Patent Publication Number: US-11665468-B2

Title: Bass reflex type loudspeaker enclosure

Description:
The invention relates to the field of bass reflex type loudspeaker enclosures. 
     BACKGROUND OF THE INVENTION 
     Much modern electrical equipment incorporates a loudspeaker enclosure for playing back an audio signal. Such electrical equipment includes in particular residential gateways, set-top boxes, TV sets, voice assistants, etc. 
     A loudspeaker enclosure in that type of electrical equipment conventionally comprises a cabinet and a loudspeaker fastened to the cabinet. The loudspeaker plays back the audio signal by generating sound waves propagating from the cabinet. The loudspeaker produces the sound waves from an electric current that is applied to a coil of the loudspeaker by an audio amplifier. 
     The low-frequency performance of the loudspeaker enclosure can be improved by adding a vent in the cabinet. The enclosure is then said to be of the “bass reflex” type. The air passing through the vent between the inside volume of the cabinet (behind the loudspeaker) and the outside space (in front of the loudspeaker) forms a mechanical system that resonates at a specific frequency. 
     Naturally, efforts are made to reduce the cost and the size of such electrical equipment. 
     OBJECT OF THE INVENTION 
     An object of the invention is to reduce the cost and the size of electrical equipment of the kind described above. 
     SUMMARY OF THE INVENTION 
     In order to achieve this object, there is provided a loudspeaker enclosure of the bass reflex type comprising a cabinet, a loudspeaker, and a first vent, the loudspeaker enclosure being characterized in that it further comprises a second vent and an internal heatsink situated inside the cabinet and for being thermally coupled with an electrical component in order to dissipate, inside the cabinet, heat produced by the electrical component; the first vent, the second vent, and the internal heatsink being positioned in such a manner that a flow of air passing through the first vent, the second vent, and inside the cabinet exhausts the heat produced by the electrical component to outside the cabinet. 
     The internal heatsink is positioned inside the cabinet. This limits the total volume required for the functions both of cooling of the electrical component and also of playing back sound. This serves to reduce the overall size of the electrical equipment incorporating the loudspeaker enclosure of the invention. 
     Since a flow of air passes naturally through the inside of the cabinet via the first and second vents, it is not essential to use a fan in order to improve cooling. This serves to reduce the cost of the electrical equipment incorporating the loudspeaker enclosure of the invention. 
     There is also provided an acoustic device comprising a loudspeaker enclosure as described above and a printed circuit board having the electrical component mounted thereon. 
     There is also provided electrical equipment comprising a loudspeaker device as described above. 
     Other characteristics and advantages of the invention appear on reading the following description of particular, nonlimiting embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is made to the accompanying drawings, in which: 
         FIG.  1    shows a loudspeaker enclosure in a first embodiment of the invention; 
         FIG.  2    shows a loudspeaker enclosure in a second embodiment of the invention; 
         FIG.  3    shows a loudspeaker enclosure in a third embodiment of the invention; 
         FIG.  4    shows a loudspeaker enclosure in a fourth embodiment of the invention; 
         FIG.  5    shows a loudspeaker enclosure in a fifth embodiment of the invention; 
         FIG.  6    shows a loudspeaker enclosure in a sixth embodiment of the invention; 
         FIG.  7    shows a loudspeaker enclosure in a seventh embodiment of the invention; 
         FIG.  8    shows an internal heatsink of the loudspeaker enclosure of the seventh embodiment of the invention; 
         FIG.  9    shows a loudspeaker enclosure in an eighth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG.  1    and in this example, the invention is implemented in a residential gateway  1 . 
     The residential gateway  1  includes a printed circuit board  2  carrying a plurality of electrical components  3  forming part of an audio amplifier (i.e. the electrical components  3  contribute to performing an audio amplifier function). The audio amplifier produces electric current used for reproducing an audio signal. 
     Among the electrical components  3 , the electrical component  4  is the electrical component that generates the most heat. 
     In a first embodiment of the invention, the residential gateway  1  also includes a loudspeaker enclosure  5 . 
     The loudspeaker enclosure  5  comprises a cabinet  6  defining an internal cavity of defined volume, and a loudspeaker  7 . The loudspeaker  7  is situated on a first face  8  of the cabinet  6 , which in this example is a front face of the cabinet  6 . 
     The loudspeaker  7  includes a coil. The electric current produced by the audio amplifier passes through the coil of the loudspeaker  7  so that the loudspeaker  7  generates sound waves, thereby playing back the audio signal. 
     The loudspeaker enclosure  5  also includes a first vent  10  and a second vent  11 . 
     The first vent  10  is situated in the proximity of a first end of the first face  8 . The first end is a top end. The second vent  11  is situated in the proximity of a second end of the first face  8 . The second end is a bottom end. The term “in the proximity of” is used to mean that a maximum distance between a vent and an end of the face is less than one third of the total length of the face. 
     The first vent  10  extends horizontally from the first face  8  into the inside of the cabinet  6 . The second vent  11  extends horizontally from the first face  8  into the inside of the cabinet  6 . 
     Naturally, the terms “top”, “bottom”, “horizontally”, and “vertically” are to be interpreted in a configuration in which the loudspeaker enclosure  5  is positioned in a nominal utilization position. 
     In this example, the loudspeaker  7  is positioned between the first vent  10  and the second vent  11 . 
     The positions and the dimensions of the first vent  10  and of the second vent  11  are selected to enable air to pass naturally inside the loudspeaker enclosure  5 , such that a flow F of air passes naturally through the second vent  11 , inside the cabinet  6 , and through the first vent  10 . The direction of the air flow F could naturally be different from that shown in  FIG.  1   . 
     The positions and the dimensions of the first vent  10  and of the second vent  11  are also selected to optimize the acoustic performance of the loudspeaker enclosure  5 , in particular at low frequencies. 
     The dimensions of the first vent  10  and of the second vent  11 , both of which are of the “bass reflex” type, are determined by using the definition of a Helmholtz resonator for each vent. 
     Thus, for each vent:
 
(Δ/2) 2 =( L+k ·Ø)· V/S,  
 
where λ is the wavelength of the resonant frequency of the vent, L is the length of the vent, Ø is the diameter of the vent, V is the volume defined in the internal cavity of the cabinet  6 , and S is the section of the vent. The coefficient k is a coefficient representative of the discontinuity states of the ends of the vent. The coefficient k tends towards 0.5 if a vent termination is flared. The coefficient k tends towards 1 if a vent termination is flush.
 
     Also: 
     λ=c/F, where F is the wavelength at the resonant frequency and c is the speed of sound. 
     For example, in order to have a “bass reflex” resonator at 100 hertz (Hz) in a loudspeaker enclosure  5  presenting a defined volume of 3 liters (L), the first vent  10  and the second vent  11  may have dimensions such that each of them presents a diameter of 4 centimeters (cm) and a length of 13 cm. 
     The loudspeaker enclosure  5  also includes an internal heatsink  12 , specifically a finned heatsink. The internal heatsink  12  includes a baseplate  13  and a plurality of fins  14  extending from the baseplate  13 , perpendicularly to the baseplate  13 . 
     When the internal heatsink  12  is mounted in the cabinet  6 , the internal heatsink  12  extends in the proximity of a second face  15  of the cabinet  6  that is situated facing the first face  8 . Thus in this example the second face  15  is a rear face of the cabinet  6 . 
     The baseplate  13  of the internal heatsink  12  extends parallel to and is fastened to an inside wall of the second face  15 . The term “wall” is used herein to mean one of the sides of a face. The fins  14  of the internal heatsink  12  then extend towards the inside of the cabinet  6 . 
     The printed circuit board  2  of the residential gateway  1  is located outside the cabinet  6  of the loudspeaker enclosure  5 . The printed circuit board  2  is positioned parallel to an outside wall of the second face  15  of the cabinet  6  of the loudspeaker enclosure  5 . 
     The baseplate  13  of the internal heatsink  12  is thermally coupled to the electrical component  4  of the printed circuit board  2 . 
     In order to provide the thermal coupling, the internal heatsink  12  has a metal stud  17  that extends from the baseplate  13  of the internal heatsink  12  from its side opposite from the fins  14 . When the internal heatsink  12  is installed in the cabinet  6 , the metal stud  17  extends through the second face  15  of the cabinet  6 . When the loudspeaker enclosure  5  and the printed circuit board  2  are incorporated in the residential gateway  1 , the electrical component  4  is in contact with the metal stud  17 . Thus, in this example, the thermal coupling is by direct contact. 
     Thus, the heat produced by the electrical component  4  is dissipated by the internal heatsink  12  inside the cabinet  6 . The air flow F, which also passes along the internal heatsink  12  and over the fins  14  of the internal heatsink  12 , exhausts the heat produced by the electrical component  4  towards the outside of the cabinet  6 . 
     With reference to  FIG.  2   , a loudspeaker enclosure  105  in a second embodiment of the invention includes a fan  120 . The fan  120  is positioned outside the loudspeaker enclosure  105 , at an inlet of the second vent  111 . The fan  120  extends facing the inlet of the second vent  111 . The term “inlet” used herein to mean the orifice of a vent that opens to the outside of the cabinet  106 , and the term “outlet” is used herein to mean the orifice of a vent that opens to the inside of the cabinet  106 . 
     The fan  120  is an axial propeller fan. The static pressure of the fan  120  is relatively small, and for example it is less than 20 pascals (Pa) or 30 Pa. The fan can thus be mounted directly at the inlet of the second vent  111 , and it could equally well be mounted at an outlet of the second vent  111 , or indeed inside the second vent  111 . 
     It is possible to select a fan of some other type, and in particular a turbine fan having greater static pressure, e.g. of the order of 100 Pa or 150 Pa. Under such circumstances, the fan  120  should be spaced apart from the second vent  111  by a few millimeters (mm), e.g. in the range 5 mm to 10 mm in order to avoid disturbing the performance of the second vent  111 , while still performing its function of stirring air. 
     The fan  120  is selected on the basis of acoustic criteria. The fan  120  is silent and balanced. The fan  120  does not generate vibration in the structure of the loudspeaker enclosure  105 , and it does not interfere with the primary function of the loudspeaker enclosure  105 , which is to play back an audio signal. 
     The fan  120  is mounted via a damper device that is incorporated in the fan  120  and is situated between the body of the fan  120  and the cabinet  106 . Such flexible mounting serves to limit the transmission of residual vibration produced by the fan  120 . The fan  120  could also be mounted rigidly while taking certain precautions to avoid transmitting vibration. 
     The dimensions of the second vent  111  must naturally be compatible with the dimensions of the fan  120 . In this example, the diameter of the fan  120  is greater than the diameter of the second vent  111 . 
     The fan  120  serves to improve the thermal performance of the loudspeaker enclosure  105 . The fan  120  forces air to pass through the second vent  111 , inside the cabinet  106 , and through the first vent  110 , and also along the internal heatsink  112 . The air flow F is thus greater and the heat produced by the electrical component  104  is exhausted to the outside of the cabinet  106  of the loudspeaker enclosure  105  in more effective manner. 
     It should be observed that the low extra pressure generated by the fan may be considered as a continuous load that is negligible for the loudspeaker  107 , for the first vent  110 , or for the second vent  111 . This continuous load does not impede the operation of the loudspeaker  107 , of the first vent  110 , and of the second vent  111 . 
     It should be observed that the fan  120  could also be mounted at the inlet, at the outlet, or inside the first vent  110 . 
     With reference to  FIG.  3   , a loudspeaker enclosure  205  in a third embodiment of the invention includes a fan  220 . The fan  220  is positioned inside the loudspeaker enclosure  205 , at an outlet of the second vent  211 . The diameter of the fan  220  is close to the diameter of the second vent  211  (but it could be greater or smaller). 
     With reference to  FIG.  4   , a loudspeaker enclosure  305  in a fourth embodiment of the invention includes a first fan  320  and a second fan  321 . The first fan  320  is positioned inside the loudspeaker enclosure  305 , at an outlet of the first vent  310 . The second fan  321  is positioned inside the loudspeaker enclosure  305 , at an outlet of the second vent  311 . 
     With reference to  FIG.  5   , it can be seen, in a fifth embodiment  405  of the invention, that it is possible to position the printed circuit board  402  inside the cabinet  406  of the loudspeaker enclosure. 
     The printed circuit board  402  extends parallel to and is fastened to the inside wall of the second face  415  (rear face). The baseplate  413  of the internal heatsink  412  extends parallel to and is fastened to an inside wall of the second face  415 . The printed circuit board  402  is positioned between the baseplate  413  of the internal heatsink  412  and the inside wall of the second face  415 . The metal stud  417  is in contact with the electrical component  404 . 
     This configuration further improves incorporation of the loudspeaker enclosure  405  containing the internal heatsink  412  and the printed circuit board  402 , and reduces the total volume needed by the loudspeaker enclosure  405  containing the internal heatsink  412  and by the printed circuit board  402 . 
     Naturally, it would be possible to add one or more fans to the loudspeaker enclosure  405  in positions as described above. 
     With reference to  FIG.  6   , the internal heatsink  512  of a loudspeaker enclosure  505  in a sixth embodiment of the invention is incorporated in the structure of the loudspeaker enclosure  505 . 
     A plane surface of the internal heatsink  512  forms at least a portion of an outside wall of a face of the cabinet  506 . In this example, specifically, this plane surface is a surface of the baseplate  513  of the internal heatsink  512 . The baseplate  513  forms the entire second face (rear face)  515  of the cabinet  506  of the loudspeaker enclosure  505 . 
     The printed circuit board  502  then extends outside the cabinet  506  of the loudspeaker enclosure  505 , parallel to the second face  515  of the cabinet  506 . The metal stud  517  of the internal heatsink  512  is in contact with the electrical component  504 . 
     The baseplate  513  of the internal heatsink  512  and the rear face of the cabinet  506  thus coincide. This reduces the weight and the total cost of the loudspeaker enclosure  505 , which performs the functions both of playing back the audio signal and also of dissipating heat, and thus reduces the weight and the cost of the residential gateway in which the loudspeaker enclosure  505  is incorporated. 
     With reference to  FIGS.  7  and  8   , the internal heatsink  612  is once more incorporated in the structure of the loudspeaker enclosure  605  in a seventh embodiment of the invention. The baseplate  613  of the internal heatsink  612  once more forms the entire second face (rear face)  615  of the cabinet  606  of the loudspeaker enclosure  605 . 
     The first vent  610  and the second vent  611  are incorporated in the internal heatsink  612 . The first vent  610  and the second vent  611  thus extend inside the cabinet  606  from the second face  615  of the cabinet  606 . 
     Each of the first and second vents  610  and  611  is constituted by a cylinder that extends at least in part inside the internal heatsink  612 . The cylinder forming the first vent  610  extends between two fins  614   a  and  614   b . The cylinder forming the second vent  611  extends between two fins  614   c  and  614   d . Each cylinder has its axis perpendicular to the baseplate  613  of the internal heatsink  612  and parallel to the planes in which the fins  614  extend. It should be observed that the cylinders extend between two different pairs of fins, which is one possibility, but not essential. By way of example, it is also possible to envisage that the axis of a vent corresponds with the axis of a fin. 
     In this example, the first vent  610 , the second vent  611 , and the internal heatsink  612  form a single part. By way of example, this single part may be made entirely or partially out of metal or out of a thermally conductive plastics material, e.g. out of polyimide. 
     With reference to  FIG.  9   , and in an eighth embodiment of the invention, a casing of a residential gateway  701  includes a loudspeaker enclosure  705 . The loudspeaker enclosure  705  includes an internal heatsink  712 . The residential gateway  701  further includes an external heatsink  722  positioned outside the loudspeaker enclosure  705 . 
     The internal heatsink  712  and the external heatsink  722  are both finned heatsinks, similar to those described above. 
     The internal heatsink  712  is positioned inside the cabinet  706 . The baseplate  713  of the internal heatsink  712  is mounted against the inside wall of the second face  715  of the cabinet  706 . The printed circuit board  702  extends parallel to the outside wall of the second face (rear face)  715  of the cabinet  706 , outside the cabinet  706 . 
     The external heatsink  722  is positioned outside the cabinet  706 . A baseplate  723  of the external heatsink  722  extends parallel to the outside wall of the second face  715  of the cabinet  706 . Fins  724  of the external heatsink  722  extend from the baseplate  723 , perpendicularly to the baseplate  723 , towards a face  725  of the casing of the residential gateway  701  situated opposite from the first face (front face)  708  of the loudspeaker enclosure  705  (and of the residential gateway  701 ). 
     The external heatsink  722  is also thermally coupled with the electrical component  704 . For this purpose, the external heatsink  722  includes a metal stud  727  that comes into contact with the electrical component  704 . The metal stud  717  of the internal heatsink  712  comes into contact with a surface of the printed circuit of the printed circuit board  702  that extends under the electronic component  704 . 
     It should be observed that the first vent  710  is once more situated in the proximity of the first end of the first face  708 , and that the second vent  711  is once more situated in the proximity of the second end of the first face  708 . 
     However, the first vent  710  now extends vertically inside the cabinet from a third face  730 . The third face is a top face of the cabinet  706 . 
     Likewise, the second vent  711  extends vertically inside the cabinet, from a fourth face  731 . The fourth face is a bottom face of the cabinet  706 . 
     Naturally, the invention is not limited to the embodiments described, but covers any variant coming within the ambit of the invention as defined by the claims. 
     Above, the thermal coupling between each heatsink and an electrical component is described as direct contact via a metal stud. The thermal coupling could be indirect coupling, e.g. coupling via a thermally conductive component, which may optionally be springy. 
     Although the first vent and the second vent are described above as extending inside the cabinet, one or both of the vents could perfectly well extend outside the cabinet, or could extend in part inside and in part outside the cabinet. 
     It is also possible for only one of the two vents to extend horizontally, and only one of the two vents to extend vertically. 
     Above, the internal heatsink and the external heatsink are described as being arranged to cool the same electrical component. Naturally, the internal heatsink could perfectly well cool a first electrical component and the external heatsink could cool a second electrical component. By way of example, the second electrical component could be situated on the same printed circuit board, but on another face, or it could be situated on another printed circuit board. 
     Naturally, the internal (and/or external) heatsink could cool not only one electrical component, but a plurality of electrical components. The electrical component(s) thermally coupled with the internal (and/or external) heatsink need not necessarily form part of an audio amplifier: the component may be any type of electrical component that becomes hot in operation, and for example it could be a processor, a radio transmitter, etc. 
     The first vent could be situated through any face of the cabinet. Preferably, the end of the first vent is situated high up so as to exhaust hot air. Likewise, The second vent could be situated through any face of the cabinet. Preferably, the end of the second vent is situated low down so as to enable cool air to enter. 
     It is stated above that the first vent is situated in the proximity of a first end of the first face, that the second vent is situated in the proximity of a second end of the first face, and that the first end is a top end and the second end is a bottom end. Other configurations could be devised. Thus, by way of example, if the first face including the loudspeaker is a top face, the first end of could be a left end and the second end could be a right end of the first face.