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JP3137080

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP3137080
PROBLEM TO BE SOLVED: To reduce the vibration transmitted to a structure attached to a
loudspeaker driver. SOLUTION: The vibration reducing device comprises: a baffle which receives
vibration; a first electro-acoustic transducer characterized by a first mass placed on the baffle;
and a first transducer or a periphery of the first transducer And a second electro-acoustic
transducer mechanically connected to the nearby baffles. The back side of the diaphragm of the
first and second transducers is not connected to the listening area. The first and second
transducers are configured to receive a common electrical signal, and the movable element of the
first transducer and the movable element of the second transducer are responsive to the common
electrical signal. It moves in antiphase and significantly reduces the vibrational force applied to
the baffle. [Selected figure] Figure 1
Baffle vibration reduction device
[0001]
The present invention relates generally to baffle vibration reduction devices, and more
particularly to a novel device for reducing vibrations transmitted to a structure mounted on a
loudspeaker driver.
[0002]
If an electro-acoustic transducer such as a loudspeaker driver is attached to a structure such as a
package shelf, vehicle door, enclosure wall, other wall or other baffle, the attachment is usually
around the frame of the transducer The driving (motor) of the energized (energized) transducer
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produces a force responsive to the energized electrical signal.
The force generated by the driving force causes the transducer diaphragm to move relative to the
transducer frame. These forces are also transmitted from the frame to the structure via the
attachment points of the frame. Package shelves and vehicle door panels are often made of thin
materials such as sheet metal. The stiffness of such structures is usually insufficient to withstand
the vibrations and usually only a slight damping of the vibrations. As a result, the force applied to
the structure near the modal resonant frequency of the structure results in excessive vibration of
the structure perceived as acoustically undesirable noise, ie degradation of the frequency
response of the emitted sound.
[0003]
An important objective of the present invention is to reduce these structurally transmitted
vibrations.
[0004]
According to the invention, a first electroacoustic transducer (transducer) incorporating a
movable diaphragm is installed and structurally coupled to the panel.
The transducer is mechanically connected to a device containing a compensating movable mass
that is driven out of phase with the movement of the diaphragm of the first electroacoustic
transducer, resulting in a significant reduction of the force applied to the panel Do. Typically, the
device with the compensating mass is a second electro-acoustic transducer identical to the first
transducer. According to another feature of the invention, the acoustic output from the first side
of the first transducer is coupled directly to a listening environment, such as a passenger
compartment or a living room of a vehicle. The acoustic output from the side of the second
transducer facing away from the first transducer direction is also an acoustic element (single or
more) such as a compliant volume and / or port. Coupled to the listening environment, whereby
the acoustic output from the oppositely facing side of the second transducer to the passenger
compartment is the first side of the first transducer over the desired frequency range And the
output to the passenger compartment are practically in phase. The acoustic element is such that
the output from the other side of the second transducer is the output from the second side of the
first transducer or the output from the first side of the second transducer And not configured to
be acoustically coupled. Thus, the present invention achieves both a significant reduction of
unwanted mechanical vibrations of the support structure and an improvement of the acoustic
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output from the second transducer.
[0005]
Other features, objects and advantages of the present invention will become apparent upon
reading the following description taken in conjunction with the accompanying drawings.
[0006]
Referring now to the drawings, and in particular to FIG. 1 of the drawings, there is shown a
schematic view of an embodiment of the present invention having a structure mounted on an
infinite baffle 11, which is typically a loudspeaker driver 12. , Etc., the loudspeaker driver 12 is
preferably mechanically connected via a mechanical link 14 to a second transducer, such as the
loudspeaker driver 13 identical thereto. Connected.
These two transducers are ideally mounted in substantially parallel planes so that the
diaphragms move in the same axial direction. The front side of the transducer 12 is directly
coupled to the listening area 18. If the baffle 11 is the rear package shelf of a vehicle, the
listening area 18 is the passenger compartment of the vehicle. The second side of the transducer
12 is coupled to the volume 30, which is the trunk of the vehicle when the baffle 11 is a rear
package shelf. The second side of the diaphragm 22 of the driver 13 is coupled to the listening
area 18 via the compliant column 15 and the port tube 16. The front of the diaphragm 22 of the
transducer 13 is coupled to the volume 30. The power amplifier 17 energizes the first
loudspeaker driver 12 and the second loudspeaker driver 13 with the same signal but drives
them with opposite polarity. The system is configured such that when the diaphragm 21 of the
first driver 12 moves upward, the diaphragm 22 of the second driver 13 moves downward,
whereby the force applied to the baffle 11 and the resulting baffle 11 Undesirable vibrations are
significantly reduced. Also, the output from the back of the second driver 13 is coupled by the
compliant column 15 and the port tube 16 to emit in substantially the same phase as the output
from the front of the first driver 12. The output from the back of the second driver 13 can also
be coupled to the listening area 18 without loss of generality via a conduit of substantially
constant or smooth (smooth) change in cross section.
[0007]
The second converter need not be the same converter. What is required for a significant
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reduction of the vibration is that the movable mass of the second transducer and the generated
driving force are approximately equal to the generated driving force of the first transducer. Such
components can be manufactured at lower cost than the same converter as the first converter.
However, the frames of the two transducers are similar so that the second transducer can be
attached to the first at the same attachment point that the first transducer is attached to the
baffle Is desirable. An alternative means of assembly is to connect the upper part of the drive
structure of the second driver 13 to the back of the drive structure of the first driver 12 with a
rigid connecting member 19 (FIG. 1A), such as a metal screw rod. It is to fix using (shown by a
dotted line).
[0008]
FIG. 3 shows an alternative configuration. Here, the driver 13 is physically reversed with respect
to the driver 12. Although FIG. 3 shows that the back surface of the drive structure of the driver
12 is fixed to the back surface of the drive structure of the driver 13 via the spacer 20, the
spacer 20 may be omitted. The structural coupling of the two transducers can also be achieved
by mounting around the frame of the transducers, as shown in the system of FIG. The
arrangement of FIG. 3 works equally well if each of the transducers 12 and 13 is reversed from
that shown. In this case, structural connections can be more easily achieved by mounting around
the frame of the transducer.
[0009]
Because the drivers 12 and 13 are physically reversed with respect to each other, providing a
signal of the same relative polarity to each transducer results in vibration cancellation. When the
diaphragm 21 of the driver 12 is moved downward by the signal supplied to the driver 12, the
signal output from the amplifier 17 connected to the driver 13 causes the diaphragm 22 of the
driver 13 to move upward in the direction opposite to the movement of the diaphragm 21. Thus,
each driver is attached to the output of amplifier 17.
[0010]
Above a certain frequency, the output from the second converter is not in phase with the output
from the first converter. The frequency response of the combined system is: if the difference in
path length between the front face of the first transducer and the listening position and the back
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face of the second transducer and the listening position is a half wavelength It may indicate the
behavior (properties) of the comb filter where one null occurs.
[0011]
One way to reduce the effect of this comb filter's behavior is to use a low pass filter to limit the
spectral components presented to both drivers to those below the first null and the higher
frequency spectrum It is done by using other transducers to regenerate the component. The low
pass filter used may be identical for both drivers or may have different orders and / or corner
frequencies. The output from one of the drivers can be limited to be below the predetermined
cutoff frequency, and the other can operate in a wider frequency range. Preferably, the first
converter operates in a wider frequency range than the second converter. Such results can be
achieved by placing a low pass filter only in the signal path of the second transducer, or by a low
pass filter with a higher corner frequency and / or lower order than the low pass filter in the
signal path of the second transducer. This can be achieved by placing one in the signal path of
the converter. Also, in combination with, or only by, the appropriate design that the acoustic
element connects the second driver to the listening area so that the acoustic elements together
form one low pass filter. Results can be achieved.
[0012]
It may also be advantageous to include a low pass filter in the signal path of the second converter
and an all pass filter complementary to the signal path of the first converter. The complementary
all pass filter has the same phase response as the corresponding low pass filter as a function of
frequency. This function may, for example, if the corner frequencies of the low pass filter and the
all pass filter are substantially identical, then the second order high attenuation low pass filter in
the signal path of the second converter and the first order all pass filter as the first converter.
This can be achieved by using in the signal path of
[0013]
According to another embodiment, it is also possible to use a fourth-order low-pass filter in the
signal path of the second converter and a second-order all-pass filter in the signal path of the
first converter. Other examples of complementary all pass filter / low pass filter combinations
will be apparent to those skilled in the art.
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[0014]
The use of complementary all pass filters and low pass filters as described above, in combination
with other signal processing disclosed in US Pat. No. 5,023,914, incorporated herein by
reference, improves the frequency response of the system And vibration reduction can be
achieved simultaneously.
[0015]
Referring to FIG. 2, a graph of the force on the baffle as a function of frequency is shown for
various structures.
Curve 21 shows the response resulting from using two Bose 8 inch Nd drivers in accordance with
the invention in an acoustic system having a low pass filter. Curve 22 shows the force applied
when only one 8-inch Nd driver is used with a low pass filter. Curve 23 shows the force applied
when using only two 8-inch Nd loudspeaker drivers connected according to the present invention
without a low pass filter. Curve 24 shows the force applied when only one 8-inch Nd loudspeaker
driver is used. These graphs show that the force applied to the baffle is greatly reduced using the
present invention and the advantages of incorporating a low pass filter into the system.
[0016]
The embodiment shown in FIGS. 1 and 3 shows the use with an infinite baffle 11. Although this
configuration is shown to have area 18 as the listening area, this area is not necessary. The
invention works equally well with the volume 30 or the area 18 which functions as a listening
area without loss of generality.
[0017]
FIG. 4 illustrates an application of the present invention using an alternate converter
configuration. FIG. 4 shows transducers 32 and 33 physically reversed from each other using
drive structures that are inverted relative to the drive structures of transducers 12 and 13.
Transducers 32 and 33 have diaphragms 41 and 42, respectively. The use of the converter of the
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inversion drive structure is not limited to the orientation shown. Any of the above described
configurations described for non-inverted drive converters are also applicable to converters
having inverted drive structures. The use of the reversing drive structure transducer of the
present invention can significantly reduce the overall thickness of the plurality of transducer
assemblies, thereby reducing the ingress of the assembly within the trunk of the vehicle, i.e. The
transducer-based configuration allows the system to fit in a wall space that does not fit. It is also
noted that the mechanical link 14 can be much thinner than the link 14 shown in FIG. 1 in an
embodiment using a transducer that is not a reverse drive structure.
[0018]
It will be apparent to those skilled in the art that many uses and modifications of the devices and
techniques disclosed herein, as well as modifications from such devices and techniques, may be
made without departing from the inventive concepts. Accordingly, the present invention resides
in the devices and techniques disclosed herein and limited only by the spirit and scope of the
claims of the utility model registration or in any novel combination of any and all novel features
and characteristics of such devices and techniques. It should be interpreted as including.
[0019]
FIG. 1 is a schematic view of an embodiment of the present invention with the assembly mounted
on an infinite baffle, such as a rear deck or door of a vehicle. FIG. 7 is a graph showing the force
exerted on the structure as a function of frequency for various systems. FIG. 7 is a schematic
view of an alternative embodiment of the present invention with the assembly mounted on an
infinite baffle, such as a rear deck or door of a vehicle. FIG. 7 is a schematic view of an alternative
embodiment of the present invention where the assembly is mounted on an infinite baffle such as
the rear deck or door of a vehicle incorporating a converter having an inverted drive structure.
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