[GaryProtein]

When a speaker is designed and sold with a removable grille, the designer would have to know that grills "on" or "off" would be an option for the purchaser. If they design the speaker with a grill, it would seem they expect it to be "on" and that it would be acoustically transparent, or else the frequency response of the speaker would be affected, especially for the upper midrange and tweeters. Of course, if the grilles are acoustically transparent, and modern grills are usually very fine, thin material, the question of "on" or "off" becomes one of esthetics. The old days of heavy tweed cloth grills are gone!