A loudspeaker has a diaphragm with a voice coil disposed about its perimeter
and
extending in a gap into which the flux of an annular rare earth magnet is focused.
An opening behind the diaphragm communicates through the speaker frame. The voice
coil may have two or more windings that are connected in parallel, and may, e.g.,
be layered on top of one another, so that the impedance of the coil, as well as
its depth in the front/back direction of motion, are low. The voice coil is preferably
implemented using a polyamide form or bobbin, which has patterned lead-in conductors
embedded therein to bring power to wire windings on the perimeter of the coil.
The lead-in conductors extend to, or through, the central opening of a ring magnet,
providing a robust ribbon input connection.