Opened up the RS1 for a collegue who ask me to upgrade the crossover. Tweeter cap was replaced with mundorf silver in oil and mundorf silver/gold wire.
After the change, the hardness in sound was right away gone. Sound was more open, cleaner and clearer. Currently the speakers are still under break-in but my collegue is already very happy with the outcome.
The bass/mid driver is using plastic frame. The tweeter are quite small.
Closer view of the drivers.
Crossover.
Original caps (6uf) vs. Mundorf silver in oil (5.6uf)
Mundorf installed.