I know there are some keen DIY'ers here on WigWam, so this my (our) current project - a Tractrix horn build.
Calculations, Cad drawings, staining, varnishing etc all done by me - the wood turning is done by a pro-friend at mates-rates.
Initial detail -
wooden tractrix horn.
Drive unit - TAD 4002
Tractrix horn - 300hz horn, I cross it over between 600-800hz, we will have to see what sounds best on the new horn.