Patent Application
20120257783
Not Applicable
Not Applicable
1. Technical Field
The present invention relates generally to acoustic transducers. More particularly, the present invention relates to coaxial loudspeaker drivers having independent voice coil elements each being driven by a single magnet.
2. Related Art
Loudspeakers, or acoustic transducers, are universally known and utilized in sound reproduction systems. Essentially, loudspeakers convert electrical energy to acoustic energy according to any one of a variety of well-understood operational principles. Such operational principles are embodied in various designs generally categorized as electrodynamic, electrostatic, piezoelectric, or discharge, among others.
The most common type of loudspeaker is of the electrodynamic variety, in which an electrical signal representative of the specified audio is applied to a voice coil wound around a bobbin and suspended between opposite poles of a magnet. The region between the poles is known as the air gap, and the magnetic field present therein interacts with the electrical signal conducted through the voice coil. The electromagnetic force moves the voice coil, and thus the bobbin, within the air gap, and the displacement or movement thereof is controlled by the magnitude and direction of current in the voice coil and the resulting axial forces. The bobbin is also attached to a cone-shaped semi-rigid diaphragm, and the vibration of the bobbin is correspondingly transferred to the diaphragm. The vibration of the diaphragm causes pressure differences in the surrounding air, thereby producing sound. The base of the diaphragm is flexibly suspended from the rim of the loudspeaker basket, thereby allowing constrained movement while providing lateral stability.
In general, loudspeaker designs aim for faithful re-creation of the sound or acoustic waveform represented by the electrical signal. The typical acoustic waveform is a combination of continuous waveforms of different magnitudes, frequencies, and phases. In this regard, the electrodynamic loudspeaker was characterized by a number of advantages over other designs, including a wide frequency range and efficiency. However, a single loudspeaker cannot reproduce sounds across the entire audible frequency range, due to limitations imposed by weight and size of the diaphragm and bobbin. For instance, while a large diaphragm is capable of handling acoustic waveforms of high magnitudes or louder sounds, its increased weight limits the capability to vibrate at higher frequencies. On the other hand, a small diaphragm is capable of vibrating at higher frequencies, but because of its fragility, higher magnitude waveforms may result in tearing or other damage. Essentially, the size and relative density of the diaphragm are to be configured for a particular frequency range of the acoustic waveform. Although so-called full range loudspeakers have been developed, the response at the peripheral frequencies is less than optimal and results in distortion.
To overcome the above-noted deficiencies, a number of solutions have been proposed for achieving optimal sound reproduction as an alternative to so-called full-range loudspeaker drivers. For example, a standalone system may include more than one loudspeaker driver, each being configured for a particular frequency range. The system may include a tweeter, or loudspeaker driver for high frequency sound reproduction, a midrange driver, and a woofer, or loudspeaker driver for low frequency sound/bass reproduction. It is understood that tweeters have a frequency range of approximately 2,000 to 20,000 Hz, midrange drivers have a frequency range of approximately 300 to 5,000 Hz, and woofers have a frequency range of approximately 40 to 1,000 Hz.
Oftentimes it is undesirable or even impractical to utilize more than one loudspeaker driver in a given installation. In response, loudspeakers having a separate tweeter attached in a co-axial relation to the woofer or midrange driver have been conceived, the earliest example of which is U.S. Pat. No. 2,269,284 to Olson. The Olson device contemplates multiple diaphragms of successive size arranged in a nested, overlapping relationship, with one diaphragm being connected to another with a flexible compliance. The voice coils coupled to the respective one of the diaphragms are also in a nested relation. In response to the complexity associated with the interrelated movement of the diaphragms and voice coils in the Olson device, U.S. Pat. No. 5,295,194 to Christensen contemplates the addition of a tweeter to the voice coil bobbin of the woofer. The tweeter of the Christensen device is piezoelectric, and so is driven independently of the woofer. When the voice coil bobbin of the woofer vibrates at a low frequency, so does the entire tweeter. Thus, one diaphragm is mechanically linked to another.
Alternatively, coaxial loudspeaker devices with drivers that were neither linked mechanically not electrically to the other drivers in the device have been contemplated, such as that disclosed in U.S. Pat. No. 4,552,242 to Kashiwabara. The straightforward solution provided for the stacking of one driver on top of another, with each having its own electromagnetic circuit and diaphragm. However, the Kashiwabara device increased the weight and profile of the loudspeaker.
Accordingly, there is a need in the art for an improved coaxial loudspeaker.
In accordance with one embodiment of the present invention, a coaxial loudspeaker for reproducing an electrical sound signal is provided. The coaxial loudspeaker may include a magnetic driver assembly having a top end portion, where the top end portion defines a first annular slot of a first circumference. Additionally, the magnetic driver assembly may have an opposed bottom end portion that defines a second annular slot of a second circumference. The first annular slot may be coaxial with the second annular slot, with each annular slot establishing a permanent magnetic field therein. The coaxial loudspeaker may also include first and second voice coils positioned within the respective one of the first and second annular slots. Each of the first and second voice coils may be axially driven based upon interactions between the electrical sound signal delivered thereto and the corresponding one of the permanent magnetic fields. It is contemplated that the first voice coil is driven independently of the second voice coil.
An embodiment of the coaxial loudspeaker may also include a cylindrical yoke with a cylinder body and a top inward flange. Further, the coaxial loudspeaker may include a top pole piece having a pole body and a bottom outward flange, where the cylindrical yoke is coupled to the top pole piece. The coaxial loudspeaker may also include a ring magnet attached to the cylindrical yoke and the top pole piece. A portion of the pole body may be spaced in an opposed relation to the top inward flange to define the first annular slot. Further, a portion of the cylinder body may be spaced in an opposed relation to the bottom outward flange to define the second annular slot.
The present invention will be best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.
These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which:
a and 4b are perspective views of the magnetic driver assembly, illustrating the differences between a first annular slot on the top end portion and a second annular slot on the bottom end portion;
Common reference numerals are used throughout the drawings and the detailed description to indicate the same elements.
The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. It is understood that the use of relational terms such as first and second, top and bottom, and the like are used solely to distinguish one from another entity without necessarily requiring or implying any actual such relationship or order between such entities.
With reference to
Referring to
The magnetic driver assembly 22 also includes a top pole piece 36 that has a pole body 38 and a bottom outward flange 40. In further detail, the pole body 38 is segregated into a first section 44 and a narrowed second section 46. The pole body also defines an outer surface 48 that is perpendicular to a top surface 50. The bottom outward flange 40 defines an outer flange lip 52 that extends in a parallel relation to the outer surface 48, an upper horizontal flange surface 54, and an opposed bottom horizontal flange surface 56.
The cylindrical yoke 24 is receptively coupled to the top pole piece 36, and connected via an annular magnet 60. The magnet 60 defines an inner circumference 62 and an outer circumference 64, and connecting the inner and outer circumferences 62, 64 and extending in a perpendicular relation thereto are a top magnet surface 66 and an opposed bottom magnet surface 68. The annular magnet 60 is coupled to the top pole piece 36 in a sleeved relationship, and thus the inner circumference 62 of the annular magnet 60 faces the outer surface 48 of the top pole piece 36. The bottom outward flange 40 of the top pole piece 36 is attached to the annular magnet 60, specifically, the upper horizontal flange surface 54 is in frictional engagement with the bottom magnet surface 68. Further, the top inward flange 28 of the cylindrical yoke 24 is attached to the annular magnet 60, where the top magnet surface 66 is in frictional engagement with the inner surface 29. The outer circumference 64 faces the yoke wall 25 in this configuration. It is contemplated that the thickness of the magnet 60 is such that upon engagement to the cylindrical yoke 24 and the top pole piece 36, the top flange surface 35 is coplanar with the top surface 50, and the base surface 31 is coplanar with the bottom horizontal flange surface 56.
It is noted that the cylindrical yoke 24 and the top pole piece 36 are connected through the annular magnet 60, and thus the magnetic driver assembly 22 includes annular slots defined by its constituent parts. In further detail as illustrated in
In addition to mechanically linking the cylindrical yoke 24 to the top pole piece 36, the annular magnet 60 generates a magnetic field within the first and second annular slots 74, 76. As best illustrated in
Positioned within the first annular slot 74 or air gap is a first or tweeter voice coil 78. More particularly, the tweeter voice coil 78 is a coil of lightweight wire wrapped around a first bobbin 80, and has one or more lead lines connected to an electrical signal source. As explained above, the electrical signal transmitted through the tweeter voice coil 78 interacts with the permanent magnet field in the first annular slot 74, thereby driving the first bobbin 80 in a reciprocating manner along the primary axis 12. Opposite the tweeter voice coil 78, the first bobbin 80 is attached to a tweeter dome 82, which defines a convex outer surface 84 and an opposed concave inner surface 86. The tweeter dome 82 is further defined by an outer rim region 88, to which the first bobbin 80 is attached. The outer rim region 88 is also attached to a flexible tweeter surround 90 having an arcuate compliant portion 92, and a flat linking portion 94. It is understood that the flexible tweeter surround 90 supportively suspends the first bobbin 80, and thus the tweeter voice coil 78, within the first annular slot 74 while allowing limited movement therein.
A top plate 96 vertically offsets the tweeter surround 90 and the tweeter dome 82 from top flange surface 35 to provide sufficient excursion space for the first bobbin 80. The top plate 96 defines an inner rim 98 that has a third diameter D3 that is greater than the first diameter D1. The inner rim 98 defines an opening with which the first bobbin 80 is aligned. The top plate 96 is cooperatively engaged to the cylindrical yoke 24. In particular, the cylindrical yoke 24 defines a notched corner shoulder 100 in the junction between the top inward flange 28 and the substantially perpendicular cylinder body 26. Along these lines, the top plate 96 includes a perpendicular lip 102 or outer rim that is sized and configured to mate with the notched corner shoulder 100. It is contemplated that the combined structure of the perpendicular lip 102 and the notched corner shoulder 100 centers the top plate 96 about the primary axis 12, so long as the cylindrical yoke 24 is centered about the primary axis 12 as well.
It is to be understood that the tweeter 18 includes the aforementioned tweeter voice coil 78, the first bobbin 80, the tweeter dome 82, the flexible tweeter surround 90, and the top plate 96. As indicated above, the tweeter 18 is understood to reproduce a first or high frequency range. Thus, first frequency components of the composite electrical signal are transmitted to the tweeter voice coil 78, which interacts with the permanent magnet and causes the first bobbin 80 to vibrate at the first or high frequency range. Vibration of the first bobbin 80, in turn, is translated into a corresponding vibration of the tweeter dome 82. One of ordinary skill in the art will be able to ascertain the appropriate materials with which the tweeter dome 82 is constructed, and are generally characterized by an optimal combination of rigidity, low weight, and high damping. Such materials include titanium, silk, paper, or fabric.
In one embodiment, the magnetic driver assembly 22 may be bare as illustrated in
Positioned within the second annular slot 76 is a second or woofer voice coil 104 wound to a second bobbin 106. As described in relation to the tweeter voice coil 78, the woofer voice coil 104 is likewise a coil of lightweight wire wrapped around the second bobbin 106. The woofer voice coil 104 includes one or more lead lines connected to an electrical signal source. The electrical signal conducted through the woofer voice coil 104 interacts with the permanent magnetic field in the second annular slot 76, thereby driving the second bobbin 106 in a reciprocating manner along the primary axis 12.
With reference to
The second bobbin 106 is understood to have a diameter larger than that of the bottom pole piece 116, and is in a sleeved relation to the same. The woofer voice coil 104 is attached to a top end of the second bobbin 106, and the opposed bottom end is attached to a woofer diaphragm 132. The woofer diaphragm 132 defines a central opening 134 best shown in
The woofer diaphragm 132 is suspended from the flat frontal rim 110 via a woofer suspension 140. It is understood that the woofer suspension 140 is defined by a rigid inner rim 142, a flexible portion 143 having an arcuate cross section, and a rigid outer rim 146. The rigid inner rim 142 is attached to the outer perimeter 138 of the woofer diaphragm 132, while the rigid outer rim 146 is attached to the flat frontal rim 110 of the frustoconical basket 108. As will be appreciated by those having ordinary skill in the art, the woofer suspension 140 may be constructed of any sufficiently flexible material such as foam or rubber. Thus, the woofer diaphragm 132 may vibrate along the primary axis 12 in conjunction with the second bobbin 106, subject to the flexing limitations of the woofer suspension 140.
Further lateral support of the second bobbin 106 and the woofer diaphragm 132 is provided by a first annular damper 144, otherwise known in the art as a spider. The first annular damper 144 is defined by an outer rim 146 attached to a ledge 148 of the basket 108, and an inner rim 150 attached to the junction between the second bobbin 106 and the woofer diaphragm 132. The first annular damper 144 includes a corrugated center portion 152 that limits the lateral excursion of the second bobbin 106. Additionally, with reference to
The woofer 20 includes the aforementioned woofer voice coil 104, the second bobbin 106, the woofer diaphragm 132, the woofer suspension 140, and the first annular damper 144. As indicated above, the woofer 20 is understood to reproduce a second or low frequency range. Thus, second frequency components of the composite electrical signal are transmitted to the woofer voice coil 104, which interact with the permanent magnet. This interaction causes the second bobbin 106 to vibrate at the second or low frequency range, which in turn is translated into a corresponding vibration of the woofer diaphragm 132. The woofer diaphragm 132 may be constructed of paper, polypropylene, carbon-fiber composite material, hemp, Kevlar, or any other sufficiently lightweight yet resilient material suitable for acoustic applications. Although in the illustrative embodiment of the present invention the face of the frustoconical basket 108 and the woofer diaphragm 132 is elliptical in shape, it will be appreciated that other shapes, such as circular shapes, are within the scope of the present invention.
As indicated above, the first annular slot 74 is located on the top end portion 70 of the magnetic driver assembly 22, while the second annular slot 76 is located on the bottom end portion 72 of the same. Accordingly, it is understood that the tweeter voice coil 78 is vertically offset relative to the woofer voice coil 104. It is contemplated that while the axial movement of the tweeter voice coil 78 is independent of the woofer voice coil 104 because the two are electrically isolated, the single source of the permanent magnetic flux with which they interact is the annular magnet 60. In other words, both the tweeter voice coil 78 and the woofer voice coil 104 are driven by a single magnet, i.e., the annular magnet 60. Accordingly, the overall profile and weight of the coaxial loudspeaker 10 is reduced. As illustrated in
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11769093 | Jun 2007 | US |
| Child | 13430409 | US |
