A coax[ial] is a 2-way (two driver) loudspeaker with an independent tweeter mounted in the centre of the main driver -they require a crossover to be used. The Markaudio drivers are full-range units, but to a point function as mechanical coax units: the central cap is directly bonded to the end of the voice coil so it acts rather like a dome tweeter, & the main cone progressively decouples as frequency increases -no crossover is needed with them, or similar units.
