high frequency speaker soviet-made 3gd-31, 5 gdv-1-8 . revision and repair of vintage acoustics

15as208 3gd31 acoustics ancient antique antivibration audio bass car carbon case design dirty disassemble driver exfoliated fiber frequency gdv18 glue high interior media membrane midrange monitors music panel paper passive pva radiator restoration revision revival russian sealing silk small soviet speaker studio system tweeter twitter ussr vega view vintage weave white wooden