Sean,I always wondered about that. The original foam wasn't like the replacement and it did result in an audible difference and I can't really say for the better.
Simplyspeakers says these are OEM replacement woofers. However, the magnet structure is round instead of square. Also, the visible spyder wires on the outside center of the cone cap are sealed instead of visible wire showing. I know there were production changes over the last few years right before Advent was bought out and then right after that. I don't know where these fit. I'm sure Ken K. would know this also. These woofers do resemble the units out of the "New Advent", not the original version.
I have been using a pair for a while and I'm not sure of the verdict. I have a pair of originals that are still usable but they are old and the foam is fragile. I'm afraid to use very much volume on them.