surface. As yet, I've seen no authoritative and reliable tests demonstrating that humans can perceive sound above 20-kHz. I've read various "mush" claiming that humans can detect +20-kHz, but its mere conjecture, nothing reliably demonstrated and proven to acceptable scientific standards. Therefore in my case, I would say that extending the overall range of my cones has improved their output in the "hearing" human range.

Commercially, arrrrh, a different matter. Similar to the "pixel" growth race in digital cameras, audio makers try to out-do each other. A major focus in recent years has been increased range. For many buyers, especially those who aren't so concerned with the technicalities, they feel more comfortable buying into the extra performance. It's similar to car buying. How many of us own a car that can easily exceed the highest speed limits (allot). I haven't owned a car here in Hong Kong for nearly 10 years because its a small place with excellent public transport. But there are more high powered BMW's and Mercs here per Km of Hong Kong roadway that anywhere else. These cars rarely change up beyond second gear such is the traffic congestion! Consumption at almost any price is ingrained in much of human nature, sadly at the cost of our children's future. Sorry to be sounding negative but its the main reason I'm a believer in Full Range; Because it's about doing more with less. Equally pressing is I've got to pay the rent and Full Range is a very small market. So I'm trying to make an economical woof and tweet with the knowledge I've gained from Full Range.

Hope this helps.

Mark.

Last edited by markaudio; 17th January 2010 at 07:31 PM. Reason: typo mending
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Old 17th January 2010, 09:22 PM   #3
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Quote:
Originally Posted by markaudio View Post
Very interesting points. Extending frequency range beyond the upper limits of human hearing has been a "hot" topic over the years and will no doubt continue. Take a look at some of the ribbon tweets that claim +40-kHz outputs!

Does extended range make any difference?
Kunchur has shown that humans can detect timing differences of <5 uS, which if you flip it over to FR is >40 KHz.

The ear does have seperate mechanism for time detection vrs FR detection, so one may have FR limited to <15k yet able to hear timing anomolies equivalent to >40 KHz bandwidth.

dave
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Old 17th January 2010, 11:39 PM   #4
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Kunchur has shown that humans can detect timing differences of <5 uS, which if you flip it over to FR is >40 KHz. The ear does have seperate mechanism for time detection vrs FR detection, so one may have FR limited to <15k yet able to hear timing anomolies equivalent to >40 KHz bandwidth.

dave
Hi Dave,
Please quote Kunchur's trial publication data, trail methodology, sample size and a list of other institutions that have verified his work in a science publication. If he's got it done to the point of acceptability, it will be in a science journal. What will matter is if his work agrees and verifies your "flip" statement.

Ear has a separate mechanism? Please quote the scientific sources that have trial outcomes that clearly demonstrate this mechanism allows humans to perceive frequencies to 40-kHz. Please include their published trials dates and the name of publication.

I could be convinced if there's a published large scale robust body of research from a recognised scientific institution that has:

1 - control and sample groups greater than 2000 subjects.
2 - verifiable test and data analysis methodologies.
3 - other institutions have repeated the research in order to authenticate the original.
4 - been published in recognised science journals.

I'd quite like to have my scepticism lifted. It would help to put me towards the front the extended frequency FR driver race.

I'm wondering if it may be useful to start a new thread on this issue? I expect its been done in other threads but it could be re-visited? I'm happy to do it my Markaudio section.

Mark

Last edited by markaudio; 18th January 2010 at 01:04 AM. Reason: additional thinking - typo mending
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Old 18th January 2010, 09:14 PM   #5
gfiandy is offline gfiandy  United Kingdom
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Hi, For anyone interested here;

Information for prospective students

http://www.physics.sc.edu/kunchur/papers/FAQs.pdf

Are his papers.

This site has a good discussion on some of the probelms with his work.

Interesting Papers re temporal resolution - Hydrogenaudio Forums

I am open minded but yet to be convinced.

Regards,
Andrew
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Old 18th January 2010, 09:29 PM   #6
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Originally Posted by markaudio View Post
Hi Dave,
Please quote Kunchur's trial publication data, trail methodology, sample size and a list of other institutions that have verified his work in a science publication. If he's got it done to the point of acceptability, it will be in a science journal. What will matter is if his work agrees and verifies your "flip" statement.
Andrew beat me to the link. 3 articles published in 3 different referreed (sp?) Journals, plus another researcher producing the same results. Pretty solid work to my mind.

The forum link was interesting. The same kind of threads you see on cables & tubes vrs transistors... strongly held beliefs being challenged can bring lots of discussion.

dave
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Old 18th January 2010, 09:39 PM   #7
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Hi Andrew,
By the way, many thanks for your contribution on baffle influence. Sorry I've not had time to investigate. I hope to in the anechoic chamber later next week.

Many thanks for posting the links to Kunchur. I'll take look over the next few days. Let's see if this research:

1 -has sufficient human control and test samples
2 -has an evidential relationship demonstrating human ability to perceive sounds > 20-kHz.
3- its trial work has been repeated and verified.

I think this is worth making a new thread and migrating these latest posts to it.

Thanks

Mark.

Last edited by markaudio; 18th January 2010 at 09:51 PM. Reason: typo mending
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Old 18th January 2010, 09:57 PM   #8
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Hi Guys,
I've made this new thread since this is a subject of sufficient merit. There's been other threads on this subject in past but it may be useful to continue the discussion here in the light of my work in extending the HF performance of full range drivers.

I've moved recent posts on this subject from:
Mark's proto 6.5" Woofer, 1" silk Tweet combo

Thanks

Mark.

Last edited by markaudio; 18th January 2010 at 10:20 PM. Reason: additional info.
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Old 18th January 2010, 10:37 PM   #9
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Hi Andrew,
I hope to in the anechoic chamber later next week.

Mark.
Walking around in those things listening to my heart beat in my ears always made me feel a little queasy
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Old 18th January 2010, 10:54 PM   #10
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Agreed C2. It took me some time to become familiar and comfortable. It was very spooky the first time I walked into an anechoic chamber
Cheers
Mark.
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