Axi2050 horn design considerations

Been thinking about coming up with suitable horns for my Axi2050.

In the article below, Kolbrek showed a throat expansion that was inspired by an old Western Electric patent.
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Tracked down the patent. It's US patent 1996743. See Fig. 5 and Fig. 8.
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Not a whole lot of existing horns exist for 2" driver. But, PWK's sketch in post #282 in the post below came to mind.

But, 15" is a bit short. Need the horn to be at 300Hz since my intended crossover is 600Hz. It turns out that extending the length to 16" coupled with the 2" throat bring the horn down to 300Hz. Perfect.

As a practical consideration, my BC808 horn built had to be printed in 9 pieces and glued together. No fun. But, if there is an affordable large format printer, the entire horn can be printed as one piece - There is!

I give you the PWK1506. (2" throat, 15 cells, 600Hz). 20" wide x 12" high x 16" deep
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Throat expansion inspired by Kolbrek and WE patent 1996743. Each successive sketch/pattern has the exact cross section area as dictated by the exponential equation.
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Below is the horn on a 600x600x600mm printer. The horn will weigh nearly 8 lbs and will take days to print.
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All part of a plan......
 
Masterful and inspirational work.
Curious, the gaps between the cells was a necessity in the days of old due to the construction technique. In some cases, those gaps were filled with tar to good effect. Given a 3D printing capacity of sufficient size, couldn't you just eliminate the gaps with the printed material? Might have some sonic benefits?
 
Masterful and inspirational work.
Curious, the gaps between the cells was a necessity in the days of old due to the construction technique. In some cases, those gaps were filled with tar to good effect. Given a 3D printing capacity of sufficient size, couldn't you just eliminate the gaps with the printed material? Might have some sonic benefits?
"To be or not to be?". I've given the gaps quite a bit of thoughts. Yes, eliminate the gaps will likely make the horn easier to print and possibly have some sonic benefits. In the end, I kept them for the following reasons: 1) Retaining the "classic" multicellular look. Filling out the cell gaps would make the whole horn look too "blocky/uncool" (IMHO). 2) Leaving the gaps allows for the possibility of filling them later with tar-like or sound deadening materials. 3) The last reason is more practical. Will use less 3D print filaments!
 
Do you think filament layering will affect the sound much? Will you be able to use acetone or some other method to smooth them out some?
 
First, a disclaimer: I am not a physicist nor an audio engineer. I am just a hack.

In designing my horns, correct horn expansion and wall rigidity are of the utmost importance. Correct horn expansion means correct impedance to the driver; Wall rigidity means minimum unwanted resonance from the horn material/construction.

On the subject of the 3D printed "skin" or layering, I've given the subject of the 3D printed skin/layer quite a bit of thoughts. An ideal horn surface would be totally neutral. It should not resonate nor reflect unwanted frequencies back to the driver causing distortion. A perfectly smooth surface would do this. However, because of the horn mouth effect, some unwanted frequencies will be diffracted back to the horn and then the driver. I believe this horn mouth diffraction was what JMLC was trying to minimize with his horn designs. Also, this is the reason why most horns are crossed at an octave over their theoretical designs to prevent the "honkiness". While a 3D printed skin is not neutral, it's rough texture helps to diffuse sound waves coming out from the driver as well as diffracted sounds coming back from the mouth. The net effect is likely better as compared to a smooth surface which does not diffuse sound refraction from the mouth. An apt analogy is the surface of a submarine. It's most definitely not smooth. The surface of the submarine absorbs and diffuses sonar waves/energies so they do not reflect back to the sonar source. Similarly, the 3D printed surface "may" absorb and diffuse sound waves both from the driver and the mouth. Therefore minimizing distortion.

I do not have any quantitative data to back up anything - only what I think.

Other than sealing the surfaces to prevent moisture absorption, I do not intend to smooth out 3D printed horns.
 
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Makes sense to me. Maybe in the future you may end up making more and can experiment with as printed vs. smooth for audio posterity. Don't reply too in depth too soon as I have already started New Years eve festivities. ;)
 

MrEd

Senior Nobody
Wow.. Happy happy joy joy...
That's awesome.
3 bolt flange, is that large format Atlec?
 
Right. Because of the orientation, there are less features to print near the top. The last 2" should go really fast. I am expecting the print to finish late tonight.
 
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