The invention relates generally to the field of waveguides, and, more particularly, to a skewed or off-angle horn for a loudspeaker system
With the advent of better multi-channel audio technology for movie soundtracks encoded in formats such as DTS, DOLBY DIGITAL®, DVD Audio, DVD-A, Super Audio Compact Disc, SACD, and the like, surround-sound speakers capable of producing wide dispersion output have been in increasingly high demand for both auditorium and home theatre applications. Surround speaker requirements include diffuse dispersion in the horizontal plane to blur the time arrivals to the listener's ear. This concept is referred to as “reverb.” The audio source may be music, a sound effect, or the like. Multiple speakers can be grouped together to provide a wide dispersion of sound, but there is a nontrivial likelihood that the interaction between such acoustic sources will be acoustically destructive, degrading the sound quality heard by a listener.
Ideally, a point source solution is the answer to this difficulty, but due to size limitations (i.e., most compression drivers are roughly cylindrical with outside diameters between about 5 and 8 inches, making close placement difficult) and limitations of power output capabilities, such a design is impractical and unfeasible in most working applications. Accuracy and intelligibility of acoustic signal is a result of the way the loudspeaker reconstructs the temporal and spectral response of the reproduced wave front. Phase coherence of the signal or wave front is a result of the temporal response when reconstructed. A number of difficulties arise when attempting to sum acoustic wavefronts from multiple drivers including standing waves interference and constructive/destructive amplitude interference caused by overlapping polar patterns between mutually driven acoustic sources.
In practice, the surround-sound speaker design has generally been approached by providing a di-, bi- or tri-polar speaker with 180 degrees dispersion in the horizontal axis. The difficulty with this design is that most transducers tend to narrow the dispersion angle as the wavelength of the output becomes smaller than the area of the transducer mouth and continues to narrow even more as the wavelength becomes smaller than the diameter of the voicecoil. This effect is referred to as “beaming”. The waveguide geometry and/or the throat dimension of the compression driver and/or the diaphragm area of a dome tweeter, along with voicecoil diameter considerations, are the primary contributors to beaming. To avoid beaming, multiple transducers can be used in an arc or array to maximize the dispersion angle in the horizontal axis at the higher frequencies. Unfortunately, in some cases, the complication in this approach is that the polar patterns of dispersion tend to overlap or mesh at the lower frequencies, and thus do not sum acoustically as one wavefront in the axis wherein the transducers are placed due to polar patterns. The polar patter overlapping give rise to constructive/destructive interference, which is interpreted by the listener as a reduction in fidelity and sound quality. Therefore, beaming is reduced at the higher frequencies at the expense of sound quality from an incoherent wavefront reconstruction.
There are other horn designs wherein multiple transducers are arrayed and have polar patterns that match the desired effect of having a wide, consistent polar pattern, even at higher frequencies. The drawback is that the resultant configurations do not even approximate the desired flat front of the horn.
There are horns known in the art that have been developed to provide skewed areas of sound output. One such horn 1 is shown in
Thus, there remains a need for a flat-mouth surround-sound speaker design that can provide surround-sound through a consistent and un-truncated area of expansion, through wider skew angles and over wider frequency ranges without experiencing both beaming and destructive interference. The present invention addresses this need.
The present invention relates to a horn having a substantially flat mouth opening connected to a transducer by an expanding area section or duct to a throat. A centerline oriented perpendicular to the transducer extends from the transducer along the throat to the mouth. The area of expansion or flare rate is substantially constant along the throat to the mouth. The angular dispersion of the horn is asymmetrical, and may be as great as 45 degrees. The horn does not require any baffling or diffraction slotting to achieve sonic dispersion.
One object of the present invention is to provide an improved loudspeaker horn design. Related objects and advantages of the present invention will be apparent from the following description.
FIG. 2AB is a front plan view a second prior art horn.
For the purposes of promoting an understanding of the principles of the invention and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
Overview
A waveguide or horn loudspeaker may be thought of as an electro-acoustic transducer that translates an electrical signal into a directed acoustic signal. As use herein, “waveguide” means a conical or expanding duct or channel designed to confine and direct the propagation of modulated air pressure (i.e., acoustic waves) in a longitudinal direction. A waveguide typically consists of a coupling flange at its acoustical entrance for connecting a compression driver transducer thereto. The waveguide also typically terminates at a mouth and defines an expanding conduit or duct that exits to the ambient air. The waveguide also typically includes a mounting flange to affix the waveguide to a baffle board or other such enclosure, which may be an elaborate framework device or nothing more than a recess or cavity formed in a wall. An expanding duct extends between the acoustical entrance or throat (i.e, the transducer connection) and the mouth, and is typically characterized by an expanding cross-sectional area traveling from the transducer to the mouth. The path of the duct from the throat to the mouth is not always direct or linear, and may take one or more turns.
Generally, sound is generated by a transducer, such as a compression driver, operationally connected via the throat through the duct to the mouth of the horn. Horn speakers sound very dynamic and reproduce fast transients in their output due to their relatively low moving mass. For applications with total, symmetrical dispersion of less than about 90 degrees, a single horn using a single driver is usually adequate. For applications requiring wider dispersion angles and/or dispersion of higher frequencies, additional horns and drivers traditionally have been required. For applications requiring asymmetrical coverage patterns, skew horns are used.
A first embodiment of the present invention is illustrated in
The flared duct 18 is typically rectangular in cross-section, and more typically has the shape of a truncated cone at the throat end 20 characterized by an internal angle of between about 75 degrees and about 30 degrees. The flared duct 18 is further characterized by a major axis 26 extending therethrough. The major axis 26 intersects the coupling flange 12 and the mouth 16, and typically intersects the center or middle point of the coupling flange 12 perpendicularly and intersects the mouth 16.
The coupling flange 12 is typically flat and defines a coupling flange plane. Likewise, the transducer 14 typically has a flat face that abuts the coupling flange 12 at the coupling flange plane. The coupling flange plane 12A is typically not oriented parallel to the mouth plane 16A, but instead defines a horn angle 28 between the two planes 12A, 16A. The horn angle 28 is typically between about 0 degrees and about 60 degrees, and is more typically about 35 degrees. The horn angle 28 drives the skew or dispersion of the speaker 10.
In one particular embodiment, the mouth 16 is typically characterized by an area of between about 180 square centimeters and about 300 square centimeters, and is more typically characterized by an area of about 230 square centimeters. Likewise, in this particular embodiment, the mouth 16 is rectangular in shape; in other embodiments, the mouth 16 may be oval, circular, or any desired shape.
Typically, the array 110 includes two horns 10 defining two nonparallel axes 26; more typically, the axes 26 are oriented at an angle of at least about 60 degrees relative each other; still more typically, the axes 26 are oriented at an angle of about 90 degrees relative each other. When three horns 10 are arrayed, the outer horns 10 are typically oriented symmetrically about the middle horn, and more typically, each outer horn 10 is oriented at an angle of between about 45 degrees and about 60 degrees with the middle horn 10.
In operation, the drivers 14 is connected to a signal source, such as an audio amplifier, a tuner, an A/V receiver, or the like, and is energized by a signal from the same. The driver 14 transduces the signal into an acoustic signal (i.e., modulated pressure waves) that propagates along the connected duct 18 and exits the mouth 16 of the horn 10.
As shown in
At 3000 Hertz, the polar output of prior art speaker is characterized by four deep notches and a dispersion pattern of about 145 degrees. In contrast, the speaker system 100 of the present invention is characterized by only two relatively shallow notches and a dispersion pattern of about 150 degrees. (See
The flared duct 218 is again typically rectangular in cross-section, and more typically has the shape of a truncated cone at the throat end 220 characterized by an internal angle of between about 75 degrees and about 30 degrees. As seen in
The coupling flange 212 is typically flat and defines a coupling flange plane. Likewise, the transducer 214 typically has a flat face that abuts the coupling flange 212 at the coupling flange plane. The coupling flange plane 212A is typically not oriented parallel to the mouth plane 216A, but instead defines a horn angle 228 between the two planes 212A, 216A. The horn angle 228 is typically between about 0 degrees and about 60 degrees, and is more typically about 35 degrees.
In operation, the horn 200 skews acoustic output energy or polar patterns in two planes. For example, the horn 200 may be placed in a corner of a room (typically flush-mounted in the ceiling) and the acoustic output is directed towards the center of the room instead of bouncing off of the walls. Further, by arraying horns 200 together, coverage in one or more desired output planes may be substantially broadened.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the invention are desired to be protected.
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