I have old Luxor 8071 Transmissionline horn speakers and the pins for the fronts where busted or missing. Yesterday I sat in the sofa watching a movie and boom I figured I can make new ones in Fusion 360... So I fetched my caliper, pen and paper and drew them up in Fusion 360. They work perfect!
You need to use supports and 100% infill. Be careful when removing the supports.