The present invention generally relates to an improved process for the hydrothermal conversion of coral into hydroxyapatite, a process for coating an object with hydroxyapatite, a process for coating an object with a divalent metal phosphate and uses of objects prepared by these processes. The satellite signals travel along a satellite signal route within a look angle about the centerline of the antenna. Sound generated by the woofer emanates to a surrounding environment through both the woofer chambers, wherein the enclosure defines a plurality of venting holes communicating with the other one of the woofer chambers.