Years ago car dealers used to take a car with cigarette smell, put a large can of new coffee grinds in the can (before Starbucks), cut apple slices and lay on top of the coffee. Sounds crazy but I tried it and it worked. Takes 3 to 4 days. Works better if its has some heat (sunlight) to make the odors more intense. I know this sounds off the wall but it wouldn't be invasive to your speakers. Good Luck!
JJ
JJ