moving system of the mid-range speaker 20gds-3 of soviet production. diffuser and magnetic coil speaker

15gd11 1985 20gds 20gds3 amplifier audio basket bass broadcast cap coil conceptual detail diffuser dynamic electronic enjoy equipment factory ferrite frequency magnet magnetic midrange mobile music power production professional radio radiotehnica recording rectangular reflex repair retro revision sixties sound soviet speaker studio suspension system technology turntable tweeter upgrade ussr veneer vintage woofer