Xmax - A measure (in inches or millimeters) of a speaker cone's maximum excursion (back and forth motion) in one direction while still maintaining a linear behavior (moving in a straight line with high precision). Defined as the width of the voice coil that extends beyond the front plate plus 15%. This relates to how far the speaker can move in either direction without appreciable distortion.

XM Radio - A satellite radio subscription service that broadcasts over 170 digital-quality channels including 69 commercial-free music channels, news, sports and children's programming.

Y Cable or Adapter - A y-shaped cable used to split a signal into two parts or combine two signals into one. Most common variations available are one male - two female terminals or one female - two male terminals.

Zero Bit Detection - A circuit in a D/A converter that monitors the digital audio bit stream. Upon encountering all zero bits (bits low), the output of the D/A is disconnected from the preamp improving the signal-to-noise ratio specification.

Zero Output - The absence of output signal or output power.

Zobel Filter - All voice coil type drivers exhibit a rising impedance caused by the voice coil inductive reactance. This capacitor / resistor filter is added to a crossover to stabilize speaker impedance at the crossover frequency. To figure values: Resistor (R) = 1.25 x Re, Capacitor = Le / R squared