Abstract: A loudspeaker grille made of stiff material such as stiffened grille cloth, has at least a major proportion of the length of its edge so shaped that, when seen in cross section, one part extends rearwardly, approximately perpendicularly to the plane of the grille, and another part returns forwardly again from the rear edge of the first part and at an acute angle to the first part so as to present a free edge lying to the rear of the plane of the grille and outwardly of the first part. Both parts of the edge portion, when seen in cross section, may be straight and define a generally V-shaped configuration of which the included angle may be between 30 degrees and 45 degrees prior to fitting the grille in position in a loudspeaker. The edge portion is then held in a groove in the housing of a loudspeaker as a result of the resilience of the edge portion.

Abstract: In a moving coil loudspeaker of the type including a pair of co-axial speech coils, one driving a cone and the other a high-frequency diaphragm at the rear of the loudspeaker, the speech coils operating in respective annular air gaps in series with one another and formed in a magnetic assembly comprising an outer ring magnet, a pair of annular magnetic plates fitted at the ends of the ring magnet and a central magnetic pole piece formed with an axial passage defining a horn for the acoustic output of the diaphragm and extending into the openings in the annular plates to define the two air gaps, the central pole piece is formed with an encircling flange forward of its rear end which is secured to the rear annular plate by way of a non-magnetic member to constitute the sole fixing for the pole piece.

Abstract: A moving coil loudspeaker of the type including a pair of co-axial speech coils, one for driving a high frequency diaphragm at the rear of the loudspeaker to provide an output along a horn and the other for driving a cone forming a continuation of the horn and reproducing the lower frequencies has an acoustic lens fitted in the region where the horn contour is taken over by the cone, the lens being shaped over its external surface so as to conform snugly with the contour of the cone and being effective to increase the divergence of the beam of acoustic radiation from the horn in the operative plane of the lens. The acoustic lens is preferably so designed that the divergence of the acoustic beam from the horn matches that from the cone and may be of the slant-type, being held by a cruciform mounting extending across the mouth of the horn proper.