Loudspeaker lower bass response using negative resistance and impedance loading

TLDR: In this article, an apparatus and a method for improving the bass response characteristics of an electrodynamic loudspeaker is described, where an electrical network through which electrical energy corresponding to the sound to be reproduced is applied to the voice-coil of the loudspeaker.

Abstract: An apparatus and method for improving the bass response characteristics of an electrodynamic loudspeaker is described. The loudspeaker normally exhibits actual mechanical parameters such as damping, compliance, and mass which normally determine the bass response and lower cut-off frequency of the loudspeaker. The method and apparatus of the present invention cause the loudspeaker to exhibit apparent mechanical parameters which differ from the actual mechanical parameters to substantially change the effect of the actual mechanical parameters on the bass response. The apparatus in a preferred embodiment includes an electrical network through which electrical energy corresponding to the sound to be reproduced is applied to the voice-coil of the loudspeaker. The electrical network has an effective output impedance including a negative impedance in series with a plurality of impedances connected in parallel. The value of the negative impedance (including negative resistance) is chosen to be substantially equal to the impedance of the voice-coil. The plurality of parallel impedances have values which cause the loudspeaker to exhibit apparent mechanical parameters which are substantially different from the actual mechanical parameters in the bass response of the loudspeaker.