No, it’s not.  Using speakers that aren’t rated for outdoor use would void the warranty.

That doesn’t mean you can’t bring it out for temporary use under good conditions, but placing the speaker outdoors would expose it to temperatures, moisture (or lack there of),   or getting knocked around, that it isn’t designed to handle. Placing under cover will help, but it still can shorten the life or cause it to fail early. 

Moderator edit: Corrected typo “voice” to “void”