CA2021162A1 - Multiple chamber loudspeaker system - Google Patents
Multiple chamber loudspeaker systemInfo
- Publication number
- CA2021162A1 CA2021162A1 CA 2021162 CA2021162A CA2021162A1 CA 2021162 A1 CA2021162 A1 CA 2021162A1 CA 2021162 CA2021162 CA 2021162 CA 2021162 A CA2021162 A CA 2021162A CA 2021162 A1 CA2021162 A1 CA 2021162A1
- Authority
- CA
- Canada
- Prior art keywords
- subchamber
- enclosure
- passive radiating
- accordance
- improved loudspeaker
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Landscapes
- Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
Abstract
Abstract of the Disclosure A loudspeaker system has an enclosure with a baffle dividing the interior into first and second subchambers. The smaller subchamber is directly coupled to the region outside the enclosure by a port tube. The larger subchamber is coupled to the region outside the enclosure via the smaller subchamber by a port tube. The dividing baffle carries a woofer.
Description
2 ~ 2 .~
~JITIPLE C~BER LOUDSPEAKER S~STEM
.;~' ,.
BacXqround of thq ~entio~
The present invantion relates in general to improving the per~ormanr.e o~ a loudspeaker system at lower frequencies, and more particularly concerns an improved louds~eaXer system characterized ~y improved performance in the low frequency range that has structure which is relati~ly easy and inexpensive to fabricate.
A major problem in maXing a loudspeaker system for low ~reguency reproduction is.obtaining a high output at low frequencies while l~miting loudspëaker`cone excursions.
Typically, loudspeaker topologies are configured such that cone - excursions are reasonably within the displacement limits o~ the attached motor structuxe such that sonic output is relatively free`fro~ audible distortion. ~he siz,e of the displ w ement region must be sufficiently limited to keep ~he cost o~
- manu~a¢turing loudspea`kers ~rom becoming excessive.
~ any prior art low ~reguency speaker systems comprise a simplé woofer wi~h no enclosure, for e~ample ln te}evision and 20 - radio sets and some publ~c addres sys~ems. A dîfficulty with these systems is that there îs no means ~or~preventing the -radiation from the back of ~he speaker from canceling the . radiatio~ from the front. In such ~ syste~ peak sonic output is limited by the requirement of very large cone excursions at low frequencies.
~ one prior art approach for reducing b~c~ radiation~ and cone excursion, is to place the loudspeak:er driver in a closed box, : ~ fo~ming what is ofte~ called an acoustic suspen~ion system. An acousti~ suspensicn system provides a reactance against which the loudspeaker driver works, limiting th~ cone exc~ sion and also pre~enting ~he radiation from the bac~ of the loud~peaker from canceling that ~rom the front.
Althoug~ this embodiment provides f~r increased low freguency output compared to the enclosureless embodiment, the low 2 ~ 2 frequency peak output is still limited by the displacement region limits of the motor structure.
One prior art improvement on the acoustic suspension system is a ported enclosure system. A ported system typically includes a woofer in the enc~osure and a port tube serving as a passive radiating means. The air in the port tube provides an acoustic mass that provides system designers with an extra reac-tance which can be used to tune the loudspeaker response~
typically altering the frequency response at the low end. A
ported system is characterized by a resonant frequency at which the mass of air in the port reacts with the volume of air in the cabinet to create a resonance (port resonance). At the port resonance the cone excursion of the loudspeaker is minimized. A
ported system exhibits improved sensitivity at port resonance and decreased cone excursion. The result of the decreased cone excursion requirements at frequencies near the port resonance is an increase in low frequency peak output and a decrease in distor-tlon when compared to the acoustic suspension systems. Another result of the improved sensitivi-ty at port resonance is often an extension of the lower cutoff frequency of the loudspeaker to a lower value.
A dual-chamber system has also been used to improve the performance of an acoustic suspension system. Such systems are disclosed in United States Patent 4 549 631, assigned to the same assignee as the present application. A dual-chamber system has an enclosure divided into first and second subchambers by a dividing 2~2i~2 member. The dividing member is formed with an opening which contains a loudspeaker, the loudspeaker beir~g oriented such that one surface of the loudspeaker cone is exposed to the first sub-chamber, and the other surface of the loudspeaker cone is exposed to the second subchamber.
In some dual-chamber systems, the first and second ports directly couple the first and second subchambers to the region outside of the enclosure. In other systems, the larger subchamber is directly coupled to the region outside of the enclosure, and the smaller subchamber is coupled to the region outside of the enclosure via the larger subchamber.
In dual-chamber systems, subchambers are coupled to each other or to regions outside the enclosure either by ports or by equivalent drone cones. This results in further increases in low frequency sensitivity and peak output when compared to the simpler ported enclosure system.
Summary of the Invention It is an impoxtant object of this invention to provide an improved dual-chamber ported ~oudspeaker sys~em.
~0 According to the invention, there is enclosure means for supporting at least one loudspeaker driver means for converting electrical energy into acoustic energy. There is dividing means for dividing the enclosure means into at least first and second subchambers having smaller and larger volumes, respectively. The dividing means prefexably comprises means for supporting the loud-speaker driver means and coacting therewi~h to separate the first :,. , , - .~ , 2 ~ 2 - 3a - 60412-2096 and second subchambers. There are at least first and second port means in said first and second subchambers respectively for pro-viding first and second acoustical masses respectively. The first port means directly couples the first subchamber to the region outside the enclosure, and the second port means couples the second subchamber to the first subchamber.
Preferably, the invention radiates insignificant acoustical energy spectral components above a predetermined bass frequency, preferably no higher than 30Q Hz, so that human auditory apparatus cannot easily localize on the enclosure means.
Thus, in accordance with a broad aspect of the invention there is provided an improved loudspeaker system comprising:
electroacoustic transducing means ha~ing a vibratable cone, enclosure means for supporting said electroacoustic transducing means for converting an input electrical signal into a correspond-ing acoustic output signal, dividing means caacting with said eIectroacoustic transducing means for dividing the interior of said enclosure means into first and second subchambers, said first sub-chamber being smaller in volume than said second subchamber, a first surface of said electroacoustic transducing means contacting said first subchamber and a second surface of said electroacoustic transducing-means contacting said second subchamber, first and second passive radiating means each characterized by acoustic mass, said first passive radiatlng means coupling said first sub-chamber to the region outside said enclosure means, said second passive radiating means coupling said second subchamber to the ':
~: :
2 ~ 2 ~
- 3b - 60412-2096 region outs.tde said enclosure means via said first subchamber.
Numerous other features, objecks and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:
Brie~ Description of thè D~awings .
Figure lA is a diagrammatic representation of a prior art loudspeaker system;
2 o~
FIG. lB is a graphical representation o~ power output and cone excursion o~ the ~ystem of FI~ lA;
FIG. 2A is a diagrammatic representation o~ an embodiment o~
th8 ~n~ention;
S ~ FIG~ 2B is a graphical repre~entation vf power output and cone excursion of the ~ystem o~ FIG~ 2B;
FIGo 3 is a diagrammatic representation o~ an alternative embodiment of the lnvention with drone cones.
With re~erence now to the drawing and more particularly FIG. 1 thereo~, there is shown a diagrammatic representation of a prior art loudspeaker syste.m'ha~ing,an enclosure'10 of rectangular cross'section'divided into two''subchambers 12 and 14 ~y a dividing member 16. 'Di~iding member 16 is formed with an opening 18 which exposes'chamber 12 to the ~ront surface of the cone of a loudspeaker driver 20. ,The back surface of dri~er 20 is ëxposed to subchamber 14. :Port tube 22 couples the interior . :o~ s ~ chamber 14 to the region outside of enclosure lO. .Port tube 24 couples ~he interior,of subchamber 12 to the region ~ outsidë of enclosure lO'via subchamber 14.~ Subchamber 1~ has a :20 substantially smaller volume than subchamber-14.
Re~erring to FIG. lB, there is shown a graphical representation of cone'excurs~on and ou~p~t power as a ~unction of frequency for ~he prior art system shown in Fig. lA. The output power curve shows that'the prior art system has a resonance in the passband sub~tantially 15 dB higher'than the : response in ~he remainder of the passband.
Referring to FIG. 2A, t~ere is shown a diagrammatia representation o~ an embodiment of the invention comprising an : enclosure ~0 of rectangular cross s2ction divided into two su~chambers 12 and 14 by a divlding member 16. Dividing ~ember - 16 is ~ormed with an opening 18 which exposes chamber 12 to the front suxface o~ the cone of a loudspea~er driver 20. ~he back surface o~ ~ri~er Z0 is exposed to subchamber 14~ Por~ tube 22 couples the int~rior o~ subcham~ex 12 to the xegion outside o~
enclosuxe lO. Port tube 24 couples the interior o~ subchamber 14 2~2~2 to th~ region outside o~ enalosure lO via subcha~ber 12.
Subchamber 12 has a sub~tantially smaller vol~me than subch~m~er 14.
Referring to FIG. 2B, there is show~ a ~raphical rèpresentation o~ cone excursion as a function o~ frequency ~or the embodiment of tha invention shown in FIG. 2B. ~he output power curve shows a smooth response throughout. the passband, without the resonance seen i~ ~he prior art system.
- . A pre~erred embodiment o~ the invention employs the dimensions and parameters given below ~or the various el~mants:
Resistance of Voice Coil 5 4 ohms; ~ . -. - Flux Density in Motor Structure ~agnetic Gap Multiplied by . .--.... ...... ... ....Length o~ Wire in Magnetic Gap ~ 8.? We~erslm;
~ - Cone ~ Voice Coil Mass (= Moving ~ass3 = 0.02 kg; -- Driver (Woofer~ Free Air Resonance Frequency = 50 ~z;
cone ArPa - 0.026 m2 (Approx. 8 inch diameter woofer);
- Small Subchamber Volume ~ 0.~063m3 ~approx 380 in3);.
Large Subchamber VQlume - 0.0224 m3 (approx 1370 in3);
~ Acoustic ~ass o* Small Subcha~ber Port . .~.. -. (COnn2CtiIlg to Exterior o~ Box~ ~ 70 kglm4 (approx. O.Q06 m2 area by~0.3 m long~;
. - Acoust~c ~ass of Port Between S~bchambers = 80 kglm ~approx. 0~006 ~2 area by 0.35 m long~;
. A number o~ Yariations may he practiced within the principles o~ the in~ention. For example, the driver could be coupled to additional subchambers. The passi~e radiators may be embodied by port tubes as shown in FIG. ~A, by ~drone cones" 2~', 24' as shown in FIG. 3~ or other passive radiating ~eans. m e single woo~er ~ay be replaced by multiple transducers to achieve desired . 30 total axea, ~otor force and/or power handling capabilities.
There ~as been ~escribed apparatus and techniques ~or providing flatter output response o~ loudspeakers in the bass region. It is evident that,those sXilled ~n the art may now m~ke numerous ot~er modifications o~ and departures from the specific apparatus and techniques herein disclosed without departing from , ~ , ~ . .
2~2~
the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.
~JITIPLE C~BER LOUDSPEAKER S~STEM
.;~' ,.
BacXqround of thq ~entio~
The present invantion relates in general to improving the per~ormanr.e o~ a loudspeaker system at lower frequencies, and more particularly concerns an improved louds~eaXer system characterized ~y improved performance in the low frequency range that has structure which is relati~ly easy and inexpensive to fabricate.
A major problem in maXing a loudspeaker system for low ~reguency reproduction is.obtaining a high output at low frequencies while l~miting loudspëaker`cone excursions.
Typically, loudspeaker topologies are configured such that cone - excursions are reasonably within the displacement limits o~ the attached motor structuxe such that sonic output is relatively free`fro~ audible distortion. ~he siz,e of the displ w ement region must be sufficiently limited to keep ~he cost o~
- manu~a¢turing loudspea`kers ~rom becoming excessive.
~ any prior art low ~reguency speaker systems comprise a simplé woofer wi~h no enclosure, for e~ample ln te}evision and 20 - radio sets and some publ~c addres sys~ems. A dîfficulty with these systems is that there îs no means ~or~preventing the -radiation from the back of ~he speaker from canceling the . radiatio~ from the front. In such ~ syste~ peak sonic output is limited by the requirement of very large cone excursions at low frequencies.
~ one prior art approach for reducing b~c~ radiation~ and cone excursion, is to place the loudspeak:er driver in a closed box, : ~ fo~ming what is ofte~ called an acoustic suspen~ion system. An acousti~ suspensicn system provides a reactance against which the loudspeaker driver works, limiting th~ cone exc~ sion and also pre~enting ~he radiation from the bac~ of the loud~peaker from canceling that ~rom the front.
Althoug~ this embodiment provides f~r increased low freguency output compared to the enclosureless embodiment, the low 2 ~ 2 frequency peak output is still limited by the displacement region limits of the motor structure.
One prior art improvement on the acoustic suspension system is a ported enclosure system. A ported system typically includes a woofer in the enc~osure and a port tube serving as a passive radiating means. The air in the port tube provides an acoustic mass that provides system designers with an extra reac-tance which can be used to tune the loudspeaker response~
typically altering the frequency response at the low end. A
ported system is characterized by a resonant frequency at which the mass of air in the port reacts with the volume of air in the cabinet to create a resonance (port resonance). At the port resonance the cone excursion of the loudspeaker is minimized. A
ported system exhibits improved sensitivity at port resonance and decreased cone excursion. The result of the decreased cone excursion requirements at frequencies near the port resonance is an increase in low frequency peak output and a decrease in distor-tlon when compared to the acoustic suspension systems. Another result of the improved sensitivi-ty at port resonance is often an extension of the lower cutoff frequency of the loudspeaker to a lower value.
A dual-chamber system has also been used to improve the performance of an acoustic suspension system. Such systems are disclosed in United States Patent 4 549 631, assigned to the same assignee as the present application. A dual-chamber system has an enclosure divided into first and second subchambers by a dividing 2~2i~2 member. The dividing member is formed with an opening which contains a loudspeaker, the loudspeaker beir~g oriented such that one surface of the loudspeaker cone is exposed to the first sub-chamber, and the other surface of the loudspeaker cone is exposed to the second subchamber.
In some dual-chamber systems, the first and second ports directly couple the first and second subchambers to the region outside of the enclosure. In other systems, the larger subchamber is directly coupled to the region outside of the enclosure, and the smaller subchamber is coupled to the region outside of the enclosure via the larger subchamber.
In dual-chamber systems, subchambers are coupled to each other or to regions outside the enclosure either by ports or by equivalent drone cones. This results in further increases in low frequency sensitivity and peak output when compared to the simpler ported enclosure system.
Summary of the Invention It is an impoxtant object of this invention to provide an improved dual-chamber ported ~oudspeaker sys~em.
~0 According to the invention, there is enclosure means for supporting at least one loudspeaker driver means for converting electrical energy into acoustic energy. There is dividing means for dividing the enclosure means into at least first and second subchambers having smaller and larger volumes, respectively. The dividing means prefexably comprises means for supporting the loud-speaker driver means and coacting therewi~h to separate the first :,. , , - .~ , 2 ~ 2 - 3a - 60412-2096 and second subchambers. There are at least first and second port means in said first and second subchambers respectively for pro-viding first and second acoustical masses respectively. The first port means directly couples the first subchamber to the region outside the enclosure, and the second port means couples the second subchamber to the first subchamber.
Preferably, the invention radiates insignificant acoustical energy spectral components above a predetermined bass frequency, preferably no higher than 30Q Hz, so that human auditory apparatus cannot easily localize on the enclosure means.
Thus, in accordance with a broad aspect of the invention there is provided an improved loudspeaker system comprising:
electroacoustic transducing means ha~ing a vibratable cone, enclosure means for supporting said electroacoustic transducing means for converting an input electrical signal into a correspond-ing acoustic output signal, dividing means caacting with said eIectroacoustic transducing means for dividing the interior of said enclosure means into first and second subchambers, said first sub-chamber being smaller in volume than said second subchamber, a first surface of said electroacoustic transducing means contacting said first subchamber and a second surface of said electroacoustic transducing-means contacting said second subchamber, first and second passive radiating means each characterized by acoustic mass, said first passive radiatlng means coupling said first sub-chamber to the region outside said enclosure means, said second passive radiating means coupling said second subchamber to the ':
~: :
2 ~ 2 ~
- 3b - 60412-2096 region outs.tde said enclosure means via said first subchamber.
Numerous other features, objecks and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:
Brie~ Description of thè D~awings .
Figure lA is a diagrammatic representation of a prior art loudspeaker system;
2 o~
FIG. lB is a graphical representation o~ power output and cone excursion o~ the ~ystem of FI~ lA;
FIG. 2A is a diagrammatic representation o~ an embodiment o~
th8 ~n~ention;
S ~ FIG~ 2B is a graphical repre~entation vf power output and cone excursion of the ~ystem o~ FIG~ 2B;
FIGo 3 is a diagrammatic representation o~ an alternative embodiment of the lnvention with drone cones.
With re~erence now to the drawing and more particularly FIG. 1 thereo~, there is shown a diagrammatic representation of a prior art loudspeaker syste.m'ha~ing,an enclosure'10 of rectangular cross'section'divided into two''subchambers 12 and 14 ~y a dividing member 16. 'Di~iding member 16 is formed with an opening 18 which exposes'chamber 12 to the ~ront surface of the cone of a loudspeaker driver 20. ,The back surface of dri~er 20 is ëxposed to subchamber 14. :Port tube 22 couples the interior . :o~ s ~ chamber 14 to the region outside of enclosure lO. .Port tube 24 couples ~he interior,of subchamber 12 to the region ~ outsidë of enclosure lO'via subchamber 14.~ Subchamber 1~ has a :20 substantially smaller volume than subchamber-14.
Re~erring to FIG. lB, there is shown a graphical representation of cone'excurs~on and ou~p~t power as a ~unction of frequency for ~he prior art system shown in Fig. lA. The output power curve shows that'the prior art system has a resonance in the passband sub~tantially 15 dB higher'than the : response in ~he remainder of the passband.
Referring to FIG. 2A, t~ere is shown a diagrammatia representation o~ an embodiment of the invention comprising an : enclosure ~0 of rectangular cross s2ction divided into two su~chambers 12 and 14 by a divlding member 16. Dividing ~ember - 16 is ~ormed with an opening 18 which exposes chamber 12 to the front suxface o~ the cone of a loudspea~er driver 20. ~he back surface o~ ~ri~er Z0 is exposed to subchamber 14~ Por~ tube 22 couples the int~rior o~ subcham~ex 12 to the xegion outside o~
enclosuxe lO. Port tube 24 couples the interior o~ subchamber 14 2~2~2 to th~ region outside o~ enalosure lO via subcha~ber 12.
Subchamber 12 has a sub~tantially smaller vol~me than subch~m~er 14.
Referring to FIG. 2B, there is show~ a ~raphical rèpresentation o~ cone excursion as a function o~ frequency ~or the embodiment of tha invention shown in FIG. 2B. ~he output power curve shows a smooth response throughout. the passband, without the resonance seen i~ ~he prior art system.
- . A pre~erred embodiment o~ the invention employs the dimensions and parameters given below ~or the various el~mants:
Resistance of Voice Coil 5 4 ohms; ~ . -. - Flux Density in Motor Structure ~agnetic Gap Multiplied by . .--.... ...... ... ....Length o~ Wire in Magnetic Gap ~ 8.? We~erslm;
~ - Cone ~ Voice Coil Mass (= Moving ~ass3 = 0.02 kg; -- Driver (Woofer~ Free Air Resonance Frequency = 50 ~z;
cone ArPa - 0.026 m2 (Approx. 8 inch diameter woofer);
- Small Subchamber Volume ~ 0.~063m3 ~approx 380 in3);.
Large Subchamber VQlume - 0.0224 m3 (approx 1370 in3);
~ Acoustic ~ass o* Small Subcha~ber Port . .~.. -. (COnn2CtiIlg to Exterior o~ Box~ ~ 70 kglm4 (approx. O.Q06 m2 area by~0.3 m long~;
. - Acoust~c ~ass of Port Between S~bchambers = 80 kglm ~approx. 0~006 ~2 area by 0.35 m long~;
. A number o~ Yariations may he practiced within the principles o~ the in~ention. For example, the driver could be coupled to additional subchambers. The passi~e radiators may be embodied by port tubes as shown in FIG. ~A, by ~drone cones" 2~', 24' as shown in FIG. 3~ or other passive radiating ~eans. m e single woo~er ~ay be replaced by multiple transducers to achieve desired . 30 total axea, ~otor force and/or power handling capabilities.
There ~as been ~escribed apparatus and techniques ~or providing flatter output response o~ loudspeakers in the bass region. It is evident that,those sXilled ~n the art may now m~ke numerous ot~er modifications o~ and departures from the specific apparatus and techniques herein disclosed without departing from , ~ , ~ . .
2~2~
the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.
Claims (9)
1. An improved loudspeaker system comprising:
electroacoustic transducing means having a vibratable cone, enclosure means for supporting said electroacoustic transducing means for converting an input electrical signal into a corresponding acoustic output signal, dividing means coacting with said electroacoustic transducing means for dividing the interior of said enclosure means into first and second subchambers, said first subchamber being smaller in volume than said second subchamber, a first surface of said electroacoustic transducing means contacting said first subchamber and a second surface of said electroacoustic transducing means contacting said second subchamber, first and second passive radiating means each characterized by acoustic mass, said first passive radiating means coupling said first subchamber to the region outside said enclosure means, said second passive radiating means coupling said second subchamber to the region outside said enclosure means via said first subchamber.
electroacoustic transducing means having a vibratable cone, enclosure means for supporting said electroacoustic transducing means for converting an input electrical signal into a corresponding acoustic output signal, dividing means coacting with said electroacoustic transducing means for dividing the interior of said enclosure means into first and second subchambers, said first subchamber being smaller in volume than said second subchamber, a first surface of said electroacoustic transducing means contacting said first subchamber and a second surface of said electroacoustic transducing means contacting said second subchamber, first and second passive radiating means each characterized by acoustic mass, said first passive radiating means coupling said first subchamber to the region outside said enclosure means, said second passive radiating means coupling said second subchamber to the region outside said enclosure means via said first subchamber.
2. An improved loudspeaker in accordance with claim 1 wherein said passive radiating means are port tubes.
3. An improved loudspeaker system in accordance with claim 1 wherein said passive radiating means are drone cones.
4. An improved loudspeaker system in accordance with claim 1 wherein the volumes of said subchambers and the acoustic masses of said passive radiating means establish a frequency response of said enclosure so that said passive radiating means radiate only bass acoustic spectral components below a bass frequency sufficiently low so that human auditory apparatus cannot easily localize on said enclosure means.
5. An improved loudspeaker system in accordance with claim 4 wherein said bass frequency is at least as low as 300 Hz.
6. An improved loudspeaker in accordance with claim 4 wherein said passive radiating means are port tubes.
7. An improved loudspeaker system in accordance with claim 4 wherein said passive radiating means are drone cones.
8. An improved loudspeaker in accordance with claim 5 wherein said passive radiating means are port tubes.
9. An improved loudspeaker system in accordance with claim 5 wherein said passive radiating means are drone cones.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US379,886 | 1989-07-14 | ||
| US07/379,769 US4945011A (en) | 1988-07-20 | 1989-07-14 | Storage battery provided with electrolytic solution stirring device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2021162A1 true CA2021162A1 (en) | 1991-01-15 |
Family
ID=23498606
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2021162 Abandoned CA2021162A1 (en) | 1989-07-14 | 1990-07-13 | Multiple chamber loudspeaker system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2021162A1 (en) |
-
1990
- 1990-07-13 CA CA 2021162 patent/CA2021162A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
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