Acoustic Horn Design – The Easy Way (Ath4)

[Skiivari]

I tried it in the same WG as the T25A above. This kind of tweeter would need a different approach...

View attachment 1175066 View attachment 1175068

Agreed, top octave very similar behaviour to what I've seen in my various simulations and actual measurements in one of augerpro's waveguides.

I've been working on a theoretical mitigation! Here's some sims concentrating on the top octaves. I took inspiration and formulas from your WSP implementation, it's great. Here I think we should have a reasonably well-known wavefront.

I may be able to print this, but it's definitely not the kind of printing I have enjoyed in the past. Loading is very high, I hope it wouldn't cause nonlinear behaviour in the diaphragm.

Interestingly, playing with the throat dimensions result in the same kind of trade-offs as I've seen in my past playing with Hornresp and horn subwoofer alignments. Wavelengths are just a little different.

 

[mabat]

That's some serious wave shaping!
(Would love to see it in action but I think I would rather use a different tweeter instead...)

- I wonder why we don't see the Peerless DA25TX00-08 or the DA32TX00-08 more often (?). Those seem to me as a great value for the money.

 

[Skiivari]

Agreed, the results from purifi's dome tweeter and your Beyma simulations are surprisingly high dispersion in the top octave. And more radiating surface area as well.

Oh well, now I wonder how rough the real-world response from a small fullrange + custom WSP would be.

 

[TNT]

Perhaps with 2.5-in-SB65WBAC25-4?

//

 

[nc535]

It's been used on one of the 18sound waveguide, I think by @bushmeister

 

[mabat]

Agreed, the results from purifi's dome tweeter and your Beyma simulations are surprisingly high dispersion in the top octave. And more radiating surface area as well.

Oh well, now I wonder how rough the real-world response from a small fullrange + custom WSP would be.

It was Bliesma, not Beyma, and you probably meant the ESP (External Shaping Plug).

Generally speaking, the bigger the source the higher the chance it won't produce a coherent wavefront, which limits the highest usable frequency. Then it's all just random... I wouldn't hold my breath.

 

[mabat]

From the few cases I tried I think that a concave surround has an advantage over a convex one. If I was to search for a tweeter, I would probably try some of those first (both the above Bliesmas have concave surrounds). The Peerless unfortunatelly not.

 

[jzagaja]

What are the problems on SPL?

 

[mabat]

Actually it's not that bad, only not as good.
This is without an attempt to optimize the edge (DA25):

 

[Skiivari]

Yes, sorry for butchering the names!

True, it is at minimum a step into the unknown for me. However, I have hopes there is some signal in the random even for us hobbyists: my inspiration is https://www.audiosciencereview.com/...gn-via-shape-and-topology-optimization.23453/

Perhaps with 2.5-in-SB65WBAC25-4?

View attachment 1175110

//

Thanks for the dimensions! I have a pair of these, thanks to @Patrick Bateman s recommendation.

 

[mabat]

The quality of the mesh around the source can be further improved by using "Mesh.ZMapElementSize":
(Not often used but here it's handy.)

Mesh.ZMapElementSize = 0.1,0.3,0.25,0.85
...
Mesh.ThroatResolution = 2

; Peerless DA25TX00-08
Source.Contours = {
  dome WG0 26 5.6 3 1.5 4 1
}

 

[mabat]

The simulation with Bliesma T34B in a higher resolution mesh:

 

[mabat]

Flush-mounted in the front baffle:

(To do this, set Mesh.LengthSegments = 0.)

It's remarkable how the waveguide widens the pattern above 10 kHz. This will reduce the on-axis sensitivity though.

 

[mabat]

The flat baffle (top row) vs the WG (bottom row), pressure response at 8k, 12k, 16k, 20k:

(Only now I see that the enclosures don't have the same width... I should have checked that better.)

ABEC.AxialField:1 = {
  Inclination = 0          ; [deg]
  Radius = 0.3              ; [m]
  z0 = -0.22                  ; [m]
  z1 = 0.3                 ; [m]
  Resolution = 10,10,20,20  ; [mm]
}

 

[mabat]

The WG at 12 kHz.

 

[mabat]

I thought that something might be visible in the pressure isophase contours (wavefront shapes by definition) but there's nothing -

 

[TNT]

The left one looks more circular as opposed to the right one which looks a bit more elliptical?

//

 

[AllenB]

Yes, due to diffraction. It is occluded from the source. It separates from the horn and it diffracts.

 

[mabat]

It separates from the horn and it diffracts.

That's only an artefact of the calculation / mesh boundary.

 

[mabat]

Here's a sharp-edged box -