The compression driver needs a mounting flange, so I decided to turn it up and do it neat, using some ply scraps.
The hole flares out and is the start of the horn.
Now all the pieces are cut, firstly with square edges. Most of the time was spent getting these angles right, although the horn is 60 degree included angle, the actual angle of the cuts isn't 30 degrees. It took some time to work out what they actually should be.
The sides need a precise angle and this was done with the "buzzer," a plane with a side fence that can be angled. The buzzer like all power tools is a very dangerous piece of equipment. My poppa chopped off part of his index finger many years ago. When I heard about his accident as a little boy, it inspired caution with power tools.
In case you are wondering, that isn't me. That's my technical consultant aka Dad. There is nothing quite like a father-son project.
Testing out the angles:
All pieces now cut with angles:
Holes have also been cut (ports for the mids).
You can see the holes are quite tricky, because of where they must be placed to come to the corner on the inside. I had to cut these with a spade bit, and actually modify it because none of them were the right diameter. I filed a 19mm bit back to suit with a metal file.
Here you can see the hole size relative to the driver.
Next step is checking everything, then glue and screw.