magnetic system of the soviet speaker 20gds-3. disassembled mid-range speaker

15gd11 20gds 20gds3 analog ancient audio basket cabinet cap classic coil conceptual core device diffuser disassembled driver dynamics equipment ferrite foam frequency glue grids magnet magnetic membrane midfrequency midrange object obsolete old professional repair revision riga rubber smartphone soviet speaker studio subwoofer suspension system turntable tweeter upgrade view vintage wooden