Dog pissed on speaker

As long as the dog stays you have only  Two options:

Train the dog to stay out of the room. Always.-Invisible fence.

Cover the speakers. 

Meantime buy a new driver and consider the fence option.

Yes he will do it again. In the same spot too!

The Urine-Off enzymatically changes the source of the order, it does not cover it up. Covering it up doesn’t work! This does. Something I deal with a lot (not on audio gear but in homes). You could replace everything but I would try the hand spray version of this first. You can also spray it on a cloth and wipe down the areas you want to control moisture with a few applications.

Try mild blow of Hair dyer for long hours, Try talcum, Chickpea flour, activated charcoal even Soda ash But don't forget brush it off/ careful vacuum or air blowing. Don't use fine powder but rough powder, if not readily available sieve it your self. IPA/glass cleaner( may harm impregnated resin OR coat) smell Masking agents like vinegar/ scents. But try everything mentioned on near similar paper doped with dogs urine if result is satisfactory go ahead with care in horizontal position for many hours until you are happy with result.

Who allows a piddling dog inside the house? My terriers NEVER peed indoors. True, I could use only wall-mounted bookshelf speakers, but that was because of the cats, who would scratch anything if you displeased them by, say, leaving home for too long. At least they used their box as per training, except that time they pooped on our pillows to express their displeasure.