Abstract: A audio system for skateboards comprising an audio module and speakers mounted to the bottom side of a skateboard. The audio module is battery-operated and has a Bluetooth receiver and a stereo amplifier. The speakers face downwards. While the rider is traveling on the skateboard, the sound from the speakers bounces back from the road's surface so that the rider may enjoy music in safe manner without loss of maneuverability.

Abstract: The loudspeaker has a first pair of drivers arranged in a line, a center point along the line, wherein the pair of drivers are substantially centered about the center point with a center to center distance, d0, between the drivers in the first pair of drivers, whereby the maximum frequency with out high amplitude side lobes is equal to c/2d0, and at least a subsequent pair of drivers arranged in the line array with the first pair of drivers and substantially centered about the center point, wherein the subsequent pair of drivers are spaced such that the center to center distance between each driver in the subsequent pair, dn, is equal to 4nd0, where n=0 at the innermost pair of drivers and n increases by 1 with each pair of drivers sequentially added. Each pair of drivers for n>0 has a first order low pass filter with a frequency equal to 2c/dn.