Abstract:
A speaker cabinet including at least one bass speaker having a voice coil aligned by a magnetic fluid without a ‘spider’ and having an anodised metal cone, and at least one further speaker having a thin conductive membrane, and having integrated preamplifiers and at least one power amplifier, for use with musical instruments, for playing small to medium sized venues and/or for use as a personal monitor speaker on a performance stage for playing medium to large venues. Multiple channels are provided to amplify more than one instrument, and microphone inputs are provided for acoustic instruments and/or voice amplification. A line level input is also provided for external signal sources. An auxiliary input is provided to facilitate the monitoring of accompanying musicians, thus permitting the loudspeaker system to also function as a stage monitor. Reverberation and notch filtering, as well as tone control, may also be provided.

Description:
RELATED APPLICATION 
       [0001]    This application is related to U.S. Provisional Application Ser. No. 60/763,495, filed Jan. 30, 2006, in the name of the same inventor listed above, and entitled, “AccuSonic-One Acoustic Instrument Cabinet”. The present patent application claims the benefit under 35 U.S.C. §119(e). 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to speaker enclosures for audio reproduction and, more particularly, to a novel arrangement of speakers integrated with a preamplifier and a power amplifier to form an acoustic instrument cabinet with improved performance. 
       BACKGROUND OF THE INVENTION 
       [0003]    Musicians playing small to medium sized venues typically must transport a variety of electronic equipment to the venue in addition to their instruments. Even if an integrated power amplifier and speaker is available, separate equipment may be needed for special effects. In addition, a preamplifier may be needed with acoustic instruments for the signal from a microphone or pick-up to drive a power amplifier. 
         [0004]    While there exists prior art examples of musical instrument equipment that combine a number of the above described elements; a problem with current equipment concerns the ‘spider’ usually used as a mechanical support for the voice coil in loudspeakers. The spider acts as a small speaker cone itself, and tends to generate unwanted vibrations. 
         [0005]    Therefore, a need exists to provide a device and method to overcome the above problem. 
       SUMMARY OF THE INVENTION 
       [0006]    A speaker cabinet including a bass speaker having a voice coil aligned by a magnetic fluid without a ‘spider’ and having an anodised metal cone, and a further speaker having a metal ribbon, and having integrated preamplifiers and power amplifier, for use with musical instruments, for playing small to medium sized venues and/or for use as a personal monitor speaker on a performance stage for playing medium to large venues. Multiple channels are provided to amplify more than one instrument, and a microphone input is provided for acoustic instruments and/or voice amplification. A line level input is provided for external signal sources. An auxiliary input is provided to facilitate the monitoring of accompanying musicians, thus permitting the loudspeaker to function as a stage monitor. Reverberation and notch filtering, as well as tone control, may also be provided. 
         [0007]    The present invention is best understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a bass speaker according to a preferred embodiment of the invention. 
           [0009]      FIG. 2A  is a cross-sectional side view of a first side of a speaker cabinet according to a preferred embodiment of the invention. 
           [0010]      FIG. 2B  is a second side view of a speaker cabinet according to a preferred embodiment of the invention. 
           [0011]      FIG. 3  is a front view of a speaker cabinet according to a preferred embodiment of the invention. 
           [0012]      FIG. 4  is a schematic of a preamplifier circuit. 
           [0013]      FIG. 5  shows connections for input jacks and for gain control and tone control potentiometers according to a preferred embodiment of the invention. 
           [0014]      FIG. 6  shows an effects insertion circuit according to a preferred embodiment of the invention. 
           [0015]      FIG. 7  shows a socket, switch and resistors for an internal effects module according to a preferred embodiment of the invention. 
           [0016]      FIG. 8  shows an active notch filter according to a preferred embodiment of the invention. 
           [0017]      FIG. 9  shows an output driver circuit according to a preferred embodiment of the invention. 
           [0018]      FIG. 10  shows an exemplary power supply regulation circuit according to a preferred embodiment of the invention. 
       
    
    
       [0019]    Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
       DETAILED DESCRIPTION 
       [0020]    A speaker cabinet according to a preferred embodiment of the invention is provided with inputs for two musical instruments (channel  1  and channel  2 ) and an input for a microphone input and a line level input. In addition, an active notch filter is provided in channel  1 , and tone controls are provided in both channels, and a power amplifier is provided to drive a bass speaker driver and a speaker driver for high frequencies and mid range. The high frequency/mid-range speaker driver preferably employs a planar magnetic driver, preferably of a neodymium ribbon type. The speaker cabinet provides enhanced functionality. The speaker cabinet can be utilized either as a musician personal instrument cabinet/monitor or as a self contained high quality sound reinforcement system capable of reproducing the sound of two instruments, a microphone and a line level signal source simultaneously. 
         [0021]    Referring to  FIG. 1 , a speaker driver  100  is shown. The speaker  100  has a diaphragm  110 , a basket  120 , a surround  130 , a magnet  140  and a voice coil  150 . Diaphragm  110  is preferably made of metal, preferably aluminium, and is preferably anodised. Applicant has found that anodising the diaphragm  110  improves strength and reduces unwanted vibration. Basket  120  is preferably made by casting. Surround  130  may be made of a suitable composite material. The space  160  around the voice coil  150  is filled with a magnetic fluid known as a ferrofluid. The magnetic fluid provides a means of centering the voice coil  150  relative to the magnet  140 . Unlike in conventional designs, no mechanical alignment device or ‘spider’ is employed between the voice coil and the magnet. The elimination of the ‘spider’ will remove unwanted vibrations. 
         [0022]    In general, most prior art speakers cannot reproduce the entire frequency spectrum on their own. Therefore, these speaker systems must use multiple speaker drivers fed by distinct frequency ranges split up through a crossover. Since this process most certainly leads to some degree of signal degradation, it is desirable to minimize the number of cross-over frequency points to as few as possible. The present loudspeaker cabinet&#39;s unique combination of planar magnetic drivers and spider-less cone type drivers provides for improved acoustic performance. 
         [0023]    The speaker cabinet of the present invention will use multiple speaker drivers  100 . The speaker cabinet will have a planar magnetic driver for mid and high frequency ranges and a spiderless conical voice coil driver for low frequency reproduction. Planar magnetic drivers are very light weight thereby reducing the overall weight of the speaker cabinet. Planar-magnetic drivers work by having a thin conductive membrane that carries the audio signal, suspended between strong magnets. When the audio signal passes through the conductive membrane, this sets up a magnetic field that is attracted or repelled by the permanent magnets. The membrane moves, creating the sound heard. It should be noted that one or more planar magnetic drivers may be used for different mid and high frequency ranges. It also should be noted that one or more spiderless conical voice coil drivers can be used for low frequencies. 
         [0024]    The combination of the one or more planar magnetic drivers for mid and high frequency ranges and one or more spiderless conical voice coil drivers for low frequency reproduction will provide for a high performance speaker cabinet in terms of frequency response, waveform accuracy, transient response and overall dynamic range. 
         [0025]    Referring to  FIGS. 2A-2B , side views of the speaker cabinet  200  are shown. The speaker cabinet  200  is generally constructed of a wood material. The speaker cabinet  200  is generally shaped with a flat bottom section and a curved/rounded back section. The speaker cabinet  200  has a partition  210  and a double baffle  220  supporting multiple speaker drivers  100  and a control panel  250 . An opening  230  is formed in one side of the speaker cabinet  200 . Opening  230  is used as a pole mount. One or more elongated openings  240  are formed on a second side of the speaker cabinet  200 . The elongated openings  240  are used has hand grips to allow a person to grasp the speaker cabinet  200  in a secure manner in order to move the speaker cabinet  200 . 
         [0026]      FIG. 3  is a front view of the speaker cabinet  200  of  FIG. 2  showing the location of the speaker driver  100  and control panel  250  in the speaker cabinet  200 . 
         [0027]      FIG. 4  shows one embodiment of a preamplifier circuit for channel  1 . A similar circuit may be employed for channel  2 .  FIG. 4  is just one example of a preamplifier circuit. Other preamplifer circuits may be used without departing from the spirit and scope of the present invention. The preamplifier circuit of  FIG. 4  comprises amplifier stages U 41 , U 42  with capacitors C 41 , C 42 , C 43  and resistor R 421 , and tone control components comprising C 44 -C 47  and R 431 -R 437 .  FIG. 5  shows connections for input jacks  520  and  540  for channel  1  input and line input, and for the gain control potentiometer R 51  as well as tone control potentiometers R 53 , R 54  and R 55  for low, mid and high frequency ranges respectively. Connections  401 - 418  connect the components of  FIG. 4  with those of  FIG. 5 . A similar arrangement can be provided for channel  2 . 
         [0028]    In accordance with another embodiment of the present invention, a tube preamplifier circuit may be used instead of a solid state preamplifier circuit disclosed above. The tube preamplifier circuit adds unique tonal qualities generally preferred by musicians for stringed instruments such as acoustic guitars. The tube preamplifier circuit would plug into and thus be inserted between the instrument input jack and the solid state circuitry. Alternatively, the tube preamplifier circuit could replace the solid state preamplifier circuit in the speaker cabinet. 
         [0029]      FIG. 6  shows an effects insertion circuit according to one embodiment of the invention. The circuit shown is for channel  1 , and a similar circuit can be employed for channel  2 . Other insertion and/or selection circuits may be used without departing from the spirit and scope of the present invention. The input of the circuit of  FIG. 6  is connected to the output of the channel  1  preamplifier and to the channel  1  effects input pin (pin  11 ) of socket  720  in  FIG. 7 . The input stage comprises amplifier U 61 , the non-inverting input of which is driven by a channel  1  pre-amplifier and has R 612  connected in shunt. U 61  is provided with a feedback network comprising R 611 , R 613  and C 61 , and is connected via resistor R 614  to jack  640 . An external effects unit can be connected between jack  640  and jack  650 , and jack  650  is connected via resistor R 615  to the non-inverting input of amplifier U 63  in the output stage. U 63  is also provided with feedback resistor R 633 . When no external effects unit is connected between jacks  640  and  650 , the audio signal is passed through, unimpeded. In addition, the signal from the preamplifier is also fed directly to the inverting input of U 63  via R 635 . In addition to being fed to the non-inverting input of U 63 , the signal taken from the junction of R 615  and R 635  is also fed via fixed resistor R 631 , variable resistor R 624  and fixed resistor R 623  to a network comprising C 64 , C 65 , C 66 , R 625 , R 626  and R 627  to effects output pins  15  and  13  of socket  720  shown in  FIG. 7 . The voltage across C 66  is also fed back via R 621  and R 622  to the inputs of U 62 , which is also provided with feedback capacitor C 62  and with C 67  in shunt with the non-inverting input. The output of U 62  is then fed back to the junction of R 623  and R 624 .  FIG. 7  comprises socket  720 , switch  750  and resistors R 75 - 78 . 
         [0030]      FIG. 8  shows an active notch filter according to a one embodiment of the invention. Other designs may be used for the notch filter without departing from the spirit and scope of the present invention. The filter of  FIG. 8  employs an input amplifier U 81  with input resistors R 811  and R 812 , feedback resistor R 813  and capacitor C 81 , and an output amplifier U 85  with input resistor R 851  and feedback resistor R 852 . The notch filter can be switched out by switch S 81  grounding the positive input of U 81 . When the non-inverting input of U 81  is not grounded, it is connected to the output of U 83 . A signal is taken from the junction of R 814  and R 815  and fed via R 816  to the non-inverting input of U 82 , the inputs of which are grounded via R 821  and R 822 , and which is provided with feedback resistor R 823 . The output of U 82  is fed via R 824  and R 831  to the inverting input of U 83 , which has capacitor C 83  in it&#39;s feedback loop. The output of U 83  is fed via R 833  and R 841  to the negative input of U 84 , which has feedback capacitor C 84 , and the output of which is fed back to the negative input of U 82  via R 845 . The output of U 83  is also fed back to the positive input of U 82  via R 835 . R 824  and R 833  are variable resistors and are ganged together with each other. 
         [0031]      FIG. 9  shows an output driver circuit according to a one embodiment of the invention. Other driver circuits may be used without departing from the spirit and scope of the present invention. Signals from channel  1  and channel  2  are combined at the inverting input of amplifier U 91  via resistors R 911  and R 912 . Amplifier U 91  is also provided with negative feedback via resistor R 913 . The output of amplifier U 91  is fed via amplifiers U 92  and U 93  to an XLR connector  900 , and via amplifiers U 94  and U 95  to a power amplifier. More specifically, the output of U 91  is fed via resistor R 921  to the inverting input of U 92  and also fed to the non-inverting input of U 93 . Amplifiers U 92  and U 93  are provided with feedback resistors R 923 , R 933 , series output resistors R 924 , R 934 , output capacitors C 92 , C 93  and shunt output resistors R 925 , R 935  respectively. Similarly, the output of U 91  is fed via variable resistor R 931  and fixed resistor R 941  to the non-inverting input of U 94 , which is provided with feedback resistor R 943 . The output of U 93  is fed via the output network comprising R 944 , C 94 , R 945  to the negative input of the power amplifier, and also via resistor R 951  to the inverting input of U 95 . Amplifier U 95  is provided with feed back resistor R 953  and the output of U 95  is fed via output network R 954 , C 95 , R 955  to the positive input of the power amplifier. 
         [0032]    An exemplary power supply regulation circuit is shown in  FIG. 10 , comprising regulators U 1001 , U 1002  and U 1003 , capacitors C 1001 -C 1005  and resistors R 1001 -R 1004 . Other suitable supply regulation means may of course be employed. 
         [0033]    In a preferred embodiment the signal flow from the input jacks goes via preamplifier stages to the circuit of  FIG. 6  and to a similar circuit for channel  2 , then the channel  1  signal only is passed through the circuit of  FIG. 8 , and then both channels go to the circuit of  FIG. 9  to the direct output jack and to the power amplifier. The amplifier stages shown in the drawings may be operational or differential amplifiers of any suitable type, or may be substituted with discrete bipolar transistors, FETs, vacuum tubes or other active devices with the addition of suitable additional passive components. Any suitable crossover circuit may be employed to divide the output of the power amplifier between the different frequency range loudspeakers. Or, any suitable crossover circuit may be employed at the output of the preamplifier; so as to provide separate audio signals, low frequency and high frequency, to facilitate the use of individual power amplifiers for the low and high frequencies. 
         [0034]    This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.