LOUDSPEAKER ASSEMBLY

Abstract: The assembly has a moving cone (4) which is mounted with its apex towards the desired direction of sound propagation. The cone (4) is driven by a moving coil (13) in the field of a central magnet (7) acting via pole pieces (6) and (8).

Description: LOUDSPEAKER ASSEMBLY The present invention relates to a loudspeaker assembly in particular,, but not exclusively, for use in high fidelity sound reproduction. t In conventional loudspeakers., the cone is mounted such that the cone apex points in the opposite direction from desired sound waves. This normally requires that the magnet assembly is mounted on a bell-shaped chassis. This chassis has to be strongly built and is a costly item. This bell-shaped chassis, known just as the chassis, will nevertheless possess inherent weaknesses for loudspeaker performance due to its bell shape and the fact that the heavy magnet assembly is mounted on the rear of this chassis whilst the whole unit is mounted to the cabinet from the front outer flange. The chassis resonates and produces distortion. This results in increased materials and assembly time, which, in turn, increase the cost and weight of the loudspeaker. In addition, with such cones, a tunnel effect is produced, which also introduces distortion. The object of the present invention is to obviate or mitigate these disadvantages. According to the present invention, a loudspeaker assembly is provided having a cone portion, said cone portion being mounted with its apex extending in the direction of intended sound travel, said cone portion being mounted by suspension means, such that said cone portion is caused to vibrate in response to electrical signals passed through a coil which is placed within a magnetic field. Preferably, said loudspeaker assembly includes a magnet and a first pole piece, said first pole piece having a generally elongate portion, said magnet and said first pole piece being arranged such that the elongate portion extends along the cone axis. Preferably also a second pole piece is connected to the magnet assembly,, the * second pole piece producing a magnetic circuit with gap between the elongate first pole piece portion and the second pole piece, and the magnet assembly and the cone portion being mounted 5 in substantially the same axis. Preferably also, the second pole piece is generally cone-shaped to reduce the length of the speaker coil former. Preferably also, said cone portion is supported τ_0 by first and second cone suspension means, said first suspension means extending axially from the end of the elongate portion of the first pole piece, and said suspension means mounting the cone portion to the surround means. 3 ^ 5 Preferably also, said second pole piece is mountable onto the loudspeaker surround and cabinet. Alternatively the loudspeaker is attached to the cabinet by an extension of rear or first pole piece. Preferably also, a coil is located within said 2o cone, said coil being arranged around said extending member. Preferably also, said first pole piece includes a disc portion, said disc portion having at least one aperture therein to permit the passage of air there- 25 through in response to movement of the cone portion. Preferably also, the apex of the loudspeaker cone is truncated, said apex being covered by a membrane, which may or may not permit the passage of air. Preferably also, the second pole piece and the 3 Q magnet are secured to each other and to the surround by a ceramic anaerobic adhesive compound or by other suitable fastening means such as glues, screws, bolts etc. Embodiments of the present invention will now be described by way of example with reference to the 35 accompanying drawings which are a cross-sectional view of a loudspeaker assembly in accordance with the present invention. Referring now to the * Fig. 1, a loudspeaker assembly comprises a cabinet 2 and a speaker portion 3. The speaker portion 3 comprises a cone 4 which is mounted by a rubber surround 5 onto a pole piece 6. The pole piece 5 6 contains apertures 6a by which it may be secured to the cabinet or baffle 2. The baffle 2 has a circular aperture 2& in which is located a long-shaped magnet 7 of square cross section. A second pole piece 8 is secured to the magnet 7, the second pole piece 8 being 10 disc-shaped and having an elongate portion 8a_ extending from the centre of the disc along the cone axis towards the apex 4a_. The pole piece 8 has a plurality of apertures 8b_ therein to allow the passage of air from inside the cone ' to the exterior during movement. 15 The cone 4 is mounted by two suspensions 9 and 10. Suspension 9 extends from portion 8a. which engages a stiffened porous felt pad 11 located at the apex 4a. of the cone. Suspension 10 is the standard type of spy er. An anaerobic ceramic adhesive compound is used to secure 20 the suspension 10, the pole piece 6, and the magnet 7 together. The ceramic adhesive may also be used to secure the pole piece 6 to the magnet 7 and the magnet 7 to the pole piece 8. The loudspeaker coil 13 and . electrical terminals 14 are located within the cone 4 25 and are mounted over the portion 8a and the suspension 10. In use, in response to electrical driving signals, the coil and cone 4 is caused to vibrate and sound energy is emitted principally in the direction A with accoustic dispersion which is generally dome-shaped and which has 30 no tunnel distortion. S In the embodiment shown in Fig. 2, the second pole piece 8 is mounted on the baffle 2. The first pole piece 6 is ring-shaped and has a rectangular cross-section. The suspension 10 is mounted on a ring-bracket 10a mounted 35 on the pole piece 6. Otherwise the construction is the same as the first embodime'nt and like numerals denote like parts. Without departing from the scope of the invention various modi ications may be made to the apparatus as hereinbefore described; the magnet 7 and the pole piece 8 may be other than disc shaped; the suspensions 9 and 10 may be arranged in a different manner although remaining consistent with the desired performance of the cone when driven, and the pole pieces 6 or 8 may be secured to the surround by any other suitable fastening means such as adhesive, screws or rivets. Advantages of the preferred embodiment of the invention include; distortion is reduced by eliminating the tunnel effect, the structural arrangement of a cone is retained, with improved dispersion characteristics * and few of the disadvantages of a dome, the mechanism is coupled to the cabinet and surround directly close to or at its centre of gravity providing improved sound balance and audio characteristics such as linearity, and the braced heavy bell-shaped chassis is not required which makes such loudspeakers more economic. or

Claims: * CLAIMS 1. A loudspeaker assembly having a cone portion, said cone portion being mounted with its apex extending in the direction of intended sound travel, said cone ■ * portion being mounted by suspension means, such that said cone portion is caused to vibrate in response to electrical signals passed through a coil which is placed within a magnetic field. 2. The assembly of claim 1, including a magnet and a first pole piece, said first pole piece having a generally elongate portion, said magnet and said first pole piece being arranged such that the elongate portion extends along the cone axis. 3. The assembly of claim 2, in which a second pole piece is connected to the magnet assembly, the second pole piece producing a magnetic circuit with a gap between the elongate first pole piece portion and the second pole piece, and the magnet assembly and the cone portion being mounted in substantially the same axis. 4. The assembly of claim 3, in which, the second pole piece is generally cone-shaped. 5. The assembly of any of claims 2 to 4, in which said cone portion is supported by first and second cone suspension means, said first suspension means extending axially from the end of the elongate portion of the first pole piece, and said suspension means mounting the cone portion to the surround means. 6. The assembly of claim 3, in which said * second pole piece is mountable onto the loudspeaker surround and cabinet. 7. The assembly of any of claims 1 to 5, in which the loudspeaker is attached to a cabinet by a rearward extension of the first pole piece. 8. The assembly of any preceding claim, in which - 6 - * said first pole piece includes a disc portion, said disc portion having at least one aperture therein, to permit the passage of air therethrough in response to movement of the cone portion. 9. The assembly of any preceding claim, in which the apex of the loudspeaker cone is truncated, said apex being covered by a membrane. 10. ^ he assembly of claim 9, in which the membrane is permeable to air. 11. The assembly of claim 9, in which the membrane is impermeable to air. 12. The assembly of claim 3, in which the ^ second pole piece and the magnet are secured to eaάh other and to the surround by a ceramic anaerobic adhesive compound. O F

Inventors: TIEFENBRUN IVOR SIGMUND, TIEFENBRUN, IVOR, SIGMUND
Applicants: LINN PROD LTD, LINN PRODUCTS LIMITED
Application year: 1982
Main classification: H04R9
IPC codes: H04R9