A loudspeaker driver 100 with new horn throat configuration 120 has a phase plug summation plane radius that is also the effective throat of the driver. The selected plane “D” where the elements of the horn that provide directional information to the wave front are implemented is made part of the geometry of the magnetic return circuit back plate 108. The portion of the back plate that is coincident with the selected plane “D” has a lumen or opening that is made equal to the radius of the circle defined by the phase plug summation plane. The geometry of the back plate's lumen controls projected sound's radiation pattern.