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Old 1st March 2012, 08:56 PM   #3001
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by bcarso View Post
Including our ears, as for example anyone playing some of the Telemann recorder duets can discover (it's been suspected that Georg Phillip selected pitches sometime to intentionally produce a difference-frequency bass line).
You might find that paper at least interesting if not exiting : http://igitur-archive.library.uu.nl/...%20Ru%20EN.pdf
EDIT: For a shortcut, start at pg. 25


There is a piece of software to recreate the experiments from the paper, available from the author's web page :
three compartment cochlear model

The SW is also very good to test audibility of phase distortion and absolute phase, just detune the harmonics for a continuous shift, or use the phase offsets. In my limited understanding the text doesn't offer a solution to those effects, but maybe I'm just missing something...

Last edited by KSTR; 1st March 2012 at 09:16 PM.
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Old 1st March 2012, 09:30 PM   #3002
bcarso is offline bcarso  United States
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Quote:
Originally Posted by KSTR View Post
You might find that paper at least interesting if not exiting : http://igitur-archive.library.uu.nl/...%20Ru%20EN.pdf
EDIT: For a shortcut, start at pg. 25


There is a piece of software to recreate the experiments from the paper, available from the author's web page :
three compartment cochlear model

The SW is also very good to test audibility of phase distortion and absolute phase, just detune the harmonics for a continuous shift, or use the phase offsets. In my limited understanding the text doesn't offer a solution to those effects, but maybe I'm just missing something...
Sehr interessant! Thanks for that. Did they ever get published in a journal, finally?
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Old 2nd March 2012, 03:32 AM   #3003
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Quote:
Originally Posted by jcx View Post
news to quite a number of people...
all it takes is to clearly measure is a cheap condenser mic and a classic bookself speaker with long throw 4-6" mid-woofer
Please do show me intermodulations between 50Hz and 2000Hz in a two-way speaker and compare them with what an amp can produce.
Or even closer frequencies if you want... to go on a single speaker.
Sure, there are plenty of THD (mostly lower orders), due mostly to the mechanic friction, but you probably you assume they are the same thing like IMD and... you miss completelly my point.

Last edited by SoNic_real_one; 2nd March 2012 at 03:34 AM.
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Old 2nd March 2012, 03:42 AM   #3004
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Hi,

Quote:
Originally Posted by SoNic_real_one View Post
Please do show me intermodulations between 50Hz and 2000Hz in a two-way speaker and compare them with what an amp can produce.
First, please review the poster from Klippel I have linked. It shows how to measure the intermodulation and how to predict it from the drivers behaviour.

Quote:
Originally Posted by SoNic_real_one View Post
Sure, there are plenty of THD, but you probably you assume they are the same thing and you miss completelly my point.
In a simple non-linear system IMD and HD are results of precisely the same non-linearity and have the same levels. So if we have at 1KHz -60dB H2 and -80dB H3 and present the DUT with equal amounts of 1KHz and 1.133KHz giving the same peak level as the HD measurements the 2nd order difference tone will be at 133Hz with -60dB and and the 3rd order one at 876Hz and 1266Hz with -80dB.

Come on, this really basic stuff and essentially geometric/mechanical in nature. It will hold true for any non-feedback system and to a certain degree also for ones with correctly inverse feedback.

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Old 2nd March 2012, 10:50 AM   #3005
DF96 is offline DF96  England
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Quote:
Originally Posted by ThorstenL
In a simple non-linear system IMD and HD are results of precisely the same non-linearity and have the same levels.
Yes! This simple fact seems to have escaped far too many people.

You can deliberately engineer a system with IMD and HD at different levels, and there are frequency-dependent mechanisms which can affect them differently, but as Thorsten says the straightforward situation is that they are generated in the same way.
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Old 2nd March 2012, 09:42 PM   #3006
tvrgeek is offline tvrgeek  United States
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Working through Self's second book, Small Signal. Just one view, but he is pretty hard core: It's the circuit, stupid. His statements on "if you can't measure it it, you can't heard it" still leave us with which measurements are the ones that matter.
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Old 2nd March 2012, 10:07 PM   #3007
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by FrankWW View Post
Sure but their 5ths and 7ths wind up some place i can't probably hear anyway. They sure can sometimes sound nasty, no doubt.

Gotta admit i was thinking of harmonics of low frequencies. If they come from upstream in the electronics, then you've got problems because of the energy component - more than 50% of energy in music is below 1000 Hz - because they show up in 700 Hz - 6kHz range. And we're really sensitive to sound from @2kHz to @ 5 -7 kHz.....

That's why I think you can hear surprisingly low amounts of distortion in an amplifier from a speaker that doesn't seem, by comparison to the amp, to have very good distortion figures.
On the surface, but what about IM? My working theory on my wife's uber hearing is high order distortions causing aggravation of tweeter issues above hearing, but causing IM that is down in the critical 4K range. There is SOMETHING going on.
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Old 2nd March 2012, 10:11 PM   #3008
DF96 is offline DF96  England
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Doug Self is worth reading, even for those who disagree with him. He will help you design circuits which do what you want, whatever that is. If the circuit is wrong, no point in worrying too much about components, grounding, unwanted coupling etc.
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Old 2nd March 2012, 10:14 PM   #3009
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Yeah, read Douglas Self and learn how to design one more opamp additionally to miriads of them already designed.

I have an idea: to design "Blameless Software" to design The Amp.

Choose desired parameters, click a button, and get BOM and all other documentation.
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Last edited by Wavebourn; 2nd March 2012 at 10:16 PM.
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Old 2nd March 2012, 10:17 PM   #3010
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by DF96 View Post
Doug Self is worth reading, even for those who disagree with him.
As a beginner in this hobby I like to refer to his writings from time to time. Often I find something I didn't notice the last time I looked.
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