Acoustic Horn Design – The Easy Way (Ath4)

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So far this is the best one I have (HF1440), here measured with 80mm extension duct, 0,5,10,15,20 mm off center.

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This should work with a wave-shaping plug right away up to 15kHz, IMHO.
The guys at Faital definitely seem to know what they're doing.

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How to run ATH on Linux (and possibly on MacOS)...

# enter newly created ATH directory in the HOME directory
cd
mkdir ATH
cd ATH
# download and extract the last ATH release with demos (to an own directory)
wget https://at-horns.eu/release/Ath-4.7.0.zip
unzip Ath-4.7.0.zip -d 4.7.0
# download and extract the last almost complete ATH release
wget https://at-horns.eu/release/ath-4.8.2.zip
unzip ath-4.8.2.zip
# download and extract gmsh
wget https://gmsh.info/bin/Windows/gmsh-4.6.0-Windows32.zip
unzip gmsh-4.6.0-Windows32.zip
# download and extract the last released win32 version of gnuplot
wget https://master.dl.sourceforge.net/project/gnuplot/gnuplot/5.2.7/gp527-win32-mingw.7z
7z x gp527-win32-mingw.7z
# download and extract the ABEC (to an own directory)
wget http://www.randteam.de/_Software/ABEC3_Pro/ABEC_Pro_v360b07_NoInstaller.zip
unzip ABEC_Pro_v360b07_NoInstaller.zip -d ABEC_Pro_v360b07
# create an output directory for ATH (the "demos" name is stored in ATH demos .cfg files)
mkdir -p output/demos
# configure paths for ATH
cd 4.8.2
# edit ath.cfg file, with any available editor ... for example nano
# and translate paths in your home directory, for example /home/miero/ATH/ to Z:\home\miero\ATH\
nano ath.cfg
OutputRootDir = "Z:\home\miero\ATH\output"
MeshCmd = "Z:\home\miero\ATH\gmsh-4.6.0-Windows32\gmsh.exe %f -"
GnuplotPath = "Z:\home\miero\ATH\gnuplot\bin\gnuplot.exe"
# try to execute ath.exe without parameters
# it has to be executed in the directory with ATH files ($HOME/ATH/4.8.2/ in this example)
wine ath.exe
Ath 4.8.2
-------------------------------------------------
DIY version for personal non-commercial use
-------------------------------------------------
Marcel Batik Czechia, 2022
PayPal: mbatikp@atlas.cz
-------------------------------------------------

Usage: ath <horn_definition_file>
# try to generate an output for a demo (using a demo from older ATH release)
# but first append report generation section at the end of file
nano ../4.7.0/demos/demo8C.cfg
Report = {
Title = demo8C
Width = 1024
Height = 768
GnuplotCode = 2x2n.gpl
MaxRadius = 150
MaxAnglePM = 180
}
Output.STL = 1
wine ath.exe ../4.7.0/demos/demo8C.cfg
Ath 4.8.2
-------------------------------------------------
DIY version for personal non-commercial use
-------------------------------------------------
Marcel Batik Czechia, 2022
PayPal: mbatikp@atlas.cz
-------------------------------------------------

-destination directory: Z:\home\miero\ATH\output\demos\demo8C
-circular symmetry mode for profile 0
-initializing
-calculating profiles
-writing ABEC project
-average mesh throat angle: 7.000 deg
-matched wavefront radius: 104.210 mm
-running 'Z:\home\miero\ATH\gmsh-4.6.0-Windows32\gmsh.exe mesh.geo -'
Info : Running 'Z:\home\miero\ATH\gmsh-4.6.0-Windows32\gmsh.exe mesh.geo -' [Gmsh 4.6.0, 1 node, max. 1 thread]
Info : Started on Tue Mar 28 23:03:47 2023
Info : Reading 'mesh.geo'...
Done.

Device width x height = 244.29 x 244.29 mm (9.618 x 9.618")
Device length = 82.46 mm (3.247")
# execute ABEC
wine ../ABEC_Pro_v360b07/ABEC3_Pro_32r.Exe
# load there project in the output/demos/demo8C/ABEC_FreeStanding directory
# start solving by pressing ... F5
# disable VACS output .... Alt+a o o
# calculate spectrum ... F7
# export spectras as text ... Ctrl+F7
# close VACS

# generate ATH report
wine ath.exe ../4.7.0/demos/demo8C.cfg -r
Ath 4.8.2
-------------------------------------------------
DIY version for personal non-commercial use
-------------------------------------------------
Marcel Batik Czechia, 2022
PayPal: mbatikp@atlas.cz
-------------------------------------------------

-destination directory: Z:\home\miero\ATH\output\demos\demo8C
-processing BEM results
-writing report 2x2n.gpl: 'demo8C'
# and finally...
# check the generated image in the output directory
open ../output/demos/demo8C/ABEC_FreeStanding/Results/demo8C.png
# and display STL file
fstl ../output/demos/demo8C/demo8C.stl
 
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Just out of interest I tried the profiles from #12,067, this time as free standing (5mm wall thickness).

Note that once the strongest mouth diffraction has been reduced, further increase of size doesn't improve it - that's the remaining diffraction at the outer edge that simply won't go away. All just shifts down in frequency due to the larger mouth size -

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s1-fs-2.PNG


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s1-s25FS.png

s1-s50FS.png
s1-s75FS.png

s1-s100FS.png
 
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further increase of size doesn't improve it - that's the remaining diffraction at the outer edge that simply won't go away. All just shifts down in frequency due to the larger mouth size -
I found that use the difference between the red and green path length would predict the location of the wiggles quite nicely for a listening distance far away.

IMG-20230329-WA0001.jpg

I could make a better image if you like. I also could try to calculate the difference analytically if anyone is interested.
 
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Yes, that then determines the main part of the delay between the direct sound and the secondary source(s) along the edge. The wiggles on a FR are a result of this delay. It works like this everywhere.

The aim of the mouth rollback is to eliminate these secondary sources. Which can be done almost perfectly, as we know.