EP0095876B1 - Multi-driver-loudspeaker - Google Patents

Multi-driver-loudspeaker Download PDF

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Publication number
EP0095876B1
EP0095876B1 EP19830302913 EP83302913A EP0095876B1 EP 0095876 B1 EP0095876 B1 EP 0095876B1 EP 19830302913 EP19830302913 EP 19830302913 EP 83302913 A EP83302913 A EP 83302913A EP 0095876 B1 EP0095876 B1 EP 0095876B1
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EP
European Patent Office
Prior art keywords
diaphragm
driver
transducer
loudspeaker combination
axis
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Expired
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EP19830302913
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German (de)
French (fr)
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EP0095876A3 (en
EP0095876A2 (en
Inventor
William Neal House
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Harman International Industries Inc
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Harman International Industries Inc
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Priority claimed from US06/383,603 external-priority patent/US4497981A/en
Application filed by Harman International Industries Inc filed Critical Harman International Industries Inc
Publication of EP0095876A2 publication Critical patent/EP0095876A2/en
Publication of EP0095876A3 publication Critical patent/EP0095876A3/en
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R23/00Transducers other than those covered by groups H04R9/00 - H04R21/00
    • H04R23/02Transducers using more than one principle simultaneously

Definitions

  • This invention relates generally to loudspeaker systems, and more particularly to systems in which the audio frequency signal is divided into upper and lower ranges for higher fidelity reproduction from transducers particularly designed for that purpose. It is well known that the size, configuration, and even the operating principles of high frequency acoustic transducers may differ substantially from those of low-frequency transducers. Separate and independently operable transducers have been available for a long time, which can faithfully reproduce sound within given frequency bands.
  • Efforts to reproduce high fidelity sound for human ears have targeted questions such as where the frequency division should be made, how a transducer should function within its assigned frequency range, how many frequency divisions and transducers should be used, how the transducers should be physically arranged and associated with one another, and perhaps many other considerations of both broad and narrow scope.
  • Coaxial loudspeakers have, in the past, employed entirely independent transducers, their interrelationship being almost entirely a matter of mechanical placement with some regard for the acoustical effects which result therefrom.
  • "coaxial" speakers systems employ one or more high frequency drivers mounted above the lower frequency system by a post or bridge- like support, and, as a result, often have irregular frequency response characteristics due to phase cancellation between the drivers and diffraction effects caused by the support apparatus.
  • the speaker system of the present invention comprises a low frequency dynamic radiator type transducer or woofer and one or more higher frequency transducer(s) or tweeter(s) mounted in a single assembly, but not requiring the elaborate and costly mounting techniques of the prior art devices.
  • the woofer unit typically is of the permanent-magnet, moving-coil configuration, its dynamic radiator being a diaphragm.
  • the tweeter is mounted in the space defined by the aforesaid diaphragm, and comprises a smaller diameter second diaphragm having situated at its apex a second driver mechanism comprising a piezoelectric element, or other driving element.
  • Figure 1 of US-A-2453521 disclose securing both the second diaphragm and the second driver mechanism separately to an intermediate region of the first diaphragm between the apex and perimeter thereof.
  • US-A-2593031 discloses a similar configuration but achieved with the use of a mounting cup carried by the intermediate region of the first diaphragm and supporting both the second diaphragm and the second driver mechanism.
  • the present invention uses a piezoelectric transducer as the second driver, and has a second diaphragm with an apex, and is characterised in that the piezoelectric transducer is supported within the interior of the first diaphragm solely by attachment of the piezoelectric transducer to the apex of the second diaphragm and attachment of the second diaphragm to an intermediate region of the first diaphragm between its apex and its interior, so that the piezeoelectric transducer moves with the first diaphragm.
  • the entire mechanism which constitutes the tweeter moves in unison with the low frequency diaphragm in the piston range and forms a part of the total moving mass of the low frequency driver.
  • This configuration eliminates the customarily used mounting post or brackets which support the high frequency unit(s) and also improves the overall frequency response, dispersion, time, and phase characteristics of the loudspeaker system.
  • the low frequency transducer or woofer is of the permanent-magnet, moving-coil type and comprises a permanent-magnet assembly 10 to which is secured a frame 12 having a generally somewhat conical configuration.
  • the frame 12 defines an aperture 13 which defines generally the frontal shape and area of the transducer.
  • the shape of the aperture 13 formed by the frame can be other than circular, for example, oval.
  • the woofer diaphragm 14 extends or flares generally conically outwardly and has its outer edge secured to the periphery of the frame 12 by means of a compliant suspension 16.
  • the inner portion of the diaphragm 14 is secured to a voice coil form 18 upon the lower portion of which is the voice coil 20 which surrounds the center pole 22 of the permanent-magnet assembly 10 with the voice coil positioned in the magnetic air gap 24 in the customary fashion.
  • the construction of the transducer is entirely conventional.
  • the high frequency transducer of tweeter comprises the tweeter cone 30, the central axis of which is typically aligned with the central axis of the woofer cone 14.
  • the tweeter cone 30 has a somewhat greaterflare rate and is of substantially smaller dimension than the woofer cone 14.
  • a foam compliance ring 34 may be positioned between the edge of cone 30 and the surface of diaphragm 14. Behind the diaphragm 30 and extending along a portion of the surface thereof, dampening or stiffening material 32 and 36 can be provided to smooth response and isolate the lead wires if desired.
  • the driver element 38 is positioned at the apex of cone 30.
  • This driver element 38 comprises a piezoelectric crystal commonly known in the trade as a bimorph or multimorph.
  • the electrical leads 40 are coupled to the crystal 38, and extend out through the woofer cone 14 in conventional manner to input terminals 44 mounted upon a portion of the frame 12.
  • the leads 40 from the crystal 38 join leads 43 which couple terminals 44 to the voice coil 20.
  • the crystal 38 and voice coil 20 are thus electrically coupled in parallel.
  • connection of the single pair of input leads to both drivers 38 and 20 without utilization of a crossover network is made possible because the crystal driver 38 functions as a high-pass filter as well as a tweeter driver, and depending upon the thickness, coupling coefficient and diameter of the crystal 38 and the diameter of cone 30 and its shape, etc., provides an effective crossover frequency in the range anywhere from one to ten kilohertz.
  • An external filter network can be used if desired.
  • the damping rings 32 and 36 which illustratively can be formed of fibreglass insulating material, are to suppress undesired vibrational modes while the foam compliance ring 34 provides a means to control the mechanical coupling between the woofer and tweeter cones 14, 30 in the crossover region of response.
  • a desirable acoustic response can thus be achieved by appropriate selection of the material, the dimensions, the symmetry, and the position of the tweeter mechanism as well as variations in the decoupling ring 34 and damping rings 32 and 36.
  • the tweeter cone 30 can be suspended in front of the woofer cone in several ways.
  • the tweeter cone 30 perimeter can be attached to the woofer cone directly, or through a compliant member.
  • the tweeter cone 30 can be mounted to any suitable portion of the woofer cone 14 body, in order to provide wide angle dispersion.
  • the transducer assembly When operating in response to low frequency electrical signals, the transducer assembly appears much as if it were a single piston.
  • the operation in response to high frequency signals above the crossover frequency adds to the translational motion of the high frequency cone 30 essentially as if it were acting alone except that it is, in effect, mounted upon a support which exhibits little or no movement at these high frequencies.
  • the decoupling arrangement disposed between the woofer cone 14 and tweeter cone 30 provides a method to control the degree of motion and phase between the two cones in the midband and upper band response regions, thus providing a means to control the electromechanical feedback to the tweeter driving element, as described by the reciprocity principle. This provides a smooth frequency response characteristic in the mid- and upper band response regions.
  • This mounting arrangement between the diaphragms 14,30 leads to improved frequency response and dispersion for the overall system and to improved time phase coherence throughout the desired frequency range. From a mechanical point of view, the arrangement of the present invention also eliminates the need for the supplemental mounting brackets customarily used in other coaxial systems to support the higher frequency drivers.
  • a permanent-magnet assembly 110 is secured to a frame 112 having a generally elliptical or oval frontal opening, illustratively 6 inches by 9 inches (15.24 cm by 22,86 cm).
  • the woofer diaphragm 114 extends generally conically outwardly.
  • the outer rim of diaphragm 114 is secured to the oval front opening of the frame 112 by means of a compliant suspension 116.
  • the inward portion of the diaphragm 114 is secured to a voice coil form 118 to which is attached a woofer voice coil 120 positioned in the magnetic air gap 124 in the customary fashion.
  • the tweeter of this embodiment comprises a tweeter cone 130, the central axis of which is about 45° off the axis of the woofer cone 114, as best illustrated in Fig. 3.
  • a junction area 131 is provided at the outer perimeter of cone 130. This junction area 131 is glued or otherwise attached, with or without a compliant member, to the perimetral edge 135 of an opening 133 provided in the woofer cone 114.
  • a piezoelectric bimorph crystal driver element 138 is positioned at the apex of cone 130. Electrical leads 140 are coupled to the crystal 138 and extend to terminals 145 provided on the outside surface of woofer cone 114. The leads 140 from the crystal 138 are coupled by leads 142 to the input terminals 144 provided on the supporting frame 112. Leads 142 also couple terminals 144 to the woofer voice coil 120. The woofer voice coil 120 and tweeter driver 138 thus are coupled in parallel.
  • a permanent-magnet assembly (not shown) is secured to a frame 121 having a generally circular frontal opening.
  • the tweeter cones 230 can be molded into the woofer cone body 214, making the surrounding portion of the woofer cone 214 an extension of the tweeter cone body.
  • a woofer diaphragm 214 flares generally conically outwardly. Its outer perimeter is secured to a circular frontal opening provided in the frame 212 by means of compliant suspension 216.
  • the inner portion of the diaphragm 214 is secured to a voice coil form upon which is provided a voice coil which surrounds the center pole of the permanent-magnet assembly with the voice coil positioned in the air gap, all in a manner previously discussed.
  • Each tweeter 229 comprises a tweeter cone 230, the central axis of which is illustratively 45° off the central axis of the woofer cone 214, as in the embodiment of Figs. 2 and 3.
  • the tweeter cones' axes are also positioned at 90° intervals about the woofer cone 214 axis.
  • the tweeter cones 230 have somewhat greater flares and are of substantially smaller dimension than the woofer cone 214.
  • a piezoelectric driver element (not shown) is positioned at the apex of each cone 230.
  • the electrical terminations (not shown) to the crystals which drive tweeter cones 230 are made as in the preceding embodiments.
  • the crystal drivers function as high-pass filters, and the frequency responses of the drivers are selectable in part by proper selection of the physical parameters of the various drivers and tweeter cones 230.
  • Fig. 5 illustrates the frequency response of a prior art 6" by 9" (15.24 cm by 22.86 cm) oval speaker with a coaxial secondary cone called a "whizzer".
  • the three-frequency response curves correspond to the on-axis (0°) frequency response of the speaker, the 30° off-axis frequency response of the speaker, and the 45° off-axis frequency response of the speaker. It will be appreciated that, even with the whizzer cone, the off-axis (30° and 45° off-axis) response of the speaker is significantly below the on-axis response (1-3 dB) even at such low frequencies as 2 KHz.
  • Fig. 6 illustrates the frequency responses of a 6" by 9" (15.24 cm by 22.86 cm) elliptical constructed in accordance with Fig. 1.
  • the off-axis response at 2 KHz remains down about 1 and 3 dB (at 30° off-axis and 45° off-axis, respectively)
  • the 30° off-axis response is down only about 1-1.5 dB, a 3.5-4 dB improvement over Fig. 5
  • the 45° off-axis response is only down 8-8.5 dB, a 5.5-6 dB improvement over Fig. 5.
  • the improvement is equally as significant, with the 30° off-axis response being down only about 10.5 dB, a 2.5 dB improvement over Fig. 5, and the 45° off-axis only being down 8.5 dB, a 5.5 dB improvement over Fig. 5.
  • Fig. 7 The frequency response characteristics of the Figs. 2 and 3 embodiment of the invention are illustrated in Fig. 7.
  • the apex of the tweeter cone projected into the plane of the surrounding woofer cone lay half-way from the woofer cone axis to the compliance ring.
  • the tweeter was mounted half-way out the woofer cone from the axis to the compliance ring.
  • the 30° off-axis response was down about 1.5-2 dB and the 45° off-axis response was down 5 dB.
  • the 30° off-axis performance was actually 1-1.5 dB above the on-axis performance and the 45° off-axis performance was only about 1.5-2 dB lower than on-axis, both substantial improvements over the embodiment of Fig. 5.
  • the 30° off-axis performance and 45° off-axis performance were actually both substantially above the on-axis performance with 30° being about 4-5 dB above and 45° being about 10 dB above the on-axis performance.

Description

  • This invention relates generally to loudspeaker systems, and more particularly to systems in which the audio frequency signal is divided into upper and lower ranges for higher fidelity reproduction from transducers particularly designed for that purpose. It is well known that the size, configuration, and even the operating principles of high frequency acoustic transducers may differ substantially from those of low-frequency transducers. Separate and independently operable transducers have been available for a long time, which can faithfully reproduce sound within given frequency bands. Efforts to reproduce high fidelity sound for human ears have targeted questions such as where the frequency division should be made, how a transducer should function within its assigned frequency range, how many frequency divisions and transducers should be used, how the transducers should be physically arranged and associated with one another, and perhaps many other considerations of both broad and narrow scope.
  • It has been a practice for some time to provide speaker systems wherein the audio signal is divided into upper and lower frequencies and distributed to transducers particularly designed to best reproduce low or high frequency sound. It has also been common, for various reasons, to construct within a single assembly a combination of two or more transducers in which the high frequency transducer is coaxially mounted with respect to the low frequency transducer.
  • Coaxial loudspeakers have, in the past, employed entirely independent transducers, their interrelationship being almost entirely a matter of mechanical placement with some regard for the acoustical effects which result therefrom. Typically "coaxial" speakers systems employ one or more high frequency drivers mounted above the lower frequency system by a post or bridge- like support, and, as a result, often have irregular frequency response characteristics due to phase cancellation between the drivers and diffraction effects caused by the support apparatus.
  • Typical of the above features of the prior art, but by no means all-inclusive, are U.S. Patents Nos. 4,146,110 (Maloney); 3,796,839 (Torn); 3,158,697 (Gorike); and 2,259,907 (Olney). These patents all incorporate to varying degrees the features mentioned above.
  • It is also well known that in acoustic transducers, there are at least two types of drive mechanisms: the permanent-magnet, moving-coil type and the piezoelectric type. U.S. Patent No. 4,246,447 (Vorie) is an example of the piezoelectric mechanism.
  • The speaker system of the present invention comprises a low frequency dynamic radiator type transducer or woofer and one or more higher frequency transducer(s) or tweeter(s) mounted in a single assembly, but not requiring the elaborate and costly mounting techniques of the prior art devices. The woofer unit typically is of the permanent-magnet, moving-coil configuration, its dynamic radiator being a diaphragm. The tweeter is mounted in the space defined by the aforesaid diaphragm, and comprises a smaller diameter second diaphragm having situated at its apex a second driver mechanism comprising a piezoelectric element, or other driving element.
  • Figure 1 of US-A-2453521, disclose securing both the second diaphragm and the second driver mechanism separately to an intermediate region of the first diaphragm between the apex and perimeter thereof. US-A-2593031 discloses a similar configuration but achieved with the use of a mounting cup carried by the intermediate region of the first diaphragm and supporting both the second diaphragm and the second driver mechanism.
  • It is an object of the present invention to provide an improved multi-driver loudspeaker construction having improved overall frequency response, dispersion, and time and phase characteristics.
  • It is also an object of the present invention to provide an improved multi-driver loudspeaker construction which eliminates the need for a separate mounting apparatus for the mid or upper frequency driving units.
  • Accordingly the present invention uses a piezoelectric transducer as the second driver, and has a second diaphragm with an apex, and is characterised in that the piezoelectric transducer is supported within the interior of the first diaphragm solely by attachment of the piezoelectric transducer to the apex of the second diaphragm and attachment of the second diaphragm to an intermediate region of the first diaphragm between its apex and its interior, so that the piezeoelectric transducer moves with the first diaphragm.
  • In this configuration, the entire mechanism which constitutes the tweeter moves in unison with the low frequency diaphragm in the piston range and forms a part of the total moving mass of the low frequency driver. This configuration eliminates the customarily used mounting post or brackets which support the high frequency unit(s) and also improves the overall frequency response, dispersion, time, and phase characteristics of the loudspeaker system.
  • The present invention will be more readily understood by those skilled in the art upon reading the following detailed description in conjunction with the accompanying drawing in which:
    • Fig. 1 is a cross-sectional view of a multi-driver loudspeaker system constructed according to the present invention;
    • Fig. 2 is a front elevational view of a multi-driver loudspeaker system constructed according to the present invention;
    • Fig. 3 is a sectional view of the system of Fig. 2, taken generally along section lines 3-3 thereof;
    • Fig. 4 is a front elevational view of a multi-driver loudspeaker system constructed according to the present invention; and
    • Figs. 5-7 are frequency response characteristics of a prior art speaker and two speakers constructed according to the present invention.
  • In the embodiment of the invention illustrated in Fig. 1, the low frequency transducer or woofer is of the permanent-magnet, moving-coil type and comprises a permanent-magnet assembly 10 to which is secured a frame 12 having a generally somewhat conical configuration. The frame 12 defines an aperture 13 which defines generally the frontal shape and area of the transducer. The shape of the aperture 13 formed by the frame can be other than circular, for example, oval. The woofer diaphragm 14 extends or flares generally conically outwardly and has its outer edge secured to the periphery of the frame 12 by means of a compliant suspension 16. The inner portion of the diaphragm 14 is secured to a voice coil form 18 upon the lower portion of which is the voice coil 20 which surrounds the center pole 22 of the permanent-magnet assembly 10 with the voice coil positioned in the magnetic air gap 24 in the customary fashion. Up to this point in the description, the construction of the transducer is entirely conventional.
  • The high frequency transducer of tweeter comprises the tweeter cone 30, the central axis of which is typically aligned with the central axis of the woofer cone 14. The tweeter cone 30 has a somewhat greaterflare rate and is of substantially smaller dimension than the woofer cone 14. At the outer periphery of cone 30, a foam compliance ring 34 may be positioned between the edge of cone 30 and the surface of diaphragm 14. Behind the diaphragm 30 and extending along a portion of the surface thereof, dampening or stiffening material 32 and 36 can be provided to smooth response and isolate the lead wires if desired. The driver element 38 is positioned at the apex of cone 30. This driver element 38 comprises a piezoelectric crystal commonly known in the trade as a bimorph or multimorph. The electrical leads 40 are coupled to the crystal 38, and extend out through the woofer cone 14 in conventional manner to input terminals 44 mounted upon a portion of the frame 12. The leads 40 from the crystal 38 join leads 43 which couple terminals 44 to the voice coil 20. The crystal 38 and voice coil 20 are thus electrically coupled in parallel.
  • The connection of the single pair of input leads to both drivers 38 and 20 without utilization of a crossover network is made possible because the crystal driver 38 functions as a high-pass filter as well as a tweeter driver, and depending upon the thickness, coupling coefficient and diameter of the crystal 38 and the diameter of cone 30 and its shape, etc., provides an effective crossover frequency in the range anywhere from one to ten kilohertz. An external filter network can be used if desired.
  • The damping rings 32 and 36, which illustratively can be formed of fibreglass insulating material, are to suppress undesired vibrational modes while the foam compliance ring 34 provides a means to control the mechanical coupling between the woofer and tweeter cones 14, 30 in the crossover region of response. A desirable acoustic response can thus be achieved by appropriate selection of the material, the dimensions, the symmetry, and the position of the tweeter mechanism as well as variations in the decoupling ring 34 and damping rings 32 and 36. The tweeter cone 30 can be suspended in front of the woofer cone in several ways. The tweeter cone 30 perimeter can be attached to the woofer cone directly, or through a compliant member. The tweeter cone 30 can be mounted to any suitable portion of the woofer cone 14 body, in order to provide wide angle dispersion.
  • When operating in response to low frequency electrical signals, the transducer assembly appears much as if it were a single piston. The operation in response to high frequency signals above the crossover frequency adds to the translational motion of the high frequency cone 30 essentially as if it were acting alone except that it is, in effect, mounted upon a support which exhibits little or no movement at these high frequencies. The decoupling arrangement disposed between the woofer cone 14 and tweeter cone 30 provides a method to control the degree of motion and phase between the two cones in the midband and upper band response regions, thus providing a means to control the electromechanical feedback to the tweeter driving element, as described by the reciprocity principle. This provides a smooth frequency response characteristic in the mid- and upper band response regions. This mounting arrangement between the diaphragms 14,30 leads to improved frequency response and dispersion for the overall system and to improved time phase coherence throughout the desired frequency range. From a mechanical point of view, the arrangement of the present invention also eliminates the need for the supplemental mounting brackets customarily used in other coaxial systems to support the higher frequency drivers.
  • In another embodiment of the invention illustrated in Figs. 2 and 3, a permanent-magnet assembly 110 is secured to a frame 112 having a generally elliptical or oval frontal opening, illustratively 6 inches by 9 inches (15.24 cm by 22,86 cm). The woofer diaphragm 114 extends generally conically outwardly. The outer rim of diaphragm 114 is secured to the oval front opening of the frame 112 by means of a compliant suspension 116. The inward portion of the diaphragm 114 is secured to a voice coil form 118 to which is attached a woofer voice coil 120 positioned in the magnetic air gap 124 in the customary fashion.
  • The tweeter of this embodiment comprises a tweeter cone 130, the central axis of which is about 45° off the axis of the woofer cone 114, as best illustrated in Fig. 3. A junction area 131 is provided at the outer perimeter of cone 130. This junction area 131 is glued or otherwise attached, with or without a compliant member, to the perimetral edge 135 of an opening 133 provided in the woofer cone 114. A piezoelectric bimorph crystal driver element 138 is positioned at the apex of cone 130. Electrical leads 140 are coupled to the crystal 138 and extend to terminals 145 provided on the outside surface of woofer cone 114. The leads 140 from the crystal 138 are coupled by leads 142 to the input terminals 144 provided on the supporting frame 112. Leads 142 also couple terminals 144 to the woofer voice coil 120. The woofer voice coil 120 and tweeter driver 138 thus are coupled in parallel.
  • Again, the coupling of the single pair of input leads 142 to both drivers 138 and 120 without a divider or crossover network is made possible because the crystal driver 138 acts as a high pass filter.
  • In another embodiment of the invention illustrated in Fig. 4, a permanent-magnet assembly (not shown) is secured to a frame 121 having a generally circular frontal opening. The tweeter cones 230 can be molded into the woofer cone body 214, making the surrounding portion of the woofer cone 214 an extension of the tweeter cone body. A woofer diaphragm 214 flares generally conically outwardly. Its outer perimeter is secured to a circular frontal opening provided in the frame 212 by means of compliant suspension 216. The inner portion of the diaphragm 214 is secured to a voice coil form upon which is provided a voice coil which surrounds the center pole of the permanent-magnet assembly with the voice coil positioned in the air gap, all in a manner previously discussed.
  • Four high frequency transducers or tweeters 229 are mounted in the woofer diaphragm 214 in a manner similar to the tweeter diaphragm mounting illustrated in Fig. 3. Each tweeter 229 comprises a tweeter cone 230, the central axis of which is illustratively 45° off the central axis of the woofer cone 214, as in the embodiment of Figs. 2 and 3. The tweeter cones' axes are also positioned at 90° intervals about the woofer cone 214 axis. As before, the tweeter cones 230 have somewhat greater flares and are of substantially smaller dimension than the woofer cone 214. A piezoelectric driver element (not shown) is positioned at the apex of each cone 230. The electrical terminations (not shown) to the crystals which drive tweeter cones 230 are made as in the preceding embodiments. Again, the crystal drivers function as high-pass filters, and the frequency responses of the drivers are selectable in part by proper selection of the physical parameters of the various drivers and tweeter cones 230.
  • The advantages of the off-axis placement of the tweeter axes from the woofer axis in the embodiments of Figs. 1-4 can best be appreciated with reference to Figs. 5-7.
  • Fig. 5 illustrates the frequency response of a prior art 6" by 9" (15.24 cm by 22.86 cm) oval speaker with a coaxial secondary cone called a "whizzer". The three-frequency response curves correspond to the on-axis (0°) frequency response of the speaker, the 30° off-axis frequency response of the speaker, and the 45° off-axis frequency response of the speaker. It will be appreciated that, even with the whizzer cone, the off-axis (30° and 45° off-axis) response of the speaker is significantly below the on-axis response (1-3 dB) even at such low frequencies as 2 KHz. At about 4 KHz, the off-axis performance has degraded even more seriously (30° off-axis down about 5 dB, 45° off-axis down 14 dB). At 15 KHz, 30° off-axis is down 13 dB, and 45° off-axis is down about the same amount.
  • Fig. 6 illustrates the frequency responses of a 6" by 9" (15.24 cm by 22.86 cm) elliptical constructed in accordance with Fig. 1. Although the off-axis response at 2 KHz remains down about 1 and 3 dB (at 30° off-axis and 45° off-axis, respectively), at 5 KHz, the 30° off-axis response is down only about 1-1.5 dB, a 3.5-4 dB improvement over Fig. 5, and the 45° off-axis response is only down 8-8.5 dB, a 5.5-6 dB improvement over Fig. 5. At 15 KHz, the improvement is equally as significant, with the 30° off-axis response being down only about 10.5 dB, a 2.5 dB improvement over Fig. 5, and the 45° off-axis only being down 8.5 dB, a 5.5 dB improvement over Fig. 5.
  • The frequency response characteristics of the Figs. 2 and 3 embodiment of the invention are illustrated in Fig. 7. In the embodiment tested for Fig. 7, the apex of the tweeter cone projected into the plane of the surrounding woofer cone lay half-way from the woofer cone axis to the compliance ring. In other words, the tweeter was mounted half-way out the woofer cone from the axis to the compliance ring. At 2 KHz, the 30° off-axis response was down about 1.5-2 dB and the 45° off-axis response was down 5 dB. At 4 KHz, the 30° off-axis performance was actually 1-1.5 dB above the on-axis performance and the 45° off-axis performance was only about 1.5-2 dB lower than on-axis, both substantial improvements over the embodiment of Fig. 5. At 15 KHz, the 30° off-axis performance and 45° off-axis performance were actually both substantially above the on-axis performance with 30° being about 4-5 dB above and 45° being about 10 dB above the on-axis performance.

Claims (10)

1. A multi-driver loudspeaker combination comprising a first generally cone-shaped diaphragm (14); a first driver (10, 18, 20) including a magnet structure (10) defining an air gap, a voice coil (20) lying within the air gap, and a voice coil former (18) for coupling the apex of the first diaphragm to the first driver, the voice coil being provided on the voice coil former, the first diaphragm and driver being effective to reproduce sound in the lower portion of the audio frequency range; a second driver (38) comprising a piezoelectric transducer; and a second generally cone-shaped diaphragm (30), the second diaphragm and driver being effective to reproduce sound in the upper portion of the audio frequency range; characterised in that the piezoelectric transducer is supported within the interior of the first diaphragm solely by attachment of the piezoelectric transducer to the apex of the second diaphragm and attachment of the second diaphragm to an intermediate region of the first diaphragm between its apex and its interior, so that the piezoelectric transducer moves with the first diaphragm.
2. The loudspeaker combination of claim 1, characterised in that the first diaphragm defines a first axis about which the first diaphragm is generally symmetrical, the second diaphragm defines a second axis about which the second diaphragm is generally symmetrical, and the angle between the first and second axes is non- zero.
3. The loudspeaker combination of either of claims 1 and 2, characterised in that there is a plurality of said second diaphragms and a plurality of said second drivers.
4. The loudspeaker combination of anyone of claims 1 to 3, characterised in that the second transducer is mounted on the first diaphragm by intermediate mounting means (34) permitting the second transducer to move with the diaphragm in an unrestrained manner.
5. The multi-driver loudspeaker combination of claim 4, characterised in that the intermediate mounting means comprise an annular base terminating at an edge, the second transducer including a diaphragm having an edge joined to the first-mentioned edge to support the second transducer from the annular base.
6. The loudspeaker combination of claim 5, characterised in that the said edge of the base and the diaphragm edge are closed generally planar curves.
7. The loudspeaker combination of any one of claims 4 to 6, characterised in that said intermediate mounting means comprises a compliance ring (34), mounted from the interior of the first diaphragm (14) and means for mounting the second diaphragm from the compliance ring.
8. The loudspeaker combination of any one of claims 1 to 6, characterised in that said second diaphragm (130) is mounted non-concentrically with respect to said first diaphragm (114).
9. The loudspeaker combination of any one of claims 1 to 8, characterised in that said first diaphragm (114) includes said second diaphragm (130) as an integral part thereof, the second transducer being separately driven.
10. The loudspeaker combination according to claim 1, characterised in that the second diaphragm (30) is concentric with respect to the first diaphragm (14).
EP19830302913 1982-06-01 1983-05-20 Multi-driver-loudspeaker Expired EP0095876B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US06/383,603 US4497981A (en) 1982-06-01 1982-06-01 Multi-driver loudspeaker
US383603 1982-06-01
US48932283A 1983-04-28 1983-04-28
US489322 1995-06-12

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EP0095876A2 EP0095876A2 (en) 1983-12-07
EP0095876A3 EP0095876A3 (en) 1985-08-28
EP0095876B1 true EP0095876B1 (en) 1988-11-23

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EP19830302913 Expired EP0095876B1 (en) 1982-06-01 1983-05-20 Multi-driver-loudspeaker

Country Status (7)

Country Link
EP (1) EP0095876B1 (en)
JP (1) JPH0646839B2 (en)
AU (1) AU559440B2 (en)
CA (1) CA1204498A (en)
DE (1) DE3378559D1 (en)
DK (1) DK161295C (en)
MX (1) MX159045A (en)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4554414A (en) * 1983-04-28 1985-11-19 Harman International Industries Incorporated Multi-driver loudspeaker
JPS606398U (en) * 1983-06-24 1985-01-17 オンキヨー株式会社 composite speaker
US4590333A (en) * 1984-06-14 1986-05-20 John Strohbeen Multidriver loudspeaker
GB2248996A (en) * 1990-10-17 1992-04-22 Canon Res Ct Europe Ltd Speaker assembly
WO1992007449A1 (en) * 1990-10-17 1992-04-30 Canon Research Centre Europe Ltd Sound output device
FR2706723A1 (en) * 1993-06-18 1994-12-23 Rigondeau Robert Electro-acoustic transducer consisting of two separate motors integral with each other
GB2427522B (en) 2005-06-22 2008-07-16 Gp Acoustics Compound Loudspeaker
CN102106158A (en) * 2008-07-24 2011-06-22 珍尼雷克公司 Nested compound loudspeaker drive unit
GB2597988A (en) * 2020-08-13 2022-02-16 Full Stack Acoustic Ltd Loudspeaker apparatus, Loudspeaker system, display panel and systems thereof

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2453521A (en) * 1942-05-30 1948-11-09 Rca Corp Superimposed duplex loud-speaker
US2593031A (en) * 1948-05-01 1952-04-15 Gulton Mfg Corp Loud-speaker
GB830351A (en) * 1956-08-02 1960-03-16 Whiteley Electrical Radio Comp Improvements in or relating to electric transducers
JPS499227U (en) * 1972-04-22 1974-01-26
US4122315A (en) * 1977-06-13 1978-10-24 Pemcor, Inc. Compact, multiple-element speaker system
JPS5511753Y2 (en) * 1977-08-12 1980-03-13
JPS565431U (en) * 1979-06-28 1981-01-19
JPS5852634Y2 (en) * 1979-07-06 1983-11-30 アルプス電気株式会社 Circuit board with electroluminescent elements
JPS5694900A (en) * 1979-12-27 1981-07-31 Seiko Instr & Electronics Ltd Multiway speaker
JPS5734681U (en) * 1980-07-29 1982-02-23
JPS6035344Y2 (en) * 1980-08-22 1985-10-21 オンキヨー株式会社 Composite speaker
JPS58135200U (en) * 1982-03-05 1983-09-10 オンキヨー株式会社 2 way speaker

Also Published As

Publication number Publication date
AU1495783A (en) 1983-12-08
DK161295B (en) 1991-06-17
DK244983D0 (en) 1983-05-31
JPH0646839B2 (en) 1994-06-15
MX159045A (en) 1989-04-13
DK161295C (en) 1991-12-30
DE3378559D1 (en) 1988-12-29
EP0095876A3 (en) 1985-08-28
EP0095876A2 (en) 1983-12-07
CA1204498A (en) 1986-05-13
JPS5941999A (en) 1984-03-08
AU559440B2 (en) 1987-03-12
DK244983A (en) 1983-12-02

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