It was mentioned before but its worth repeating - prob some 3 way design in which one driver handles only the midrange. Sure there may or may not be integration / crossover issues but you can't get a purer midrange than that.
ATC, Harbeth, Linkwitz and PMC all have obvious examples but there must be many others.
ATC, Harbeth, Linkwitz and PMC all have obvious examples but there must be many others.