GB1591181A

GB1591181A - Loudspeaker apparatus

Info

Publication number: GB1591181A
Application number: GB1650077A
Authority: GB
Original assignee: ARD ANSTALT
Current assignee: ARD ANSTALT
Priority date: 1977-04-20
Filing date: 1977-04-20
Publication date: 1981-06-17

Description

(54) mI1PROIVEMENTS m OR R1iiLATING TO LOUDSPEAKER APPARATUS (71) We A.R.D. ANSTALT of P O Box 34.613, 9490 Vaduz, Liechtenstein, a body corporate organised under the laws of Liechtenstein do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a loudspeaker apparatus.

According to the invention, there is provided a loudspeaker apparatus comprising enclosure means, first and second diaphragms movably mounted at respective apertures in the enclosure means wall for radiation of sound externally of the enclosure means and so as to be pneumatically coupled together within the enclosure means, first and second electro-mechanical transducers operatively connected with the first and second diaphragms respectively, an electric signal source connected to the first electro-mechanical transducer means for driving the first diaphragm in response to the signal, and an electrical load connected to the second electro-mechanical transducer means for consuming an electric current generated in the second electromechanical transducer means in response to movement thereof due to the pneumatic coupling with the first diaphragm.

The invention is further described below, by way of example, with reference to the accompanying drawing, in which Figure 1 is a sectional schematic side view of a first loudspeaker apparatus embodying the invention; and Figures 2 and 3 are like views of second and a third loudspeaker apparatus embodying the invention respectively.

The loudspeaker device of the invention shown in Figure 1 comprises three loudspeaker units 112, 113 and 114. The diaphragms of the units 112 and 113 are pneumatically driven by the unit 114 which has a diaphragm 115 driven by a plurality of electro-mechanical transducers 116, and a passive radiator diaphragm 117, provided with an outwardly flaring conical centre piece, the diaphragms 115 and 117 being coupled together by the air within a sealed chamber between them.

The diaphragms of the units 112 and 113 carry the moving coils of electro-mechanical transducers 118, 119 respectively, which are variably loaded, and which can be used to supply or receive signals for damping or control purposes. The coils of the electro-mechanical transducers 118, 119 can instead or as well be supplied with signals within respective frequency band widths selected from the input signal to be reproduced as sound by the device as a whole. In this way each of the units llQ, 113 receives both a pneumatic input covering the entire frequency range to be reproduced, and an electrical signal in a lesser frequency range therewithin.

As schematically shown in Figure 1, a full frequency range audio input at 120 is supplied directly to the transducers 116 through a multi-section filter means 121.

Transducers 118, 119 are pneumatically coupled. It will be understood that the voice coil formers of the electro-mechanical transducers of Figure 1 carry as many separate coils as are required.

The units 112, 113 and 114 are mounted in respective enclosures 1 12A, 113A and 114A. The interiors of these enclosures are in communication by way of a duct llA which may be flexible but which may be constituted by a rigid tube or tubes by which the enclosures can be suitably located for use. The duct 11A can for example comprise a pair of telescopically related tubes with spring means acting between them so that their ends can be urged into engagement with opposed walls or between a ceiling and a floor. The connections between the duct and the enclosures can be such as to permit selection of a desired orientation of each enclosure to the duct.

The relative sizes of the transducer diaphragms, their weights, -their form, their suspension, the voice coil size or weight or impedance, as well as the load values applied to the voice coils or the field strength of the associated magnet systems, will determine the frequency ranges handled by each of the pneumatically operated transducers. In this and various other embodiments of the invention, these factors are distinctively different among the various speakers, with the result that the frequency ranges of the various speakers will be different, although they may overlap. Thus the driven speaker may have a full frequency range, while the pneumatic one or ones may correct e.g. the bass or the top.

The pneumatic speaker or speakers control the acousical characteristics of the enclosure or cabinet, to improve efficiency at specific frequencies, which can be narrow bands or wide bands.

In the loudspeaker system 126 of the invention shown in Figure 2, three loudspeaker diaphragms, 122, 123 and 124 are mounted each in a respective wall of an enclosure 125. An internal baffle 127 provides substantial acoustic separation between the diaphragms 122 and 123 but allows each to be in communication with the diaphragm 124. The diaphragms are in this system provided by conventional loudspeaker units but one or more extra coils on the voice coil former are required if control signals are to be applied in addition to signals to be reproduced.

The signal supply arrangements provided for the system of Figure 1 can be employed with that of Figure 2 and there may be provided also as shown in Figure 2, switching means 128 to enable the user to select which of the units is to function as the motor unit.

In any loudspeaker system of the invention, the physical positioning of the various diaphragms is chosen with reference to the phase differences introduced by the transmission of sound between them and the frequency range which it is intended that the outwardly radiating diaphragm or diaphragms should handle. The motor diaphragm can but need not itself have a surface exposed to the exterior of the enclosure.

The use in accordance with the invention of the signals obtained from an electro-acoustic transducer operated by a pneumatically driven diaphragm is now further described with reference to Figure 3.

The voltage generated in an electroacoustic transducer associated with a pneumatically driven diaphragm can be used additionally or instead to drive a further loudspeaker unit. As shown in Figure 3, the electrical output of the coil 135 in a first enclosure 131, whose loudspeaker is pneumatically driven by an electrically driven loudspeaker whose coil is shown at 137 is taken to the voice coil 137A of a loudspeaker unit 132A mounted in a second enclosure 131A, which also mounts a diaphragm 133A pneumatically coupled with the diaphragm of the unit 132A. The drive to the loudspeaker system of the enclosure 131A is thus electrical but the electrical signal is obtained through a pneumatic coupling in the enclosure 131. The system comprising the two enclosures 131 and 131A can of course be extended by addition of further enclosures, and the enclosures can be in adjacency or physically spaced. Switching means can be provided to permit selection as to which of the enclosures receives the original signal input.

It will be noted from Figures 1 and 3, that the plural diaphragms face the same way. This is a preferred feature of the present invention.

It is to be understood that the provision of pneumatically driven diaphragms in accordance with the present invention is not confined to loudspeaker systems concerned only with the reproduction of signals at the lower end of the audio frequency range. The additional diaphragms of the with loudspaker units which handle either invention can be employed in conjunction the entire audio frequency range or any selected part of it.

The or each electro-acoustic transducer unit and the or each additional radiator of the loudspeaker systems described, or of conventional systems, can be constructed with a diaphragm formed conventionally from sheet material. The diaphragm design is preferably such as to minimize weight and aerodynamic resistance to movement and to maximize rigidity and thus resistance to distortion in use.

WHAT WE CLAIM IS: 1. A loudspeaker apparatus comprising enclosure means, first and second diaphragms movably mounted at respective apertures in the enclosure means wall for radiation of sound externally of the enclosure means and so as to be pneumatically coupled together within the enclosure means, first and second electro-mechanical transducers operatively connected with the the first and second diaphragms respectively, an electric signal source connected to the first electro-mechanical transducer means for driving the first diaphragm in response to the signal, and an electrical load connected to the second electro-mechanical transducer means for consuming an electric current generated in the second electro-mechånical transducer means in response to movement thereof due to the pneumatic coupling with the first diaphragm.

2. A loudspeaker apparatus as claimed in claim 1 wherein the electrical loadJcom- prises a third electro-mechanical transducer operatively connected with a third diaphragm movably mounted at an aperture in the wall of a second enclosure means for radiation of sound externally thereof.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. each of the pneumatically operated transducers. In this and various other embodiments of the invention, these factors are distinctively different among the various speakers, with the result that the frequency ranges of the various speakers will be different, although they may overlap. Thus the driven speaker may have a full frequency range, while the pneumatic one or ones may correct e.g. the bass or the top. The pneumatic speaker or speakers control the acousical characteristics of the enclosure or cabinet, to improve efficiency at specific frequencies, which can be narrow bands or wide bands. In the loudspeaker system 126 of the invention shown in Figure 2, three loudspeaker diaphragms, 122, 123 and 124 are mounted each in a respective wall of an enclosure 125. An internal baffle 127 provides substantial acoustic separation between the diaphragms 122 and 123 but allows each to be in communication with the diaphragm 124. The diaphragms are in this system provided by conventional loudspeaker units but one or more extra coils on the voice coil former are required if control signals are to be applied in addition to signals to be reproduced. The signal supply arrangements provided for the system of Figure 1 can be employed with that of Figure 2 and there may be provided also as shown in Figure 2, switching means 128 to enable the user to select which of the units is to function as the motor unit. In any loudspeaker system of the invention, the physical positioning of the various diaphragms is chosen with reference to the phase differences introduced by the transmission of sound between them and the frequency range which it is intended that the outwardly radiating diaphragm or diaphragms should handle. The motor diaphragm can but need not itself have a surface exposed to the exterior of the enclosure. The use in accordance with the invention of the signals obtained from an electro-acoustic transducer operated by a pneumatically driven diaphragm is now further described with reference to Figure 3. The voltage generated in an electroacoustic transducer associated with a pneumatically driven diaphragm can be used additionally or instead to drive a further loudspeaker unit. As shown in Figure 3, the electrical output of the coil 135 in a first enclosure 131, whose loudspeaker is pneumatically driven by an electrically driven loudspeaker whose coil is shown at 137 is taken to the voice coil 137A of a loudspeaker unit 132A mounted in a second enclosure 131A, which also mounts a diaphragm 133A pneumatically coupled with the diaphragm of the unit 132A. The drive to the loudspeaker system of the enclosure 131A is thus electrical but the electrical signal is obtained through a pneumatic coupling in the enclosure 131. The system comprising the two enclosures 131 and 131A can of course be extended by addition of further enclosures, and the enclosures can be in adjacency or physically spaced. Switching means can be provided to permit selection as to which of the enclosures receives the original signal input. It will be noted from Figures 1 and 3, that the plural diaphragms face the same way. This is a preferred feature of the present invention. It is to be understood that the provision of pneumatically driven diaphragms in accordance with the present invention is not confined to loudspeaker systems concerned only with the reproduction of signals at the lower end of the audio frequency range. The additional diaphragms of the with loudspaker units which handle either invention can be employed in conjunction the entire audio frequency range or any selected part of it. The or each electro-acoustic transducer unit and the or each additional radiator of the loudspeaker systems described, or of conventional systems, can be constructed with a diaphragm formed conventionally from sheet material. The diaphragm design is preferably such as to minimize weight and aerodynamic resistance to movement and to maximize rigidity and thus resistance to distortion in use. WHAT WE CLAIM IS:

1. A loudspeaker apparatus comprising enclosure means, first and second diaphragms movably mounted at respective apertures in the enclosure means wall for radiation of sound externally of the enclosure means and so as to be pneumatically coupled together within the enclosure means, first and second electro-mechanical transducers operatively connected with the the first and second diaphragms respectively, an electric signal source connected to the first electro-mechanical transducer means for driving the first diaphragm in response to the signal, and an electrical load connected to the second electro-mechanical transducer means for consuming an electric current generated in the second electro-mechånical transducer means in response to movement thereof due to the pneumatic coupling with the first diaphragm.

3. A loudspeaker apparatus as claimed

in claim 2 having a fourth diaphragm movably mounted at a second aperture in the wall of the second enclosure means so as to be pneumatically coupled with the third diaphragm within the second enclosure means.

4. A loudspeaker apparatus as claimed in claim 3 having a fourth electro-mechanical transducer coupled with the fourth diaphragm and electrically connected to a fifth electro-mechanical transducer operatively connected with a fifth diaphragm movably mounted at an aperture in a wall of a third enclosure means.

5. A loudspeaker apparatus as claimed in claim 1 wherein the enclosure means comprises first and second enclosures and a passage connecting together the interiors of the first and second enclosures, the first and second diaphragms being mounted at apertures in the walls of the first and second enclosures respectively, and wherein the electrical load is selectively variable.

6. A loudspeaker apparatus as claimed in claim 5 having a third enclosure, a third diaphragm movably mounted at an aperture in the third enclosure wall, and a third electro-mechanical transducer operatively connected with the third diaphragm and electrically connected with a variable load, the passage connecting together the interiors of the first, second and third enclosures whereby the third diaphragm is pneumatically driven by the first diaphragm.

7. A loudspeaker apparatus as claimed in claim 1 wherein the enclosure means comprises a cabinet having an internal baffle providing substantial acoustic separation between the first diaphragm and a third diaphragm operatively connected with a third electro-mechanical transducer movably mounted at an aperture in the cabinet wall but allowing communication between the first, second and third diaphragm.

8. A loudspeaker apparatus as claimed in claim 6 or 7 including means for supplying to the second and third electromechanical transducers signals within respective frequency band widths selected from the signal supplied by the source to the first electro-mechanical transducer means.

9. A loudspeaker apparatus substantially as herein described with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawing.