What is cone breakup?

Cone breakup refers to way in which piston drivers bend at the top end of their bandwidth. At lower frequencies the piston moves as a unit, but at a certain point based on the mass, stiffness and geometry bending modes cause sharp peaks in response and resonant ringing. At this point the driver will most likely become unuseable. Stiff cones tend to have sharper breakup with a high Q peak that is easily seen in the response. Soft cones provide damping of cone breakup so that it may in some cases not be visible in the response. As a result, metal cone drivers will tend to have lower distortion prior to breakup and will often need a notch filter, steeper low pass filtering and a lower crossover point. Soft cone drivers may not require any special treatment in the crossover.