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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Audio Measurement and Testing => Topic started by: Jeff Bailie on February 08, 2014, 10:19:00 AM

Title: Needs help with Horn Theory math
Post by: Jeff Bailie on February 08, 2014, 10:19:00 AM

I am trying to learn how to equate the low knee of a particular horns mouth.

I understand the relationship between frequency and wavelength.

I also understand that coupling horns together flattens the response down low due to the overall mouth size increasing. 

But I do not yet understand the mathematical relationship between how a horns mouth size and and wavelength works exactly.   

Would someone like to enlighten me? 

Thanks

Title: Re: Needs help with Horn Theory math
Post by: Art Welter on February 08, 2014, 01:42:33 PM

Quote from: Jeff Bailie on February 08, 2014, 10:19:00 AM

I am trying to learn how to equate the low knee of a particular horns mouth.

But I do not yet understand the mathematical relationship between how a horns mouth size and and wavelength works exactly.   

Would someone like to enlighten me? 

Thanks

You have asked a rather broad question, as there are many different types of horns, the mouth size does not equate directly to LF cutoff.
You can model all the different types with this free program to see the differences:

http://www.hornresp.net/

Have fun!

Title: Re: Needs help with Horn Theory math
Post by: Hayden J. Nebus on February 08, 2014, 02:48:46 PM

Quote from: Jeff Bailie on February 08, 2014, 10:19:00 AM

I am trying to learn how to equate the low knee of a particular horns mouth.

I understand the relationship between frequency and wavelength.

I also understand that coupling horns together flattens the response down low due to the overall mouth size increasing. 

But I do not yet understand the mathematical relationship between how a horns mouth size and and wavelength works exactly.   

Would someone like to enlighten me? 

Thanks

You can check out some of Don Keele's AES papers here at http://www.xlrtechs.com/dbkeele.com/papers.htm (http://www.xlrtechs.com/dbkeele.com/papers.htm), including "What's So Sacred About Exponential Horns" ('75)) and "Optimum Horn Mouth Size" ('73) .

I'd also reccomend Mark Ureda's paper here http://devcn.jblpro.com/pub/tour/AES%20May%2001%20Ureda%20Line%20Arrays.pdf (http://devcn.jblpro.com/pub/tour/AES%20May%2001%20Ureda%20Line%20Arrays.pdf) to see how some of this is applicable to vertical arrays.   

Title: Re: Needs help with Horn Theory math
Post by: Martyn ferrit Rowe on February 13, 2014, 12:27:14 PM

Hey Jeff,
Try these from Bjorn Kolberg Horn theory part 1

https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf

Part 2

http://www.audioxpress.com/files/2008/04/kolbrek2885.pdf
Although they use Websters equations that are "one-dimensional", Dr. Earl Geddes wrote a letter of criticism.

Also Martin Kings website with the Excellent Mathcad worksheets.
http://www.quarter-wave.com/Horns/Horn_Theory.html

HTH

Ferrit