Abstract:
This invention provides a transducer having at least two surrounds supporting a cylinder. With at least two surrounds, the transducer may handle more power. This increased power may be used to drive the voice coil that is wrapped around the cylinder enabling a greater excursion range of the diaphragm. With a greater excursion range, the transducer may operate at low frequency as well as mid to high frequencies. The two surrounds may also be coupled to the cylinder increasing stability of the cylinder. With the two suspensions stabilizing the cylinder, the side-to-side movement of the cylinder may be reduced minimizing the chance of the voice coil short-circuiting with the other electrical and/or mechanical circuits in the transducer. In addition, the cylinder made a substantially rigid material may better support the two flexible surrounds so that the two surrounds do not induce wobbling in the diaphragm.

Description:
1. INCORPORATION BY REFERENCE OF A RELATED APPLICATION  
       [0001]    This application incorporates by reference U.S. Provisional application serial No. 60/279,314 entitled “Tangential Stress Reduction in a Surround Speaker” filed on Mar. 27, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    2. Field of the Invention  
           [0003]    This invention relates to a dual suspension configuration for a loudspeaker transducer. In particular, this invention is well suited for use in space-constrained applications.  
           [0004]    3. Related Art  
           [0005]    In the design of miniature loudspeakers, there is usually a tradeoff between the size of the loudspeaker and its performance. As the size of the loudspeaker gets smaller, its ability to generate bass sound at low frequencies may be diminished because a smaller loudspeaker acting as a piston may not be able to “pump” a large volume of air to generate bass sound. This pumping or displacement volume of air is a product of the diaphragm&#39;s area and the amplitude of its excursion range. In particular, as the size of the transducer gets smaller there may be certain physical limitations as to the excursion range of the diaphragm. For instance, a transducer with one surround suspension may not be able to handle the delivered power driving the diaphragm to a higher excursion.  
           [0006]    In many instances, a “woofer” may be provided with miniature loudspeakers to provide a full range of frequency response. The woofer for low frequency response, and the miniature loudspeakers for mid to high frequency response. Including a woofer into a speaker system, however, adds to the cost of the speaker system. When such miniature loudspeakers are incorporated into a laptop computer, the miniature loudspeakers alone cannot respond to a full range of frequencies without the woofer.  
           [0007]    Another problem with transducers is wobbling of the diaphragm. This may degrade the acoustic sound produced by the diaphragm. A diaphragm should be light and as stiff as possible so that the residence frequencies may be high. Conversely, the suspension supporting the diaphragm should be flexible or as soft as possible so that it does not resist the oscillation movement of the diaphragm. But when a stiff diaphragm is surrounded by a flexible suspension, the diaphragm acts like a wobbling member rather than acting like a stiff member. Such wobbling can induce not only unwanted vertical movement of the diaphragm but also lateral or horizontal movements, which hinders the performance of the loudspeaker. Therefore, there still is need for a loudspeaker that can minimize the wobbling and respond to a full range of frequencies.  
         SUMMARY  
         [0008]    This invention provides a loudspeaker system employing at least two surrounds to support the cylinder housing the diaphragm in a transducer mount. By incorporating at least two surrounds, the transducer may handle increased power loads enabling a larger excursion range of the diaphragm. With a greater excursion range, the loudspeaker may increase its operational range to include low frequencies as well as mid to high frequencies. This way, the loudspeaker may operate as a full range loudspeaker and the two surrounds that may be coupled to the cylinder may act to increase stability of the cylinder. With the two suspensions stabilizing the cylinder, side-to-side movement of the cylinder may be minimized reducing the chance of a short circuit from occurring between the voice coil and the electrical circuits in the transducer. In addition, the cylinder composition may include a substantially rigid material assisting the two flexible surrounds in the reduction of wobbling of the diaphragm.  
           [0009]    Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]    The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0011]    [0011]FIG. 1 is a top view of a diaphragm.  
         [0012]    [0012]FIG. 2 is a side view of a transducer housing.  
         [0013]    [0013]FIG. 3 is a cross-sectional view of a transducer.  
         [0014]    [0014]FIG. 4 is a close-up cross-sectional view of the encircled region of FIG. 3.  
         [0015]    [0015]FIG. 5 is a cross-sectional view of a transducer with parabolic cross-sectional shaped surrounds.  
         [0016]    [0016]FIG. 6 is an enlarged, cross-sectional view of the parabolic surround.  
         [0017]    [0017]FIG. 7 is a cross-sectional view of a transducer.  
         [0018]    [0018]FIG. 8 is a cross-sectional view of a transducer.  
         [0019]    [0019]FIG. 9 is a cross-sectional view of a transducer with an alternative surrounds location.  
         [0020]    [0020]FIG. 10 is a cross-sectional view of a transducer illustrating another surrounds location.  
         [0021]    [0021]FIG. 11 is a schematic diagram representing the spring constants of the surrounds.  
         [0022]    [0022]FIG. 12 is a schematic diagram representing the dual surround relative to the center of mass.  
         [0023]    [0023]FIG. 13 is a cross-sectional view of a transducer.  
         [0024]    [0024]FIG. 14 is a perspective view of a diaphragm. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    This invention may be suitable for application of the transducer in small enclosures. Such enclosures include application in small “surround sound” speaker systems, multimedia speaker systems (audio systems coupled to computers) and automotive speaker system.  
         [0026]    [0026]FIG. 1 illustrates a top view of a transducer  100  including a diaphragm  102  coupled to a cylinder  104  designed to vibrate up and down within a housing  108 . To guide the cylinder  104 , a first surround suspension  106  and a second surround suspension (not shown here) may be between the cylinder  104  and the housing  108 . The two suspensions  106  and  108  substantially stabilize the cylinder as it moves up and down. Extending from the housing  108  may be a pair of hookup wires  110  to provide power to the transducer  100 . In one example, the diaphragm  102  may be disposed within the cylinder  104 .  
         [0027]    [0027]FIG. 2 is a side view of the transducer  100  with a roll  200  of the first surround  106  protruding from the housing  108 . FIG. 3 illustrates a cross-sectional view of the transducer  100  having a first surround suspension  300  (first surround) and a second surround suspension  302  (second surround) at a predetermined distance “X” from each other. The diaphragm  102  may be concave and positioned on the upper edge  318  the cylinder  104 . However, the diaphragm  102  may have other shapes as well, such as convex or any other type of diaphragm known to one ordinarily skilled in the art. The edge of the diaphragm  102  may have a flat narrow flange that is adhesively attached to the upper edge  318  of the cylinder  104 . The two surrounds  300  and  302  may be located between the cylinder  104  and the housing  108 . The two surrounds may symmetrically oppose each other such that the respective rolls  304  and  306  for each of the surround  300  and  302  may face away from each other. The inner edges  308  and  310  of the respective two surrounds  300  and  302  may be adhesively attached to the cylinder  104 . The inner edge  308  of the first surround may be below the upper edge  318  of the cylinder  104 . The outer edges  312  and  314  of the respective two surrounds  300  and  302  may be coupled to the housing  108 .  
         [0028]    A voice coil  316  may wrap around the cylinder  104  showing a cylindrical cross-sectional shape. The voice coil  316  may have a corresponding cylindrical shape as it wraps around the cylinder  104 . The cylinder  104  and the voice coil  316  may have other cross-sectional shape as well, such as elliptical and triangular cross-sections. The voice coil  316  may include a pair of semicircular ends and a pair of straight edges connecting the pair of semicircular ends. That is, the shape of the voice coil  316  may be any type known to one skilled in the art. The two hookup wires  110  may extend outwardly through the housing  108  between the two surrounds  300  and  302 . In such a case, the distance X between the two surrounds may be predetermined so that the two surrounds may move up and down within the housing  108  without damaging or touching the two hookup wires  110 . Alternatively, the two wires  110  may run between the second surround  302  and the voice coil  316 .  
         [0029]    [0029]FIG. 4 is an enlarged view of the encircled area of FIG. 3, illustrating the voice coil  316  within a magnetic gap  400  between an upper pole piece  402  and a pot  404 . As electrical signals pass through the voice coil  316 , current passing through the voice coil  316  interacts with the magnetic field in the magnetic gap  400 . This interaction causes the voice coil  316  to oscillate in accordance with the electrical signal, and drive the combination of the cylinder  104  and diaphragm  102  to oscillate within the housing. The peak to peak up and down movement of the diaphragm  102  may be generally described as an excursion range.  
         [0030]    There are several advantages to having two suspensions in accordance with the invention. First, a transducer with at least two surrounds may handle more power from the voice coil  316  to drive the diaphragm to a wider excursion range. With a greater excursion range, the transducer  100  may operate at lower frequencies to generate bass sound. Thus, the transducer  100  may operate as a full range loudspeaker being able to operate between low and high frequencies. Second, with two surrounds  300  and  302  coupled to the cylinder  104 , the cylinder  104  may be more stable as it moves up and down in the magnetic air gap  400 . In other words, with the two suspensions  300  and  302  stabilizing the cylinder  104 , there may be less chance that the cylinder  104  will rock from side to side to cause a short circuit between the voice coil  316  and the pot  404 .  
         [0031]    The two surrounds may also be coupled directly to the cylinder  104 . Wobbling or unintended vibrations in the diaphragm  102  may be reduced because the surround (generally made of a flexible material) is coupled to cylinder  104  rather than to the diaphragm  102 . When a surround is directly coupled to the diaphragm, the flexibility of the surround may induce wobbling in the diaphragm as the combination of the diaphragm and surround oscillate up and down. The two surrounds  300  and  302 , however, may be directly coupled to the cylinder  104 . In this way, the cylinder  104  may firmly support the inner edges  308  and  310  of its respective surrounds  300  and  302  so that the flexibility of the surrounds has minimal influence on the diaphragm  102 . In other words, the diaphragm may not wobble without the direct influence of the surrounds. It is also possible for the first surround  300  to be coupled to the diaphragm  102 , while a second surround  302  is coupled to the cylinder  104 .  
         [0032]    [0032]FIG. 3 also illustrates a substantially symmetrical first surround  300  with respect to the second surround  302 . The symmetry between the two surrounds  300  and  302  allows the two surrounds to act like two parallel springs, so that the spring tensions in the two surrounds can be summed. This means that the two suspensions work together to substantially minimize the distortion in the cylinder  104  because the spring constant of the two suspension members  300  and  302  are substantially similar in the up and down strokes of the cylinder  104 . Conversely, a non-symmetrical pair of suspensions may cause some distortion in the movement of the cylinder  104  because the spring constant of a non-symmetrical suspension member may be different for an up stroke versus a down stroke. However, it is not necessary to have the two substantially similar suspensions to minimize distortion. The distortion may be minimized by arranging the two substantially similar surrounds in a symmetrical fashion, instead of adjusting the distortion through design of the transducer.  
         [0033]    The two surrounds  300  and  302  may have a cross-section shape of  304  and  306 , respectively. For example, the shape may be substantially shaped like a half-circle as illustrated in FIG. 3. However, the two surrounds may have other cross-sectional shapes. For example, as shown in FIGS. 5 and 6, the two surrounds  500  and  502  may have a shape substantially shaped like a parabolic cross-sectional shape. This allows the diaphragm  102  in the transducer  100  to have a greater excursion range because the two parabolic shape surrounds  500  and  502  may have a peak  504  that may be higher than the peak of the half-circle roll surround. With a higher peak in the surround, the cylinder  104  may have a greater range of up and down movements or greater excursion range. Thus, a smaller diameter speaker having a greater excursion range may be used as a full range loudspeaker producing a wide range of frequency sound from low to high frequencies. Alternatively, the parabolic shape surround may be used in a single surround embodiment rather than in a dual surround embodiment.  
         [0034]    [0034]FIG. 7 illustrates another embodiment of the invention, where the two surrounds  700  and  702  are symmetrical but are inverted toward each other. There are several advantages to this arrangement. First, due to its symmetry, there may be minimal distortion in the cylinder  104  similar to tile embodiment illustrated in FIG. 3. Second, since the two surrounds are facing toward each other, rather than facing away from each other as in FIG. 3, the overall distance “H1” between the two surrounds  700  and  702  may be less than the distance between the two surrounds  300  and  302  in FIG. 3. This means that the overall height “H1” of the transducer  100  may be reduced as well. This way, the transducer  100  may be fitted into an enclosure with a small depth, such as a screen of a portable laptop computer.  
         [0035]    [0035]FIG. 8 illustrates two downward facing surrounds  800  and  802 . This arrangement allows for a reduced “H2” of the transducer  100  between the two surrounds  800  and  802  as shown in FIG. 3. The two surrounds  800  and  802  may also be asymmetric creating some distortion in the movement of the cylinder  104 . To minimize the distortion in the transducer  100 , the spring constant in one of the surrounds may be adjusted to compensate for the distortion. This may be accomplished by adjusting the thickness of one of the surrounds or by using a different material for one of the surrounds with different softness characteristics. When the first surround  800  faces down, the half-circle roll may be flush within the transducer  100  further minimizing the overall depth “H2” of the transducer  100 .  
         [0036]    [0036]FIG. 9 illustrates an embodiment having two upwardly facing surrounds  900  and  902 . With this arrangement, the depth “H3” of the transducer  100  may be smaller than the transducer illustrated in FIG. 3. Because the second surround  902  is facing up rather than facing down, the transducer  100  size may be minimized with respect to the transducer illustrated in FIG. 8. In other words, the depth or height “H3” maybe less than the depth “H2.” 
         [0037]    [0037]FIG. 10 illustrates the location of the voice coil  316  between the two surrounds  1000  and  1002 . The cylinder  104  may be elongated to accommodate the second surround  1002  near the lower end  1004  of the cylinder  104 . Alternatively, the voice coil  316  may be positioned so that the cylinder  104  may be shortened. FIG. 10 also illustrates a schematic diagram of FIG. 11, where “K1” represents the spring constant of the first surround  1000 , “K2” represents the spring constant of the second surround  1002 , and “M” represents the mass of the voice coil  316 . An assumption may be made that the majority of the mass of both the voice coil  316  and cylinder  104  may be from the voice coil  316 . In some instances, the voice coil  316  may have significantly greater mass than the cylinder  104 .  
         [0038]    One of the advantages of having the voice coil  316  located in between the two surrounds  1000  and  1002  is that it may minimize wobbling of the diaphragm for at least the following reasons. First, the two surrounds  1000  and  1002  are spaced farther apart from each so that there may be more leverage acting between the two surrounds  1000  and  1002 . Second, because the center of mass is located between the two surrounds  1000  and  1002 , the two surrounds may exert more leverage to control the mass M.  
         [0039]    [0039]FIG. 12 may schematically represent the embodiments illustrated in FIGS.  3 - 9 , where the mass M of the voice coil  316  may be near the lower end  1204  of the cylinder  104 . Having the mass M located near the end  1204  may allow the cylinder  104  to wobble more freely. To minimize the wobbling, the second suspension  1202  may be positioned close as possible to the mass M. This way, the leverage the mass M has on the second suspension  1202  may be minimized so that the mass M may be more stabilized. Furthermore, the first and second suspensions  1200  and  1202  may be further apart so that the two suspensions may have more leverage to control the center mass M.  
         [0040]    [0040]FIG. 13 illustrates the two surrounds  1300  and  1302  with its respective outer edges  1304  and  1306 , coupled to the housing  1308 . One of the two outer edges  1304  and  1306  may be smaller than the other. The inner edges  1310  and  1312  for the respective surrounds  1300  and  1302  may be substantially similar in order to couple to the cylinder  104 . The height X of the two surrounds  1300  and  1302  may be substantially similar so that the two surrounds  1300  and  1302  may support the cylinder  104  with substantially similar excursion range.  
         [0041]    [0041]FIG. 14 illustrates the first surround  1400  having a sinusoidal face (the second surround having a sinusoidal face not shown). The surround  1400  may have a peak  1402  that substantially forms a sine wave along the circumference of the surround  1400 . This allows the surround to expand in the radial and well as in its circumference direction as the cylinder  104  oscillates up and down.  
         [0042]    The invention may also be practiced with variations and any combination from the embodiment described above without departing from the spirit of the invention. For example, a parabolic cross-sectional surround may be used in place of a half-circular roll in any of the embodiments. In addition, the transducer  100  may have more than two surrounds.  
         [0043]    While various embodiments of the application have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.