The present disclosure is generally related to audio transducers used for sound generation and reproduction. More particularly, the present disclosure is directed to positionable audio speakers.
Audio transducers (also known as and equivalently referred to as “speakers”) have been a staple of consumer and industrial electronics for some time. First introduced as sound delivery tools, the basic premise of such transducers is the movement of air or gas through a medium driven by a coil and a magnet. An electrical signal modulated by an audio signal changes the position of the coil about a magnet and drives the medium to move the air, thus reproducing the audio signal generated or captured at another location.
As the audio transducer art progressed, it addressed the desire and need for higher quality reproduction. Stereo and multiple signal and audio transducer systems created a more realistic sound environment, adding direction and depth to the listening experience. Audio transducers improved in quality as well. Scientists have been perfecting the art of audio reproduction by using better and different materials, structures and combination to provide a more realistic and higher quality sound reproduction, which to this date is primarily based on the movement of air by electromagnetical assemblies and components.
One of the improvements in the audio transducer art is the segregation of lower and higher audio signals. The industry recognized that the physical requirements for higher quality low-end audio signals generated by the so-called “woofers” introduce limitations on the higher end of the audio spectrum generated by the “tweeter.” Similarly, audio transducers that are designed for optimized higher frequency audio signals are not optimized for low-end sound generation. Accordingly, the audio transducer industry split the delivery of such signals between two or more audio transducers, thus allowing each of the audio transducers to produce a portion of the overall sound content within its optimized configuration.
In time, the industry recognized the need for aesthetic and placement accommodation and sought seamless integration into complex environments. Speakers evolved into integrated placement in entertainment centers, ceilings, walls, car compartments and other electronic devices. As such, the placement of the speakers often compromised the sound fidelity, as many locations are suboptimal for high fidelity audio reproduction. To address this deficiency, the industry introduced adjustable high frequency audio transducers. Such adjustable devices allowed the user to direct or adjust the sound flow toward the “sweet spot” or the targeted listening area. However, as will be described in further detail herein, when a tweeter is placed in the audio field of a woofer, the tweeter may interfere with the fidelity of the woofer.
Prior-art swivel tweeters typically place the center of rotation behind the tweeter radiating surface. This causes several deficiencies in the high and mid frequency performance as the tweeter is swiveled. More particularly, in the prior art, when the tweeter position is adjusted with respect to the woofer, the tweeter output frequency, its phase response, woofer output frequency, tweeter-woofer sound pressure level and phase interactions change.
Most prior art swivel tweeter mechanisms place the center of rotation at the base of the tweeter, at its end closest to the woofer. Such placement provides efficiency in manufacture and a substantial range of angular movement. However, in the downside, the center of the tweeter changes with its position relative to the woofer. Consequently, the angular and radial displacement is substantial. Such movement has an undesirable affect on the amplitude and phase relationship of sound energy from the tweeter with respect to sound energy from the woofer, making it difficult or impossible to design a single compensating network or crossover for all tweeter positions.
Further, the typical prior art swivel tweeter affects the sound radiation pattern and amplitude from the woofer. As the tweeter is swiveled, its body moves closer to the woofer diaphragm on one end and further on the other. This affects both the acoustic loading and the sound radiation pattern of the woofer diaphragm. As before, because the acoustic loading and sound radiation pattern from the woofer diaphragm is a complex function of the tweeter position, it is difficult to design a single or cost effective compensating network for all tweeter positions.
Diffraction is also a notable side effect of adjustable components in a speaker. When sound waves emanate from a speaker every change in surface they encounter (a bump, edge or ridge) causes the waveform to reflect and re-radiate. This is a form of acoustic distortion called “diffraction.” Diffraction causes frequency response errors and other audible problems mostly in the midrange and high frequency areas that can make the speaker sound “boxy” and “nasal.” Given a static obstruction, audio engineering is able to compensate for obstacles. However, when the obstacles are dynamic, compensation is more complicated or impractical. Diffraction also has an adverse effect on broad, even dispersion. For example, U.S. Pat. No. 7,178,628B2 (the “'628 patent”) describes a tweeter that swivels about a point in space in front of a speaker diaphragm in order to reduce sound reflection from the speaker housing. However, in this design, even slight amounts of tweeter swivel will cause asymmetric changes in the diffraction of the high frequency sound field from the edges of the tweeter support. Further, the method disclosed in the '628 patent will cause the geometric center of the front surface of the tweeter diaphragm to move with respect to the geometric center of the low frequency diaphragm when the tweeter is swiveled. These inherent characteristics produce phase and amplitude interactions between the high frequency transducer sound field and the low frequency transducer sound field that vary with the tweeter positions. Such architecture makes it difficult or impossible to design of a high performance, compensating network.
Similarly, in the prior art adjustable tweeter assemblies, the acoustic profile of the tweeter changes from the point of view of the woofer, and the tweeter edge profile changes throughout its range of adjustment. As the tweeter swivels in prior art “ball-in-socket” designs, typically the edge geometry around the tweeter radiating surface changes. Such configurations cause undesirable changes in the radiated sound pressure level due to diffraction at the corner geometry. This limitation is evident in U.S. Pat. Nos. 5,133,428 and 6,683,963.
Another significant limitation of prior art coaxial speakers is the airflow between the tweeter and the woofer. Namely, as the woofer drives air, the resulting airflow tends to produce undesirable acoustic byproducts as the air moves through the fittings and the mounting structure of the tweeter assembly. The undesirable byproducts are often perceived as hissing or whistling appearing at bass notes and large excursions.
Moreover, many prior art adjustable tweeters do not have sufficient mechanical stability to remain in a constant adjusted position in view of the inherent forces introduced by the vibration. Thus, over time the adjusted position changes and the fidelity sought by the user diminishes.
The disclosed embodiments recognize the deficiencies presented by the prior art adjustable tweeters. Placing the center of rotation at the base of a tweeter body in a ball-socket configuration is advantageous for the wide range of motion and ease of manufacture. However, it also changes the acoustic center of the tweeter. As the tweeter rotates off-axis, the acoustic center of the tweeter moves laterally away from the woofer axis and the distance from the tweeter acoustic center to the woofer cone changes. Moving the acoustic center of the tweeter changes the phase and amplitude interactions between the tweeter and woofer. When the phase and amplitude interactions between the tweeter and woofer change with position, it is impossible for the manufacturer to design a high quality crossover. The crossover designer is forced to optimize the crossover with the tweeter in one position, typically on axis, and accept that the acoustic quality will degrade when the tweeter is moved.
The disclosed exemplary embodiments place the center of rotation of the adjustable tweeter at the surface of the tweeter, i.e. at the center of the tweeter's acoustic radiation, as opposed to its base. Accordingly, the relative position of the acoustic center of sound radiation from the tweeter is fixed with respect to the acoustic center of sound radiation from the woofer, allowing the acoustic designer to optimize a crossover for multiple or all positions of the tweeter without compromise. Moreover, the rounded diffraction edges of the disclosed adjustable tweeter assembly do not change as the tweeter is repositioned, allowing the acoustic designer to optimize a crossover for multiple or all positions of the tweeter without compromise.
Notably, the acoustic profile of the disclosed adjustable tweeter referenced to the woofer cone does not change as the tweeter is swiveled or adjusted and the obstruction it poses to the woofer is independent of the direction and amount of its position with respect to the woofer, once again contributing to the elimination of sound diffraction. Accordingly, the woofer sound field is constant over the range of tweeter movement, thereby allowing a compensating crossover design.
In another exemplary embodiment, a spring is disclosed as means for applying a force to hold the tweeter in the desired position regardless of the tweeter orientation or vibration forces exerted on the tweeter during its use. The disclosed embodiment provides sufficient force to maintain the tweeter in its designated position and resist the movement of the tweeter exerted by forces emanating from the sound energy produced by the tweeter and woofer and the ambient operating environment.
In another exemplary embodiment, a mechanism is disclosed to allow limited axial range of motion to prevent over twisting of wire leads connected to the tweeter. Disclosed embodiment uses a ring/stop configuration allowing two elements to each have a range of motion greater than zero degrees, but less than 360 degrees. In sum, the disclosed configuration provides a defined range of motion greater than 360 degrees and less than 720 degrees, which allows the user a full range of orientation for the tweeter, while maintaining the integrity of the wire leads.
In another exemplary embodiment a barrier means such as a barrier, seal and/or baffle, is/are utilized to minimize and/or eliminate the movement of air produced by bass notes through the tweeter assembly. Such means limits and/or eliminates perceivable air movement produced by the woofer through the tweeter assembly. As the reader will recognize, when a relatively large volume of air is moved through a relatively small opening, such movement may and often does produce an audio response, often a high frequency response. In the sound reproduction applications, such audio response is undesirable, as it is perceived by a listener as hissing or whistling coincident with low and midrange notes. Thus, the use of a barrier means to redirect, dampen or eliminate the airflow through the tweeter assembly improves the audio fidelity of the speaker.
Other aspects, advantages, and features of the present disclosure will become apparent after review of the entire application, including the following sections: Brief Description of the Drawings, Detailed Description, and the Claims.
Referring to
The pole 120 supports a tweeter mounting post 152, which supports a tweeter assembly 150. The tweeter assembly 150 comprises a tweeter holder 151, which further comprises a base 151B at its bottom end and a tweeter waveguide 153 at its opposite, top end. A base 151B is shown in spherical form movably residing in a complimentary annular aperture 152T formed at the top end of the mounting post 152. A frictional force F1 maintains the base 151B in a user selected position within the annular aperture 152T. Accordingly, a user can orient the direction of the tweeter 158 by swiveling the tweeter assembly 150 about the mounting post 152.
The configuration of
Another disadvantage inherent in this design, is that the tweeter assembly 150 can be continuously twisted about the y-axis without sufficient restriction. Accordingly, the leads connected to the tweeter 158 may sever from the tweeter 158 or become damaged if the user continues to rotate the tweeter 158.
Moreover, audio fidelity is also significantly compromised in the design of
The embodiments of
The pole 120 supports a tweeter mounting post 252, which in turn supports a tweeter assembly 250. The tweeter assembly 250 in part comprises a tweeter holder 251, the tweeter waveguide 153 and the tweeter 158. The tweeter 158 is positioned in the tweeter waveguide 153, which is attached to the holder 251. The holder 251 is positioned between a flange 254T and the top end of the mounting post 252 such that frictional force is exhibited between the flange 254T and the holder 251, and between the holder 251 and the top of the mounting post 252. The flange 254T is formed on the top end of the retaining post 254 to reciprocally match the inner surface of the tweeter holder 251. Similarly, the top of the mounting post 252 is formed to reciprocally match the outer surface of the tweeter holder 251. In combination, the tweeter holder 251 is positioned for a radial range A of motion 0 to A2 degrees, which effectively extends to −A2 to A2 degrees, as the holder 251 is axially rotatable in excess of 360 degrees. In one embodiment, it may be desirable to limit the range of motion to a range less than −A2 to A2 degrees in order to preserve the overlap of the top portion of the mounting post 252, the flange 254T and the holder 251. This effectively prevents air leaks and undesirable audible byproducts such as hissing or whistling effects commensurate with such air leaks. In other embodiments, one could define the range of motion from −A2 to A2 degrees and provide for alternate means to compensate for such air leaks. As can be seen by reference to
Further, the tweeter retaining post 254 extends from its flange end 254T toward its bottom end 254B and is in a coaxial arrangement with or parallel with the tweeter mounting post 252. A frictional holding force F2 is provided by leveraging the retaining post 254 against the mounting post 252 along their longitudinal, Y-axis, by means of a compression spring 256. The spring 256 is coupled to and leverages the bottom 254B of the retaining post 254 through a retaining ring 257 on its bottom end 254B and is coupled to and leverages the mounting post 252 against a notch in the mounting post 252 to exert the force F2 through the flange end 254T against the movable/adjustable tweeter holder 251 and top of the mounting post 252. Accordingly, the force F2 provides for frictional force created between the flange 254T, the tweeter holder 251 and the top of the mounting post 252 by applying the normal bias of the spring 256 through the retaining post 254 and the mounting post 252 to compress the tweeter holder 251 between the flange 254T and the top end of the mounting post 252. This structure allows sufficient movement and radial range for the tweeter holder 251 together with the tweeter 158 with respect to the tweeter mounting post 252 and the body 146. Such force and structure allow a stable position that exceeds the environmental forces, gravitational forces and vibration emanating from the audio signals generated by the speaker 200. As will be appreciated by one of ordinary skill in the art, the force F2 can be increased or decreased by the force of the spring 256.
Notably, the disclosed embodiments of
Shown in
In the disclosed embodiments, once the retaining post 254 meets its first limit of stop 259T, in either positive or negative direction, further rotational force applied to retaining post 254 will exert such force to ring 259 and its stop 259B, which will further have a range of motion limited by a stop 452S integral or attached to the mounting post 252. The mounting post 252 is configured with an aperture opening to accommodate the retaining post 254 therein and correspondingly, the lower portion of the retaining post 254 is tailored to accommodate mating to such opening. Similarly, the range of axial motion of the retaining post 254 and the ring 259 within the mounting post 252 is limited to the range of motion defined by the freedom of movement defined by the stop 259B and the stop 252S, which is less than 360 degrees. However, in the aggregate, the degree of motion defined by the stops 452S and 259B plus the degree of motion defined by the stops 259T and stop 254S, is greater than 360 degrees and less than 720 degrees. One of skill in the art could extend or contract this range by adding more stops and rings or by limiting the degree of motion at one or both of the pairs of cooperating stops. Note that in one embodiment, the combined degree of motion is 540 degrees, representing 270 degrees of motion defined by the stops 254S and 259T and another 270 degrees of motion defined by the stops 259B and 452S. Moreover, additional means for limiting the range can be achieved by manipulating the dimensions of the stops or placing multiple stops. In other embodiments, the axial degree of motion may be achieved by a thread design, where the thread allows the retaining post to have a predetermined range of movement. However, as described above, a threaded design may change the position of the tweeter with respect to the woofer, thus causing uncompensated and undesirable diffraction and distortion.
In the disclosed embodiments, the acoustic profile of the tweeter 250 does not impose a change from the point of view of the woofer, and the tweeter 250 edge profile does not change throughout its range of adjustment. Conversely, as the tweeter swivels in prior art “ball-in-socket” designs, typically the edge geometry around the tweeter radiating surface changes. Such configurations cause undesirable changes in the radiated sound pressure level due to diffraction at the corner geometry of prior art tweeter assemblies. More particularly, in the prior art swivel tweeters, the tweeter output frequency and phase response, woofer output frequency, phase response, tweeter-woofer sound pressure level and phase interactions change as the tweeter is swiveled. As the prior art tweeter position changes, the woofer sound field also changes, thereby making it difficult to design a compensating network for all tweeter positions. In the disclosed embodiments, the acoustic radiation emanating from the woofer cone “sees” the same tweeter assembly 250 acoustic profile independent of the direction and amount of tweeter 158 swivel. In the disclosed embodiments, the complex phase and amplitude relationships between the sound field of the woofer and/or midrange and the sound field of the tweeter 158 are held relatively constant for all tweeter assembly 250 positions permitting the design of a high performance compensating network which is independent of the swivel of the tweeter assembly 250.
As described, the embodiments disclosed herein provide substantial improvements over the prior art by holding the tweeter assembly 250 stable relative to the woofer and by maintaining the acoustic center of front surface of the tweeter 158 diaphragm in substantially the same position for all angles of rotation, without additional diffraction of the sound field from either the high or low frequency transducers. In addition to its virtual static positioning, to limit the undesirable diffraction, the embodiments disclose relatively continuous surface of the tweeter holder 251 and the waveguide 153. Reader will note that in the disclosed embodiments, as the tweeter holder 251 changes its position, from the woofer's perspective the profile of the tweeter assembly 250 remains constant due to the spherical structure of the tweeter holder 251 in combination with the waveguide 153, absence of sharp reflective structures in the tweeter holder 251 and the waveguide 153 and the lack of the axial or radial displacement X2, Y2 and A2. Accordingly, from the woofer's perspective, the tweeter assembly 250 remains static (even if changed by the user). Therefore, a sufficient compensating network can be designed for the disclosed coaxial assembly 200, despite the dynamic positioning of the tweeter 158.
The description of the disclosed embodiments above is provided to enable a person skilled in the art to make or use the disclosed embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope possible consistent with the principles and novel features as defined by the following claims.
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Number | Date | Country | |
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20100322457 A1 | Dec 2010 | US |