a driver's diaphragm is capable of moving from the at-rest position. Maximum
linear excursion (Xmax) refers to how far a driver cone can move while the
still under control of the motor. Mechanical excursion is how far the cone
can physically move including portions where the voice coil is out of the
magnetic gap. Typically, excursion figures represent the amount of movement
in one direction from the at-rest position. However, movement in both directions
is sometimes given with a peak-to-peak rating.