Originally Posted by
grumpy
The JBL p/n (61098) for those little blue caps are polypropylene.
No one would use ceramic caps for bypassing larger values in a crossover.
Definitely replace the L-pads if you have them in-hand.
If you're hell bent on replacing the caps, you could both get higher quality
capacitors (obviating the need for the bypass caps at all), and double up
on the values of the yellow ones and get two of each: to replace each single
cap with a pair in series. Then introduce a dc bias voltage (9v battery works)
through a several-Mohm resistor to the point between the caps. Google
"charge coupled crossover" or "dc-biased crossover".