For piano gloss finishes I have tried the detailer sprays from Mothers and Mcguires . The best results though I have had for streak free clean shine is Pledge multi surface cleaner . The trick is , don,t spray it on the surface of the speaker . Use a good clean micro fibre cloth for polishing autos , spray it on the cloth . Keeps the NHT 2.9s I have always looking new . Cheers
