A shaped piece of high permeability metal, usually soft iron, which serves to concentrate and direct the magnetic field of a permanent magnet to maximize efficiency of devices like loudspeakers, magnetic cartridges, and cutterheads. Pole pieces are needed because magnets are hard (expensive) to make in the complex shapes that can be needed. In layman’s terms, the Pole Piece is the part of the speaker magnet assembly that the voice coil (see WFTD archive voice coil) slips over. It is the center round piece. Guitar and bass pickups work on similar concepts, though the function is the opposite of a loud speaker. Instead a guitar pickup’s job is to turn mechanical vibration into electrical output. Magnetic guitar pickups often have individual pole pieces positioned under each string to help maximize or otherwise tailor their output.