EP3611934A1

EP3611934A1 - Portable audio system with acoustic waveguide

Info

Publication number: EP3611934A1
Application number: EP18189089.8A
Authority: EP
Inventors: Kai-Li Wang; James Thomson
Original assignee: Tymphany Hong Kong Ltd
Current assignee: Tymphany Hong Kong Ltd
Priority date: 2018-08-15
Filing date: 2018-08-15
Publication date: 2020-02-19

Abstract

A portable audio system includes a housing defining a common acoustic cavity a woofer disposed at a first end of the housing in the common acoustic cavity and a tweeter disposed at a second end of the housing, opposite to the first end, in the common acoustic cavity facing the woofer. A waveguide is disposed in the common acoustic cavity between the woofer and the tweeter to separate the woofer and the tweeter. The waveguide disperses and distributes sound waves generated by the woofer and tweeter.

Description

Field of the invention

The present invention relates to an audio system and more particularly to an audio system including an acoustic diffuser, for example an acoustic waveguide, between the drivers of the audio system.

Background of the invention

Drivers are transducers that generate various ranges of sound frequencies. Audio systems with speakers are known to include a plurality of drivers that are configured to generate sounds of varying frequencies. Audio systems often use multiple drivers to enhance sound quality. For example, audio systems often will use tweeters for producing sound in a high-frequency range, woofers for producing sound in a low frequency range and midrange drivers for producing sound in midrange frequencies. Providing such combinations of multiple drivers can advantageously cover all ranges of audible sound. Typically, the drivers are mounted coaxially. Such speakers are commonly referred to as omnidirectional speakers.
For example, U.S. Patent No. 8,130,994 is directed to a speaker with two drivers. Specifically, the speaker includes a woofer and tweeter that are coaxially aligned and project sound toward a same direction. The speaker also includes a waveguide that works as a low pass filter for facilitating low frequencies.
Furthermore, U.S. 9,549,237 is directed to a speaker having two drivers, each having a waveguide. The two drivers include a woofer and tweeter coaxially aligned and disposed apart from one another.
A problem with such speakers, however, is that it is difficult to reduce the size of the audio system/speaker. Additionally, using, for example, a woofer in combination with a tweeter can result in intermodulation distortion.

Summary of the invention

In view of the foregoing and other exemplary problems, drawbacks, and disadvantages of the conventional methods and structures, an exemplary feature of the present invention is to provide a speaker/audio system with improved omnidirectional sound quality.
The invention relates to an audio system, comprising two loudspeaker drivers having different diaphragm dimensions and configured for different frequency bands. The two loudspeaker drivers are disposed coaxially and facing each other in a common acoustic cavity. An acoustic diffuser is disposed between the two loudspeaker drivers in the common acoustic cavity. The acoustic diffuser has two main surfaces, each facing a respective one of the two loudspeaker drivers and the two main surfaces being coaxial with the two loudspeaker drivers. The two main surfaces have different shapes.
In accordance with the present invention is thereby provided an omnidirectional speaker/audio system with improved sound directivity (i.e., more even from different angles). Furthermore, the speaker/audio system is able to provide a flatter frequency response. Finally, the speaker/audio system is able to reduce or eliminate intermodulation distortion as a result of the drivers (e.g., tweeter and woofer) acoustically interacting with each other.
In an advantageous embodiment, the two loudspeaker drivers comprise a woofer configured for a lower frequency band of said different frequency bands, and a tweeter configured for an upper frequency band of said different frequency bands.
In an advantageous embodiment, the audio system includes only one acoustic diffuser. The diameter of the acoustic diffuser preferably corresponds to the diameter of the diaphragm of one of the two loudspeaker drivers or any diameter between them.
In an advantageous embodiment, the tweeter is recessed in a cavity by a recess wall within the common acoustic cavity, the recess wall preferably being smoothly rounded.
In an advantageous embodiment, the acoustic diffuser comprises a waveguide, and wherein the first main surface and the second main surface are preferably smoothly connected to each other. The diameter of the circumference of the acoustic diffuser preferably does not exceed in size a diameter of a diaphragm of the woofer.
In an advantageous embodiment, the acoustic diffuser is mounted within the audio system by a plurality of mechanical elements, which are preferably substantially acoustically transparent. The first main surface is preferably convex facing the woofer, and the second main surface facing the tweeter is preferably bell-shaped.
In an advantageous embodiment, the shape of a diaphragm cone of the woofer substantially corresponds to the shape of the first main surface, and/or the first main surface is substantially parallel to a diaphragm cone of the woofer. In an advantageous embodiment, the first main surface and the second main surface have different shapes.
The present invention further relates to a portable audio system, comprising the audio system according to any of the above; and a housing defining the common acoustic cavity. A first of the two loudspeaker drivers is a woofer disposed at a first end of the housing in the common acoustic cavity and a second of the two loudspeaker drivers is a tweeter disposed at a second end of the housing, opposite to the first end, in the common acoustic cavity facing the woofer.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention as claimed will become apparent to those skilled in the art from this detailed description.

The drawings

Various embodiments of the invention will in the following be described with reference to the drawings where

fig. 1 illustrates a cross-sectional principle diagram of a portable speaker according to an exemplary embodiment of the present invention,
fig. 2 illustrates schematically the coaxial configuration of an embodiment of the invention,
fig. 3 illustrates a more detailed cross-sectional view of a portable speaker according to an exemplary embodiment of the present invention,
figs. 4-6 are cross-sectional views of various embodiments of waveguides according to an embodiment of the invention,
fig. 7 is a perspective view of a waveguide of a portable speaker of an embodiment of the invention, and
figs. 8-10 are perspective views of audio systems according to embodiments of the present invention.

Detailed description

Referring now to the drawings, exemplary embodiments of the present invention are described in more detail below.
Figure 1 illustrates an audio system 100, for example a compact speaker, for example a portable speaker such as a Bluetooth speaker, or a compact satellite speaker for a home theater setup, in accordance with an exemplary, non-limiting embodiment of the present invention. The speaker 100 has an outer housing 110 defining an acoustic cavity 112. In the compact speaker 100 of the present invention, the acoustic cavity 112 is a common acoustic cavity in that all components of the speaker 100 are disposed within a same acoustic cavity.
The speaker 100 includes a pair of loudspeaker drivers. Specifically, the speaker 100 includes a tweeter 130 and a woofer 120. Besides their exemplary diaphragms 122 and 132, only the circumferences of the drivers are illustrated in dashed lines to indicate the numerous various possible configuration of loudspeaker drivers as appreciated by the person skilled in loudspeaker driver design. The tweeter 130 and the woofer 120 are optimized to be efficient, reproducing different frequencies. That is, the tweeter 130 and the woofer 120 are configured to reproduce different frequency bands. Together, the woofer 120 and the tweeter 130 are preferably able to generate sound over a range from low bass at 20 - 80 Hz to high treble at 15,000 - 20,000 Hz, ideally from 20 Hz to 20,000 Hz. The woofer 120 is optimized for generation of sound in the lower band up to a crossover frequency, and the tweeter 130 optimized for the higher band from the crossover frequency and up. The crossover frequency is selected in accordance with the specific drivers, the intended usage, etc., as the skilled person is well aware. The crossover frequency may for example be selected between 350 Hz and 5,000 Hz, for example at 2,000 Hz, whereby for example the tweeter 130 is a high frequency driver that may generate sound over a range of 2,000 Hz to 20,000 Hz, and the woofer 120 is a low frequency driver that may generate sound over a range of 40 Hz to 2,000 Hz. In another example, the tweeter 130 is ranged from 500 Hz to 20,000 Hz, and the woofer 120 is ranged from 40 Hz to 500 Hz. The speaker 100 preferably comprises a suitable crossover filter, splitting the input audio signal into the two frequency bands suitable for the woofer 120 and tweeter 130, respectively. In another embodiment, the speaker 100 is optimized for use together with an external woofer, subwoofer or other bass driver, and the woofer 120 may then for example be a mid-range driver ranged from, e.g., 300 Hz to 3,000 Hz, and the tweeter 130 from, e.g., 3,000 Hz to 20,000 Hz. In another embodiment where the woofer 120 is a mid-range driver, a low bass woofer may be mounted in either end of the speaker 100 with a separate waveguide or no waveguide.
Moreover, as illustrated, one of the drivers is much larger than the other driver; in this specific example the dimensions, in particular the diaphragm 122 dimensions, of woofer 120, are significantly larger than the dimensions, in particular the diaphragm 132 dimensions, of tweeter 130. In various embodiments, the driver configured for the lower frequency band will typically be larger than the driver configured for the higher frequency band, in particular with regards to the diaphragm diameter.
The woofer 120 and tweeter 130 are configured to radiate sound within the speaker 100. Moreover, the woofer 120 and the tweeter 130 are mounted coaxially with respect to each other. That is, a center of the tweeter 130 and a center of the woofer 120 are aligned over a common vertical axis 116. The two drivers 120 and 130 are facing each other along the axis 116; that is, their diaphragms 122 and 132 are facing each other.
The speaker 100 also includes an acoustic diffuser 140 in the form of a waveguide positioned in the common acoustic cavity 112 between the woofer 120 and the tweeter 130. The waveguide 140 is positioned coaxially with the drivers 120 and 130 along axis 116. The dimension of the waveguide is preferably approaching the dimensions of the woofer 120, i.e. the dimensions of the diaphragms of the woofer 120, thereby preferably significantly larger than the dimensions of the tweeter 130.
In accordance with certain exemplary embodiments of the present invention the speaker 100 includes only a single waveguide 140 common for the woofer 120 and the tweeter 130. That is, in accordance with the present invention, it is not required to provide separate waveguides for the individual drivers.
The waveguide 140 is an acoustic diffuser that is configured to disperse and distribute the sound waves from the woofer 120 and the tweeter 130 so that the speaker 100 provides an omnidirectional radiation pattern at least along one axis. This is achieved by two waveguide surfaces 142 and 143. The waveguide 140 eliminates the intermodulation distortion as a result of both transducers acoustically interacting with each other, specifically at above approx. 8kHz.
Fig. 2 illustrates the coaxial configuration of the radiation surface 122 of the woofer 120, the radiation surface 132 of the tweeter 130 and the waveguide 140 along the common axis 116. As mentioned above, one of the drivers is larger than the other, and the diameter of the waveguide is in the range between the two drivers, possibly the same diameter as one of the drivers. Specifically in this example, the woofer radiation face 122 is the largest diameter, the tweeter radiation face 132 is the smallest diameter, and the waveguide 140 is between the two driver diameters, closer to the largest diameter.
Fig. 3 illustrates an embodiment of an audio system of the invention in more detail. The woofer 120 and tweeter 130 are held within the housing 110 by a frame 150. The frame 150 has a first frame portion 152 holding the woofer 120 and a second frame portion 154 holding the tweeter 130. The first frame portion 152 and the second frame portion 154 are connected by frame columns 156. The first frame portion 152 has a bottom portion 152a. The woofer 120 is secured to the bottom portion 152a. The second frame portion 154 has a top portion 154a. The tweeter 130 is secured to the top portion 154a. The woofer 120 and the tweeter 130 are mounted such that they face each other. Furthermore, the woofer 120 and tweeter 130 are contained together in the common acoustic cavity 112.
As further illustrated in Fig. 3, the first portion 152 of the frame 150 forms an acoustic cavity 153, within the common acoustic cavity 112, for the woofer 120. The diaphragm cone 122 of the woofer has a shape that substantially matches the shape of the first main surface 142 of the waveguide 140. Thus, the diaphragm cone 122 and the first main surface 142 are disposed substantially in parallel.
Furthermore, the second portion 154 of the frame 150 forms another acoustic cavity 155 for the tweeter 132 within the common acoustic cavity 112. The tweeter 130 is recessed into the acoustic cavity 155 so that the recess wall 158 around the tweeter 130 acts as a primary tweeter waveguide. The recess wall 158 is preferably smoothly rounded.
As is also illustrated in Fig. 3, the waveguide 140 is in this particular embodiment mounted to the bottom portion 152a of the first portion 152 of the frame 150. Specifically, the waveguide 140 is mounted by mechanical elements 146. The mechanical elements 146 are configured to hold the waveguide 140 in place and to not significantly modify the sound waves generated by the drivers. Specifically, the mechanical elements 146 are configured to be as acoustically transparent as possible.
Various other configurations of mounting the waveguide 140 between the woofer 120 and tweeter 130 are within the scope of the invention, for example reversing the mechanical elements 146 upside down so that the waveguide 140 can be mounted to the top portion 154a of the second portion 154 of the frame 150, or for example mounting the waveguide 140 to the frame columns 156 by means of suitable mechanical elements.
The outer housing 110 comprises a slit, grille, mesh or other kind of acoustic openings 114 to allow sound generated by the included drivers, e.g. the woofer 120 and tweeter 130, to escape from the speaker 100. The acoustic openings 114 may in various embodiments cover more or less of the surface of the outer housing 110, but are preferably at least located in the general area of the waveguide 140 and the radiation surfaces of the two drivers, for example as illustrated in Fig. 3 or Fig. 10, so as to correspond to the primary radiation directions of sound waves from the waveguide 140.
The outer housing 110 preferably forms additional space, e.g. as illustrate in Fig. 3, for housing electronics, such as a cross-over filter and input terminals for a passive speaker system, and in addition for an active speaker system, a power supply and an amplifier. The power supply may be batteries, an AC-DC adapter or simply an input for an external power supply, e.g. a USB charger or an AC-DC adapter. The electronics may also comprise an equalizer allowing optimization for the specific audio system configuration. A user interface comprising buttons and/or a display may also be provided in the housing. The audio system may further comprise wireless connectivity, e.g. for receiving audio signals and/or control signals via Bluetooth, WIFI, etc. The electronics such as cross-over filter and a possible equalizer, may for example be implemented by discrete electronic components and/or by means of a generic microprocessor or dedicated integrated circuits.
The waveguide 140 is illustrated in further detail in Figs. 4 - 7. The waveguide 140 includes a first main surface 142 and a second main surface 143. In the embodiment of Fig. 4, the two main surfaces 142, 143 are smoothly connected to one another. In the embodiment of Fig. 5, the waveguide is a monolithic piece comprising both main surfaces 142, 143. The monolithic waveguide in the embodiment of Fig. 5 is illustrated as a solid part, but may also be hollow.
As is illustrated in Fig. 6, regardless of the waveguide being assembled from two or more pieces as in Fig. 4 or being a monolithic piece as in Fig. 5, the waveguide 140 may preferably include, for example, four mechanical elements 146 for connection to a frame portion, e.g. as described below.
Fig. 7 illustrates an embodiment of a waveguide 140. The first main surface 142 and the second main surface 143 are held by a frame portion 144 with mechanical elements 146. For mounting in an audio system, e.g. the speaker 100, the mechanical elements 146 may be mounted on a frame, e.g. first frame portion 152 or second frame portion 154 of frame 150. For this mounting, the mechanical elements 146 may be mounted direction to frame 150 or frame columns 156, or be mounted by means of a mounting ring, such as the mounting ring 148 shown in Fig. 7. The first main surface 142 and the second main surface 143 respectively face the woofer 120 and the tweeter 130.
In a preferred embodiment, the two main surfaces 142, 143 of the waveguide 140 do not present steep geometries. Instead, the main surfaces are smooth so that air turbulences are minimized. Furthermore, both of the main surfaces 142, 143 are asymmetric presenting different geometries. That is, the main surface that faces the largest of the drivers has a convex geometry while the main surface that faces the smallest of the drivers has a very smooth cone or bell-like geometry. As noted above, according to certain exemplary embodiments of the invention, the woofer 120 is larger than the tweeter 130. Thus, in the exemplary configurations, e.g. in Figs. 1, 3 and 8 - 10, the first main surface 142 faces the woofer 120 and has a convex geometry toward the woofer 120. The second main surface 143 faces the tweeter 130 and has a very smooth cone or bell-like geometry.
The diameter of the waveguide 140 is configured to not exceed the diameter of the radiation surface of the larger of the two drivers/loudspeakers. Again, as noted above, according to certain exemplary embodiments of the invention, the woofer 120 is larger than the tweeter 130. Thus, the diameter of the waveguide 140 is configured to not exceed, in size, the diameter of the radiation surface of the woofer 120.
Figs. 8 - 9 illustrate perspective views of the assembled drivers, waveguide and frame according to embodiments of the present invention. The speaker 100 comprises a frame 150 with first frame portion 152 and second frame portion 154 connected by frame columns 156. In the viewing direction of Fig. 8 is most clearly seen the woofer diaphragm 122 of woofer 120 mounted to the bottom portion 152a of first frame portion 152, together with the mechanical parts 146 mounting the waveguide 140 to the bottom portion 152a. Further, the second main surface 143 of the waveguide 140 is seen. In the viewing direction of Fig. 9 is most clearly seen the tweeter diaphragm 132 of tweeter 130 recessed by recess wall 158 in the top portion 154a of second frame portion 154. Further, the first main surface 142 of the waveguide 140 is seen.
Fig. 10 illustrates a perspective view of a part of audio system 100 according to an embodiment of the invention. An outer housing 110 comprises acoustic openings 114, through which can be seen the waveguide 140 with first main surface 142 opposite the woofer diaphragm 122, and second main surface 143 opposite the tweeter diaphragm 132 slightly visible within the recess wall 158. Acoustic waves generated by the diaphragms of the woofer and tweeter are directed through the acoustic openings by means of the waveguide in order to form an omnidirectional two-way speaker.
It will be obvious that the above-described embodiments may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the invention, and all such modifications as would be obvious to one skilled in the art from the present disclosure and claims are to be included within the scope of the following claims.

Claims

An audio system (100), comprising:
two loudspeaker drivers (120, 130) having different diaphragm (122, 132) dimensions and configured for different frequency bands, the two loudspeaker drivers (120, 130) being disposed coaxially and facing each other in a common acoustic cavity (112); and

an acoustic diffuser (140) disposed between the two loudspeaker drivers (120, 130) in said common acoustic cavity (112), the acoustic diffuser (140) having two main surfaces (142, 143), each facing a respective one of the two loudspeaker drivers (120, 130) and the two main surfaces (142, 143) being coaxial with the two loudspeaker drivers (120, 130), wherein the two main surfaces (142, 143) have different shapes.
The audio system according to claim 1, wherein the two loudspeaker drivers (120, 130) comprise a woofer (120) configured for a lower frequency band of said different frequency bands, and a tweeter (130) configured for an upper frequency band of said different frequency bands.
The audio system according to claim 1 or 2, wherein the audio system (100) includes only one acoustic diffuser (140).
The audio system according to any of the claims 1-3, wherein the diameter of the acoustic diffuser (140) corresponds to the diameter of the diaphragm (122, 123) of one of the two loudspeaker drivers (120, 130) or any diameter between them.
The audio system according to any of the claims 2-4, wherein the tweeter (130) is recessed in a cavity by a recess wall (158) within the common acoustic cavity (112), the recess wall (158) preferably being smoothly rounded.
The audio system according to any of the claims 1-5, wherein the acoustic diffuser (140) comprises a waveguide (140), and wherein the first main surface (142) and the second main surface (143) are preferably smoothly connected to each other.
The audio system according to any of the claims 2-6, wherein a diameter of the circumference of the acoustic diffuser (140) does not exceed in size a diameter of a diaphragm (122) of the woofer (120).
The audio system according to any of the claims 1-7, wherein the acoustic diffuser (140) is mounted within the audio system (100) by a plurality of mechanical elements (146).
The audio system according to any of the claims 2-8, wherein the first main surface (142) is convex facing the woofer (120).
The audio system according to any of the claims 2-9, wherein the second main surface (143) facing the tweeter (130) is bell-shaped.
The audio system according to any of the claims 2-10, wherein the shape of a diaphragm cone of the woofer (120) substantially corresponds to the shape of the first main surface (142).
The audio system according to any of the claims 2-11, wherein the first main surface (142) is substantially parallel to a diaphragm cone of the woofer (120).
The audio system according to any of the claims 1-12, wherein the first main surface (142) and the second main surface (143) have different shapes.
The audio system according to claim 8, wherein the mechanical elements (146) are substantially acoustically transparent.
A portable audio system, comprising:
the audio system (100) according to any of the claims 1-14; and

a housing (110) defining the common acoustic cavity (112);

wherein a first of the two loudspeaker drivers is a woofer (120) disposed at a first end of the housing (110) in the common acoustic cavity (112) and a second of the two loudspeaker drivers is a tweeter (130) disposed at a second end of the housing (110), opposite to the first end, in the common acoustic cavity (112) facing the woofer (120).