The process:
"The System" Installation
964 System Door speaker installation-tweeter mounting:
This is the Nakamichi tweeter mounting cup. Take a pair of pliers and bend the outer part just a bit to make the overall diameter a bit smaller. On the Focal tweeter cups, file the opening in the factory tweeter mount a bit larger, then the cup will slide in from the front.
The tweeter can now be mounted in the tweeter cup and it fits into the rear of the factory mounting ring. Make sure you know which is front and back! Fit the tweeter into the metal mounting cup, then simply snap it into the factory tweeter mounting ring in the same fashion that you unsnapped the factory tweeter.
All Done!