On the other hand, even without the vanes, the measured polars do match the predition for an ideal source almost perfectly to 20 kHz. That would lead me to think there actually can't be much of non-symmetric content. It's hard to grasp what is actually resonating with what, but in the polars it's definitely independent of angle. And then some of these resonances, like the one at 5 kHz, which is pretty low in frequency, dissapear with the vanes... A mystery to me.
What is close to both Fibonacci and Fractals is the Golden spiral: https://en.wikipedia.org/wiki/Golden_spiral
I invite anyone to test any shape, it's easily done via Ath by using the "Profile" definition, which accepts any user-given coordinates: https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-7228138
If I understand correctly, the comparison for which we have data is between an empty throat and the peace plug. The plug contains the 'shell', which changes the area for the wavefront in the throat. That should lead to changes in the ripples of the frequency response.
Thank you CinnamonRolls for the data, and the measurements of rockwool in the throat. I do find it interesting that the unfilled plug reduced the 5k resonance.
Thank you! I now got "error: gmsh call status = 1" instead
Switched to Ath 4.8.3b2 from the newest 230531 build and that seemed to solve it, but now getting this with some scripts. I managed to get some scripts working, though. I guess I'll experiment more with the versions
Code:
Error : Unknown number option 'Mesh.MeshSizeExtendFromBoundary'
Error : Unknown number option 'Mesh.MeshSizeFromCurvature'
This appears almost as the Mercedes Benz logo. In the peace sign the vertical bar would have to continue across the whole diameter ☮.
Try disabling STL output in the scripts STL=0Thank you! I now got "error: gmsh call status = 1" instead
That might help too.
Printed and measured a set of Internal Ring styles. They may not be easy to see in the images so I included STL files for 3D viewing.
Control: Empty duct
3a: 3 channels, 5mm recess from waveguide (0.75 millimeter thick fins)
3b: 3 channels, 10mm recess from compression driver phase plug exit (0.75 millimeter thick fins)
3c: 3 channels, no recess, split in middle and rotated 60 degrees (0.75 millimeter thick fins)
6a: 6 channels, 3 fins 4mm long (0.75 millimeter thick fins)
6b: 6 channels, 3 fins 6mm long (1 millimeter thick fins)
6c: 6 channels, all fins same length, recessed 5mm from waveguide (1 millimeter thick fins)
When I created the 6b,c models I made the fins a little thicker by accident. I accidentally deleted the 6a STL so only the 6b photo and STL are attached.
Control: Empty duct
3a: 3 channels, 5mm recess from waveguide (0.75 millimeter thick fins)
3b: 3 channels, 10mm recess from compression driver phase plug exit (0.75 millimeter thick fins)
3c: 3 channels, no recess, split in middle and rotated 60 degrees (0.75 millimeter thick fins)
6a: 6 channels, 3 fins 4mm long (0.75 millimeter thick fins)
6b: 6 channels, 3 fins 6mm long (1 millimeter thick fins)
6c: 6 channels, all fins same length, recessed 5mm from waveguide (1 millimeter thick fins)
When I created the 6b,c models I made the fins a little thicker by accident. I accidentally deleted the 6a STL so only the 6b photo and STL are attached.
My intuition at this point is the fins have minor effect other than the amount they wind up blocking the passage (their effect on impedance?). Yesterday I was thinking the Geddes Tickler might allow the ability to increase or decrease impedance along portions of the duct without disturbing the wave front but I didn't understand what it was originally intended to do. - plus I was hoping it would allow CircSym.
take 2" wide angle throat driver and put 1" insert with waveguide part inside
foam in the throat is not new to me - a month ago I was experimenting with fullrange in 500Hz horn. Axidriver predicted flat power response while reality was far from this - wool felt helped to some extent. Only DonVK could simulate real life in Abec/Akabak. Patrick Bateman reports midrange resonance in Metlako III - same with FR in a horn. I've tried compensate acoustically with internal resonator but they are high Q and usually no match.
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Do you know such driver?take 2" wide angle throat driver and put 1" insert with waveguide part inside
The closest I could find is the Radian 760 (1.3") - already have'em.
BTW, I still believe that Faital HF146 would be also a great choice for this (would be closer to 1") but obviously I can't buy all the drivers that look promising.
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