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Ever think of building a Cornu Spiral horn? Now you can!
Ever think of building a Cornu Spiral horn? Now you can!
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Old 1st March 2015, 10:47 PM   #2051
colinegreen is offline colinegreen  United States
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The images did not load - here they are -
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Old 1st March 2015, 10:51 PM   #2052
xrk971 is online now xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
The expansion is very slow and then opens up much like a trumpet. I am afraid it may have a "brass horn" like sound aka - mildly honking sound from resonance. You could model this in HR or Akabak pretty easily and get an idea.
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Old 1st March 2015, 10:54 PM   #2053
colinegreen is offline colinegreen  United States
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Thanks xrk971

This is as I suspected - I went for horn length in a small space over other variables.

I could do one with fewer loops (shorter) but getting wider faster.

Any other comments?

Colin
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Old 2nd March 2015, 04:22 AM   #2054
xrk971 is online now xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Only other comment is to try making it with cheap and fast FC - especially when you have a new design. CNC milling all that MDF just discover a not so good sounding speaker would be, for me, kind of disappointing.
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Old 2nd March 2015, 05:20 AM   #2055
colinegreen is offline colinegreen  United States
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xrk71 - I was not planning any CNC for this project - that was for the big Cornus I still have to finish.

This was going to be printed guides spray mounted to each plywood sheet, then cut by hand on a scroll saw.

Colin
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Old 3rd March 2015, 01:45 AM   #2056
colinegreen is offline colinegreen  United States
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OK -

After fighting to keep the overall size low and weight down, I came up with a way to push the horn down through the layers and emerge from the side in lower layers so I still get a big mouth without a big baffle. This is about 15" square, and uses a 3" driver.

The horn goes from 0.5" in the middle to almost 15" at the mouth. The midline of this horn is about 90" long.

xrk971, is this better?

Other thoughts?

Colin
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Old 3rd March 2015, 01:52 AM   #2057
colinegreen is offline colinegreen  United States
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btw, each layer is 1/2" plywood.
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Old 3rd March 2015, 04:20 AM   #2058
xrk971 is online now xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Neat idea - looks like it could work.
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Old 3rd March 2015, 04:29 AM   #2059
colinegreen is offline colinegreen  United States
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Thanks XRK.

I will make a few more refinements and then try to build one.

Colin
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Old 7th March 2015, 10:26 PM   #2060
colinegreen is offline colinegreen  United States
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XRK -

There is enough room in all the layers of plywood for the cylindrical opening behind the driver to be deeper and higher volume.

In my current design this open space is ~3" in diameter, and the spiral section is 1.5" deep - 3 layers of 1/2" plywood.

All of the open areas of the the lower layers are outside of this area, so it would be possible to extend the depth of this cylindrical area behind the driver up to 6".

Is there an advantage to making this chamber directly behind the driver have higher volume? I can make this volume 2x bigger without changing the design, the horn dimensions would stay the same.

Make sense? Thoughts?
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