Apparatus and instruments for conducting, switching, transforming, accumulating, regulating and controlling electricity; electronic entertainment apparatus, especially apparatus for reception, recording, transmission and reproduction of sound and images; electric, electronic, electro-acoustic and optical amplifiers, amplifier cables, adjusted amplifier enclosures, headsets, loudspeakers, loudspeakers with integrated amplifiers, loudspeaker systems, loudspeaker boxes, sound systems, enclosures...