Abstract: A surround sound processor system for multichannel redistribution of stereophonic signals has digitally controlled gains in each input and each output channel, controlled by a microprocessor, which receives an input signal from a microphone placed at the preferred listening location within the listening area for automatically balancing the input signals and setting both input and output gains during a calibration process so as to provide the listener with the best possible surround sound reproduction of the stereophonic source material. As a visual aid, the microprocessor displays menus and messages on a video screen, and a visual display shows the relative levels of the six axes of control signals within the surround sound processor.

Abstract: A filter cartridge of the type made from a sheet of filter paper pleated as an accordion on a cylindrical surface. It is produced by pinching pairs of contiguous pleats at various levels in order to make on the outer surface of the cartridge a plurality of honeycombs. The invention results in substantially prolonged life of the filter cartridges, which have applications in a variety of uses, including regeneration of solvents of washing baths for dry cleaning machines, filtration of air for internal combustion engines and water filtration.