an antique soviet woofer 5gd-3 from vintage acoustics symphony

symphony acoustics vintage perforation cardboard cap resonant frequency rare antique resistance gray cast case bracket cobalt alnico shielding radio soviet woofer speaker 5gd3 old cases speakers retro 1960s 60s 70s lamp system funky sound tape recorder broadcasting mass media desk microphone volume stereo play plywood veneer singer fm helmholtz resonator varnished interview threeway