There’s your answer , I recently finished upgrading a pair of older Klipsch
the capacitors get dryed out and start loosing their harmonics it just gets worse
I replace the resistor so with much better quality then the old cement typeresistors which are gritty , and the stock capacitors in most speakers under $15k is nothing special. I learned upgrades when I owned a Audio store
go to Humble homemade hifi capacitor test, you should pul a bass driver out and take a picture, if you are lucky the wires from the Xover are just slide on terminals
where you can remove the Xover ,if not it’s soldered-in place . If you like them and plan on keeping them that’s what I would do first ,upgraded Xovers sound much better then stock parts ,it’s Like going from a stock engine to a Hot rod.