Making round horns

version francaise

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150Hz tractrix round horn

This web page shows how to make a round horn unlimited in size and without a lathe.

drawing the plans

-choose a curve, the length, the throat diameter, the mouth diameter. Many books or web pages tell how to do it.
-choose the slice thickness which is the tickness of the wooden boards used, 16mm for exemple.
example: the curve designed by Lecleach
-some softwares allow to display the horn. Here is an exemple for a 150Hz horn, it is 860mm large:

simulation of a 150Hz horn

building a wooden round horn

First draw the slices with a large compas on the MDF boards. Draw the inside and outside circles on both sides of the boards. Then use a jigsaw to roughly cut the slices. The maximum cut angle is usually 45 degres and that is not enough for most tractrix horns.
Here is an example of slices on top of each other to build a 300Hz horn for a 2 inch compression driver. The outside diameter is about 550mm.
slices on top of each other

Because the slices have been roughly cut with a angle limited to 45 degres, a diy milling machine can be used to improve the shape of each slice as shown in the next picture:
milling machine

Then this is what you get after putting the slices on top of each other:

milled slices on top of each other

Then use glue and screws to put the slices togeter. Don't use screws for the largest slice and don't use glue for the smallest slice because it has to be removable to fix the compression driver. When the glue is dry rasp to swooth the horn, this is a painfull task:

rasping

Then file down, varnish and then sand the horn.

finished 300Hz horn

Another example: a 150Hz horn for a 6 or 8 inch cone driver with a 2 inch adapter.
tractrix 150Hz avec compression radian 950PB

Response of the 150hz horn with a 2 inch Radian 950PB compression driver, almost 220Hz-16KHz with no EQ.
response with Radian 950PB

tweeter horn, Lecleac'h curve:
lecleach

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