I believe my Pioneer CS-A31s have a horn, as I do have all the parts stocked. Also loved my BIC Venturi Formula 2's, also 3-ways with horns and a bottom 'venturi' port.
What really surprised me were the 1960s Jensen SP paper tweeters I had in my Altec Model Three cabs with the really THIN cones and closed frames...those get the highs out there LOUDLY/BRIGHTLY to the point of needing to attentuate them for being almost shrill!