soviet made 20gds-3 speaker diffuser caps. spare parts from the speaker. dust cap

audio equipment cap dustproof shiny paper midrange speaker suspension diffuser repair 20gds3 20gds 15gd11 basket coil magnet ferrite vintage frequency revision upgrade soviet professional tweeter studio sound technology monitor driver preservation detail 1985 back old radio factory record conceptual antique device listen style speakers object engineering vocal electroacoustic hifi