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

audio equipment magnetic system soviet dynamics 20gds3 disassembled speaker midrange core coil basket foam rubber glue suspension diffuser repair 20gds 15gd11 cap magnet ferrite vintage frequency revision upgrade professional tweeter ussr music radiotehnica grids view player small dynamic turntable back radio factory midfrequency circle power conceptual bass reflex metal musical technology subwoofer