In the March and April 2008 issues of audioXpress there is an article in two parts by yours truly. Part 1 deals mainly with classical horn theory, its uses and limitations, and also touches a few of the common horn types and their attributes. Part 2 reviews several other horn types, and also discusses methods of directivity control, nonlinear distortion and higher order modes.
Fig. 1 is missing in part 1, it can be found here.
The original article can be found here.
Since there seem to be misunderstandings regarding the purpose of the article, I want to point out the following: The title is “Horn Theory: an Introduction”. It is thus an introduction, and does not pretend to be a complete summary of how horns work (as one may believe from the front page of audioXpress). It actually does not present any very fundamental description of how horns work physically, but rather presents the theory, and shows some properties of horns. The second line in the abstract also says a lot: “[The article] reviews the basic assumptions behind classical horn theory as it stands, presents the different types of horns, and discusses their properties.”
Also note that the oblate spheroidal waveguide is described from the point of view of classical horn theory.
The article was written in the summer/autumn of 2007, and it reflects my knowledge and understanding at that time. I have learned a lot about horns since then. It will hopefully be presented in papers, articles, and on these pages in the time to come.
Modes in horns
During the fall of 2011, I implemented the method for propagation of higher modes in horns as described by Kemp in his thesis, as the project in the course Numerical Acoustics. The report can be downloaded here.
Update: Spring 2012 I did a more detailed evaluation of the modal propagation method, to check the accuracy and computation times etc. The report can be downloaded here.
The Matlab toolbox for the Modal Propagation Method can be found here.