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BACKGROUND OF THE INVENTION The present invention relates to devices that generate sound
by electrical impulses, and more particularly to devices that generate low frequency sound. A
typical loudspeaker system has an inherent HJ that can not be reproduced well with low
frequency sounds, for example below 200 Hz. Conventional cone-speech forces of conventional
dimensions are not efficient at low frequencies due to limited cone displacement, cone collapse,
and the need for special enclosures. SUMMARY OF THE INVENTION The present invention
overcomes the shortcomings of the prior art by using a woofer (low frequency speaker) device
that adds additional signal power to drive highly efficiently over a wide power range. The woofer
device according to the present invention comprises two or more sets of opposing substantially
rigid panels mounted for movement back and forth between the panels. A servomotor with
mechanical power is connected to the panel by means of mechanical link engagement such that
the panel moves back and forth in unison. The panels are, for example, mounted around the axis
of the motor shaft and actuated simultaneously by mechanical link engagement. A separate
amplifier is connected to the audio output to drive the woofer device at the desired volume and
to use the negative feedback corresponding to the interlocking of the panels to improve the
sound accuracy. DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2,
the loudspeaker system of the present invention comprises a plurality of vertical struts such as
16 shown in FIG. A 0 substantially rigid acoustic panel 18 consisting of a single closed box 10
connected is resiliently supported or connected from its upper end between each row of adjacent
vertical columns 16 to form a closed box . The connection between the lip of the acoustic panel
18 and the support 18 can be configured in the form of a flexible shape-retaining strip 20. Of
course, other suitable connection types can be used. Although the invention is described for four
rectangular or square panels as shown, the apparatus can use only one panel or any plurality of
panels. However, it is desirable to use at least two opposing panels, and six, four or more panels
can be used to operate all sides of the enclosure with optimum efficiency. Also, while the panels
are shown as flat squares, other shapes may be used. However, it is desirable for the final closed
box to be reasonably air tight and for the panel and its supporting structure to be of substantially
the same size and weight.
In particular, when thin and light acoustic panels 18 are used, it is desirable to reinforce them
with a modest frame or framework as generally indicated at 22. It is desirable that such a
conservative or reinforcing frame be in the same space as the inner surface and uniformly
support the panel to prevent bending by mechanical actuators, as will be described later. A
suitable pivot support 24 is secured to the innermost center point of each skeleton 22. A motor
26 with a vertical axis 28 is mounted at the center of the interior of the enclosure 10 on a
support 30 which is rigidly fixed to the bottom 14 or other suitable support. The motor shaft 28
is positioned to be substantially equidistant from the vertical centerline of each panel. A device is
provided for converting the rotational interlocking of the motor shaft into appropriate movement
for simultaneously driving the rigid frame 22 fixed to the panel 18 or the panel. The device
comprises, for example, a rod 32 as follows, which rod 32 is pivotally connected to one end of
each support and is perpendicular to a disc 36 which is mounted for rotation with the motor
shaft 28 It is pivoted by a pin pivot 34. Preferably, the pivot points of the four pivots 34 are at
equal distances from the axis of the axis 28 so that substantially equal drive forces are
transmitted to each rod 32 and its connecting skeleton 22 and the acoustic panel 18. Also, in the
illustrated embodiment, the pivots 34 of the opposing panels are on a common center line
through the panels so that the overall device is very symmetrical and balanced. When power is
applied to the motor 26, the shaft 28 and the disc 36 rotate in a counterclockwise direction to
displace the pivots 34 in the direction of the respective panels and displace the respective panels
outward. To realize this effect, it is obvious that the position of the pivot when not applying
power is on the disc on one side of the centerline passing through the opposing panel to give the
necessary leverage for interlocking . The mechanical configuration, in essence, consists of a
series of composite levers or toggles capable of transmitting linear motion directly to the panel.
The motorized 4fi 26 is preferably a high speed DC servomotor or commutating servomotor
which can be reversed very rapidly in response to changes in input power and frequency and
which can maintain a constant force on the armature. A particularly suitable motor type is that of
the commercially available rotating coil type and is sold under the brand name 'Electro' 0 roft ',
model number M-'145.0 / M-1460. An alternative form of usable mechanical link attachment is
shown in FIG.
This embodiment is similar in operation to that shown in FIG. 2, but includes a plurality of disclike members 40 mounted on a shaft 42 and a plurality of equidistantly spaced along the
periphery of the disc. And the ear 44. The ear 44 is connected to the rod 46 by a relatively thin
strip 48 rather than the mechanical joint shown in FIG. Thus, the embodiment shown in FIG. 6 is
a one-piece construction made of a strong and flexible polymer, which minimizes the formation
of slopes in mechanical devices. There are many other known means that can be used to convert
the rotational movement of the motor 26 into a suitable movement to drive the panel 18.
However, in the preferred embodiment, as the most viable structure, the acoustic panels are
uniformly disposed about a common axis. Preferred circuits and components for driving the
loudspeaker system are shown in FIG. Since only known general components are used, the
function will be briefly described. As shown, audio signals from any signal source are applied to
the crossover network 50. Crossing network 50 is an electrical filter that separates the output
signal into two or more distinct frequency bands. In this example, for example, 100 J (two or
more high frequencies are separated and added to other speakers, so a frequency of 100 JLz or
less is added to the present apparatus. Because the input signal from a conventional signal
source is generally insufficient to drive motor 26 with the desired output, it is desirable to
amplify the input signal by amplifier 52 to the desired value. In addition, it is preferable to
provide a negative feedback device around the motor 26 and the amplifier 52, for use as a
correction device for improving the operation. As shown, position sensor 54 responds to the
movement of the acoustic panel to apply the output of the sensor to differential amplifier 56
connected between crossover network 50 and amplifier 52. The voltage detected is proportional
to the degree of oscillatory movement of the acoustic panel. As shown, the position sensor 54 is
of the required resistance type and has an arm directly connected to one of the acoustic panel
braces 22. Thereby, the relative position of the panels is detected and added to the differential
amplifier 56. Other electromechanical sensor devices can be used, including optical and
pneumatic devices. Differential amplifier 56 is, in effect, an amplifier connected so that two
similar input circuits respond to the difference between the two voltages or currents, but
effectively suppress similar voltages or currents. . Thus, the differential amplifier is converted to
an output signal to generate an error signal that decays with time.
Negative feedback effectively controls the movement of the acoustic panel 18 to correct the
coupling of the acoustics to the input signal to improve the distortion characteristics. In
operation, the input signal is amplified and applied to the motor, causing the shaft 28 to move
counterclockwise first, then to vibrate rapidly in response to the input frequency, wave number.
Thereby, the acoustic panels interlock with each other in the same phase and in the inward and
outward directions to generate low frequency sound waves. As a device for connecting the output
shaft 2B of the motor 26 to the panel 18, one of unusual types as shown in FIGS. 5, 6 and 7 can
be used. As shown in FIGS. 5 and 6, a gear or toothed surface, designated 60, is mounted on the
shaft 28 '. The crucible 32 shown in the previous embodiment is replaced by a rigid long beam
62 and 64. Beams 62 and 64 have bifurcated ends that overlap with axis 28 и as shown at S. Or,
the ribs 62 and 64 may be wider in the direction parallel to the axis, increasing stiffness in the
direction perpendicular to their length. As shown in FIGS. 5 and 6, one end of the flexible toothed
belt 66 is defined at a position 68 close to the end of the beam 62, one side of the shaft 28 'is
wound and the other end is the other beam. Fix at a position TO close to the 64 terminals. A
second belt 72 is placed around the other side of the upper shaft of the first belt to secure its
ends at positions 74 and 76 inside the ends of beams 62 and 64. The teeth of the belt engage
with the teeth of the shaft 28 'to prevent slippage between them. In practice, the belts form
opposing loops around the axis and the belts are tightly fixed to one another in order to avoid
free play. As shown in FIG. 6, a second set of belts 78 and 80 can be used to increase the
integrity of the device. A similar mechanical device is shown in FIG. In this figure, a pair of
bendable but substantially rigid strips 82 and 84 are disposed along opposite sides of axis 28
'and secured to respective beams 62' and 64 'as described above. The strips 82 and 84 can be
composed of a suitable material such as spring steel. In this embodiment, positive engagement
between the shaft 28 'is realized by means of fasteners 85 or other attachments provided
between the strip and the shaft. Fasteners 85 are preferably mounted approximately at the
center of each strip to allow maximum rotation of the axis in either direction. In operation, the
belts 66 and 72 and the strips 82 and 84 are operatively connected to the shaft and serve to
push or pull both beams simultaneously in the opposite direction as the shaft rotates in one
The embodiments shown in FIGS. 5 to 7 have many advantages, one of which is that there is little
or no opportunity for link hang-up to adversely affect speaker operation. It is. In addition, the
beam reciprocates in a direction substantially perpendicular to the surface of the speaker panel.
This is different from the previously described embodiment, which required an angle shift from
the vertical. This also allows the speaker panels to have more accurate parallel motion and avoids
the tendency for linkages to deviate from the vertical axis of the opposing panels. The inventive
loudspeaker has many advantages over the prior art. Rather than using a single large radiator,
the present invention utilizes many small radiators operating simultaneously from the same
signal source to achieve the same effect. Transient characteristics are greatly improved when the
total radiation area is made identical as compared to a single large radiator. The rotary rectifier
coil drive speaker device can greatly improve the conversion efficiency from electricity to sound.
Any number of panels can be used for this speaker device. Also, because it is highly efficient, it
uses a small closed box that would not be possible using a regular speaker. FIG. 6 is a plan view
of the loudspeaker shown in FIG. 1 but with the top removed to show basic internal features; FIG.
6 shows another form of mechanical link attachment useful in the context of the present
invention FIG. 4 schematically illustrates mechanical and electrical components useful in the
practice of the present invention; and FIGS. 5, 6 and 7 connect the output shaft of the motor to a
panel. Is a schematic view of another apparatus for 10 ? ? ? Speaker device (? ij closed box)
18 иии Acoustic panel 26 иии Motor 28, 28 ? иии Electric motor shaft representative Asamura Takumi
4 people
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