tiapetra

I read here that the speakers were prone to moisture damage. I replaced all 4 with plastic coned Fosgate cheapies to help prevent any future issues.
I didn't realize the extent of the water intrusion. The car was parked outside during a mild rainstorm. The left rear new speaker wasn't working so I pulled the door panel again and found this amount of water on the speaker baffle. This is a lot of water for a 15 minute shower. The car is in great shape and the weatherstripping looks like new, still soft and pliable.

Ultimately it was the connector that was the problem. Contacts had oxidized obviously from the water over time.
I ended up putting the connection inside the baffle as well.

Besides supposedly bettering the sound, these baffles are a godsend for speakers and I will religiously use them going forward.

sleeper

Not sure where your point of water entry is, but:

Many years back here, we used clear silicone to seal around the wiring boots that led into the doors & also on around the door jamb wiring boots.

Mine is still sealed well. Clear so it's can't even be seen.

And use Dielectric grease on the speaker connections for good measure.

donbrew

Used to be they used felt or rubber to seal the outside of the window, now it is a bit too stiff and not very plush so water runs right through it.

That and when the door trim panel is put back on by somebody in a hurry it does not put enough pressure on the inside to press against the seal.