Hi Gary,
I had refinished the speakers a few years ago and had stained them Walnut. When I did that refinish I used 300 grit sand paper to take off the oak oil, sticker residue (yes stickers...these speakers were owned by a college radio station that I ran prior to me acquirering them), and sand down other blemishes.
For the recent refinish, because they were mostly smooth at that point, I used 180 grit sand paper to rough up the wood and remove some of the stain so the paint would adhere.
For paint I used two coat of Rust-Oleum American Accents flat black smooth finish latex paint and three coats of Cabot fast drying super clear semi-gloss brushing lacquer.
I did not need to sand between coat of paint or lacquer. I did the entire process inside to cut down on dust. (Just besure to open a window in the house because the lacquer is a killer.)
Thanks,
Mike