^ Maybe my modification of a Mylar NAD RP-18 will help with your Kapton version.
NAD RP-18 Mylar Version: Repairs and Modification
Replaced cables below Y-splitter, re-soldered connections, and added new heat shrink.
STAX Micron Glass Wool over back of drivers = 45mm disks.
Treble Reflecting Ring with 35 mm opening over STAX Micron Glass Wool (from eBay Germany).
55 mm soft felt disk over inside of grill and new speaker grill cloth.