had no low-pass and used an evolved high-pass 3rd order, eq and an Fs trap, on the big dome tweeter -3db @ 3.5khz. 35mm VC, main driver has a 38mm VC
The cone is shaped like one of those flat bottomed soup bowls made by Corning, which is part of the clean roll-off
Made near Canberra in the late 1970s through into the 1980s.
2-way spheres with Triangle drivers are still being made down here.