Acoustic Horn Design – The Easy Way (Ath4)

[mabat]

This is a full script sample that works for me. You can take this as a starting point.

Throat.Diameter = 25.4
Throat.Angle = 10
Coverage.Angle = 45
Length = 60
Term.s = 1
Term.n = 4
OS.k = 1.0
Term.q = 0.98

Mesh.Enclosure = {
  Spacing = 30,30,30,200
  Depth = 200
  EdgeRadius = 20
  EdgeType = 1
  FrontResolution = 8,8,16,16
  BackResolution = 20,20,20,20
}

;Mesh.Quadrants = 14        ; 1/2 symmetry

Mesh.LengthSegments = 24
Mesh.AngularSegments = 64
Mesh.ThroatResolution = 4
Mesh.MouthResolution = 8.0
Mesh.SubdomainSlices =

Mesh.ZMapPoints = 0.5,0.2,0.5,0.8

ABEC.SimType = 2            ; free space
ABEC.MeshFrequency = 1000
ABEC.NumFrequencies = 24
ABEC.f1 = 800
ABEC.f2 = 10000

ABEC.Polars:SPL_H_norm = {
  MapAngleRange = 0,90,19
  NormAngle = 10
}

ABEC.Polars:SPL_V_norm = {
  MapAngleRange = 0,90,19
  NormAngle = 10
  Inclination = 90
}

Output.ABECProject = 1
Output.STL = 0

 

[mabat]

Some projects that were fine with ATh4.70 are no longer working with Ath4.82
Is that expected?

Do you have an example?

 

[mabat]

How do I set microphone level in observations.txt?

You mean where the mic is positioned - between the WG and the woofer, for example?
That would need to be incorporated in the mesh itself (i.e. to move all its points). I can add a parameter for that. I don't think it's possible to move the axis for polars additionally in an observation stage. At the moment it's always the axis of the horn.

 

[mabat]

[...]
Fixed! I had an lua54.dll in the ath4 folder. Seems to compile cfg's again now.

That's strange. Anyway, you shouldn't need any DLLs now, just the file ath.exe.

 

[mabat]

View attachment 1039914

Looking at the mesh, it seems to me there's no space left between the WG and the edges. I'm not sure if this will be handled properly. For now I would suggest to set the Spacing values safely larger than the EdgeRadius (like one element distance).

 

[maiky76]

Do you have an example?

Your example solves in 73s for me!
That is just awsome.
PM for the file...

 

[mabat]

BTW, this would be the vertical polars for my example above with the mic placed at the lower edge of the waveguide (1/2 symmetry) -
(the polar map is only "upside-down", I think)

 

[limacon]

Thanks @mabat - processing "project2" cabinet now using your suggested settings.

I do like your chart colour profile

Is the ABEC.Polars / Offset param required?

 

[mabat]

There was a new bug in the source definition script, now it's fixed. I'll release an update soon.
- A dome tweeter in a baffle - you can easily experiment with different embedding, etc.:

 

[mabat]

I do like your chart colour profile

Is the ABEC.Polars / Offset param required?

That's the "Otto" color scheme available in VACS layout settings.
No, you don't need the Offset in free field (i.e. for ABEC.SimType = 2).

 

[limacon]

4.8.2 results of "project2" - horizontal polars

 

[mabat]

All I can see is a harmless on-axis dip just above 2 kHz.
Horizontals are easy...

(I'm working on a woofer addition.)

 

[sheeple]

The desmos graph was handy to work out settings to get a better mesh

View attachment 1038451

Would you share the values you chose for MapZ and Mesh?

 

[sheeple]

(I'm working on a woofer addition.)

You must be god!

 

[limacon]

All I can see is a harmless on-axis dip just above 2 kHz.
Horizontals are easy...

(I'm working on a woofer addition.)

Project2 - verticals.

I will look at the ZMapPoints settings and try a better mesh, resolution, freq range. Leave it churning overnight.

It will be interesting to measure this with the HF10AK in place. Hopefully at the weekend.

Woofer! I guess it will work in a similar way to the tweeter https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-6984405 ?

 

[fluid]

Would you share the values you chose for MapZ and Mesh?

Mesh.ZMapPoints = 0.5,0.1,0.76,0.733

I only changed the last two for the mouth edge

 

[limacon]

Mesh.ZMapPoints = 0.5,0.1,0.76,0.733

I only changed the last two for the mouth edge

Thanks for the tip, I think this looks much better.

; -------------------------------------------------------
; Mesh Setting
; -------------------------------------------------------

Mesh.AngularSegments = 120
Mesh.LengthSegments = 64
Mesh.ThroatResolution = 4.0 ; [mm]
Mesh.InterfaceResolution = 10.0 ; [mm]
Mesh.InterfaceOffset = 5.0 ; [mm]
Mesh.CornerSegments = 10
Mesh.SubdomainSlices =
Mesh.Quadrants = 14
Mesh.ZMapPoints = 0.5,0.1,0.76,0.733

 

[mabat]

I would increase the second ZMapPoints value a bit. That will further reduce the number of elements at the throat - as it is it still seems to me as unnecessary.
Or perhaps also reduce the number of length segments (~40?) - you can try both.

 

[sheeple]

Mesh.InterfaceOffset is currently giving me a headache. With low values <3, I will have HF bleed outs already at 13kHz, increasing it to 5 is introducing a LF bump at 1.5 khz. Something to watch for!

 

[mabat]

Here it's probably best to not use subdomains at all if possible, i.e. set "Mesh.SubdomainSlices = " and get rid of the interface altogether.
That said, I already saw a situation where the model wouldn't solve properly without subdomains, for some (not at all obvious) reasons. I can't help with that.