+1 for checking with the manufacturer. I would try a good carnauba paste wax. I use it on my wood finish speakers and they are easy to dust and keep clean. There is some British paste wax that's supposed to be best for speakers and I don't recall the name but I just use good ole' SC Johnson.
http://www.whatsinsidescjohnson.com/us/en/brands/sc-johnson/sc-johnson-paste-wax
http://www.whatsinsidescjohnson.com/us/en/brands/sc-johnson/sc-johnson-paste-wax