EP0793216A2 - Pressure chamber driver - Google Patents

Abstract

The pressure chamber (2) over its periphery is connected with a central sound outlet channel (14). The membrane (5) is V-shaped in cross-section and the point (4) of the V is connected with the vibrating coil (3). The arms of the membrane are arched to the acute angle which they enclose. The edges (6,7) of the arms of the V-shaped cross-section membrane are directly tensioned and the membrane comprises a pliable material at least in the area of the tension. The wall (10) of the pressure chamber opposite to the membrane on the side turned away from the vibrating coil is formed in a complementary V formation to the membrane.

Description

The invention relates to a pressure chamber driver of the type mentioned in the preamble of claim 1.

Pressure chamber drivers of the type in question are generally known. They are used to reproduce high tones in particular and have a voice coil which is movable in an annular air gap of a magnet system and which drives a membrane. In these known pressure chamber drivers, the membrane is dome-shaped and extends between the front edges of the voice coil. Opposite the inside of the dome-shaped membrane runs at a distance a surface of a solid body which is complementary to the membrane and through which channels extend in the form of rays from various points in the pressure chamber to a central sound outlet channel. Since the channels mentioned determine the phase position of the sound arriving in the sound outlet opening due to their length, the solid body having the channels is often referred to as a "phasing plug". The voice coil and thus also the diaphragm are guided in their movement by bead parts extending inside and outside the voice coil.

In such known pressure chamber drivers must the dome-shaped membrane has a high mechanical stability so that the deformations caused by the pressures in the pressure chamber remain low. This high mechanical stability is often achieved by using metal foils or plastics with a larger material thickness. But this increases the mass of the membrane, so that a higher power is required to drive it, which lowers the efficiency. This applies in particular to higher frequencies. If, on the other hand, the membrane is lighter, which can only be achieved by using a smaller thickness or lighter material, it is also regularly less stiff, so that deformations which result in distortions result in particular when high frequencies are reproduced.

The invention has for its object to provide a pressure chamber driver of the type in question, which does not have the disadvantages described, which therefore has a better efficiency, in particular reproduces higher frequencies better and without distortion.

The object on which the invention is based is achieved by the teaching specified in the characterizing part of claim 1.

The basic idea of this teaching is to no longer arrange the membrane in the area between the front edges of the voice coil, but only in the area of the front edges of the voice coil, which results in an annular shape of the membrane. As a result, all parts of the membrane are in the maximum possible proximity to the voice coil, and at the same time the effective area of the membrane in the area near the coil is large in relation to its mass. Because of the relatively reduced mass, the power required to drive the membrane is lower. The natural resonance is increased and the reproduction, in particular of the high frequencies, is improved. Because of the reduced Area expansion reduces the risk of partial vibrations occurring in the membrane, so that distortions are also reduced. Due to the reduced mass, swing-in and swing-out processes are also improved.

A further development of the invention is that the membrane is V-shaped in cross section, the tip of the V being connected to the voice coil. This results in a spatial stiffening of the membrane, whereby the mass of the membrane is reduced, the power required for driving is also reduced and the property with regard to the formation of partial vibrations of the membrane and the fidelity is improved, in particular at high frequencies.

An expedient development of this embodiment of the membrane consists in that the limbs of the membrane are curved toward the acute angle they enclose. This further improves the spatial stiffening.

Basically, it is possible to guide and center the membrane over bead parts. Such bead parts, however, entail the risk of partial vibrations forming. A useful development of the invention to avoid this disadvantage is that the edges of the legs of the cross-sectionally V-shaped membrane are clamped directly and that the membrane consists of a material that is flexible at least in the area of the clamping. Due to the great rigidity of the membrane, such an effective movement of the central part of the membrane in the area of the voice coil is given by this that larger forces can be overcome due to the immediate clamping of the edges of the membrane. However, these forces are reduced in that the membrane consists of a flexible at least in the clamping area Material exists.

In the case of the membrane having a V-shaped cross section, an expedient development of the invention is that a wall of the pressure chamber, which is opposite the membrane on the side facing away from the voice coil, is complementary V-shaped to the membrane. This results in a very small volume of the pressure chamber, so that the compressibility of the air therein has a less adverse effect.

In all of the aforementioned developments of the invention, it is expedient for individual channels of the same length or a rotationally symmetrical channel to lead to a central sound outlet channel from the pressure chamber from an area uniformly distributed with respect to the voice coil. Since the annular pressure chamber is at the same distance from the central sound outlet channel at all points, the same length of the individual channels can be realized in a simple manner, a particularly favorable form of connection between the pressure chamber and the sound outlet channel being provided by the rotationally symmetrical design of the connecting channel . The rotational symmetry results in a gap extending over the circumference between the pressure chamber and the sound outlet channel. The pressure chamber is thus connected in the same form to the sound outlet channel at all points, so that there are no transit time differences and therefore no impairment of the realistic reproduction of sound.

The individual channels connecting the pressure chamber to the sound exit channel or the rotationally symmetrical channel expediently open out in the region of a bottom of the sack-shaped sound exit channel, it being particularly expedient that the bottom of the sound exit channel is raised, in particular conical. This results in a favorable phase adjustment between the channels and the sound outlet channel.

If, according to the invention, the voice coil is V-shaped in cross section, the voice coil engaging at the tip of the V, this results in an overall symmetrical configuration, so that lateral deflections of the diaphragm and also the voice coil are avoided when driven by the voice coil. In order to give the voice coil maximum symmetry in relation to the combination of voice coil and V-shaped membrane, it is expedient to also design the voice coil symmetrically in the area of its winding. According to a development of the invention, this is achieved in that the voice coil has a coil body and the wire of the voice coil is arranged partly on the inside and partly on the outside of the coil body. This arrangement has the additional advantage that the cooling is improved and the dependence on the different temperature expansions of the voice coil materials is reduced.

According to a very expedient development of the invention, a partition is provided in the radiation direction in front of the membrane, in which there are radial slots arranged next to one another in the circumferential direction. Through this partition with the slots, an acoustic lens is practically formed, which has the purpose of guiding the sound from all membrane parts to the output of the pressure chamber driver and thus to the input of a connected horn with minimal loss. A flat acoustic wave is formed that continues to the horn entrance. In addition, the acoustic membrane / air transformation is improved by the acoustic lens, thus ensuring optimal membrane utilization. Through the many radial slots, the through channels for the beam, there are also minimal wave losses.

In the chamber or cavity in front of the acoustic lens, the individual parts of the sound generated by the membrane are summed in phase and thus flat waves are formed. The slots expediently extend over the entire radial extent of the membrane.

wobei λ die Wellenlänge des übertragenen Schalls ist. Die Breite der Schlitze kann dabei auch kleiner als dieser Wert sein. Bei diesen Werten wird bewirkt, daß sich eine flache Schallwelle ausbreitet. In bezug auf eine solche flache Schallwelle läßt es sich in dem Übertragungskanal zu dem Ausgang des Druckkammertreibers in einfacher Weise sicherstellen, daß der Weg jedes aus einem Schlitz austretenden Schalls zu dem Ausgang des Druckkammertreibers gleich ist, so daß dort die einzelnen Schallwellenteile phasengerecht zusammenlaufen, so daß sich nur minimale Verluste ergeben.According to an expedient development of this embodiment of the invention, the width d of the slots of the formula is sufficient $$\text{d =}\frac{\text{λ}}{\text{1.7}}$$

where λ is the wavelength of the transmitted sound. The width of the slots can also be smaller than this value. These values cause a flat sound wave to propagate. With regard to such a flat sound wave, it can be easily ensured in the transmission channel to the output of the pressure chamber driver that the path of any sound emerging from a slot to the output of the pressure chamber driver is the same, so that the individual sound wave parts converge there in phase, so that there are minimal losses.

A particularly expedient development of the invention consists in that two annular membranes and pressure chambers are provided opposite each other in the direction of movement of the membranes, with the pressure chambers each being uniformly distributed in the circumferential direction from an area opposite the voice coil and alternately once from one pressure chamber and once from the other Pressure chamber run individual channels to a central sound outlet channel. In this embodiment, therefore, lie in the direction of movement of the membranes and thus in the axial direction of the Systems two pressure chamber systems according to the basic tenets of the invention and work against each other with appropriate feeding. The sound pressure generated by them is then conducted separately through the individual channels coming alternately from one pressure chamber and once from the other pressure chamber to the central sound outlet channel. There the sound pressure is added. This arrangement is particularly advantageous if the two opposing pressure chamber systems are fed with different frequencies or frequency bands, so that the requirements imposed by the different frequencies or frequency bands can be taken into account in each case.

The channels leading away from a pressure chamber expediently have the same length, and it is also expedient that all channels leading away from the pressure chambers have the same length among themselves.

As already mentioned, the sound pressure in the central sound outlet channel is a combination of the sound pressures of the individual pressure chamber systems. Since the sound waves through the respective diaphragms are initially directed in the direction of movement of the diaphragm, i.e. in the axial direction of the system, and the central sound exit duct lies radially within it, an inevitably partial radial course of the ducts connecting the individual pressure chambers with the central sound exit duct results. In this area, the sound waves are directed in the same direction. It is therefore possible for the channels leading away from the pressure chambers to at least partially form a common rotationally symmetrical channel in this area.

Fig. 1

zeigt geschnitten in prinzipieller Darstellung ein Ausführungsbeispiel der Erfindung,

Fig. 2

zeigt in geringfügig anderer und vergrößerter Darstellungsweise den linken Teil von Fig. 1 ergänzt gemäß einer Abwandlung der Erfindung,

Fig. 3

zeigt eine Einzelheit aus Fig. 2,

Fig. 4

zeigt einen Teilschnitt ähnlich Fig. 2 einer Ausführungsform der Erfindung mit zwei in Bewegungsrichtung der Membranen gegenüberliegenden Druckkammersystemen und

Fig. 5

zeigt ähnlich wie Fig. 3 aus Fig. 2 Einzelheiten aus Fig. 4.

The invention will be explained in more detail using an exemplary embodiment with reference to the drawing.

Fig. 1

shows in section a basic representation of an embodiment of the invention,

Fig. 2

shows in a slightly different and enlarged representation the left part of FIG. 1 supplemented according to a modification of the invention,

Fig. 3

shows a detail from Fig. 2,

Fig. 4

shows a partial section similar to FIG. 2 of an embodiment of the invention with two pressure chamber systems and opposite in the direction of movement of the membranes

Fig. 5

shows details from FIG. 4 similar to FIG. 3 from FIG. 2.

Fig. 1 shows a pressure chamber driver with a magnet system 1, in the air gap 2, a voice coil 3 is movably arranged, one end edge of which is connected to a tip 4 of a V-shaped membrane 5, which with its outer flexible edges 6 and 7 is fixed the inner wall of an outer ring 8 and the outer wall of an inner ring 9 are connected.

Between the membrane 5 and a complementary wall 10 of a body 11 is also a V-shaped pressure chamber 12 is formed, which in the area of the top of the V via a rotationally symmetrical channel 13 which practically forms a gap extending over the entire circumference is connected to a sound outlet channel 14, the bottom 15 of which is conical.

When the voice coil 3 is fed, it moves the membrane 5 preferably in the central region of the annular pressure chamber 12, so that the pressure vibrations formed in the pressure chamber 12 via the gap-shaped channel 13 into the region of the conical one Bottom 15 of the sack-shaped sound outlet channel 14 are transmitted.

2 and 3 serve to illustrate a modification of the embodiment according to FIG. 1. FIG. 2 is an enlarged partial section of the left half of FIG. 1 in a somewhat different representation. The same or corresponding parts are provided with the same reference numbers. The modification consists in that a partition 16 is provided in the direction of radiation in front of the membrane 5, which seals off the space in front of the membrane, but has radial slots. FIG. 3 shows the partition 3 from FIG. 2 in an individual illustration, partially cut away, so that radial slots 17 are clearly visible, which represent passages for the sound emitted by the membrane 5. The slots 17 are arranged closely next to one another in the circumferential direction. An acoustic lens is thus formed overall, which ensures the formation of a flat sound wave, which then continues to the sound exit channel 14. The channel 13 is trapezoidal and has inclined surfaces 17 and 18. Dashed lines S ₀ , S ₁ and S ₂ make it clear that sound components emerging from the slots 17 are deflected on the inclined surfaces 17 and 18 and, as a result, pass through the same paths until they enter the sound outlet channel 14. The same naturally applies to the other half of the pressure chamber system shown. This results in a flat sound wave at the foot of the sound exit channel 14, which then also continues to the mouth of the sound exit channel 14. This results in an effective radiation in relation to the power applied by the membrane 5.

FIG. 4 shows an embodiment of the invention in a representation similar to FIG. 2. The same or corresponding parts have the same reference numbers Mistake. The difference from FIG. 2 is that a membrane 20 is arranged in the axial direction with respect to the membrane 16, which is driven by a voice coil 21 and in front of which a pressure chamber 22 is formed, which is connected via a channel 23 to the central sound outlet channel 14.

5, the gap-shaped channels 13 and 23 are mutually nested in the circumferential direction so that they connect the pressure chambers 12 and 22 separately to the central sound outlet channel 14. The sound waves therefore only merge when channels 13 and 23 enter sound exit channel 14.

Since the slot-shaped channels 13 and 23 run partially radially before entering the sound outlet channel 14, that is to say the sound has the same direction in them, the channels 13 and 23 can also already be connected to one another or merge into one another in the radial course.

Claims (17)

Pressure chamber driver, - With a moving coil in an annular air gap of a magnet system and - with a membrane driven by the voice coil, characterized by that the membrane (5) and the pressure chamber (12) are annular and that the pressure chamber (12) is connected over its circumference to a central sound outlet channel (14). Pressure chamber driver according to claim 1, characterized in that the membrane (5) is V-shaped in cross-section and in that the tip (4) of the V is connected to the voice coil (3). Pressure chamber driver according to claim 2, characterized in that the legs of the membrane (5) to the of acute angles enclosed by them are arched. Pressure chamber driver according to claim 2, characterized in that the edges (6, 7) of the legs of the cross-sectionally V-shaped membrane (5) are clamped directly in and that the membrane (5) consists of a material which is flexible at least in the area of the clamping. Pressure chamber driver according to claim 2, characterized in that a wall (10) of the pressure chamber (12), which is opposite the membrane (5) on the side facing away from the voice coil (3), is complementary V-shaped to the membrane (5). Pressure chamber driver according to one of the preceding claims, characterized in that individual channels of equal length or a rotationally symmetrical channel (13) lead from the pressure chamber (12) from a region to the voice coil (3) to a central sound outlet channel (14). Pressure chamber driver according to claim 6, characterized in that the channels or the rotationally symmetrical channel (13) open in the region of a bottom (15) of the sack-shaped sound outlet channel (14). Pressure chamber driver according to claim 7, characterized in that the bottom (15) of the sound outlet channel (14) is raised, in particular conical. Pressure chamber driver according to claim 2, characterized in that the voice coil (3) has a coil body and that the wire of the voice coil (3) is arranged partly on the inside and partly on the outside of the coil body. Pressure chamber driver according to claim 1, characterized in that a dividing wall (16) is provided in the radiation direction in front of the membrane (5), in which there are radial slots (17) arranged next to one another in the circumferential direction. Pressure chamber driver according to claim 10, characterized in that the slots (17) extend over the entire radial extent of the membrane. Pressure chamber driver according to claim 10, characterized in that the width d of the slots (17) of the formula $$\text{d =}\frac{\text{λ}}{\text{1.7}}$$

corresponds, where λ is the wavelength of the transmitted sound. Pressure chamber driver according to claim 1, characterized in that the channel (13) from the membrane (5) to the foot of the sound exit channel (14) is trapezoidal, in such a way that all sound components emerging from the slots (17) have the same path. Pressure chamber driver according to claim 1, characterized in that two annular membranes (5, 20) and pressure chambers (12, 22) are provided opposite each other in the direction of movement of the membranes (5, 20) and in that each of the pressure chambers (12, 22) comes from an area with respect to the voice coil (3, 21) evenly distributed in the circumferential direction and alternately once from one pressure chamber (12) and from the another pressure chamber (22) individual channels (13, 23) run to the central sound outlet channel (14). Pressure chamber driver according to claim 14, characterized in that the channels (13 or 23) leading away from a pressure chamber (12 or 22) are of equal length to one another. Pressure chamber driver according to claim 14, characterized in that the channels (13, 23) leading away from both pressure chambers (12, 22) have the same length. Pressure chamber driver according to claim 14, characterized in that the channels (13, 23) leading away from both pressure chambers (12, 22) at least partially form a common, rotationally symmetrical channel with a radial course.

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