Patent Publication Number: US-6339649-B1

Title: Loudspeaker system with stackable loudspeaker units

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a loudspeaker system, more particularly to a loudspeaker system with stackable loudspeaker units for achieving a surround sound effect. 
     2. Description of the Related Art 
     A loudspeaker is used for an audio system and includes a loudspeaker enclosure and a loudspeaker mechanism. When sound is generated by the loudspeaker mechanism, positive and negative sound pressures are produced in front of and behind the loudspeaker mechanism. In the loudspeaker enclosure, the negative sound pressure behind the loudspeaker mechanism creates echo resonance, which can interfere with the sound pressure produced in front of the loudspeaker mechanism so as to affect adversely the quality of sound output. 
     Referring to FIGS. 1 and 2, a conventional loudspeaker  10  includes a loudspeaker enclosure and tweeter, midrange and woofer loudspeaker mechanisms  141 ,  142 ,  143  mounted on the loudspeaker enclosure. The loudspeaker enclosure includes a closed box  15 , an inner baffle wall  12  disposed in the box  15 , a ducting member  13  disposed in a bottom portion of the box  15 , and a plurality of port openings  11  formed in a front side of the box  15 . The baffle wall  12  encloses and isolates the tweeter and midrange loudspeaker mechanisms  141 ,  142  from the woofer loudspeaker mechanism  143 . The ducting member  13  includes a horizontal plate  131  and a vertical plate  132  connected to the horizontal plate  131 . As such, the sound pressures behind the tweeter and midrange loudspeaker mechanisms  141 ,  142  can be radiated directly through the upper port opening  11 , while the sound pressure behind the woofer loudspeaker mechanism  143  can be radiated through the lower port opening  11  via the ducting member  13  to avoid echo resonance. 
     The following are some of the drawbacks of the conventional loudspeaker  10 : 
     1. The loudspeaker  10  includes the tweeter, midrange and woofer loudspeaker mechanisms  141 ,  142 ,  143 , and the sound is radiated in the same direction. Thus, the loudspeaker  10  cannot provide a surround sound effect. 
     2.The radiating coverage of the port openings  11  is relatively small, and sound is hardly radiated to the whole area of an audiovisual room. 
     3.Since an inner space of the box  15  is limited, only the sound pressure due to the woofer loudspeaker mechanism  143  is designed to pass through the ducting member  13 . As such, the high frequency and midrange frequency response of the loudspeaker  10  is poorer as compared to the lower frequency response of the same. 
     SUMMARY OF THE INVENTION 
     Therefore, the main object of the present invention is to provide a loudspeaker system with stackable loudspeaker units that can achieve a surround sound effect. 
     According to this invention, a loudspeaker system includes at least two loudspeaker units. Each of the loudspeaker units includes a loudspeaker enclosure and at least one loudspeaker mechanism mounted on the loudspeaker enclosure. The loudspeaker enclosure includes an outer cabinet body and an inner baffle frame. 
     The cabinet body has an open front side, a closed rear side, opposed lateral walls, and opposed top and bottom walls that extend in a first horizontal direction between the front and rear sides. 
     The baffle frame is disposed in the cabinet body, and has parallel left and right walls that extend in a vertical direction between the top and bottom walls and that form a sound space therebetween. The left and right walls further form first clearances with the lateral walls of the cabinet body respectively, and have a front portion that is proximate to the front side of the cabinet body and that has the loudspeaker mechanism mounted thereon. The front portion of the left and right walls cooperates with the lateral walls to form a pair of acoustic port openings at front ends of the first clearances. The left and right walls further have a rear portion that forms a second clearance with the rear side of the cabinet body. The second clearance is communicated with and extends between rear ends of the first clearances in a second horizontal direction transverse to the first horizontal direction. The baffle frame further has a ducting member at the rear portion of the left and right walls. The ducting member forms an acoustic path that communicates the sound space and the second clearance such that sound pressure behind the loudspeaker mechanism can be radiated through the acoustic port openings via the sound space, the acoustic path, the second clearance and the first clearances. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
     FIG. 1 is a front view of a conventional loudspeaker system; 
     FIG. 2 is a schematic sectional side view of the conventional loudspeaker system of FIG. 1; 
     FIG. 3 is a front exploded view showing the preferred embodiment of a loudspeaker system according to this invention; 
     FIG. 4 is a perspective view showing a baffle frame of the preferred embodiment; 
     FIG. 5 is a schematic sectional top view showing a loudspeaker enclosure of the preferred embodiment; 
     FIG. 6 is a schematic sectional view showing a foot post and a post-receiving recess of the preferred embodiment; and 
     FIG. 7 is a plan view to illustrate how the preferred embodiment can be installed to achieve a surround sound effect. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 3,  4  and  5 , according to the preferred embodiment of this invention, a loudspeaker system includes three loudspeaker units  20 . Each of the loudspeaker units  20  has a loudspeaker enclosure and at least one of tweeter, midrange, woofer and subwoofer loudspeaker mechanisms  21 ,  22 ,  23 ,  24 . The loudspeaker enclosure includes an outer cabinet body  30  and an inner baffle frame  40 . 
     The cabinet body  30  is rectangular in shape, and has an open front side  302 , a closed rear side  303 , opposed lateral walls  301  and opposed top and bottom walls that extend in a first horizontal direction between the front and rear sides  302 ,  303 . 
     As shown in FIG. 4, the baffle frame  40  is disposed in the cabinet body  30 , and has parallel left and right walls  401  that extend in a vertical direction between the top and bottom walls and that form a sound space (A) therebetween. The left and right walls  401  further form first clearances  41  with the lateral walls  301  of the cabinet body  30  respectively, and have a front portion  402  that is proximate to the front side  302  of the cabinet body  30  and that has the loudspeaker mechanism  23  mounted thereon. The front portion  402  of the left and right walls  401  cooperates with the lateral walls  301  to form a pair of acoustic port openings  26  at front ends of the first clearances  41 . The left and right walls  401  further have a rear portion that forms a second clearance  42  with the rear side  303  of the cabinet body  30 . The second clearance  42  is communicated with and extends between rear ends of the first clearances  401  in a second horizontal direction transverse to the first horizontal direction. The top and bottom walls are formed with a pair of beveled edges  304  that extend between the baffle frame  40  and a respective one of the lateral walls  301  at the front side  302  of the cabinet  30  at an angle of about 45° such that the baffle frame  40  projects forwardly relative to the lateral walls  301  to increase the area of the acoustic port openings  26 . 
     As shown in FIG. 5, the baffle frame further has a ducting member  25  at the rear portion of the left and right walls  401 . The ducting member  25  forms an acoustic path (L) that communicates the sound space (A) and the second clearance  42  such that sound pressure behind the loudspeaker mechanism  23  can be radiated through the acoustic port openings  26  via the sound space (A), the acoustic path (L), the second clearance  42  and the first clearances  41 . In this embodiment, the ducting member  25  includes parallel first, second and third duct plates  251 ,  252 ,  253  that extend between the left and right walls  401  in the second horizontal direction. The first duct plate  251  is formed with a first slot  2511  that extends between the top and bottom walls in the vertical direction. The second duct  252  is formed with two second slots  2521  that are parallel to the first slot  2511  and that are staggered relative to the first slot  2511  in the second horizontal direction. The third duct plate  253  is formed with a third slot  2531  that is parallel to the second slot  2521  and that is staggered relative to the second slot  2521  in the second horizontal direction. The second slots  2521  are disposed on left and right sides of the first slot  2511 , and the third slot  2531  is aligned with the first slot  2511 . 
     Passage of the sound pressure behind the loudspeaker mechanism  23  through the sound space (A), the acoustic path (L) , the second clearance  42  and the first clearances  41  can minimize echo and resonance and can avoid interference with the sound pressure in front of the loudspeaker mechanism  23 . 
     The bottom wall of the cabinet body  30  is formed with a plurality of foot pads  27 , while the top wall of the cabinet body  30  is formed with a plurality of receiving seats  28 . As shown in FIG. 6, each foot pad  27  has a foot post  271 , and each receiving seat  28  has a post-receiving recess  281  for receiving the corresponding foot post  271  of another one of the loudspeaker units  20 . The post-receiving recesses  281  are generally concave, whereas the foot posts  271  are generally convex to complement the post-receiving recesses  281 . As such, the loudspeaker units  20  can be retained in a stacked position by the foot posts  271  and the post-receiving recesses  281 . 
     The loudspeaker system can be installed according to the type of music to be reproduced. For example, when simulating the sound effect at concert halls, the loudspeaker units can be stacked to form a single loudspeaker body. As shown in FIG. 7, when playing a film with Dolby or AC3 surround sound effect at an audiovisual room having a television  100  with two speaker  101  and a user seat  200 , in this embodiment, the subwoofer loudspeaker mechanisms  24  are adapted to disposed under the television  100  and in front of the user seat  200 . The loudspeaker units having the tweeter and midrange loudspeaker mechanisms  21 ,  22  are disposed at left and right sides in front of the user seat  200  and can serve as main speakers. The woofer loudspeaker mechanisms  23  are disposed at left and right sides behind the user seat  200  and can serve as rear speakers. Such installation of the loudspeaker system will provide a realistic surround sound effect. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.