Once upon a time, many years ago, we bought a pair of used, Gauss loaded, 18" reflex bins. As we used them over time we noticed that one sounded better than the other. Having a quick look we noticed that one of the speaker cones was wet. Very strange we thought, that's why it sounds weird. Took the speaker out and dried it in the sun and it sounded OK. Next gig it sounded strange again, checked and the speaker was wet again. We bought a hair dryer and stood it in the reflex port to dry out the speaker on every gig and by the end of the gig the speaker was wet again. We asked the good folks who had sold us the speakers if they could throw any like on this wet speaker problem and they said that it must be where their cat had taken a piss inside the cab all over the speaker.
Talking to someone about this they said that the salts in the cat's pee attracts moisture and so we would never solve the problem and we never did.
I don't know if this explanation is true but it made a lot of sense at the time, I hope that dog's pee dosn't have the same properties or it's new speaker time.
Then there's the time that my pet labrador ate the speaker in our guitarist's AC30, but I'll save that for another time.