In audio, excursion relates to a speaker’s movement. The excursion is the distance it travels back and forth (in and out) from its nominal resting position. Different types of speakers are designed to accommodate different amounts of excursion. Usually speakers designed to move massive amounts of air such as low frequency drivers or subs have more excursion than high frequency drivers. Those with more excursion may also exhibit poor damping and sound very loose or sloppy, so a designer must find a happy medium and keep in mind the enclosure and intended application when choosing speakers. If a speaker is pushed beyond its limits you may hear a “cracking” sound as the voice coil slams into the bottom of the magnetic gap (during inward movement) or slips out of the gap (during outward movement). This is called overexcursion or “bottoming out” and usually just precedes a failure.