Nokia Technology Gmbh

Harman Audio Electronic Systems Gmbh

Stefan Geisenberger

Manfred Aigner

Gerhard Krump

A loudspeaker ( ) according to the invention is presented, which contains at least one radially magnetized permanent magnet ( ), and whose receiving part is made of a paramagnetic or diamagnetic material. Such loudspeakers ( ) can be constructed in a very simple and compact manner. With the further development of loudspeakers ( ) able to utilize the stray flux from radially magnetized permanent magnets ( ), it is possible to produce derivations with two diaphragms ( &prime;) with identical reproduction frequencies, without great cost.

Loudspeaker having radially magnetized magnetic ring

A loudspeaker (10) with a magnet system (12) arranged in a space (32) surrounded by a conical diaphragm (14) has a core (20) of the magnet system (12) first connected to the loudspeaker basket (11) and only then is the pot (19) connected to the core 20. It is then possible to manufacture loudspeakers (10) with internally located magnet systems (12) on production lines which can also be used to manufacture loudspeakers with magnet systems (12) that are located on the outside of the basket (11). Because the pot (19) is only installed later in the core (20) a centering bushing (34) can be placed between the core (20) and the voice coil support (18), which leads to a considerable improvement in the production quality of such loudspeakers (10).

Loudspeakers

According to the state of the art, most centering diaphragms (10) for loudspeakers are made of paper, plastic or textile material. These centering diaphragms (10) furthermore have plastic resin coatings. The attachment of the centering diaphragms (10) to the remaining loudspeaker components is mostly made by adhesive bonding. Although such centering diaphragms exhibit good characteristics at low temperatures, they can no longer be used when the ambient temperatures are above 150.degree. degrees Celsius. The invention therefore proposes to make the centering diaphragm (10) for loudspeakers of metal. If the centering diaphragm (10) is subdivided into at least two individual components (10.1 to 10.4), these individual components (10.1 to 10.4) can be used as contact bridges between the wire ends (28) from the voice coil (24) and the audio signal line (30). If the respective surfaces in the connection areas of the individual components (10.1 to 10.4) and the remaining loudspeaker components (15, 20) are made of aluminum for example, the individual components (10.1 to 10.4), or the centering diaphragm (10), can very easily be joined to the remaining loudspeaker components (15, 20) by ultrasonic welding.

Centering diaphragm

An area between a gas exhaust pipe (23) and the front side (26) of a diaphragm (14) near the magnet system (11) is closed off by means of a corrugated cover (27). The presence of the cover (27) prevents acoustic short circuits between the front side (26) and a rear side (28) of the diaphragm (14). Since furthermore the end of the gas exhaust pipe (23, 23'), which protrudes into a space (25), does not reach the end of the diaphragm (14) which is connected with a bead (31), such a loudspeaker (10) can operate at very low continuous output.

System for cancelling sound waves

According to the state of the art, insofar as the respective components of the loudspeaker cannot be built in one piece, the respective components of the loudspeaker are joined to each other by adhesives. For example, it is known to bond the aluminum voice coil support (10) to the paper loudspeaker diaphragm (11). However, if loudspeakers with such bonded joints must operate above 120 degrees Celsius, no long-term continuous operation of the mechanically highly stressed adhesion can be expected. The invention therefore has the task of presenting a very strong mechanical joint of the loudspeaker components. The task is fulfilled according to the invention, in that at least the surface areas (13.1, 13.2) of the loudspeaker components to be joined to each other �perhaps the voice coil support (10) and the loudspeaker diaphragm (11)! are made of metals that can be ultrasonically welded to each other, and that the joint between the two components of the loudspeaker is ultrasonically weldable. Insofar as required, an insulation arrangement (16) can be placed between the two just mentioned loudspeaker components, which can be ultrasonically welded to the respective components of the loudspeaker �in this instance loudspeaker diaphragm (11) and voice coil support (10)!, through their metal coatings (19.1, 19.2), which are also made of ultrasonically weldable metal.

According to the state of the art, the voice coil (12) of a loudspeaker is connected to the voice coil support (10) in such a way, that first the coil wire, which is surrounded by a self-bonding material, is wound around the outside jacket (14) of the voice coil support (10), and then is baked. However, under mechanical load, such a connection is only temperature-stable to about 200 degrees Celsius. It is therefore the task of the invention to present a connection between voice coil (12) and voice coil support (10), which is also temperature-stable above 200 degrees Celsius. This task is fulfilled by the invention, in that holding elements (13) are placed around the outside jacket of the voice coil (12), which act against any radial and/or axial change in position of the individual winding wires of voice coil (12). These holding elements (13) can be (ultrasonically) welded to the voice coil support (10), or be attached to the inside sleeve (18) of the voice coil support (10) by simple bending.

Voice coil support for loudspeaker

According to the invention, a contact for loudspeakers (10) is indicated between the wire ends (24) of voice coil (16) and the stationary contacts (19), which is temperature-stable even above 250.degree. C. This is achieved by first conductively connecting the wire ends (24) to the connecting lines (21), and then attaching the connected parts (21, 24) at least to one side of a high-temperature-resistant plastic foil (25). The plastic foil (25) is affixed to the diaphragm (13) or the voice coil support (14) by mechanical attachment means (23). The fact that the plastic foil (25), which stabilizes the connecting lines (21), is installed afterwards, allows the connection between the wire ends (24) and the connecting lines (21) to be performed by the ultrasonic welding technique.

Connection line

In the state of the art, most loudspeaker diaphragms 10 and the voice coil supports 11 are joined by adhesives. However, even high-grade adhesives fail if such loudspeakers are subjected to continuous operating temperatures much above 120 degrees Celsius. The one-piece construction of loudspeaker diaphragm 10 and voice coil support 11 is also limited. It is particularly difficult to produce one-piece metal constructions by means of the deep-draw process. It is therefore the task of the invention to present a joint of loudspeaker diaphragm 10 and voice coil support 11, which is simple to produce, can be subjected to high temperatures and is free of adhesives. This task is fulfilled in that the upper rim 19 of the voice coil support 11 is flared together with the upper rim 16 of a neck 12 formed on the diaphragm 10. In addition the invention proposes to join the neck 12 of loudspeaker diaphragm 10 to the voice coil support 11 through the effect of a ring-shaped part 23. If the neck 12 of diaphragm 10 is located between the ring-shaped part 23 and the voice coil support 11, the latter has the function of opposing the pressure (force) exerted by the ring-shaped part 23 on the outside jacket of the neck 12.

Loudspeaker suitable for high-temperature use having a non-adhesive

In the state of the art, it is known to connect diaphragms (11) of cone loudspeakers to the loudspeaker frame (10) by means of so-called beads (13). Such beads (13) are predominantly made of plastic or rubber, and are connected to the diaphragm (11) or the loudspeaker frame (10) by means of suitable adhesives. This type of connection limits the free selection of the above named components, because not all elastic bead materials can be connected to the diaphragm (11) with the required mechanical stability. The selection of materials is further restricted when the loudspeaker is subjected to ambient temperatures above 100.degree. C., because the adhesive connections lose their strength under such conditions. The invention has therefore the task of presenting a high-strength suspension mount for the diaphragms of cone loudspeakers. This task is fulfilled in that the bead (13) is made of an injection-moldable and high-temperature resistant elastomer material (e.g. silicon rubber or fluoroelastomer) and the inner edge (18) of the bead (13) is connected to the upper edge (19) of the diaphragm (11) by vulcanization. Special high-strength connections of diaphragm (11) and bead (13) are provided when the upper edge (19) of the diaphragm (11) has perforations (20), and the areas of the inner edge (18) on both sides of the diaphragm (11) are connected by beading material through the perforations (20) of the diaphragm (11).

Suspension mount for loudspeakers

According to the state of the art, high-temperature resistant centering of loudspeakers is configured so that a rod (17) that is connected to the pole body (14) serves as a guide for a bushing (19) connected to the voice coil support (11). However, the narrow space between the rod (17) and the bushing (19) leads to friction between the rod (17) and the bushing (19) during excursion movements of the voice coil support (11), which retards the free movement of the voice coil support (11). The invention therefore has the task of providing high-temperature resistant centering for loudspeakers, in which any touching of rod (17) and bushing (19) is eliminated. The invention makes the rod (17) and the bushing (19) from magnetic material, and magnetizes this material radially to the loudspeaker axis (16). If the facing magnetic areas of rod (17) and bushing (19) have the same polarity, no-contact centering of the bushing (19) over the rod (17) is achieved by the mutual rejection.

Loudspeaker

It is known in the state of the art to dampen noise emissions by means of 'anti-sound'. In the gas exhaust installations of combustion machines, this is realized most often in that the exhaust gas flowing in the gas exhaust installation is charged with 'anti-sound' produced by loudspeakers (12). However, such arrangements are disadvantageous in that the flow of hot exhaust gases reduces the service life of the loudspeakers, or that such measures are insufficient for actively damping the sound. The invention therefore presents an arrangement that avoids the disadvantages that exist in the state of the art. According to the invention, this is achieved in that the gas exhaust tube (10) ends in one of the two chambers of a double chamber box (17), and that a bass reflex tube (21) protrudes into this chamber of the double chamber box (17). The excellent sound cancellation at low loudspeaker output is achieved because the sound cancellation takes place in the chamber of box (17), where the ends of the bass reflex tube (21) and the gas exhaust tube (10) terminate, and that the radiation axis S intersects the center line M in space A between the two tubes (10, 21) or in tube (21), and the distance L between the dividing wall (18) and center line M is 75% of the largest diameter extension of loudspeaker 12.

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Straubing, Germany

Stefan Geisenberger