Patent ID: 7697701

Claim:
A loudspeaker, comprising: a sensor for the determination of the radiation resistance of a diaphragm, the radiation resistance expressed by the velocity/acceleration of the loudspeaker diaphragm and the sound pressure in a distance from the diaphragm, and thereby, via a signal processing unit, provide a control signal to a filter unit adjusting the performance of the loudspeaker in an adaptive manner to the acoustical characteristics of the listening room, said sensor comprising a microphone for detecting the sound pressure in at least two points differently spaced from the diaphragm; a carrier means enabling the microphone to be effectively and successively exposed to the sound pressure in each of the at least two points; in which the sound pressure is detected in a first point relatively close to the diaphragm, and in a second point further spaced from the diaphragm, and in which the signal processing unit operates to calculate the real part of the product of j (square root of minus 1) and the ratio between the sound pressures in the second and the first point, respectively, and wherein a first microphone is stationarily mounted in a first position and a second microphone is mounted so as to be physically displaceable between at least one second position and a third position in close proximity to the first microphone in the first position, both of the first and second microphones being connected to a calibration unit in said signal processing unit.