Good question. I have read at least 20 posts on various forumns concerning this very subject, 10 say they must be re-magnetised and ten say that is bunk. Anyone out there want to do a hit and run on this? And while your at it any references that anyone might be familiar with that address this subject of rare earth magnets vs. ferrous metals? What about magnet strength; can there be too much magnet for a driver? Does the magnet effect the speed of the cone? Isn't the magnet combined with the cone material and designed to be underhung why Fostex and Lowther's as well as the old JBL 8" and Diatone drivers sound so lifelike?