But if the driver was bad, I would think it would make rattles on all notes and not just one. What he's got going on is sympathetic vibrations. I'm thinking that some of the padding on the inside has come loose and is flapping around there but it only makes noise on that note. You can take a speaker out and check the padding and reattach any loose pieces with a staple gun or double sided carpet tape. However, being new and all, it's something you shouldn't have to fix, plus if you do it and it still doesn't work, it could void the warranty, so the safe thing to do is exchange it.
One thing you could do that won't void the warranty is check and make sure all the screws in it are firmly screwed in. Pop the grill and check the speaker screws, too, and snug them up but don't overtighten, otherwise you can bend the speaker frame.
One thing you could do that won't void the warranty is check and make sure all the screws in it are firmly screwed in. Pop the grill and check the speaker screws, too, and snug them up but don't overtighten, otherwise you can bend the speaker frame.