I think that a random coarsness of the sufrace is something very different than axisymmetric grooves. This is what such a groove (0.8 mm deep) placed at 50 mm from the throat does. So you definitely don't want any larger dimples in the surface. But the "coarsness"? I don't know.
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To simulate surface deviations from the ideal you would have to randomly shift individual points in a full 3D mesh. To behave more like a real thing it would be a little more complex than that - perhaps interpolated between some sparse definition points, so it's not just a noise. Or smoothed somehow.
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Its har to talk about surface smoothness 
0,8mm isn't much. Its like a dent but if you sanded something and at the same time watch a football goal on TV you might end up rubbing the same spot for a while waiting for and watching the replay, and maybe create a 0,6mm recess (if not a dimple)....
I'm trying to put this into perspective of the leaf reassembling a WG from 3D printed parts and what precision is needed...
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0,8mm isn't much. Its like a dent but if you sanded something and at the same time watch a football goal on TV you might end up rubbing the same spot for a while waiting for and watching the replay, and maybe create a 0,6mm recess (if not a dimple)....
I'm trying to put this into perspective of the leaf reassembling a WG from 3D printed parts and what precision is needed...
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No, it doesn't work 
I got myself fooled badly this time - the manually added elements were meshed with too low resolution so that the results were not correct. By default I use so high number of slices on the waveguide itself that the nominal mesh resolution I use (33 kHz) is actually set much lower and obviously is still not enough for reliable data at 20 - 25 kHz..
I got myself fooled badly this time - the manually added elements were meshed with too low resolution so that the results were not correct. By default I use so high number of slices on the waveguide itself that the nominal mesh resolution I use (33 kHz) is actually set much lower and obviously is still not enough for reliable data at 20 - 25 kHz..
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I'm definitely going to give it one more chance, make more rings following the OS coordinate contours precisely, but I'm a little afraid that the acoustic summing at the exit simply won't be good enough to make a real improvement in the end.
I'm not quite sure what's this particular acoustic lens supposed to do (?). Shape a more spherical wavefront? Does it work?
My idea was to not let the diffracted waves from the throat (where the wall curvature is the highest) travel across the whole internal volume, but to direct them towards the mouth. Maybe even not give them a chance to develop in such a narrow space - that was my naive notion.
I'm not quite sure what's this particular acoustic lens supposed to do (?). Shape a more spherical wavefront? Does it work?
My idea was to not let the diffracted waves from the throat (where the wall curvature is the highest) travel across the whole internal volume, but to direct them towards the mouth. Maybe even not give them a chance to develop in such a narrow space - that was my naive notion.
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As far as I understand, this particular acoustic lens is meant to decrease beaming over 10khz.
I THINK using a "phase plug" like that, could allow to use a longer throat extension with a gentler wall curvature. but then again - I'm not sure if that's going to be the case in practice.
Could be nice to have a resin printer for experiments like that
I THINK using a "phase plug" like that, could allow to use a longer throat extension with a gentler wall curvature. but then again - I'm not sure if that's going to be the case in practice.
Could be nice to have a resin printer for experiments like that
is this what is done in a keele conic exponential horn?
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1975-05 AES Preprint) - Whats So Sacred Exp Horns.pdf
http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1975-05 AES Preprint) - Whats So Sacred Exp Horns.pdf
ah ok I think I was just confused by the ideal case for the conical horn where the wavefront is normal to the surface. Would it be possible to measure the wavefront at the compression driver and create a lense that modified it to a spherical wavefront? I belive this would allow 2" throat drivers to avoid beaming (I will see if I can find the relevant plot for this from the horn book).
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At least in principle it could be done with a phase plug that would produce spherical wavefront, instead of the more common flat. I already made some steps towards that goal (some of it was discussed in this thread) but don't have the time nor the resources to pursue it further at the moment.
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I know it´s possible to define different curves for vertcial and horizontal horn contour with ath4.
Is it also possible to define different contour for left and right (horizontal) or upper and lower side (vertical)?
This would it make possible to generate asymetric waveguides like for example the Limmer 504.
That would help me reducing the distance between midrange and tweeter when designing a double-waveguide and "melt" the two waveguides in each other.
Is it also possible to define different contour for left and right (horizontal) or upper and lower side (vertical)?
This would it make possible to generate asymetric waveguides like for example the Limmer 504.
That would help me reducing the distance between midrange and tweeter when designing a double-waveguide and "melt" the two waveguides in each other.
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I wanted to show how to do it but it turned out more complicated that I anticipated, so sadly I can't really help at the moment.
If anyone wondered what are the "inner" OS coordinate contours in cartesian coordinates, this is it (OS coordinates) -
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Incorporating the "k" is straightforward - OS coordinates
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