I have seen a few JBL woofers with multiple serial numbers, usually stamped above the original number on the foilcal. And I recently came across a 130A with a foilcal that appeared to be a little messily glued on and a sticker on the back stating:
NOTE: The serial number of your
speaker has been changed to enable
updating to the standards of our
most recent production models.
Does anyone know why this was done?
Was this a case where the magnetic gap had to be re-machined to allow fitting of a new recone kit?