I have often wondered about the possibility implementing a phase plug based on Geddes' patent:
https://patents.google.com/patent/US20060034475A1/en
https://patents.google.com/patent/US20060034475A1/en
Geddes approach is not optimal in a frequency range above the lowest acoustic mode of the compression chamber.
https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-6170616
4-slot, 1.4" throat, compression ratio ~1:5, seems pretty ordinary 
I think no expansion is the best expansion here. It means that the input area of each channel equals its output area, and that any horn with a smootly rising expansion (starting at zero) should be a good match. Of course that for a flat output wavefront the input/output volume velocities need to be the same for all the channels, but that's not difficult, I already have an implementation for that in the code.
I think no expansion is the best expansion here. It means that the input area of each channel equals its output area, and that any horn with a smootly rising expansion (starting at zero) should be a good match. Of course that for a flat output wavefront the input/output volume velocities need to be the same for all the channels, but that's not difficult, I already have an implementation for that in the code.
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could you please elaborate about the software loop you use for optimization?
I guess;
1 python script generate
2 command line start abec
3 python import results
4 python evaluate
loop
is this correct?
And could you maybe share some code snippets regarding the communication with abec?
thx!
I guess;
1 python script generate
2 command line start abec
3 python import results
4 python evaluate
loop
is this correct?
And could you maybe share some code snippets regarding the communication with abec?
thx!
They are already exactly the same length as shown. This is indicated by the black bars below the phase plug drawing.
- This is still just a quick and random try, no optimization loop yet.
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I don't think this is a problem. I'm not sure about the suggested wave direction either - are the air particles actually pushed in that (red) direction? I don't think so, I thought about this and concluded that the radial direction is the more natural one, but of course I may be wrong. Will be interesting to see the sims, this can be easily tried out.
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If anyone wants to "get a feel" for it, here's a test release (it's not useful for anything else yet):
https://at-horns.eu/ext/plotter-test-deployment.zip
(for Windows 64bit, made using Qt6)
https://at-horns.eu/ext/plotter-test-deployment.zip
(for Windows 64bit, made using Qt6)
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Just in case it may be of interest:
https://sphericalhorns.net/2024/04/27/a-new-coherent-radial-fin-horn/#more-3035
https://sphericalhorns.net/2024/04/27/a-new-coherent-radial-fin-horn/#more-3035
Yeah, I've tried something very similar. It doesn't seem to work so well in practice and my explanation was that it magnifies all the deviations from wavefront coherency to a much larger area, making it simply worse. For this to work as intended, you would probably need a perfect driver.
There was some success (not mine) with BMS 4550, but that's still a small driver:
https://www.diyaudio.com/community/attachments/bms4550_4vaneplug-png.1004919/
Make it bigger and the problems grow. @aragorus probably made the biggest effort testing these things.
There may be some room for improvement in phase plugs though. We'll see.
There was some success (not mine) with BMS 4550, but that's still a small driver:
https://www.diyaudio.com/community/attachments/bms4550_4vaneplug-png.1004919/
Make it bigger and the problems grow. @aragorus probably made the biggest effort testing these things.
There may be some room for improvement in phase plugs though. We'll see.
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Once again, this is the area progression (the bottom curve) needed to have a straight-wall slot:
For the other (straight) slots it will be different. How is even possible to equalize the impedances of all of them? I'm really starting to think that the straight channels are flawed design from the start.
For the other (straight) slots it will be different. How is even possible to equalize the impedances of all of them? I'm really starting to think that the straight channels are flawed design from the start.