Construction of the cones.
The 4 half-cones are each milled out of a pile of MDF squares, glued together.
Below a section of two half-cones together.
The half-cones are held together by a piece of M6 threaded rod and two ringnuts.
Construction drawing.
Note the ringnuts and the channel for the M6 treaded rod which keeps two half-cones together, and horizontally one hole for mounting the cones between the loudspeakers with aluminum rods. There should be 3 such holes, angled 108 - 144 - 108 degrees in the horizontal plane.
The rods shoud be inserted spring-loaded, otherwise the final mounting will be quite tricky.
The pictures below were made during the construction of a smaller version in 2004.
Drilling a chamber for the ringnut.
Glueing the square plates together.
For the milling I happened to have a motorized rotor on which the glued pieces were mounted.
The milling machine was mounted on a construction with linear ball bearings from some drawer cabinet.
Cone milling halfway.
Sanding. Be sure that all cones will have the same diameter.
The halfway finished cones. After this, fine-sanding, varnishing and drying was applied repeatedly.
The tip can be slightly rounded off, because it is prone to be damaged.
It does look a bit like Jupiter isn't it?