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5th November 2012, 01:18 AM  #28901 
diyAudio Member

Sure, no Google then. Access to networks through doors guarded by guys with AK47.
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The Devil is not so terrible as his math model is! 
5th November 2012, 01:30 AM  #28902 
diyAudio Member


5th November 2012, 02:29 AM  #28903  
diyAudio Member

Quote:
And, what stops people who do know from using a combo of 8 and 9kHz ... unless, it might be too revealing ... Frank Last edited by fas42; 5th November 2012 at 02:38 AM. 

5th November 2012, 07:26 AM  #28904 
diyAudio Member
Join Date: Nov 2011
Location: Cooktown, Oz

I might have done this in 1980 but this is beyond my brain capacity this millenium. Yus gurus, please point to something that dun nid Higher Maths for Dummies. I'm sure there's loadsa stuff if you have done HM4D.

5th November 2012, 09:47 AM  #28905 
diyAudio Member
Join Date: May 2007

Harmonics and IMD both come from trigonometry. Take two sines (or cosines or one of each). Multiply them together. There are trigonometric identities which tell you how to write the result in terms of other sines and cosines involving the sum and difference of the angles. That is how harmonics and IMD are formed: multiplying sines together in nonlinearity.
Yes, when you slaved over triangles as a bored teenager in school you were learning the mathematical basis for low distortion amplifier design, but unfortunately the teacher never told you because he probably did not realise this himself. 
5th November 2012, 01:16 PM  #28906  
diyAudio Member
Join Date: Jan 2004
Location: away

Quote:
Quote:
jn 

5th November 2012, 02:04 PM  #28907 
diyAudio Member

If you are playing at moderatehigh levels in a large living room at listening distance, then up close to driver the spl is huge! As is distortion.
Measuring thd at 1W at 3 feet doesnt begin to tell you what you are really hearing/producing at the listening position under normal (for me) listening levels out in the room. I would imagine same for horn at throat entrance.... very high spl and distortion. Distortion is a Lot higher than typical measurement conditions/specs imply. [Just use an SPL meter.... set up listening level out in the room's listening position and then move the spl meter to the driver up close (inch) and measure.... you get really high spl, then. What is the driver doing at such high spl?] I measured once very high thd under same real world conditions. RNM Last edited by RNMarsh; 5th November 2012 at 02:18 PM. 
5th November 2012, 02:21 PM  #28908  
diyAudio Member

Quote:
This is signal processing 101, even Wiki summarizes it nicely. Even and odd functions  Wikipedia, the free encyclopedia
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Silence is so accurate. 

5th November 2012, 02:27 PM  #28909 
diyAudio Member

I was told a trumpet at full throtle was about 4W at the throat. A small silicon pressure guage could be placed at the throat of the waveguide/horn, an interesting experiment.
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Silence is so accurate. 
5th November 2012, 04:24 PM  #28910  
diyAudio Member

Quote:
Of course, besides breaking up the intragroup camaraderies (and rivalries?), perhaps a bit of this IM is part of the particular arranger's sound. 

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