Home audio speakers, such as the Dayton Reference series, come with "bucking magnets" on the back of the speaker, directly behind the speaker's magnet.
Bucking magnets are added to home audio speakers for video shielding. Due to the high strength of some speaker magnets, the stray magnetic flux of those magnets can actually screw up the picture of some televisions, computer screens, etc. So, they add a bucking magnet to those drivers, which is basically another magnet "out of polarity" with the speaker's magnet, thus canceling out that stray magnetic flux allowing you to place them within close proximity to TV's, etc.
However, this bucking magnet adds to the depth of the speaker, obviously undesireable for car audio people concerned with depth. So they "debuck" the speaker, by forcefully removing the bucking magnet.