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-   -   Acoustic Horn Design The Easy Way (Ath4) (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4.html)

mabat 7th June 2019 05:40 AM

Wow! Thank you Patrick for probing the piece. It seems you are really the right person to do it :up:
I'm sure there are still flaws. I'm making notes and will try to look at that for the next release. Thanks again.

mabat 7th June 2019 07:29 AM

Quote:

Originally Posted by Patrick Bateman (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post5815054.html#post5815054)
In "solving" for the OS waveguide, I noticed that there's one domain, but in the ath15 waveguide, there are zero.

I think the problem is in the mesh that's generated. Here's the header for the OS waveguide mesh generated by ath4.exe:

$MeshFormat
2.2 0 8
$EndMeshFormat
$PhysicalNames
3
2 10 "drive"
2 20 "wg"
2 30 "ifc"
$EndPhysicalNames
$Nodes
849

And here's the header for the ath15 mesh. Note the missing fields.

$MeshFormat
2.2 0 8
$EndMeshFormat
$Nodes
1568

Only the mesh file intended for ABEC has these physical goups, i.e. names (tags) for the several horn sections - the throat surfrace "drive", horn walls "wg" and the interface "ifc". And also it is only a quarter of the whole horn.

The mesh file in the root project folder is basically just a different form of the STL. You are not supposed to be using this mesh for a simulation. I should give these files a different names I guess.

mabat 7th June 2019 07:34 AM

Quote:

Originally Posted by Patrick Bateman (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post5815068.html#post5815068)
One caveat : I've noticed that ABEC isn't able to make it's pretty 3D pictures. I think that's because there's something missing from "observation.txt"

Having said that, you CAN see the polars in VACs, which is really what we're after, right?

What do you mean by these 3D pictures? If you mean the Fields feature (pressure distrubution accross some plane surface coded in colors), it's no problem to include that. I made these is the past, they are pretty but actually never found a real merit for them. I will make it an option in the next release. It can show you the nearfield (or the interior of the horn) nicely. But what do you really take from that?

mabat 7th June 2019 07:46 AM

1 Attachment(s)
BTW, this is how Fredrik's mesh for ABEC looks like. I guess it would take years to calculate :)
Unfortunately I don't know the cause. That looks like a question for the Gmsh authors. I will try.

I will talk more about the ABEC part later. There's much to explain I guess.

mabat 7th June 2019 11:04 AM

I could make an option of a dome tweeter instead of a plane wave (which is what it is now) for the throat. At least I believe it would be possible. Only it is not so obvious how to do it. Should I include the surround? How to define the shape? Or does that make any sense at all?

BTW, the wavefront could also by modeled as non-flat. I only don't know if there is anyone who could utilize such feature.

FredrikC 7th June 2019 11:58 AM

Tried it on my laptop now and the mesh is normal resolution there.

cowanaudio 7th June 2019 12:00 PM

I'd love to play along but when I run ath4.exe it flashes up for about a tenth of a second then disappears. I have gmsh-4.3.dll in the same directory as ath4.exe.

System is an i7 running win10

I have downloaded the sw and gmsh twice with the same result. :confused:

mabat 7th June 2019 12:11 PM

1 Attachment(s)
This is the icon you are looking for. You must run a command line window first. Search for cmd.exe (usually under C:\Windows\...), make a shortcut icon of it somewhere and in the properties set the directory of your ath4.exe ("Start in"). Then just double-click on the shortcut to get to the tool. Then you can run it as shown in the manual.

Fredrik, maybe your computer just wants to show you what it can do. I wouldn't feel safe...

cowanaudio 7th June 2019 12:33 PM

Thankyou. I'm getting closer, I'm now coming up with an error "Unknown output file format" when I try to open oswg.cfg. This error appears just after the width and height of the wg is displayed.

It has created the directory D:\Horns\ABEC_project with four files in it.

mabat 7th June 2019 12:44 PM

This is getting weird. It seems like Gmsh library does different things on different machines. This error comes from the Gmsh SDK when it doesn't recognize the file format requested to export the data. It does that by looking at the file extension (which is hardcoded in the source code!). The only explanation I can imagine is that you have a different Gmsh library, which can't do STL or MSH. But that seems also as a nonsense. I don't know :(

I will add some more detailed debug info. It may still be a bug on my side.

- You can try to comment or delete the line "Out.DestDir = ..." but I doubt that will help.


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