Almost all components such as those used in crossovers fail catastrophically, that is to say they open or they short out. Rarely will this kind of failure result in a degradation of sound, mostly the sound from that driver just quits. Not always, many here will think of examples where this might not be true but driver failure is really quite common.

So, odds are that the driver is damaged, recone services are easy to find (just type "recone speaker" into Google for example).

There are people who have done this recone themselves, it requires a great deal of manual dexterity and a good supply of tools. The drivers could be replaced by more modern ones but most liklely the crossover design would need to change. Given your original question you may not have the background or desire to learn this stuff.

Many here and on the DIY site will help, if you have the patience and time. One problem is finding the truly knowledgeable as opposed to those who merely think they know (moi? )