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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus for emitting acoustic waves, and more particularly to a simplified configuration of an
apparatus in which different transducers emit portions of an acoustic signal at different
In the state of the art it is known to emit parts of acoustic signals at different frequencies by
means of different electroacoustic transducers which are optimally designed for the individual
signal parts. For example, the division method known at this point separately reproduces the low
frequency part, the intermediate frequency part and the high frequency part of the acoustic
signal. Such an arrangement occupies a very large volume and is therefore excluded from many
applications, because of the number of electroacoustic transducers required to separately
reproduce the signal parts of different frequencies. To this end, broadband speakers are often
used when only limited volumes can be used, however, they reproduce a sound quality which is
clearly inferior to the aforementioned devices.
A compromise is the so-called coaxial loudspeaker system, which on the one hand only needs the
same volume as a broadband loudspeaker, but on the other hand allows different transducers to
transmit parts of the acoustic signal at different frequencies And, thereby, it is possible to
reproduce clearly better sound quality than a broadband speaker. Such coaxial loudspeaker
systems are advantageous in that they have cone loudspeakers which are optimally designed for
specific signal parts (low frequency or low-intermediate frequency). Another speaker designed
primarily for the high frequency response characteristics of a particular speaker is located in the
space essentially surrounded by the cone diaphragm of the cone speaker. Such an arrangement,
which is also the starting point of the present invention, is described in detail, for example, in DEGbm 9210493.
However, these loudspeakers have the disadvantage of being very expensive to manufacture.
Among other things, this is because most of the cone speakers in a coaxial speaker system
require a modified magnet arrangement to allow placement of high frequency speakers in the
cone of the diaphragm, in contrast to pure cone speakers. . Furthermore, the cost of the material
for the high frequency speaker in the cone of the diaphragm can not be neglected. The latter
include not only the cost associated with the high frequency speaker itself, but also the cost of
the elements needed to support the high frequency speaker in the cone of the cone speaker's
SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an
acoustic wave reproduction device which significantly reduces the manufacturing costs of coaxial
loudspeaker systems.
This problem is solved by the features indicated in claim 1 of the claims.
Further advantages of the invention are indicated in the claims 2 to 6 of the claims.
The basic idea of the invention is to cover the surface of the diaphragm driven by the voice coil
so that the generated acoustic waves are emitted at least partially by the layer into the listening
area, or of the electrical signal voltage The diaphragm itself (in whole or in part) is made of a
material that changes its longitudinal and / or lateral stretch with respect to the plane of the
layer by action. This construction allows the diaphragm to radiate, for example, the low
frequency or low-intermediate frequency portion of the acoustic signal, while the layer
electrically connected to the acoustic signal source produces radiation of the high frequency
portion, The layer undergoes a stretch change due to the action of the high frequency signal
A material suitable for the layer configuration known to the person skilled in the art is a
piezoceramic material as indicated in claim 2 or as indicated in claim 3 It is a polyvinyl fluoride
foil (PVDF) exhibiting piezoelectric properties.
In particular, PVD foils as material for the layer show only a slight change in thickness as part of
the stretch change due to the action of the voltage generated by the high frequency signal part,
so that the dimensions of the layer increase, ie Sufficient loudness can be generated only when
the surface itself becomes large and / or when the signal voltage generated for the layer is high.
If conversion of the signal voltage generated for the layer is not necessary, most of the surface of
the diaphragm that emits a portion of the low frequency signal must be covered with the layer if
the layer is applied to the diaphragm without gaps. You must. However, with regard to the
surface of the diaphragm covered by the layer, it is evident that the surface of the layer is
enlarged and simplified as in the folded or embossed shape, as indicated in claim 4 convenient.
Also, by forming the layer according to claim 4, most of the surface of the layer is not directly
attached to the respective support surface (eg diaphragm etc.), so that the bending vibration
effect of the layer caused by the longitudinal expansion and contraction is also sufficient Can be
used to generate various sound volumes. This makes it possible to limit the layer to the area
formed by the so-called dustproof cover in the conventional cone loudspeaker shown in DE 41
16 819, thereby making the cone of the diaphragm independent of the voice coil carrier.
Constraining the layer to the area originally used for the dustproof cover is additional that the
spherical radiation characteristics for reproducing high frequencies are achieved very simply by
curving the layer according to this area Have the following advantages.
BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below with
reference to the drawings.
In FIG. 1, a cross-sectional view of a cone speaker 10 is shown.
The cone speaker 10 is essentially formed by the speaker frame 11, the magnet arrangement 12
and the vibration system 16, the vibration system 16 being formed by the diaphragm 13, the
voice coil support 14 and the voice coil 15. There is.
The vibration system 16 is inserted into the frame 11 where the upper edge 17 of the diaphragm
13 is connected to the frame 11 by an annular bead 18 and the voice coil 15 connected to the
voice coil support 14 is a magnet arrangement It is inserted in the air gap 19 formed in 12.
When the voice coil 15 receives the signal voltage of the acoustic signal source via the
corresponding supply line (not shown in FIG. 1), the diaphragm 13 moves up and down along the
center line. As a result, the surface 20 of the diaphragm 13 emits an acoustic wave in the
direction of the listening area 21.
As can be seen in FIG. 1, the area of the diaphragm 13 close to the voice coil support 14 is
covered by a layer 22 on the surface 20 facing the listening area 21, which layer 22 is also
covered by the voice coil support 14. Are inserted into the opening 23 of the diaphragm 13 and
extend to the area connected thereto. As a result, the layer 22 in the area above the opening 23
takes over the function normally performed by the dustproof cover in a conventional
loudspeaker. For the sake of completeness of the description, it is pointed out that a gap is
provided in the area of the surface 20 of the diaphragm 13 near the voice coil support 14 and
the layer 22 to better show the relationship of FIG. Is omitted in the figure.
The basic type of loudspeaker 10 described above can be configured in a number of modified
ways. That is, for example, the layer 22 can be enlarged by making it approximately up to the
upper edge 17 of the diaphragm 13. This layer 22 can also be configured to extend beyond the
top edge 17 of the diaphragm 13 as long as it is necessary to expand the layer 22. The latter is
illustrated by the dashed line in FIG. 1 (left). The area located above the opening 23 can be closed
by means of a conventional dustproof cover, whereby the layer 22 also covers the surface of this
dustproof cover. When a conventional dustproof cover is used, it may be covered by layer 22
without a gap, or it may be placed over the contour of a conventional dustproof cover without
being attached and without a gap Can be connected only to the surface 20 of the diaphragm 13.
Furthermore, it should be pointed out that the additional formation of the layer 22 can be
omitted if the diaphragm 13 itself is made of, for example, the material forming the layer 22. A
cantilever structure of such a layer 22 is shown in the region above the opening 23 in FIG.
The material used to form layer 22 in the embodiment of the arrangement of FIG. 1 is in one
example a piezoceramic material and in another example a polyvinyl fluoride foil.
Layer 22 is a bimorph structure of two oppositely polarized, cemented, longitudinally or radially
oscillating two plates, the pair of plates being an acoustic signal source in a manner known to the
expert. When connected to (not shown in FIG. 1), the action of this signal voltage creates an
extension or contraction in both plates, longitudinally or radially opposite.
If the plates of the pair are simply clamped at their ends, they can be stretched by stretching
them in opposite directions in the longitudinal or radial direction in the two plates forming the
layer 22. It causes stretching in the transverse direction. In other words, such an arrangement
acts as a bending resonator and can be used to emit an acoustic signal. Also, in another situation,
if layer 22 or a pair of plates is not clamped at the end but is completely connected to another
layer (surface 20 of diaphragm 13 in FIG. 1), that pair Any longitudinal or radial stretching of the
plate is substantially eliminated. However, this does not mean that such an arrangement is not
suitable for the transmission of acoustic signals. In addition to longitudinal or radial expansion
and contraction, the layer 22 connected to another layer only functions as a so-called thickness
resonator, since the thickness of the pair of plates is changed by the action of the signal voltage.
It mainly limits such configurations to the transmission of acoustic signals in the ultrasound
For the sake of completeness, it should be pointed out that, in connection with this application,
longitudinal or radial stretching and changes in the thickness of the layer 22 are collectively
referred to as stretching change.
For the configuration shown in FIG. 1, the regions of the layers 22 connected without gaps to the
surface 20 of the diaphragm 13 only contribute to the transmission of sound through the
variation of their thickness, while the cantilevers on the opening 23 The area of the layer 22
which is structured and which is therefore not surface-connected to the diaphragm 13 nor to the
conventional dustproof cover contributes to the emission of sound through longitudinal or radial
stretching and changes in thickness.
If the area of the layer 22 of the cantilever structure above the opening 23 is not flat but forms
an arch (shown as a solid line in FIG. 1), the following effects are achieved by such a shape Can.
On the one hand, the arch shape increases the size of the area with respect to the dimension of
the distance over the opening 23 as compared to the area of flat structures. Consequently, due to
this increase in the surface, a greater longitudinal or radial expansion or contraction is achieved
by the action of the signal voltage applied to the layer 22, whereby the lateral clamping
connection of the area over the opening 23 is achieved. , The area stretches more strongly in the
transverse direction. The transverse deflection of the area is indicated by the dashed line in FIG.
On the other hand, in contrast to the flat area, the arched area efficiently converts the signal
voltage applied to layer 22 into transverse deflection.
Finally, by means of the said dished or arched regions, the spherical radiation properties of the
layer 22 are improved, which is particularly advantageous for the regeneration of high
If it is necessary to increase the size of the acoustic flow, ie the volume of air moved by the layer
22 per unit time, an increase in the signal voltage provided to the layer 22 can be used.
However, such methods are not non-critical, and additional effort is required to make the
corresponding voltages available.
Therefore, it is significantly easier to generate sufficient acoustic flow by increasing the surface
of layer 22. Using the diaphragm 1 shown in FIG. 1, the surface of this layer 22 is increased by
covering the surface 20 of the diaphragm 13 almost completely, for example with the layer 22, ie
to the top edge 17 without gaps. It can be done. However, covering the cone diaphragm 13
almost completely is not ideal with regard to the spherical radiation characteristics desired for
high frequency regeneration. If the spherical radiation properties of the layer 22 are still ensured
and at the same time good acoustic flow has to be generated by increasing the surface of the
layer, it is necessary to make the layer 22 in an embossed shape. The meaning of this is shown in
detail in FIG. On the left side of FIG. 3, an embossed layer 22 is shown, which has an embossed
pattern in the shape of a truncated cone 24. In the flow area 24a of the frustum 24, this layer 22
is connected to a support layer (in this example the diaphragm 13). As a result of the layer 22
being in this form, the surface of the layer 22 is consequently larger than the surface of the
support layer, which is covered and extended by this layer 22. This gain at the surface, which is
also achieved by the formation of the layer 22, results in a large longitudinal stretching of the
layer 22 by the action of the signal voltage, whereby the area of the layer of the cantilever
structure (FIG. 3 By arching the jacket area of the left frustum 24 a good acoustic flow is
provided. The layer 22 of embossed shape is no longer needed to cover or extend the majority of
the surface or the entire surface 20 of the diaphragm 13 (FIG. 1) for sufficient acoustic flow, so
Layer 22 may be limited to the area where the dustproof cover is located with a conventional
cone speaker. By confining the embossed layer 22 to the area of the conventional dustproof
cover, this area can consequently not only be embossed but also additionally arched (see FIG. 3)
It achieves very good radiation properties close to spherical radiation. Which embossing shape is
finally given to the layer 22 depends on the particulars of the case. The profile of the embossed
layer 22 to the right of the centerline of FIG. 3 is an arc shaped knob 25 which is only shown as
an example.
For the purpose of complete description, the diaphragm 13 illustrated in FIG. 3 and described as
a support layer may be a conventional known dustproof cover in an example of another
configuration not illustrated.
In FIG. 2, a cross-sectional view of the loudspeaker 10 is shown, which differs from that of FIG. 1
in that the shape of the diaphragm 13 is slightly modified. The diaphragm 13 is not conical but is
arched in the direction of the listening area 21. The arched surface 20 of the diaphragm 13
facing the listening area 21 is provided with the embossed layer 22 illustrated on the left side of
FIG. This layer 22 is produced by embossing the PVD foil and is adhesively bonded to the
diaphragm 13. On the one hand, this shape of the diaphragm 13 can achieve very good bass or
mid-bass reproduction under the drive action of the voice coil 15, while on the other hand it is
spherical when high frequencies are reproduced by the layer 22. A radiation effect is generated
that is characteristic of
Brief description of the drawings
1 is a cross-sectional view of the speaker.
2 is a cross-sectional view of the modified speaker.
FIG. 3 is a cross-sectional view of the layer.
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