Abstract:
A loudspeaker that can be bi-wired or not according to a user&#39;s preference comprises a case in which is provided a plurality of audio drivers supplied by a respective plurality of audio networks, the networks being supplied (in turn) by a respective plurality of input terminal pairs, further comprising at least one switch bridging the terminals of different pairs, and adapted to selectively connect the terminals to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This Application is a Section 371 National Stage Application of International Application No. PCT/ GB2011/000108, filed Jan. 27, 2011 and published as WO/2011-092471 A1 on Aug. 4, 2011, in English, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a loudspeaker system. 
       BACKGROUND ART 
       [0003]    Many users of audio equipment employ the principle of “bi-wiring” to connect a loudspeaker to an audio amplifier, in order to improve or optimise the output of their audio system. Normally, a single cable (i.e. two conductors) runs from the amplifier output to the terminals of the loudspeaker. From this point, connections are made to the loudspeaker elements, usually via crossover networks. Thus, higher-frequency audio signals are separated within the loudspeaker and supplied to the high-frequency drivers (tweeters) and low-frequency audio signals are separated and supplied to the low-frequency drivers (bass). 
         [0004]    In a bi-wired system, two cables (i.e. 2×2 conductors) are run from the amplifier output to the loudspeaker cabinet. One cable supplies the audio signal to a high frequency input and one cable supplies the same audio signal to a separate low frequency input. Each input then supplies the audio signal to their respective driver(s) via their respective crossover networks. 
         [0005]    Some within the audio community hold that this improves the sound quality of the system as a whole, by electrically separating the high- and low-frequency signals via the amplifier, which in turn leads to less interference. Others deny this, arguing that the two ways of making connections are electrically equivalent. 
       SUMMARY OF THE INVENTION 
       [0006]    This debate over the merits of bi-wiring places loudspeaker manufacturers in a difficult position. If they provide only a single pair of terminals then the loudspeakers are made unsuitable to those who wish to bi-wire. If two pairs of terminals are provided in order to cater for bi-wiring, then opponents of bi-wiring can be offended that the manufacturer is (seemingly) indicating its approval of bi-wiring and must make arrangements to short the respective terminals via a suitable wire link. 
         [0007]    The present invention therefore provides a loudspeaker, comprising a case in which is provided a plurality of audio drivers supplied by a respective plurality of audio networks, the networks being supplied (in turn) by a respective plurality of input terminal pairs, further comprising at least one switch electrically connected to the terminals of different pairs, and adapted to selectively connect the terminals to each other. 
         [0008]    Alternatively, the invention provides a loudspeaker comprising (i) a low-frequency signal input comprising two terminals of a first polarity and a second polarity, a low frequency network connected to the terminals of the low-frequency signal input, and a low-frequency driver connected to the output of the low-frequency network, (ii) a high-frequency signal input comprising two terminals of a first polarity and a second polarity, a high frequency network connected to the terminals of the high-frequency signal input, and a high-frequency driver connected to the output of the high-frequency network, and (iii) a switch arrangement, electrically connected to the two terminals of the low-frequency signal input and to the two terminals of the high-frequency signal input, and comprising at least one element movable between at least two positions, comprising a first position in which the terminals of the low-frequency signal input are isolated from the terminals of the high-frequency signal input, and a second position in which (a) one terminal of the low-frequency signal input is connected to one terminal of the high-frequency signal input and (b) the other terminal of the low-frequency signal input is connected to the other terminal of the high-frequency signal input. 
         [0009]    Such a loudspeaker will usually be incorporated within a casing, with the low-frequency network and the high-frequency network being accommodated within the casing, and the low-frequency signal input, the high-frequency signal input, and the switch arrangement all being accessible from outside the casing. 
         [0010]    We prefer that in the second position of the switch arrangement, the terminal of the first polarity of the low-frequency signal input is connected to the terminal of the first polarity of the high-frequency signal input and the terminal of the second polarity of the low-frequency signal input is connected to the terminal of the second polarity of the high-frequency signal input. 
         [0011]    The switch arrangement can comprise at least two discrete switches, one switch being arranged to connect the terminal of the first polarity of the low-frequency signal input to a terminal of the high-frequency signal input, and a further switch arranged to connect the terminal of the second polarity of the low-frequency signal input to a terminal of the high-frequency signal input. Alternatively, a single switch actuator can be provided with the necessary number of poles. 
         [0012]    The switch arrangement can comprise substantially any form of switch in which a moveable or removable element is able to selectively bridge at least a pair of contacts, thereby to create an electrical connection between the two contacts. Examples include a rotary switch, a toggle (dolly) switch, a rocker switch, a push-button switch, or a switch in which a removable element forms part of the electrical conduction path between the contacts, the element being removable by (for example) partially or fully unscrewing from a seat (which may form one of the contacts). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which; 
           [0014]      FIGS. 1 and 2  show a conventional bi-wiring-compatible loudspeaker used in a single-wired and a bi-wired mode, respectively; 
           [0015]      FIGS. 3 and 4  show a loudspeaker according to the present invention used in a single-wired and a bi-wired mode, respectively; 
           [0016]      FIG. 5  shows the electrical circuit of  FIGS. 3 and 4 ; 
           [0017]      FIG. 6  shows a panel incorporating the present invention; and 
           [0018]      FIG. 7  shows a section through the panel along VII-VII of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]      FIGS. 1 and 2  show a known approach to bi-wiring of loudspeakers. An amplifier  10  has a pair of output terminals of a first polarity  12  and a second polarity  14 . The loudspeaker  16  has a panel  18  with a plurality of input terminals, a tweeter driver  20  for high-frequency signals, and a base driver  22  for low-frequency signals. The tweeter  20  and the bass driver  22  are driven by appropriate crossover networks  24 ,  26  respectively. Suitable cabling  26 ,  28  runs from the appropriate crossover  24 ,  26  to the relevant driver  20 ,  22 . 
         [0020]    The bass crossover  26  is connected to a pair of bass terminals  30  that are presented on the panel  18 . These comprise a first polarity bass terminal  32  and a second polarity bass terminal  34 , from each of which run at least one conductor of a cable  36  which leads to the bass crossover  26 . Likewise, a pair of high-frequency input terminals  38  consist of a first polarity high-frequency terminal  40  and a second polarity high-frequency terminal  42 . These are connected via conductors of a cable  44  to the high frequency crossover network  24 . 
         [0021]    In the bi-wired example shown in  FIG. 1 , a first two-conductor cable  46  runs from the amplifier  10  to the bass input terminals  30 . One conductor  46   a  runs from the first polarity terminal  12  of the amplifier to the first polarity terminal  32  of the bass input terminals  30 , and the second conductor  46   b  runs from the second polarity amplifier terminal  14  to the second polarity terminal  34  of the bass input terminals  30 . Roughly in parallel to the first cable  46  is a second cable  48 , which runs from the same amplifier terminals  12 ,  14  to the high-frequency input terminals  38 . As with the first cable  46 , this comprises a first conductor  48   a  which leads from the first polarity amplifier terminal  12  to the first polarity terminal  40  of the high-frequency terminals and a second conductor  48   d  which runs from the second polarity terminal  14  of the amplifier to the second polarity terminal  42  of the high-frequency terminals  38 . 
         [0022]      FIG. 2  shows the arrangement adopted when bi-wiring is not desired. The same loudspeaker  16  is instead connected via a single cable  50 , comprising a first conductor  50   a  which leads from the first polarity terminal  12  of the amplifier  10  to either of the first polarity terminals  32 ,  40 . In this case, the conductor is connected to the first polarity terminal  32  of the bass input terminals  30 . A second conductor  50   b  of the cable  50  runs from the second polarity terminal  14  of the amplifier  10  to the corresponding second polarity terminal  34 . A pair of link wires  52 ,  54  are then connected between the respective first polarity terminals  32 ,  40  and between the second polarity terminals  34 ,  42 . Other forms of conductor might be provided as an alternative, such as pre-formed metal links. These link wires or other links might be fitted to the loudspeaker  16  during manufacture or prior to shipping, in which case they will then be removed by a user who wishes to bi-wire the loud speaker as shown in  FIG. 1 . 
         [0023]      FIGS. 3 to 5  show an arrangement according to the present invention. A loudspeaker  100  comprises a tweeter  102  and a bass driver  104 , each supplied by a respective crossover network  106 ,  108  and internal wiring identical to that of the speaker  16  of  FIGS. 1 and 2 . Again, there is a panel  110  bearing input terminals, in the form of first and second polarity bass input terminals  116 ,  120 , and first and second polarity high-frequency terminals  118 ,  122 . An externally accessible switch  124  is provided between the two first polarity terminals  116 ,  118 . A similar switch  126  sits in a corresponding situation between the second polarity input terminal  120  of the bass input terminals  112  and the second polarity input terminal  122  of the high-frequency input terminals  114 . 
         [0024]      FIG. 3  shows the switches  124 ,  126  in a first position in which the respective pairs of input terminals are electrically connected. This means that only a single cable  50  needs to be connected to the output terminals  12 ,  14  of the amplifier  10 , then can be joined to either the bass input terminals  112  or the high-frequency input terminals  114 . In this case, the cable  50  is shown connected to the bass input terminals  112 . The signal is however still supplied to the high-frequency crossover  106  via the link switches  124 ,  126 . 
         [0025]      FIG. 4  shows the arrangement adopted if bi-wiring is desired. A pair of cables  46 ,  48  supply signals separately to the bass input terminals  112  and the high-frequency input terminals  114  respectively, and the link switches  124 ,  126  are put into a second position (as shown) in which the two sets of input terminals are electrically isolated. Thus, electrically, the situation is identical to a bi-wire arrangement such as is shown in  FIG. 1 . However, in order to achieve the single-wired arrangement shown in  FIGS. 2 and 3 , no additional wire links  52 ,  54  are necessary. 
         [0026]      FIG. 5  shows the corresponding electrical circuit. Switches  124 ,  126  can be single pole single throw switches if desired. They act between the respective pairs of first polarity input terminals  116 ,  118  and second polarity input terminals  120 ,  122 , and serve to short them selectively. Thus, where there is only a single cable  50  leading from the amplifier then to the input terminals of the loud speaker  100 , the link switches  124 ,  126  can be closed thereby supplying a signal to both the bass crossover  108  and the high-frequency crossover  106  regardless of which pair of terminals the cable is connected to. If a pair of cables  46 ,  48  are provided then the link switches  124 ,  126  can be opened thereby ensuring there is no link between the respective pairs of input terminals within the loud speaker  100 , and separate signals are provided to each of the two crossover networks  106 ,  108  via the separate cable  48 ,  46 . 
         [0027]      FIGS. 3 and 4  show a pair of rotary switches  124 ,  126 . Other forms of switches could be used such as toggle switches, rocker switches or latching push-button switches (or other forms of push-button switch). Alternatively, as indicated in  FIG. 5  by a dotted line  128 , the two switch functions could be integrated into a single double-pole switch which may be of any type as above. 
         [0028]      FIGS. 6 and 7  show a possible commercial embodiment of the invention. A fascia panel  200  is provided for the various terminals and switches, and may be manufactured as a discrete item for fitting to a suitable aperture on the loudspeaker cabinet, or may be part of the cabinet itself. In this instance, the fascia panel  200  is a discrete item and has a pair of fixing holes  202 ,  204  to receive a suitable fixing such as a screw, bolt or rivet in order to secure it in place on the cabinet. 
         [0029]    The fascia panel  200  carries a pair of HF terminals  206 ,  208  which feed a signal to a high-frequency network elsewhere within the loudspeaker. Spaced from the HF terminals  206 ,  208  are a like pair of LF terminals  210 ,  212  which feed a signal to a low-frequency network. 
         [0030]    A pair of switch terminals  214 ,  216  are positioned between the HF terminals  206 ,  208  and the LF terminals  210 ,  212  in order to control the bi-wiring status of the loudspeaker as described above. Each switch terminal  214 ,  216  controls one polarity of the respective HF and LF terminals. As illustrated in  FIG. 6 , the six terminals are arranged in a 2×3 grid with the HF terminals  206 ,  208  in one pair at one end of the grid, the LF terminals  210 ,  212  in a further pair at the opposite end of the grid, and the switch terminals  214 ,  216  in a pair located between and aligned with the LF and HF terminals. This gives an aesthetically pleasing arrangement in which the nature of each terminal is intuitively apparent to most users. This is reinforced by suitable indicia moulded into, printed on, or otherwise applied to the fascia panel  200 , such as “HF” between the HF terminals  206 ,  2058 , “LF” between the LF terminals  210 ,  212 , and “LINK” between the switch terminals  214 ,  216 . Other layouts and/or indicia can be adopted, of course. 
         [0031]      FIG. 7  shows a sectional view along one HF terminal  206 , one switch terminal  214 , and one LF terminal  210 , all of the same polarity. The other three terminals are identical in construction to the three shown in  FIG. 7 , differing only in their location on the fascia panel  200  and in that they supply a signal to the other polarity input of the respective high- and low-frequency networks. 
         [0032]    The HF terminal  206  and the LF terminal  210  are also identical in construction. Referring to the HF terminal  206 , each comprises a contact  218  having an externally threaded lower rod-shaped section  220  and an internally threaded upper cylindrical section  222 . The lower rod-shaped section  220  is the narrower, and therefore the contact  218  can be secured to the fascia panel  200  by passing the rod-shaped section  220  through a suitable bore  224  and securing the contact  218  in place with a nut  226  and washer  228  on its external thread. A conductive tab  230  is fitted over the rod-shaped section  220  in advance, and is then sandwiched between the washer  228  and the fascia panel  200 , in electrical contact with the contact  218 , to provide a convenient means of electrical connection to the contact  218 . 
         [0033]    The upper cylindrically-shaped section  222  has a transverse through-hole  232  adjacent the lower blind end of its interior space. This allows the conductor of a signal cable to be inserted into the interior space via the through-hole. An externally threaded plug  234  can then be driven down via the internal threading of the cylindrical section  222  in order to trap the conductor against the blind end of the interior space and/or the edges of the through-hole  232  in order to establish a good electrical connection between the conductor and the contact  218 . An insulating cap  236  can be fitted on the plug  234  to provide a grip to assist in rotation, which can have a flared skirt  238  around the cylindrically-shaped section  222  to protect it from the environment and provide a neat external appearance. 
         [0034]    The switch terminal  214  has a contact  240  that is similar to the contact  218 , but in which the lower rod-shaped section  242  has a longitudinal internal bore that extends from the interior space of the upper cylindrical section  244  to the free lower end of the lower rod-shaped section  242 . An insulating liner  248  is fitted within the longitudinal bore, and surrounds a conductive pin  250 . This has a head portion seated at the base of the interior space of the upper cylindrical section  244 , but insulated therefrom by the liner  248 , and an elongate section that extends within the liner  248  and projects from the end of the lower rod-shaped section  242 . 
         [0035]    A plug  252  is provided for the upper cylindrical section  244 , similar in form to the plug  234 . When screwed fully home into the upper cylindrical section  244 , it makes contact instead with the head of the conductive pin  250 . As the threaded sections of the upper cylindrical section  244  and the plug  252  are in contact, this will create an electrical connection between the contact  240  and the conductive pin  250 . Likewise, when the plug  250  is partially or fully unscrewed, the contact  240  and the conductive pin  250  will become isolated from each other. As with the HF and LF terminals  206 ,  210 , an insulating cap  254  is provided for the plug  250  and has a flared skirt  256  for the cylindrically-shaped section  244 . 
         [0036]    A tab  258  is fitted to the lower rod-shaped section  242  and sandwiched between the fascia panel  200  and a retaining nut  260  and washer  262 , to provide a convenient conductive electrical contact with the lower rod-shaped section  242 . 
         [0037]    It then only remains to the provide a short wire link  264  between the tab  258  of the switch terminal  214  and the tab  230   a  of the LF terminal  210 , and a second short wire link  266  between the projecting part of the conductive pin  250  and the tab  230  of the HF Both wire links will then be located behind the facsia panel  200 , providing a neat external appearance. The switch terminal  214  can then act as a switch enabling the choice of a single- or bi-wired configuration, as described above. Connections can be made to one of the LF and HF terminals, or both, as desired. Cables  268  and  270  connected to the tabs  230 ,  230   a  of the HF and LF terminals will convey the signals to the relevant network elsewhere within the loudspeaker. 
         [0038]    Through the present invention, the need for link cables or other link conductors  52 ,  54  is avoided. The rear of the speaker is therefore less complex and less messy, and there is less opportunity to lose the links if (for example) the speaker is initially set up in a bi-wired arrangement and is later converted to a single-wired arrangement 
         [0039]    It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention.