Apparatus for recording, transmitting and reproducing sound; electroacoustic transducers; loudspeakers; control units for loudspeakers; loudspeaker systems; signal processors for audio loudspeakers; loudspeaker couplings; loudspeaker stands; cabinets for loudspeakers; racks for loudspeakers; mounting brackets adapted for loudspeakers; loudspeaker cables; loudspeaker plugs; loudspeaker switches; cases for loudspeakers; horns for loudspeakers; loudspeaker acoustic screens; earphones; headphones...