Patent ID: 7702114

Claim:
A transducer for producing sound in response to an audio signal, the transducer comprising an actuator, and a vibration surface mechanically coupled to the actuator, the actuator comprising a magnet and a coil, wherein the transducer has a moving mass selected such that a resonance frequency of the transducer is within a desired frequency range, wherein the desired frequency range is the low frequency audio range substantially between 20 Hz and 100 Hz, wherein the transducer is configured to have a peak input sensitivity of the transducer occur substantially at resonance frequency, and wherein the actuator has a force factor which is equal to the product of a magnetic flux in the coil and a length of the coil, and further wherein for the transducer to have a peak input sensitivity of the transducer occur substantially at the resonance frequency, the ratio of (i) the force factor squared and (ii) the product of (a) electrical resistance of the coil and (b) mechanical resistance of a suspension of the transducer is (iii) greater than 0.6 and smaller than 1.4.