Posting so that someone in need might find this. I picked up a pair of B&W Preference 5's the other day for cheap, and in playing them against my Polk Rti 12's, they were getting kicked all over the schoolyard. It wasn't pretty. Turns out the tweeters were offline. No cheap fix either, B&W wanted $112 per tweeter, and repair seemed impossible. Fortunately their site had good detailed support info, plus I learned the issue was the ferrofluid would gum up over time, sticking the voicecoil in place. So I was able to remove, disassemble, repair and reinstall those suckers, work fine now, much more competitive!
Repair goes something like this: Rotate the faceplate with the help of the teeth, to counterclockwise about a half inch or so, it will be obvious when it is unlocked, then carefully pull on the tweeter cover to extract the unit from the cabinet. CAREFUL! Unplug. Now remove the clamp. You're now holding the tweeter assembly. CAREFULLY separate the two pieces, do NOT pull forcefully - that is the voicecoil in black and it's stuck in the gunk of the magnet (the problem). Once separated, you can now clean the gunk out of the magnet side to your heart's content, and here you don't have to be that careful (ever try to damage a magnet?). In fact, remove the top piece of the magnet (with the hole), clean all that crap out. A little oil won't hurt. Now, important.... you must center the magnets again, leaving room on the perimeter for the voicecoil to fit. This will take a little playing, but you don't have to be careful. Once done, reassemble, you're good to go! A completely renewed B&W P5 or B&W Preference 5 speaker system.