AU2018204493B2 - Loudspeaker - Google Patents

Abstract

Loudspeakers are described that may reduce comb filtering effects perceived by a listener by either 1) moving transducers closer to a sound reflective surface (e.g., a baseplate, a tabletop or a floor) through vertical (height) or rotational adjustments of the transducers or 2) guiding sound produced by the transducers to be released into the listening area proximate to the reflective surface through the use of horns and openings that are at a prescribed distance from the reflective surface. The reduction of this distance between the reflective surface and the point at which sound emitted by the transducers is released into the listening area may lead to shorter reflected path that reduces comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds.

Description

LOUDSPEAKER

[0001] This application claims the benefit of U.S. Provisional Patent Application

No. 62/057,992, filed September 30, 2014, and this application hereby incorporates

herein by reference that provisional patent application.

[0001A] Also incorporated herein by reference, in its entirety is

PCT/US2015/053025 (published as WO 2016/054100), filed on 29 September 2015.

This application is also a divisional application of Australian Patent Application

No. 2017202861, filed on 1 May 2017.

FIELD

[0002] A loudspeaker is disclosed for reducing the effects caused by reflections

off a surface on which the loudspeaker is resting. In one embodiment, the

loudspeaker has individual transducers that are situated to be within a specified

distance from the reflective surface, e.g., a baseplate which is to rest on a tabletop

or floor surface, such that the travel distances of the reflected sounds and direct

sounds from the transducers are nearly equivalent. Other embodiments are also

described.

BACKGROUND

[0003] Loudspeakers may be used by computers and home electronics for

outputting sound into a listening area. A loudspeaker may be composed of

multiple electro-acoustic transducers that are arranged in a speaker cabinet. The

speaker cabinet may be placed on a hard, reflective surface such as a tabletop. If

the transducers are in close proximity to the tabletop surface, reflections from the

tabletop may cause an undesirable comb filtering effect to a listener. Since the

reflected path is longer than the direct path of sound, the reflected sound may

arrive later in time than the direct sound. The reflected sound may cause constructive or destructive interference with the direct sound (at the listener's ears), based on phase differences between the two sounds (caused by the delay.)

[0004] The approaches described in this Background section are approaches that could be pursued, but not necessarily approaches that have been previously

conceived or pursued. Therefore, unless otherwise indicated, it should not be

assumed that any of the approaches described in this section qualify as prior art

or common general knowledge merely by virtue of their inclusion in this section.

SUMMARY

[0004A] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and

"comprised", are not intended to exclude further additives, components, integers

or steps.

[0004B] According to a first aspect of the invention there is provided an electronic

device, comprising: a cabinet; and a plurality of audio transducers distributed

radially about an interior of the cabinet, wherein each audio transducer of the

plurality of audio transducers is acoustically coupled to an acoustic pathway

within the interior that redirects audio generated by the audio transducer first

downward toward a base of the cabinet and then radially outward through a

sound output opening defined by a sidewall of the cabinet which is at a

predefined distance from a reflective surface facing the sidewall for reflecting the

audio from the audio transducers, and wherein each audio transducer in the

plurality of audio transducers is individually and separately driven to produce

sound in response to separate and discrete audio signals received from an audio

source.

[0004C] According to a second aspect of the invention there is provided an

electronic device, comprising: a cabinet; a plurality of audio transducers radially

distributed within the cabinet and diaphragms of each of the audio transducer

oriented such that a forward face of each of the diaphragms is oriented inward

toward a central region of the cabinet, wherein each audio transducer in the

plurality of audio transducers is individually and separately driven to produce

sound in response to separate and discrete audio signals received from an audio

source; and one or more horns that direct sound from the central region to a

sound output opening in a sidewall of the cabinet which is at a predefined

distance from a reflective surface.

[0004D] According to a third aspect of the invention there is provided an

electronic device, comprising: a cabinet; and an array of audio transducers

disposed within the cabinet at a radial interval, each of the audio transducers

facing inward toward a central region and being configured to generate audio

waves that travel through an acoustic pathway first downward toward a base of

the cabinet and then radially outward to exit the cabinet through sound output

openings defined by a sidewall of the cabinet, wherein each audio transducer in

the array of audio transducers is individually and separately driven to produce

sound in response to separate and discrete audio signals received from an audio

source.

[0005] In one arrangement, a loudspeaker is provided with a ring of transducers that are aligned in a plane, within a cabinet. In one arrangement, the

loudspeaker may be designed to be an array where the transducers are all

replicates so that each is to produce sound in the same frequency range. In other

arrangement, the loudspeaker may be a multi-way speaker in which not all of the

transducers are designed to work in the same frequency range. The loudspeaker

may include a baseplate coupled to a bottom end of the cabinet. The baseplate may be a solid flat structure that is sized to provide stability to the loudspeaker so that the cabinet does not easily topple over while the baseplate is seated on a tabletop or on another surface (e.g., the floor). The ring of transducers may be located at a bottom of the cabinet and within a predefined distance from the baseplate, or within a predefined distance from a a tabletop or floor (in the case where no baseplate is used and the bottom end of the cabinet is to rest on the tabletop or floor.) The transducers may be angled downward toward the bottom end at a predefined acute angle, so as to reduce comb filtering caused by reflections of sound from the transducer off of the tabletop or floor, in comparison to the transducers being upright.

[0006] Sound emitted by the transducers may be reflected off the baseplate or other reflective surface on which the cabinet is resting, before arriving at the ears

of a listener, along with direct sound from the transducers. The predefined

distance may be selected to ensure that the reflected sound path and the direct

sound path are similar, such that comb-filtering effects perceptible by the listener

are reduced. In some arrangements, the predefined distance may be selected

based on the size or dimensions of a corresponding transducer or based on the

3a set of audio frequencies to be emitted by the transducer.

[0007] In one arrangement, this predefined distance may be achieved through the angling of the transducers downward toward the bottom end of the cabinet. This

rotation or tilt may be within a range of values such that the predefined distance

is achieved without causing undesired resonance. In one arrangement, the

transducers have been rotated or tilted to an acute angle, e.g., between 37.5° and

42.5, relative to the bottom end of the cabinet (or if a baseplate is used, relative to

the baseplate.)

[0008] In another arrangement, the predefined distance may be achieved through the use of horns. The horns may direct sound from the transducers to sound

output openings in the cabinet that are located proximate to the bottom end.

Accordingly, the predefined distance in this case may be between the center of

the opening and the tabletop, floor, or baseplate, since the center of the opening is

the point at which sound is allowed to propagate into the listening area.

Through the use of horns, the predefined distance may be shortened without the

need to move or locate the transducers themselves proximate to the bottom end

or to the baseplate.

[0009] As explained above, the loudspeakers described herein may show improved performance over traditional loudspeakers. In particular, the

loudspeakers described here may reduce comb filtering effects perceived by a

listener due to either 1) moving transducers closer to a reflective surface on

which the loudspeaker may be resting (e.g., the baseplate, or directly on a

tabletop or floor) through vertical or rotational adjustments of the transducers or

2) guiding sound produced by the transducers so that the sound is released into

the listening area proximate to the reflective surface, through the use of horns

and through openings in the cabinet that are at the prescribed distance from the reflective surface. The reduction of this distance, between the reflective surface and the point at which sound emitted by the transducers is released into the listening area, reduces the reflective path of sound and may reduce comb filtering effects caused by reflected sounds that are delayed relative to the direct sound.

Accordingly, the loudspeakers shown and described may be placed on reflective

surfaces without severe audio coloration caused by reflected sounds.

[0010] The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems

and methods that can be practiced from all suitable combinations of the various

aspects summarized above, as well as those disclosed in the Detailed Description

below and particularly pointed out in the claims filed with the application. Such

combinations have particular advantages not specifically recited in the above

summary.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which

like references indicate similar elements. It should be noted that references to

"an" or "one" embodiment of the invention in this disclosure are not necessarily

to the same embodiment, and they mean at least one. Also, in the interest of

conciseness and reducing the total number of figures, a given figure may be used

to illustrate the features of more than one embodiment of the invention, and not

all elements in the figure may be required for a given embodiment.

[0012] Figure 1 shows a view of a listening area with an audio receiver, a loudspeaker, and a listener according to one embodiment.

[0013] Figure 2A shows a component diagram of the audio receiver according to one embodiment.

[0014] Figure 2B shows a component diagram of the loudspeaker according to one embodiment.

[0015] Figure 3 shows a set of example directivity/radiation patterns that may be produced by the loudspeaker according to one embodiment.

[0016] Figure 4 shows direct sound and reflected sound produced by a loudspeaker relative to a sitting listener according to one embodiment.

[0017] Figure 5 shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker

and the sitting listener according to one embodiment.

[0018] Figure 6 shows direct sound and reflected sound produced by a loudspeaker relative to a standing listener according to one embodiment.

[0019] Figure 7 shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the loudspeaker

and the standing listener according to one embodiment.

[0020] Figure 8 shows a contour graph illustrating comb filtering effects produced by the loudspeaker according to one embodiment.

[0021] Figure 9A shows a loudspeaker in which an integrated transducer has been moved toward the bottom end of the cabinet according to one embodiment.

[0022] Figure 9B shows the distance between a transducer and a reflective surface according to one embodiment.

[0023] Figure 9C shows a loudspeaker with an absorptive material located proximate to a set of transducers according to one embodiment.

[0024] Figure 9D shows a cutaway view of a loudspeaker with a screen located proximate a set of transducers according to one embodiment.

[0025] Figure 9E shows a close-up view of a loudspeaker with a screen located proximate a set of transducers according to one embodiment.

[0026] Figure 10A shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0027] Figure 10B shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the

loudspeaker according to one embodiment.

[0028] Figure 11A shows the distances for three separate types of transducers according to one embodiment.

[0029] Figure 11B shows the distances for N separate types of transducers according to one embodiment.

[0030] Figure 12 shows a side view of a loudspeaker according to one embodiment.

[0031] Figure 13 shows an overhead cutaway view of a loudspeaker according to one embodiment.

[0032] Figure 14A shows a distance between a transducer directly facing a listener and a reflective surface according to one embodiment.

[0033] Figure 14B shows a distance between a transducer angled downward and a reflective surface according to one embodiment.

[0034] Figure 14C shows a comparison between a reflected sound path produced by a transducer directed at a listener and a transducer angled downward

according to one embodiment.

[0035] Figure 15A shows a logarithmic sound pressure versus frequency graph for sound detected at one meter and at twenty degrees relative to the

loudspeaker according to one embodiment.

[0036] Figure 15B shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0037] Figure 16A shows a cutaway side view of a cabinet for a loudspeaker that includes a horn, according to one embodiment in which no baseplate is provided.

[0038] Figure 16B shows a perspective view of a loudspeaker that has multiple horns for multiple transducers, according to one embodiment.

[0039] Figure 17 shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0040] Figure 18 shows a cutaway view of a cabinet for a loudspeaker in which the transducers are mounted through a wall of the cabinet according to another

embodiment.

[0041] Figure 19 shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0042] Figure 20 shows a cutaway view of a cabinet for a loudspeaker in which the transducers are mounted inside the cabinet according to another

embodiment.

[0043] Figure 21 shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0044] Figure 22 shows a cutaway view of a cabinet for a loudspeaker in which the transducers are located within the cabinet and a long narrow horn is utilized

according to another embodiment.

[0045] Figure 23 shows a contour graph for sound produced by a loudspeaker according to one embodiment.

[0046] Figure 24 shows a shows a cutaway view of a cabinet for a loudspeaker in which phase plugs are used to place the effective sound radiation area of the

transducers closer to a reflective surface according to one embodiment.

[0047] Figure 25 shows a loudspeaker with a partition according to one embodiment.

[0048] Figures 26A, 26B illustrate the use of acoustic dividers in a multi-way loudspeaker or a loudspeaker array in accordance with yet another embodiment.

DETAILED DESCRIPTION

[0049] Several embodiments are described with reference to the appended drawings are now explained. While numerous details are set forth, it is

understood that some embodiments of the invention may be practiced without

these details. In other instances, well-known circuits, structures, and techniques

have not been shown in detail so as not to obscure the understanding of this

description.

[0050] Figure 1 shows a view of a listening area 101 with an audio receiver 103, a loudspeaker 105, and a listener 107. The audio receiver 103 may be coupled to

the loudspeaker 105 to drive individual transducers 109 in the loudspeaker 105 to

emit various sound beam patterns into the listening area 101. In one

embodiment, the loudspeaker 105 may be configured and is to be driven as a

loudspeaker array, to generate beam patterns that represent individual channels of a piece of sound program content. For example, the loudspeaker 105 (as an array) may generate beam patterns that represent front left, front right, and front center channels for a piece of sound program content (e.g., a musical composition or an audio track for a movie). The loudspeaker 105 has a cabinet 111, and the transducers 109 are housed in a bottom 102 of the cabinet 111 and to which a baseplate 113 is coupled as shown.

[0051] Figure 2A shows a component diagram of the audio receiver 103 according to one embodiment. The audio receiver 103 may be any electronic

device that is capable of driving one or more transducers 109 in the loudspeaker

105. For example, the audio receiver 103 may be a desktop computer, a laptop

computer, a tablet computer, a home theater receiver, a set-top box, or a

smartphone. The audio receiver 103 may include a hardware processor 201 and a

memory unit 203.

[0052] The processor 201 and the memory unit 203 are generically used here to refer to any suitable combination of programmable data processing components

and data storage that conduct the operations needed to implement the various

functions and operations of the audio receiver 103. The processor 201 may be an

applications processor typically found in a smart phone, while the memory unit

203 may refer to microelectronic, non-volatile random access memory. An

operating system may be stored in the memory unit 203 along with application

programs specific to the various functions of the audio receiver 103, which are to

be run or executed by the processor 201 to perform the various functions of the

audio receiver 103.

[0053] The audio receiver 103 may include one or more audio inputs 205 for receiving multiple audio signals from an external or remote device. For example,

the audio receiver 103 may receive audio signals as part of a streaming media service from a remote server. Alternatively, the processor 201 may decode a locally stored music or movie file to obtain the audio signals. The audio signals may represent one or more channels of a piece of sound program content (e.g., a musical composition or an audio track for a movie). For example, a single signal corresponding to a single channel of a piece of multichannel sound program content may be received by an input 205 of the audio receiver 103, and in that case multiple inputs may be needed to receive the multiple channels for the piece of content. In another example, a single signal may correspond to or have encoded therein or multiplexed therein the multiple channels (of the piece of sound program content),.

[0054] In one embodiment, the audio receiver 103 may include a digital audio input 205A that receives one or more digital audio signals from an external

device or a remote device. For example, the audio input 205A may be a

TOSLINK connector, or it may be a digital wireless interface (e.g., a wireless local

area network (WLAN) adapter or a Bluetooth adapter). In one embodiment, the

audio receiver 103 may include an analog audio input 205B that receives one or

more analog audio signals from an external device. For example, the audio input

205B may be a binding post, a Fahnestock clip, or a phono plug that is designed

to receive a wire or conduit and a corresponding analog signal.

[0055] In one embodiment, the audio receiver 103 may include an interface 207 for communicating with the loudspeaker 105. The interface 207 may utilize

wired mediums (e.g., conduit or wire) to communicate with the loudspeaker 105,

as shown in Figure 1. In another embodiment, the interface 207 may

communicate with the loudspeaker 105 through a wireless connection. For

example, the network interface 207 may utilize one or more wireless protocols

and standards for communicating with the loudspeaker 105, including the IEEE

802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile

Communications (GSM) standards, cellular Code Division Multiple Access

(CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth

standards.

[0056] As shown in Figure 2B, the loudspeaker 105 may receive transducer drive signals from the audio receiver 103 through a corresponding interface 213. As

with the interface 207, the interface 213 may utilize wired protocols and

standards and/or one or more wireless protocols and standards, including the

IEEE 802.11 suite of standards, IEEE 802.3, cellular Global System for Mobile

Communications (GSM) standards, cellular Code Division Multiple Access

(CDMA) standards, Long Term Evolution (LTE) standards, and/or Bluetooth

standards. In some embodiments, the drive signals are received in digital form,

and so in order drive the transducers 109 the loudspeaker 105 in that case may

include digital-to-analog converters (DACs) 209 that are coupled in front of the

power amplifiers 211, for converting the drive signals into analog form before

amplifying them to drive each transducer 109.

[0057] Although described and shown as being separate from the audio receiver 103, in some embodiments, one or more components of the audio receiver 103

may be integrated in the loudspeaker 105. For example, as described below, the

loudspeaker 105 may also include, within its cabinet 111, the hardware processor

201, the memory unit 203, and the one or more audio inputs 205.

[0058] As shown in Figure 1, the loudspeaker 105 houses multiple transducers 109 in a speaker cabinet 111, which may be aligned in a ring formation relative to

each other, to form a loudspeaker array. In particular, the cabinet 111 as shown is

cylindrical; however, in other embodiments the cabinet 111 may be in any shape,

including a polyhedron, a frustum, a cone, a pyramid, a triangular prism, a

hexagonal prism, a sphere, a frusto conical shape, or any other similar shape.

The cabinet 111 may be at least partially hollow, and may also allow the

mounting of transducers 109 on its inside surface or on its outside surface. The

cabinet 111 may be made of any suitable material, including metals, metal alloys,

plastic polymers, or some combination thereof.

[0059] As shown in Figure 1 and Figure 2B, the loudspeaker 105 may include a number of transducers 109. The transducers 109 may be any combination of full

range drivers, mid-range drivers, subwoofers, woofers, and tweeters. Each of the

transducers 109 may have a diaphragm or cone that is connected to a rigid basket

or frame via a flexible suspension that constrains a coil of wire (e.g., a voice coil)

that is attached to the diaphragm to move axially through a generally cylindrical

magnetic gap. When an electrical audio signal is applied to the voice coil, a

magnetic field is created by the electric current in the voice coil, making it a

variable electromagnet. The coil and the transducers' 109 magnetic system

interact, generating a mechanical force that causes the coil (and thus, the attached

cone) to move back and forth, thereby reproducing sound under the control of

the applied electrical audio signal coming from an audio source, such as the

audio receiver 103. Although electromagnetic dynamic loudspeaker drivers are

described for use as the transducers 109, those skilled in the art will recognize

that other types of loudspeaker drivers, such as piezoelectric, planar

electromagnetic and electrostatic drivers are possible.

[0060] Each transducer 109 may be individually and separately driven to produce sound in response to separate and discrete audio signals received from an audio

source (e.g., the audio receiver 103). By having knowledge of the alignment of

the transducers 109, and allowing the transducers 109 to be individually and

separately driven according to different parameters and settings (including

relative delays and relative energy levels), the loudspeaker 105 may be arranged

and driven as an array, to produce numerous directivity or beam patterns that accurately represent each channel of a piece of sound program content output by the audio receiver 103. For example, in one embodiment, the loudspeaker 105 may be arranged and driven as an array, to produce one or more of the directivity patterns shown in Figure 3. Simultaneous directivity patterns produced by the loudspeaker 105 may not only differ in shape, but may also differ in direction. For example, different directivity patterns may be pointed in different directions in the listening area 101. The transducer drive signals needed to produce the desired directivity patters may be generated by the processor 201

(see Figure 2A) executing a beamforming process.

[0061] Although a system has been described above in relation to a number of transducers 109 that may be arranged and driven as part of a loudspeaker array,

the system may also work with only a single transducer (housed in a cabinet 111.)

Thus, while at times the description below refers to the loudspeaker 105 as being

configured and driven as an array, in some embodiments a non-array

loudspeaker may be configured or used in a similar fashion described herein.

[0062] As shown and described above, the loudspeaker 105 may include a single ring of transducers 109 arranged to be driven as an array. In one embodiment,

each of the transducers 109 in the ring of transducers 109 may be of the same type

or model, e.g. replicates. The ring of transducers 109 may be oriented to emit

sound "outward" from the ring, and may be aligned along (or lying in) a

horizontal plane such that each of the transducers 109 is vertically equidistant

from the tabletop, or from a top plane of a baseplate 113 of the loudspeaker 105.

By including a single ring of transducers 109 aligned along a horizontal plane,

vertical control of sound emitted by the loudspeaker 105 may be limited. For

example, through adjustment of beamforming parameters and settings for

corresponding transducers 109, sound emitted by the ring of transducers 109 may

be controlled in the horizontal direction. This control may allow generation of the directivity patterns shown in Figure 3 along a horizontal plane or axis.

However, by lacking multiple stacked rings of transducers 109 this directional

control of sound may be limited to this horizontal plane. Accordingly, sound

waves produced by the loudspeaker 105 in the vertical direction (perpendicular

to this horizontal axis or plane) may expand outwards without limit.

[0063] For example, as shown in Figure 4, sound emitted by the transducers 109 may be spread vertically with minimal limitation. In this scenario, the head or

ears of the listener 107 are located approximately one meter and at a twenty

degree angle relative to the ring of transducers 109 in the loudspeaker 105. The

spread of sound from the loudspeaker 105 may include sound emitted 1)

downward and onto a tabletop on which the loudspeaker 105 has been placed

and 2) directly at the listener 107. The sound emitted towards the tabletop will

be reflected off the surface of the tabletop and towards the listener 107.

Accordingly, both reflected and direct sound from the loudspeaker 105 may be

sensed by the listener 107. Since the reflected path is indirect and consequently

longer than the direct path in this example, a comb filtering effect may be

detected or perceived by the listener 107. A comb filtering effect may be defined

as the creation of peaks and troughs in frequency response that are caused when

signals that are identical but have phase differences are summed. An undesirably

colored sound can result from the summing of these signals. For example, Figure

5 shows a logarithmic sound pressure versus frequency graph for sound detected

at one meter and at twenty degrees relative to the loudspeaker 105 (i.e., the

position of the listener 107 as shown in Figure 4). A set of bumps or peaks and

notches or troughs illustrative of this comb filtering effect may be observed in the

graph shown in Figure 5. The bumps may correspond to frequencies where the

reflected sounds are in-phase with the direct sounds while the notches may correspond to frequencies where the reflected sounds are out-of-phase with the direct sounds.

[0064] These bumps and notches may move with elevation or angle (degree) change, as path length differences between direct and reflected sound changes

rapidly based on movement of the listener 107. For example, the listener 107 may

stand up such that the listener 107 is at a thirty degree angle or elevation relative

to the loudspeaker 105 as shown in Figure 6 instead of a twenty degree elevation

as shown in Figure 4. The sound pressure vs. frequency as measured at the thirty

degree angle (elevation) is shown in Fig. 7. It can be seen that the bumps and

notches in the sound pressure versus frequency behavior move with changing

elevation, and this is illustrated in the contour graph of Figure 8 which shows the

comb filtering effect of Figures 5 and 7 as witnessed from different angles. The

regions with darker shading represent high SPL (bumps), while the regions with

lighter shading represent low SPL (notches). The bumps and notches shift over

frequency, as the listener 107 changes angles/location relative to the loudspeaker

105. Accordingly, as the listener 107 moves in the vertical direction relative to the

loudspeaker 105, the perception of sound for this listener 107 changes. This lack

of consistency in sound during movement of the listener 107, or at different

elevations, may be undesirable.

[0065] As described above, comb filtering effects are triggered by phase differences between reflected and direct sounds caused by the longer distance the

reflected sounds must travel en route to the listener 107. To reduce audio

coloration perceptible to the listener 107 based on comb filtering, the distance

between reflected sounds and direct sounds may be shortened. For example, the

ring of transducers 109 may be oriented such that sound emitted by the

transducers 109 travels a shorter or even minimal distance, before reflection on

the tabletop or another reflective surface. This reduced distance will result in a shorter delay between direct and reflected sounds, which consequently will lead to more consistent sound at locations/angles the listener 107 is most likely to be situated. Techniques for minimizing the difference between reflected and direct paths from the transducers 109 will be described in greater detail below by way of example.

[0066] Figure 9A shows a loudspeaker 105 in which an integrated transducer 109 has been moved closer to the bottom of the cabinet 111 than its top, in

comparison to the transducer 109 in the loudspeaker 105 shown in Figure 4. In

one embodiment, the transducer 109 may be located proximate to a baseplate 113

that is fixed to a bottom end of the cabinet 111 of the loudspeaker 105. The

baseplate 113 may be a solid flat structure that is sized to provide stability to the

loudspeaker 105 while the loudspeaker 105 is seated on a table or on another

surface (e.g., a floor), so that the cabinet 111 can remain upright. In some

embodiments, the baseplate 113 may be sized to receive sounds emitted by the

transducer 109 such that sounds may be reflected off of the baseplate 113. For

example, as shown in Figure 9A, sound directed downward by the transducer

109 may be reflected off of the baseplate 113 instead of off of the tabletop on

which the loudspeaker 105 is resting. The baseplate 113 may be described as

being coupled to a bottom 102 of the cabinet 111, e.g., directly to its bottom end,

and may extend outward beyond a vertical projection of the outermost point of a

sidewall of the cabinet. Although shown as larger in diameter than the cabinet

111, in some embodiments, the baseplate 113 may be the same diameter of the

cabinet 111. In these embodiments the bottom 102 of the cabinet 111 may curve

or cut inwards (e.g., until it reaches the baseplate 113) and the transducers 109

may be located in this curved or cutout section of the bottom 102 of the cabinet

111 such as shown in Figure 1.

[0067] In some embodiments, an absorptive material 901, such as foam, may be placed around the baseplate 113, or around the transducers 109. For example, as

shown in Figure 9C, a slot 903 may be formed in the cabinet 111, between the

transducer 109 and the baseplate 113. The absorptive material 901 within the slot

903 may reduce the amount of sound that has been reflected off of the baseplate

113 in a direction opposite the listener 107 (and that would otherwise then be

reflected off of the cabinet 111 back towards the listener 107). In some

embodiments, the slot 903 may encircle the cabinet 111 around the base of the

cabinet 111 and may be tuned to provide a resonance in a particular frequency

range to further reduce sound reflections. In some embodiments, the slot 903

may form a resonator coated with the absorptive material 901 designed to

dampen sounds in a particular frequency range to further eliminate sound

reflections off the cabinet 111.

[0068] In one embodiment, as seen in Figures 9D, 9E, a screen 905 may be placed below the transducers 109. In this embodiment, the screen 905 may be a

perforated mesh (e.g., a metal, metal alloy, or plastic) that functions as a low-pass

filter for sound emitted by the transducers 109. In particular, and as best seen in

Figure 9D, the screen 905 may create a cavity 907 (similar to the slot 903 depicted

in Figure 9C) underneath the cabinet 111 between the baseplate 113 and the

transducers 109. High-frequency sounds emitted by the transducers 109 and

which reflect off the cabinet 111 may be attenuated by the screen 905 and

prevented from passing into the listening area 101. In one embodiment, the

porosity of the screen 905 may be adjusted to limit the frequencies that may be

free to enter the listening area 101.

[0069] In one embodiment, the vertical distance D between a center of the diaphragm of the transducer 109 and a reflective surface (e.g., the top of the

baseplate 113) may be between 8.0 mm and 13.0 mm as shown in Figure 9B. For example, in some embodiments, the distance D may be 8.5 mm, while in other embodiments the distance D may be 11.5 mm (or anywhere in between 8.5 mm

11.5 mm). In other embodiments, the distance D may be between 4.0 mm and

20.0 mm. As shown in Figures 9A and 9B, by being located proximate (i.e., a

distance D) from the surface upon which sound is reflected (e.g., the baseplate

113, or in other cases a tabletop or floor surface itself such as where no baseplate

113 is provided), the loudspeaker 105 may exhibit a reduced length of its

reflected sound path. This reduced reflected sound path consequently reduces

the difference between the lengths of the reflected sound path and the direct

sound path, for sound originating from a transducer 109 integrated within the

cabinet 111, e.g., the difference, reflected sound path distance - direct sound path

distance, approaches zero). This minimization or at least reduction in difference

between the length of the reflected and direct paths may result in a more

consistent sound (e.g., a consistent frequency response or amplitude response) as

shown in the graphs of Figure 10A and Figure 10B. In particular, the bumps and

notches in both Figure 10A and Figure 10B have decreased in magnitude and

moved considerably to the right and closer to the bounds of human perception

(e.g., certain bumps and notches have moved above 10kHz). Thus, comb filtering

effects as perceived by the listener 107 may be reduced.

[0070] Although discussed above and shown in Figures 9A-9C for a single transducer 109, in some embodiments each transducer 109 in a ring formation of

multiple transducers 109 (e.g., an array of transducers) may be similarly

arranged, along the side or face of the cabinet 111. In those embodiments, the

ring of transducers 109 may be aligned along or lie within a horizontal plane as

described above.

[0071] In some embodiments, the distance D or the range of values used for the distance D may be selected based on the radius of the corresponding transducer

109 (e.g., the radius of the diaphragm of the transducer 109) or the range of

frequencies used for the transducer 109. In particular, high frequency sounds

may be more susceptible to comb filtering caused by reflections. Accordingly, a

transducer 109 producing higher frequencies may need a smaller distance D, in

order to more stringently reduce its reflections (in comparison to a transducer 109

that produces lower frequency sounds.) For example, Figure 11A shows a multi

way loudspeaker 105 with a first transducer 109A used/designed for a first set of

frequencies, a second transducer 109B used/designed for a second set of

frequencies, and a third transducer 109C used/designed for a third set of

frequencies. For instance, the first transducer 109A may be used/designed for

high frequency content (e.g., 5kHz-l0kHz), the second transducer 109B may be

used/designed for mid frequency content (e.g., 1kHz-5kHz), and the third

transducer 109C may be used/designed for low frequency content (e.g., 100Hz

1kHz). These frequency ranges for each of the transducers 109A, 109B, and 109C

may be enforced using a set of filters integrated within the loudspeaker 105.

Since the wavelengths for sound waves produced by the first transducer 109A are

smaller than wavelengths of sound waves produced by the transducers 109B and

109C, the distance DAassociated with the transducer 109A may be smaller than

the distances DBand Dc associated with the transducers 109B and 109C,

respectively (e.g., the transducers 109B and 109C may be located farther from a

reflective surface on which the loudspeaker 105 is resting, without notches

associated with comb filtering falling within their bandwidth of operation).

Accordingly, the distance D between transducers 109 and a reflective surface

needed to reduce comb filtering effects may be based on the size/diameter of the

transducers 109 and/or the frequencies intended to be reproduced by the

transducers 109.

[0072] Despite being shown with a single transducer 109A, 109B, and 109C, the multi-way loudspeaker 105 shown in Figure 11A may include rings of each of the

transducers 109A, 109B, and 109C. Each ring of the transducers 109A, 109B, and

109C may be aligned in separate horizontal planes.

[0073] Further, although shown in Figure 11A as including three different types of transducers 109A, 109B, and 109C (i.e., a 3-way loudspeaker 105), in other

embodiments the loudspeaker 105 may include any number of different types of

transducers 109. In particular, the loudspeaker 105 may be an N-way array as

shown in Figure 11B, where N is an integer that is greater than or equal to one.

Similar to Figure 11A, in this embodiment shown in Figure 11B, the distances DA

DNassociated with each ring of transducers 109A-109N may be based on the

size/diameter of the transducers 109A-109N and/or the frequencies intended to

be reproduced by the transducers 109A-109N.

[0074] Although achieving a small distance D (i.e., a value within a range described above) between the center of the transducers 109 and a reflective

surface may be achievable for transducers 109 with smaller radii by moving the

transducers 109 closer to a reflective surface (i.e., arranging transducers 109 along

the cabinet 111 to be closer to the baseplate 113), as transducers 109 increase in

size the ability to achieve values for the distance D within prescribed ranges may

be difficult or impossible. For example, it would be impossible to achieve a

threshold value for D by simply moving a transducer 109 in the vertical direction

along the face of the cabinet 111 closer to the reflective surface when the radius of

the transducer 109 is greater than the threshold value for D (e.g., the threshold

value is 12.0 mm and the radius of the transducer 109 is 13.0mm). In these

situations, additional degrees of freedom of movement may be employed to

achieve the threshold value for D as described below.

[0075] In some embodiments, the orientation of the transducers 109 in the loudspeaker 105 may be adjusted to further reduce the distance D between the

transducer 109 and the reflective surface, reduce the reflected sound path, and

consequently reduce the difference between the reflected and direct sound paths.

For example, Figure 12 shows a side view of a loudspeaker 105 according to one

embodiment. Similar to the loudspeaker 105 of Figure 9, the loudspeaker 105

shown in Figure 12 includes a ring of transducers 109 situated in or around the

bottom of the cabinet 111 and near the baseplate 113. The ring of transducers 109

may encircle the circumference of the cabinet 111 (or may be coaxial with the

circumference), with equal spacing between each adjacent pairs of transducers

109 as shown in the overhead cutaway view in Figure 13.

[0076] In the example loudspeaker 105 shown in Figure 12, the transducers 109 are located proximate to the baseplate 113, by being mounted in the bottom 102

of the cabinet 111. The bottom in this example is frusto conical as shown having

a sidewall that joins an upper base and a lower base, and wherein the upper base

is larger than the lower base and the base plate 113 is coupled to the lower base

as shown. Each of the transducers 109 in this case may be described as being

mounted within a respective opening in the sidewall such that its diaphragm is

essentially outside the cabinet 111, or is at least plainly visible along a line of

sight, from outside of the cabinet 111. Note the indicated distance D being the

vertical distance from the center of the diaphragm, e.g., the center of its outer

surface, down to the top of the baseplate 113. The sidewall (of the bottom 102)

has a number of openings formed therein that are arranged in a ring formation

and in which the transducers 109 have been mounted, respectively. As was

noted above in relation to Figures 9A and 9B, by positioning the transducers 109

close to a surface upon which sound from the transducers 109 is reflected, e.g., by

minimizing the distance D while restricting the angle theta.

[0077] Referring to Fig. 14b, the angle theta may be defined as depicted in that figure, namely as the angle between 1) a plane of the diaphragm of the

transducer 109, such as a plane in which a perimeter of the diaphragm lies, and 2)

the tabletop surface, or if a baseplate 113 is used then a horizontal plane that

touches the top of the base plate 113.) The angle theta of each of the transducers

109 may be restricted to a specified range, so that the difference between the path

of reflected sounds and the path of direct sounds may be reduced, in comparison

to the upright arrangement of the transducer 109 shown in Figure 14a. A

transducer 109 that is not angled downward is shown in Figure 14A, where it

may be described as being upright or "directly facing" the listener 107, defining

an angle theta of at least ninety degrees, and a distance D1 between the center of

the transducer 109 and a reflective surface below, e.g., a tabletop or the top of the

baseplate 113. As shown in Figure 14B, angling the transducer 109 downward at

an acute angle theta (0) results in a distance D2between the center of the

transducer 109 and a reflective surface, where D2<Di. Accordingly, by rotating

(tilting or pivoting) the transducer 109 "forward" and about its bottommost

point, so that its diaphragm is more directed to the reflective surface, the distance

D between the center of the transducer 109 and the reflective surface decreases

(because the bottommost edge of the diaphragm remains fixed between Figure

14A and Figure 14B, e.g., as close as possible to the reflective surface.) As noted

above, this reduction in D results in a reduction in the difference between the

direct and reflected sounds paths and a consequent reduction in audio coloration

caused by comb filtering. The reduction in the reflected sound path may be seen

in Figure 14C, where the solid line from the non-rotated transducer 109 is longer

than the dashed line from the transducer 109 that is tilted by an angle theta, 6.

Thus, to further reduce the distance D (e.g., the distance between the center of the

transducer 109 and either the baseplate 113 or other reflective surface underneath

the cabinet 111) and consequently reduce the reflected path, the transducer 109 may be angled downward toward the baseplate 113 as explained above and also as shown in Figure 12.

[0078] As described above, the distance D is a vertical distance between the diaphragm of each of the transducers 109 and a reflective surface (e.g., the

baseplate 113). In some embodiments, this distance D may be measured from the

center of the diaphragm to the reflective surface. Although shown with both

protruding diaphragms and flat diaphragms, in some embodiments inverted

diaphragms may be used. In these embodiments, the distance D may be

measured from the center of the inverted diaphragm, or from the center as it has

been projected onto a plane of the diaphragm along a normal to the plane, where

the diaphragm plane may be a plane in which the perimeter of the diaphragm

lies. Another plane associated with the transducer may be a plane that is defined

by the front face of the transducer 109 (irrespective of the inverted curvature of

its diaphragm).

[0079] Although tilting or rotating the transducers 109 may result in a reduced distance D and a corresponding reduction in the reflected sound path, over

rotation of the transducers 109 toward the reflective surface may result in

separate unwanted effects. In particular, rotating the transducers 109 past a

threshold value may result in a resonance caused by reflecting sounds off the

reflective surface or the cabinet 111 and back toward the transducer 109.

Accordingly, a lower bound for rotation may be employed to ensure an

unwanted resonance is not experienced. For example, the transducers 109 may

be rotated or tilted between 30.00 and 50.00 (e.g., 6 as defined above in Figure 14B

may be between 30.0 and 50.0). In one embodiment, the transducers 109 may

be rotated between 37.5° and 42.50 (e.g., 6 may be between 37.5° and 42.5°). In

other embodiments, the transducers 109 may be rotated between 39.0 and 41.0.

The angle theta of rotation of the transducers 109 may be based on a desired or

threshold distance D for the transducers 109.

[0080] Figure 15A shows a logarithmic sound pressure versus frequency graph for sound detected at a position (of the listener 107) along a direct path that is one

meter away from the loudspeaker 105, and twenty degrees upward from the

horizontal - see Figure 4. In particular, the graph of Figure 15A represents sound

emitted by the loudspeaker 105 shown in Figure 12 with a degree of rotation

theta of the transducers 109 at 45°. In this graph, sound levels are relatively

consistent within the audible range (i.e., 20Hz to 10kHz). Similarly, the contour

graph of Figure 15B for a single transducer 109 shows relative consistency in the

vertical direction, for most angles at which the listener 107 would be located. For

instance, a linear response is shown in the contour graph of Figure 15B for a

vertical position of the listener 107 being 00 (the listener 107 is seated directly in

front of the loudspeaker 105) and for a vertical position between 45 and 600 (the

listener 107 is standing up near the loudspeaker 105). In particular, notches in

this counter graph have been mostly moved outside the audible range, or they

have been moved to vertical angles where the listener 107 is not likely to be

located (e.g., the listener 107 would not likely be standing directly above the

loudspeaker 105, at the vertical angle of 90°).

[0081] As noted above, rotating the transducers 109 achieves a lower distance D between the center of the transducers 109 and a reflective surface (e.g., the

baseplate 113). In some embodiments, the degree of rotation or the range of

rotation may be set based on the set of frequencies and the size or diameter of the

transducers 109. For example, larger transducers 109 may produce sound waves

with larger wavelengths. Accordingly, the distance D needed to mitigate comb

filtering for these larger transducers 109 may be longer than the distance D

needed to mitigate comb filtering for smaller transducers 109. Since the distance

D is longer for these larger transducers 109 in comparison to smaller transducers

109, the corresponding angle 6 at which the transducers are tilted, as needed to

achieve this longer distance D, may be larger (less tilting or rotation is needed), in

order avoid over-rotation (or over-tilting). Accordingly, the angle of rotation 0

for a transducer 109 may be selected based on the diaphragm size or diameter of

the transducers 109 and the set of frequencies desired to be output by the

transducer 109.

[0082] As described above, positioning and angling the transducers 109 along the face of the cabinet 111 of the loudspeaker 105 may reduce a reflective sound path

distance, reduce a difference between a reflective sound path and a direct sound

path, and consequently reduce comb filtering effects. In some embodiments,

horns may be utilized to further reduce comb filtering. In such embodiments, a

horn enables the point at which sound escapes from (an opening in) the cabinet

111 of the loudspeaker 105 (and then moves along respective direct and reflective

paths toward the listener 107) to be adjusted. In particular, the point of release of

sound from the cabinet 111 and into the listening area 101 may be configured

during manufacture of the loudspeaker 105 to be proximate to a reflective surface

(e.g., the baseplate 113). Several different horn configurations will be described

below. Each of these configurations may allow use of larger transducers 109 (e.g.,

larger diameter diaphragms), or a greater number or a fewer transducers 109,

while still reducing comb filtering effects and maintaining a small cabinet 111 for

the loudspeaker 105.

[0083] Figure 16A shows a cutaway side view of the cabinet 111 of the loudspeaker 105 having a horn 115 and no baseplate 113. Figure 16B shows an

elevation or perspective view of the loudspeaker 105 of Figure 16A configured as,

and to be driven as, an array having multiple transducers 109 arranged in a ring

formation. In this example, the transducer 109 is mounted or located further inside or within the cabinet 111 (rather than within an opening in the sidewall of the cabinet 111), and a horn 115 is provided to acoustically connect the diaphragm of the transducer 109 to a sound output opening 117 of the cabinet

111. In contrast to the embodiment of Figure 9D where the transducer 109 is

mounted within an opening in the sidewall of the cabinet 111 and is visible from

the outside, there is no "line of sight" to the transducer 109 in Figures 16A, 16B

from outside of the cabinet 111. The horn 115 extends downward from the

transducer 109, to the opening 117, which is formed in the sloped sidewall of the

bottom 102 of the cabinet 111 which lies on a tabletop or floor. In this example,

the bottom 102 is frusto conical. The horn 115 directs sound from the transducer

109 to an inside surface of the sidewall of the cabinet 111 where the opening 117

is located, at which point the sound is then released into the listening area

through the opening 117. As shown, although the transducer may still be closer

to the bottom end of the cabinet 111 than it top end, the transducer 109 is in a

raised position (above the bottom end) in contrast to the embodiment of Fig. 12.

Nevertheless, sound emitted by the transducer 109 can still be released from the

cabinet 111 at a point that is "proximate" or close enough to the reflective surface

underneath. That is because the sound is released from an opening 117 which

itself is positioned in close proximity to the baseplate 113. In some embodiments,

the opening 117 may be positioned and oriented to achieve the same vertical

distance D that was described above in connection with the embodiments of

Figures 9B, 12, 14B (in which the distance D was being measured between the

diaphragm and the reflective surface below the cabinet 111.) For the horn

embodiment here, the predefined vertical distance D (from the center of the

opening 117 vertically down to the tabletop or floor on which the cabinet 111 is

resting) may be for example between 8.0 millimeters and 13.0 millimeters. In the

case of the horn embodiment here, the distance D may be achieved in part by

inclining the opening 117 (analogous to the rotation or tilt angle theta of Figure

14B), for example, appropriately defining the angle or slope of the sidewall of the

frusto-conical bottom 102 (of the cabinet 111) in which the opening 117 is formed.

[0084] The horn 115 and the opening 117 may be formed in various sizes to accommodate sound produced by the transducers 109. In one embodiment,

multiple transducers 109 in the loudspeaker 105 may be similarly configured

with corresponding horns 115 and openings 117 in the cabinet 111, together

configured, and to be driven as, an array. The sound from each transducer 109 is

released from the cabinet 111 at a prescribed distance D from the reflective

surface below the cabinet 111 (e.g., a tabletop or a floor on which the cabinet111

is resting, or a baseplate 113). This distance D may be measured from the center

of the opening 117 (vertically downward) to the reflective surface. Since sound is

thus being emitted proximate to the baseplate 113, reflected sound may travel

along a path similar to that of direct sound as described above. In particular,

since sound only travels a short distance from the opening 117 before being

reflected, the difference in the reflected and direct sound paths may be small,

which results in a reduction in comb filtering effects perceptible to the listener

107. For example, the contour graph of Figure 17 corresponding to the

loudspeaker 105 shown in Figures 16A and 16B shows a smooth and consistent

level difference across frequencies and vertical angles (which are angles that

define the possible vertical positions of the listener 107), in comparison to the

comb filtering effect shown in Figure 8.

[0085] Figure 18 shows a cutaway view of the cabinet 111 of the loudspeaker 105, according to another horn embodiment. In this example, the transducers 109 are

mounted to or through the sidewall of the cabinet 111, but are pointed inward

(rather than outward as in the embodiment of Figure 9D, for example. In other

words, the forward faces of their diaphragms are facing into the cabinet 111.

Corresponding horns 115 are acoustically coupled to the front faces of diaphragms of the transducers 109, respectively, and extend downward along respective curves to corresponding openings 117. In this embodiment, although the transducers 109 are facing a first direction, the curvature of the horns 115A allow sound to be emitted from the openings 117, which are aimed to emit sound into the listening area 101 in a second direction (different than the first direction).

The openings 117 of the cabinet 111 in this embodiment may be positioned and

oriented the same as described above in connection with the horn embodiments

of Figures 16A, 16B. Additionally, a phase plug 119 may be added into the

acoustic path between the transducer 109 and its respective opening 117, as

shown, so as to redirect high frequency sounds to avoid reflections and

cancellations. The contour graph of Figure 19 corresponding to the loudspeaker

105 of Figure 18 shows a smooth and consistent level difference across

frequencies and vertical listening positions (vertical direction angles), in

comparison to the undesirable comb filtering effects shown in Figure 8.

[0086] Figure 20 shows a cutaway view of the cabinet 111 of the loudspeaker 105, according to yet another embodiment. In this example, the transducers 109 are

also mounted within the cabinet 111 but they are pointed downwards (rather

than sideways as in the embodiment of Figure 18 in which the transducers 109

may be mounted to the sidewall of the cabinet 111). This arrangement may

enable the use of horns 115 that are shorter than those in the embodiment of

Figure 18. As shown in the contour graph of Figure 21, the shorter horns 115

may contribute to a smoother response by this embodiment, in comparison to the

other embodiments that also use horns 115 (described above.) In one

embodiment, the length of the horns 115 may be between 20.0 mm and 45.0 mm.

The openings 117 of the cabinet 111 in this embodiment may also be formed in

the sloped sidewall of the frusto-conical bottom 102 of the cabinet 111, and may

be positioned and oriented the same as described above in connection with the horn embodiments of Figures 16A, 16B to achieve a smaller distance D relative to the reflective surface, e.g., the top surface of the baseplate 113.

[0087] Figure 22 shows a cutaway view of the cabinet 111 in the loudspeaker 105, according to yet another embodiment. In this example, each of the transducers

109 is mounted within the cabinet 111, e.g., similar to Figure 20, but the horn 115

(which directs sound emitted from its respective transducer 109 to its respective

opening 117) is longer and narrower than in Figure 20. In some embodiments, a

combination of one or more Helmholtz resonators 121 may be used for each

respective transducer 109 (e.g., an 800Hz resonator, a 3kHz resonator, or both)

along with phase plugs 119. The resonators 121 may be aligned along the horn

115 or just outside the opening 117, for absorbing sound and reducing reflections.

As shown in the contour graph of Figure 23, the longer, narrower horns 115 of

this embodiment, together with 800Hz and 3kHz Helmholtz resonators 121 may

result in a smooth frequency response (at various angles in the vertical direction).

[0088] Figure 24 shows a cutaway or cross section view taken of a combination transducer 109 and its phase plug 119, in the cabinet111 of the loudspeaker 105,

according to another embodiment. In this embodiment, the phase plug 119 is

placed adjacent to its respective transducer 109, and each such combination

transducer 109 and phase plug 119 may be located entirely within (inward of the

sidewall of) the cabinet 111 as shown. In one embodiment, a shielding device

2401 that is coupled to the outside surface of the cabinet 111 or also to the

baseplate 113 may hold the phase plug 119 in position against its transducer 109.

The shielding device 2401 may extend around the perimeter or circumference of

the cabinet 111, forming a ring that serves to hold all of the phase plugs 119 of all

of the transducers 109 (e.g., in the case of a loudspeaker array). The phase plug

119 may be formed as several fins 2403 that extend from a center hub 2405. The

fins 2403 may guide sound (through the spaces between adjacent ones of the fins

2403) from the diaphragm of the corresponding transducer 109 to an aperture

2407 formed in the shielding device 2401. Accordingly, the phase plug 119 may

be shaped to surround the transducer 109, including a diaphragm of the

transducer 109 as shown, such that sound may be channeled from the

transducers 109 to the aperture 2407. By also guiding the sound from the

transducers 109 to the openings 117, respectively, the phase plugs 119 of this

embodiment are also able to place the effective sound radiation area of the

transducers 109 closer to the reflective surface (e.g., the baseplate 113, or a

tabletop on which the loudspeaker 105 is resting). As noted above, by

positioning the sound radiation area or sound-radiating surface of the

transducers 109 closer to a reflective surface, the loudspeaker 105 in this

embodiment may reduce the difference between reflective and direct sound

paths, which in turn may reduce comb filtering effects.

[0089] Turning now to Figure 25, in this embodiment, the loudspeaker 105 has a partition 2501. The partition 2501 may made of a rigid material (e.g., a metal,

metal alloy, or plastic) and extends from the outside surface of the cabinet111

over the bottom 102 of the cabinet 111, to partially block the transducers 109 - see

Figure 12 which shows an example of the bottom 102 of the cabinet 111 and the

transducers 109 therein, which would be blocked by the partition 2501 of Figure

25. The partition 2501 in this example is a simple cylinder (extending straight

downward) but it could alternatively have a different curved shape, e.g., wavy

like a skirt or curtain, to encircle the cabinet 111 and partially block each of the

transducers 109. In one embodiment, the partition 2501 may include a number of

holes 2503 formed in its curved sidewall as shown which may be sized to allow

the passage of various desired frequencies of sound. For example, one group or

subset of the holes 2503 which are located farthest from the baseplate 113 may be

sized to allow the passage of low-frequency sounds (e.g., OOHz-1kHz) while another group or subset of holes 2503 that lies below the low-frequency holes may be sized to allow the passage of mid-frequency sounds (e.g., 1kHz-5kHz). In this embodiment, high-frequency sounds may pass between a gap 2505 created between the bottom end of the partition 2501 and the baseplate 113. Accordingly, high-frequency content is pushed closer to the baseplate 113 by restricting this content to the gap 2505. This movement of high-frequency content closer to the baseplate 113 (i.e., the point of reflection) reduces the reflected sound path and consequently reduces the perceptibility of comb filtering for high-frequency content, which as noted above is particularly susceptible to this form of audio coloration.

[0090] Turning now to Figures 26A, 26B, these illustrate the use of acoustic dividers 2601 in a multi-way version, or in an array version, of the loudspeaker

105, in accordance with yet another embodiment of the invention. The divider

2601 may be a flat piece that forms a wall joining the bottom 102 of the cabinet

111 to the baseplate 113, as best seen in the side view of Fig. 26B. The divider

2601 begins at the transducer 109 and extends outward lengthwise, e.g., until a

horizontal length given by the radius r, which extends from a center of the

cabinet (through which a vertical longitudinal axis of the cabinet 111 runs - see

Fig. 26b. The divider 2601 need not reach the vertical boundary defined by the

outermost sidewall of the cabinet 111, as shown. A pair of adjacent dividers 2601

on either side of a transducer 109 may, together with the surface of the bottom

102 of the cabinet 111 and the top surface of the baseplate, act like a horn for the

transducer 109.

[0091] As explained above, the loudspeakers 105 described herein when configured and driven as an array provide improved performance over

traditional arrays. In particular, the loudspeakers 105 provided here reduce

comb filtering effects perceived by the listener 107 by either 1) moving transducers 109 closer to a reflective surface (e.g., the baseplate 113, or a tabletop) through vertical or rotational adjustments of the transducers 109 or 2) guiding sound produced by the transducers 109 to be released into the listening area 101 proximate to a reflective surface through the use of horns 115 and openings 117 that are the prescribed distance from the reflective surface. The reduction of this distance between the reflective surface and the point at which sound emitted by the transducers 109 is released into the listening area 101 consequently reduces the reflective path of sound and reduces comb filtering effects caused by reflected sounds that are delayed relative to the direct sound. Accordingly, the loudspeakers 105 shown and described may be placed on reflective surfaces without severe audio coloration caused by reflected sounds.

[0092] As also described above, use of an array of transducers 109 arranged in a ring may assist in providing horizontal control of sound produced by the

loudspeaker 105. In particular, sound produced by the loudspeaker 105 may

assist in forming well-defined sound beams in a horizontal plane. This

horizontal control, combined with the improved vertical control (as evidenced by

the contour graphs shown in the figures) provided by the positioning of the

transducers 109 in close proximity to the sound reflective surface underneath the

cabinet 111, allows the loudspeaker 105 to offer multi-axis control of sound.

However, although described above in relation to a number of transducers 109, in

some embodiments a single transducer 109 may be used in the cabinet 111. In

these embodiments, it is understood that the loudspeaker 105 would be a one

way or multi-way loudspeaker, instead of an array. The loudspeaker 105 that has

a single transducer 109 may still provide vertical control of sound through careful

placement and orientation of the transducer 109 as described above.

[0093] While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. The description is thus to be regarded as illustrative instead of limiting.

Claims (20)

CLAIMS What is claimed is:

1. An electronic device, comprising:

a cabinet; and

a plurality of audio transducers distributed radially about an interior of

the cabinet, wherein each audio transducer of the plurality of audio transducers

acoustically coupled to an acoustic pathway within the interior that redirects

audio generated by the audio transducer first downward toward a base of the

cabinet and then radially outward through a sound output opening defined by a

sidewall of the cabinet which is at a predefined distance from a reflective surface

facing the sidewall for reflecting the audio from the audio transducers, and

wherein each audio transducer in the plurality of audio transducers is

individually and separately driven to produce sound in response to separate and

discrete audio signals received from an audio source.

2. The electronic device as recited in claim 1, further comprising a base

coupled to the cabinet and configured to support the cabinet above a supporting

surface, wherein each of the audio transducers are positioned a first distance

from the base.

3. The electronic device as recited in claim 1, wherein the audio transducers

are arranged in a ring formation within the cabinet.

4. The electronic device as recited in claim 3, wherein the cabinet has a

cylindrical geometry.

5. The electronic device as recited in claim 1, each of the audio transducers

includes a phase plug configured to redirect sounds to avoid reflections and

cancellation within the acoustic pathway.

6. The electronic device as recited in claim 5, wherein the phase plug is

disposed against the transducer.

7. The electronic device as recited in claim 1, wherein the audio transducers

are all configured to operate in the same frequency range.

8. An electronic device, comprising:

a cabinet;

a plurality of audio transducers radially distributed within the cabinet and

diaphragms of each of the audio transducer oriented such that a forward face of

each of the diaphragms is oriented inward toward a central region of the cabinet,

wherein each audio transducer in the plurality of audio transducers is

individually and separately driven to produce sound in response to separate and

discrete audio signals received from an audio source; and

one or more horns that direct sound from the central region to a sound

output opening in a sidewall of the cabinet which is at a predefined distance from

a reflective surface.

9. The electronic device as recited in claim 8, further comprising a voice coil

coupled to a rear face of each of the diaphragms.

10. The electronic device as recited in claim 8, further comprising a digital

wireless interface configured to receive one or more audio signals from an

external device.

11. The electronic device as recited in claim 8, further comprising a base

coupled to and supporting the cabinet.

12. The electronic device as recited in claim 11, wherein each one of the

plurality of audio transducers is tilted downward toward the base.

13. The electronic device as recited in claim 8, wherein the plurality of audio

transducers are first audio transducers and the electronic device further

comprises a second audio transducer disposed within the cabinet and elevated

above the first audio transducers the second audio transducer having a lower

frequency range than the first audio transducers.

14. The electronic device as recited in claim 13, wherein the second audio

transducer is a subwoofer and the first transducers are tweeters.

15. An electronic device, comprising:

a cabinet; and

an array of audio transducers disposed within the cabinet at a radial

interval, each of the audio transducers facing inward toward a central region and

being configured to generate audio waves that travel through an acoustic

pathway first downward toward a base of the cabinet and then radially outward

to exit the cabinet through sound output openings defined by a sidewall of the

cabinet, wherein each audio transducer in the array of audio transducers is

individually and separately driven to produce sound in response to separate and

discrete audio signals received from an audio source.

16. The electronic device as recited in claim 15, further comprising a base

supporting the downward facing end of the cabinet.

17. The electronic device as recited in claim 15, further comprising:

a digital wireless interface configured to receive one or more audio signals

from an external device;

a memory unit storing an operating system; and

a processor executing functions defined by the operating system.

18. The electronic device as recited in claim 15, wherein the sound output

openings are divided by acoustic dividers.

19. The electronic device as recited in claim 18, wherein each acoustic divider

is a flat piece that forms a wall.

20. The electronic device as recited in claim 13, further comprising a phase

plug configured to redirect audio waves to avoid reflections and cancellation

within an acoustic pathway guiding the audio waves between the array of audio

transducers and the sound output openings.