A dipole loudspeaker with a balanced directivity pattern.
Analytical equations describing radiation characteristics of an oscillating ring in a circular finite baffle are derived, including the limiting case of a dipole point source at the center. An oscillating sphere would represent the ideal dipole source, having a constant directivity pattern at all frequencies, but would be inconvenient to realize especially in portable devices. It is found that a planar piston with uniform surface velocity but variable phase arranged to emulate the sphere does not have such a smooth on-axis response as the sphere. Instead a planar piston with the same phase distribution but uniform pressure represents an ideal planar source with a smooth on-axis response and near constant directivity. The surface velocity is plotted and it is then shown that a similar response can be achieved using a finite number of concentric rings based on this velocity distribution.
Nokia UK Ltd, Nokia House, Summit Avenue, Farnborough, Hants GU14 0NG, United Kingdom. tim.mellow@nokia.com
Tim
T
Mellow
Leo
L
Kärkkäinen
D000162:Acoustics / Q000295:instrumentation*; D000669:Amplifiers, Electronic; D004867:Equipment Design; D008962:Models, Theoretical; D013499:Surface Properties; D013685:Telecommunications / Q000295:instrumentation*