Many years ago shortly after I got my speakers I noticed a buzzing sound during certain musical passages that had a high content of upper midrange. Finally I localized it to the left speaker. I swapped channels and it stayed with the left speaker. After some critical listening I pinned it down to the upper midrange driver. I removed it from the cabinet and saw the paper part number tag hanging over the edge of the speaker magnet. I tore off the loose end and reinstalled the midrange driver.
Voila! No more buzzing.
All this because some schmoe couldn't do his job.