A speaker unit for headphones including a magnetic circuit which has a magnetic gap and including a diaphragm which is moveable to generate sound in response to energy applied to a coil wound on a bobbin which is connected to the diaphragm and mounted within the magnetic gap and including a frame for supporting the magnetic circuit and the diaphragm and a protecting means mounted at the front of the diaphragm and having projections so as to engage the diaphragm near the region where the bobbin is mounted so as to limit the maximum motion of the diaphragm and the protecting means formed with openings such that the protector prevents the bobbin from moving completely out of the magnetic gap. The invention is applicable to speaker units for open air type headphones, for example.

A loudspeaker having a flux gap defined by central pole and a magnet surrounding the central pole, includes a plurality of low-friction ridges extending from an outer surface of a the central pole. A voice coil, connected to the loudspeaker's diaphragm, is free to reciprocate within the flux gap. The ridges are linear and run generally in an axial direction, along a length of the pole where the voice coil reciprocates. Instead of rubbing directly against a metal pole, which has relatively high friction, the voice coil will rub against the ridges, thus reducing some of the noise that would otherwise occur due to rubbing. The voice coil includes a relatively stiff structure, created in part with a ceramic or epoxy material, that is coupled to a diaphragm, and a relatively flexible multiple layer structure at the terminating free end having dampening properties.

A method of and a device for attaching a speaker to a synthetic resin body having an opening in which the speaker's elevating edge of a cylindrical shape integrally formed at a tip end portion of a metal frame, is confronted with the synthetic resin body so as to surround and close the opening. The elevating edge is heated and the speaker is pushed toward the synthetic resin body side, the synthetic resin body is fused by heating at its location where it contacts the heated elevating edge and the elevating edge is fitted into the synthetic resin body by a pressing force, whereafter the speaker is attached to the synthetic resin body by solidifying the synthetic resin body after the heating has been stopped.

An electromagnetic loudspeaker with a magnetic structure provided with a cylindrical gap and a frame supporting a diaphragm, the diaphragm carrying a voice coil suspended in the gap of the magnetic structure, the magnetic structure being provided with a thin coating of plastic such as teflon or nylon confronting the voice coil to prevent abrasion or shorting of the voice coil in the event the voice coil contacts the magnetic structure.

A speaker of a type having a voice coil wound to a greater length than the length of a magnetic gap into which it extends formed between a pole of a yoke and an annular plate. A magnetic flux density setting structure is provided for establishing a constant value of Bl, where B represents the density of the magnetic flux capable of linking the voice coil and l represents the effective length of the voice coil. The magnetic flux density setting structure may be formed as a tapered surface or surfaces on the pole of the yoke or by a separate tapered plate or plates attached to the annular plate. Further, a metal cap is mounted on the pole covering an upwardly facing cup-shaped body of magnetic material.