EP0896497A2 - Sound reproduction system - Google Patents

Abstract

According to the invention, a bass reproduction arrangement is specified in which the sound radiation from the membrane (15) to the listening room (38) occurs solely via a displacement volume (37) and at least one sound guide channel (34), the cross section of which is smaller than the cross section of the membrane (15) . Such an arrangement has the advantage that only wall surfaces that only have to accommodate the sound guide channel (s) (34) have to be provided for sound radiation. The side of the membrane (15), which faces away from the displacement volume (37), works on a closed damping volume (30), the size of which can, however, be varied over a wide range. A particularly good bass reproduction is achieved when the length of the respective sound guide channel (34) ≤ λ / 8 of the desired upper cut-off frequency.

Description

Technical field

The invention relates to a sound reproduction arrangement, in particular one for Play low-frequency tones.

State of the art

According to the prior art, it is known to use so-called electroacoustic sound signals Play converters. Such converters have as main components Membrane, a drive arrangement and fasteners for the mutual connection of Diaphragm and drive arrangement. Drive arrangements for such a membrane predominantly formed by a magnet system, which has a permanent magnet and a yoke (also called inference part). The membrane is provided with a voice coil and plunges into an air gap left in the magnet system. If the two ends of the Voice coil connected to a sound signal source, the voice coil moves in the Air gap of the magnet system, so that the membrane connected to the voice coil vibrating air volumes on the respective surfaces of the membrane be transferred. Since such an arrangement is not suitable, the entire audible One is to reproduce the frequency band of a sound signal source in a satisfactory manner started to develop so-called area converters, which only for a sub-area of the frequency band to be transmitted are optimized. Common in practice Arrangements usually have a converter for low, medium and high frequencies Beeps. Also in such arrangements, the two converters for medium and high-frequency sound signals can be emitted by just one converter. To play To improve further of low-frequency sound signals is very early on transferred, converter, which should transmit low-frequency sound signals, in the housing built in to cancel sound waves from the front of the membrane and the Back side of the membrane can be blasted. This has essentially three basic forms formed.

The first basic form, which is also referred to as a closed housing, stands out characterized in that the housing, with the exception of the converter opening, in which a converter is mounted, has no other opening. However, this works in the housing enclosed and connected with the back of the membrane air volume as additional spring, which increases the resonant frequency of the transducer and thus the lower one Cutoff frequency is shifted to higher frequencies. So with such arrangements sufficiently deep tones can still be emitted, the included one may Air volume, which is also called damping volume, does not have a minimum value fall below. A disadvantage of such arrangements that the housing at least one Must have a wall facing the listening room that is suitable for its dimensions, to accommodate the mostly large-sized bass converter in the opening. With consideration on the space or area requirements of such arrangements are these arrangements Applications fail even with limited space (such as in a motor vehicle) enable good bass reproduction.

Bass reflex boxes, which form the second basic shape, are based on the principle of the first Basic form on. Deviating from this principle, bass reflex boxes have another one Opening in the housing from which the sound waves emitted backwards by the membrane emerge in phase with the sound waves emitted from the front of the membrane and support their impact. Transducers and housings provide bass reflex arrangements two coupled systems. The bass reflex housing is a resonator, the the volume of the case and the size and depth of the additional opening dependent resonance frequency on the natural frequency of the built-in bass converter is coordinated. As a result, coupling vibrations occur. Tones in the Close to the natural resonance of the built-in transducer, the gas volume in (in Resonating) housing for particularly strong resonance. The one here Low coupling frequency that occurs causes basses from one in one closed housing can only be weakly illuminated transducers, become more audible.

Even if in the case of bass reflex arrangements compared to closed housing arrangements Sound pressure frequency response is not as linear, have bass reflex arrangements compared to that closed housing arrangements the advantage that they have a smaller size deliver higher efficiency at low frequencies. But also bass reflex arrangements like closed housing arrangements have the general disadvantage that the transducers in a wall of the (bass reflex) housing must be used, with which a variety of possible uses for these arrangements (especially those with less Space).

The provisional end of box development is the so-called bandpass arrangement which also form the third basic form. Bandpass arrangements are characterized by the fact that a closed housing by a partition in two Chambers is divided. The bass converter is inserted into this partition. In the The simplest design has bandpass arrangements in one of the two chambers Bass reflex opening that is solely responsible for the sound radiation. Basis for this Arrangements that show a very good low-frequency reproduction behavior is the use of the Special frequency response character of a Helmholtz resonator: This from a cavity existing arrangement with an opening of certain length and certain cross-section shows, excited by a transducer, a frequency response with a pronounced resonance frequency, at which the sound pressure is maximum, and with lower and higher frequencies with a slope of 12 decibels per octave falling edges. At higher frequencies however, there is an additional parasitic effect that is most likely related to the behavior of one Transmission line arrangement is to be compared. In the opening of the Helmholtz resonator standing waves are formed, the fundamental vibration of which is a wavelength of has twice the length of the opening. However, this effect can be achieved by using electrical Filters can be switched off.

It is characteristic of the bandpass arrangements that the open - because with the bass reflex opening provided - volume a volume of space which, depending on the training between about 0.4 and 0.8 of the room volume of the - for this consideration - closed Volume required. Provided that the corresponding volumes are provided, the The shape of the various chambers is largely arbitrary. If you take further into account that bandpass arrangements only require walls that have something for the sound exit are larger than the cross section of the bass reflex opening, and that i. ü. such orders Allow acceptable bass reproduction from a total volume of around 10 - 12 liters suitable for this arrangement also for applications in which only a very limited Space is available. But if you consider that also in many applications, the limited space available to accommodate bass reflex arrangements is available, can be subject to a number of changes, this means since bass reflex arrangements are based on reductions in the total volume react sensitively to a large number of bandpass arrangements in accordance with the spatial changes must be kept available.

To illustrate this with an example: Assuming that the required Space for installing a bass player under the driver's seat Cars with so-called normal equipment are available, so this volume can be about when equipping the vehicle with electric seat adjustment by the necessary Actuators are no longer available or only in changed form. The same applies if the vehicle is also available with sports seats. Even when dimensioning a bass reproduction arrangement such equipment variants in the conception of Bass playback arrangements can be taken into account at some point Point when changes (= downsizing) of the housing shape or the bass playback arrangement become necessary. In this context, only on the case noted that starting from a limousine (with a delay) Kombi or All-wheel version can be developed with modified bottom group and this to the stability of the Reduce the space under the seats of the vehicle, for example, with stiffening beads.

The invention is therefore based on the object of providing a sound reproduction arrangement Reproduction of low-frequency tones indicate which space is available can also be used very flexibly in the event of changes to this space and beyond only requires a sound radiation opening to the listening room, the cross-sectional area of which is smaller than that of the membrane.

Presentation of the invention

This object is achieved with the means specified in claim 1. Beneficial Training and further developments of the invention can be found in claims 2-8. Works the surface of the (first) membrane that the closed Damping volume is turned away, only on the displacement volume, which is very small and is closed except for at least one opening achieve a very good bass response even with variable space if the Cross-sectional areas of all openings significantly smaller than the cross-sectional area of the are the first membrane and an open sound duct connects to each of the openings, whose cross-section essentially corresponds to the cross-sectional area of the opening, with which he is connected to. The variability of such an arrangement for bass reproduction is based on the one hand that the displacement volume including the sound guide channels very much is low and that the damping volume with a wide bandwidth compared to volume changes reacted uncritically.

Vented-Box-Loudspeaker-Systems", AESJ, Juni 1973, Pages 363 ff.) erklären. Danach ergibt sich, daß bei Baßreflexboxen zu den beiden Blindkomponenten des Lautsprechers (= Masse und Nachgiebigkeit) zwei weitere Blindkomponenten und zwar die Nachgiebigkeit des Gehäusevolumens und die akustische Masse des Baßreflexrohres (auch Port genannt) hinzukommen. Aus der akustischen Analogie bzw. dem elektrischen Ersatzschaltbild wird deutlich, daß bei solchen Anordnungen drei Resonanzfrequenzen auftreten.The good reproduction behavior can best be determined by means of acoustic analogies or electrical equivalent circuit diagrams (see R. Small,

Vented-Box-Loudspeaker-Systems ", AESJ, June 1973, pages 363 ff.). It follows that with bass reflex boxes two additional blind components for the two blind components of the loudspeaker (= mass and compliance), namely the compliance of the housing volume and The acoustic mass of the bass reflex tube (also called port) is added, and it is clear from the acoustic analogy or the electrical equivalent circuit diagram that three resonance frequencies occur in such arrangements.

In contrast, the resilience of a closed housing Loudspeaker suspensions and the housing volume resulting in compliance formed, which is smaller than the flexibility of the free-standing speaker. With the free-standing loudspeaker, this only results in a resonance frequency, which however in, has a higher value than the closed box.

In contrast, the arrangement according to the invention works directly on the acoustic Mass, which is provided by or from the sound guide channels, because the Displacement volume because of its small size does not act as a housing volume. In other words, the arrangement according to the invention has one of the closed boxes Similar equivalent circuit diagram, but with the difference that in the system according to the invention to the blind component loudspeaker not the resilience of the housing, but only that acoustic mass of the sound guide channel or channels is added. This means that the acoustic mass of the sound guide channels together with the moving mass of the Loudspeaker forms a resulting mass that is greater than the acoustic mass of the Speaker. The result is that only one resonance frequency occurs because there are only two Dummy components are present and that this (new) resonance frequency is lower than that Is the resonance frequency of a free-standing speaker.

For a better understanding of the application it should be pointed out at this point that the displacement volume mentioned several times in the application is the volume of a converter must be provided so that the (first) membrane on one side under Move the maximum stroke within the structural conditions of the speaker cage can without the risk that the vibrating parts of the transducer not "strike" vibrating parts of the transducer. For example, if (First) membrane around a cone membrane of the type shown in DE-Gbm 9109452, so the displacement volume, which on the surface facing away from the magnet system Membrane is present, essentially from the effective membrane diameter and the Volume between the top of the membrane and the top of the transducer educated. If one assumes in DE-Gbm 9109452 that the ones designated there with nineteen Stabilizing elements and the centering membrane are made air-permeable that adjoining the surface of the membrane facing the magnet system (rear) displacement volume formed in the space, which is essentially from the just named surface of the membrane, the voice coil former and the basket of the Converter is limited.

In this context, it should only be pointed out for the sake of completeness that it is sufficient for good low-frequency reproduction if, according to claim 2, the displacement volume is subject to the following relationship, taking into account a one-sided maximum deflection of the membrane: Displacement volume <= effective diaphragm diameter 3rd x 0.06.

Since, according to the above, the inventive arrangement is directly based on that of the acoustic mass provided or the sound guide channels should work the reduction of the factor given in the above formula with 0.06 for realization of these relationships.

A particularly good bass reproduction is given if, according to claim 3, the length of the sound guide channel (s) ≤ λ. / 8 of the desired upper limit frequency. Is according to claim 4, a further membrane and with an axial distance to the first Arranged membrane and the drive assembly that drives the other membrane, is a very compact arrangement for sound reproduction with separate Area transducers created, in which the influence of the other membrane on the Otherwise, sound radiation from the first membrane thanks to the sound guide channels known coaxial arrangements, which a further membrane and a magnet system in Having the bell of the first membrane is unaffected.

According to claim 5, a further closed damping volume is present and will be this damping volume of walls of a housing and the further membrane formed, the further membrane for the reproduction of medium or medium-high frequencies Tone signals are used without thereby reducing the total space requirement of an arrangement is enlarged according to claims 1 to 4.

A very economical use of building materials is given if according to Claim 6 the sound guide channels at least partially from walls further Housing are formed.

Overheating of the drive arrangement is excluded according to claim 7 if Wall surfaces of the drive system via the sound guide channels with the gas volume of the listening room is in exchange.

If the drive arrangement is designed according to claim 8, each membrane forms together with their magnet system driving them a transducer of the one shown in DE-Gbm 9109452 Art. This means that each of the two transducers according to the invention largely out standardized and for example also in arrangements according to DE-Gbm 9109452 used components can be formed. The extensive elimination of the requirement, To use your own components in the system according to the application also has the other one Advantage that the two converters forming a registration system on production facilities can be prefabricated, for example for the production of Transducers according to DE-Gbm 9109452 can be used.

Brief presentation of the figures

Figur 1

eine Tonwiedergabeanordnung im Schnitt;

Figur 2

eine Draufsicht auf eine Anordnung gemäß Fig. 1;

Figur 3

eine weitere Draufsicht gemäß Fig. 2;

Figur 4

eine weitere Anordnung gemäß Fig. 1 im Schnitt; und

Figur 5

eine Schnittdarstellung einer weiteren Anordnung.

Show it:

Figure 1

a sound display device in section;

Figure 2

a plan view of an arrangement according to FIG. 1;

Figure 3

another plan view of FIG. 2;

Figure 4

a further arrangement of FIG 1 in section. and

Figure 5

a sectional view of another arrangement.

Ways of Carrying Out the Invention

The invention will now be explained in more detail with reference to the figures.
FIG. 1, which also does not illustrate a true-to-scale representation of the actual conditions in the other figures, shows a low-frequency reproduction arrangement 10. This arrangement 10 is essentially formed by an electro-acoustic transducer 11 and a closed housing 12.

The essential components of the converter 11 are a basket 13, a drive arrangement 14, a conical membrane 15 and one arranged on a voice coil former 16 Voice coil 17 on The conical membrane 15 is inserted and connected in the basket 13. This connection is realized so that the membrane edge 18, which is the largest Has a radial distance to the loudspeaker center axis, by means of a groove-shaped Bead 19 is connected to the upper edge 20 of the basket 13. The drive arrangement 14 In the present case, it forms a magnet system 21 which has a yoke formed from different parts 22 and a permanent magnet 23 comprises. The lower edge 24 of the membrane 15 is with the Voice coil former 16 connected. Is the converter 11 - as in the state shown in Figure 1 - Mounted, the voice coil 17 is immersed in an air gap 25 left in the magnet system 21 on. In addition, there is a centering membrane 26, which the voice coil bobbin 16 connects the basket 13, and a dust protection cap 27, which the voice coil bobbin 16th overstretched, present.

In a converter 11 just described, the ends of the voice coil 17 become conductive connected to a sound signal source, the membrane 15 depending on the of the sound signal source provided voltages in vibrations axially to the loudspeaker central axis offset (everything not shown in Fig. 1), so that both from the front 28th and the back 29 of the membrane 14 sound waves are emitted.

Thus, a mutual cancellation between sound waves from the front 28 or the rear side 29 of the membrane 15 are emitted, the converter 11 inserted into a housing 12 so that the transducer 11 closes the housing 12 while doing so at the same time provides a damping volume 30 inside the housing. Only the For the sake of completeness, it should be pointed out that for technical reasons in Fig. 1, the complete closedness of the damping volume 30 is not shown. Also if, in the exemplary embodiment discussed here, the basket 13 with the housing 12 is connected, one speaks with regard to the openings 31 present in the basket 13 that the membrane 15, which largely covers the opening of the housing 12, the Housing 12 closes. A spacer ring 32 is on the upper edge 20 of the basket 13 put on. Furthermore, the cross section surrounded by the spacer ring 32 has a cover 33 largely covered. Up to this point in the description of the arrangement 10 regions on both sides of the loudspeaker center axis of the regions shown in FIG. 1 Arrangement 10 is identical. However, this no longer applies to the sound guide channels 34, which extend in the direction of the loudspeaker central axis and which in the lid Connect 33 left openings 35.

As FIG. 2 also shows, that to the left of the loudspeaker center axis is shown in FIG. 1 Embodiment provided with a circular opening 35 in the lid 33, which is rotationally symmetrical to the loudspeaker center axis. In contrast, as in FIG. 3 shows - in the embodiment shown in Figure 1 to the right of the speaker center axis is, the opening 35 and the adjoining sound guide channel 34 is annular educated. If the webs 36 are neglected, which in the embodiment according to FIG Connect the middle part 33 'of the cover 33 to the rest of the cover 33, which corresponds to both 1 the cross-sectional area of the openings 35 essentially the cross-sectional area of the sound guide channels 34.

If, as explained above, the transducer 11 is set in vibration, the diaphragm 15 moves during an outward stroke into the so-called (front) displacement volume 37. This displacement volume 37 is used for an outward stroke of the diaphragm 15 between the effective diaphragm diameter resulting from the clear Cross-section of the membrane 15 calculated at the front 28 and 2 × half the width of the bead 19, the spacer ring 32 and a cover 33 having no opening 35 for this purpose. It is evident in this context that the spacer ring 32 or its height parallel to the loudspeaker central axis has the task of preventing the membrane 15 or the bead 19 from “bumping” on the cover 33. Since in the present embodiment 130 "transducer 11 was used, the size of the displacement volume 37 was only about 85 cm ^3. The displacement volume 37 set in motion by the vibrations of the membrane 15 then puts the volume resulting from the cross section and the length of the respective sound guide channel 34 in a particularly powerful manner Vibrations, whereby the particularly good bass reproduction is achieved in the listening room 38. A prerequisite for this, however, is that the length of the sound guide channels 34 is λ / 8 of the desired upper limit frequency.

An arrangement 10 explained in connection with FIGS. 1 to 3 is also relevant the bass reproduction quality in a wide range versus changes in volume size of the closed damping volume 30 is not critical. This means being one in the Figures 1 to 3 arrangement 10 shown for example in the trim of a motor vehicle door used and the closed damping volume 30 of the panel and the door skin (everything not shown) can be done later without a problem closed damping volume 30 reducing components - such as side impact protection, Actuators for power windows or extra thick safety glass without Disadvantage for the bass reproduction in the space between the door skin and the panel integrate. Even changes to the door shape or size can be viewed as uncritical.

FIG. 4 shows a further arrangement 10, which in turn has two embodiments the subject. Unless stated otherwise, the two on the right and left are the Loudspeaker center axis lying embodiments are identical. The one shown in Figure 4 In terms of function and structure, converter 11 is largely identical to converter 11 according to FIG. 1 identical. The only difference is that the converter 11 with the Front 28 of the membrane 15 "works" on the closed damping volume 30. In Figure 4, the closed damping volume 30 is not of its own Housing formed, but provided that the assembly 10 in a built-in housing 39 is used, walls 40 must be provided on the arrangement 10, which the sound waves radiated from the rear side 29 of the membrane 15 from the sound waves separate that are released from the front 28 of the membrane 15.

Furthermore, a second converter 11 'is present in FIG. 4, which essentially those Components that the converter 11 also has. Clarify this pointed out that those components of the transducer 11 'which match the components of the converter 11 are identical in their function, with the respective reference numerals of Converter 11 and an apostrophe are designated.

This converter 11 ', which is provided for the reproduction of medium-frequency tones deviating from the converter 11 equipped with two permanent magnets 23 ', which are within the are arranged by the voice coil support 16 'surrounded space. Besides, they are two transducers 11, 11 'centered on the loudspeaker center axis back to back on their Magnet systems 21, 21 'connected together. The converter 11 'also has Improvement of the reproduction quality over an independent midtone volume, which the forms further closed damping volumes 30 'in the sense of this application. This further closed damping volume 30 ', which via the openings 31' with the Back 29 'of diaphragm 15' communicates in the left of the loudspeaker central axis shown embodiment essentially of the wall 40, the basket 13, the magnet systems 21, 21 'and the basket 13' are formed. As shown in Figure 4 (left side) Shown sound guide channel 34, which the further closed damping volume 30 ' runs through, only one of several radially arranged to the loudspeaker center axis Sound guide channels 34, the further closed damping volume 30 'is also from limited the sound guide channels 34.

The embodiment to the left of the loudspeaker center axis in FIG. 4 can be clearly seen, that the rear displacement volume 37 'of the transducer 11 through the openings 31 in the basket 13, which so far form the openings 35, and the sound guide channels 34 with the Monitoring room 38 are connected. The fact that the or the sound guide channels 34 partially are formed by the permanent magnet 23, good heat dissipation from the magnet system 21 (21 ') ensured.

In the embodiment which is shown on the right of the loudspeaker center axis in FIG. 4, the closed damping volume 30 'of the wall 40, another Wall 41, the basket 13 'and the one or more sound guide channels 34 formed pull through the closed damping volume 30 '. To the tightness of the closed Damping volume 30 'to bring about is between the further wall 41 and the Basket 13 'provided a sealing element 42. Since the further wall 41 with axial Distance to the basket 13 and the magnet system 21 and thus an intermediate volume 43 is provided, the air volume of which is in contact with the drive arrangement 14 (21, 21 ') stands, this intermediate volume 43 ensures good heat dissipation from the drive arrangement 14 achieved without an elaborate guidance of the or the sound guide channels 34 is necessary.

FIG. 5 shows another embodiment of the invention. This embodiment largely corresponds to the embodiments shown in FIG. 4. The difference is, however the sound guide channel 34 is not through the further closed damping volume 30 ' guided, but rather in Figure 5, the sound guide channel 34 connects radially to the closed damping volume 30 'and uses its wall 40. Even if in the embodiments according to FIGS. 4 and 5 such a further converter 11 ' are shown with a conical membrane 15 ', in this other - not shown - Embodiment of the transducer 11 for bass reproduction with a transducer Dome membrane can be combined. This results because converters with Dome membrane compared to transducers 11 'with a conical membrane 15' usually one have a smaller diameter, space advantages on the side of the arrangement 10, which the Listening room 38 is facing, because in this case, because transducers with dome membrane do not need their own damping volume 30, the sound guide channels 34 lead to the listening room 38 at a short distance from the center axis of the loudspeaker.

Claims (8)

Sound display device with a first membrane (15) for reproducing low-frequency tones, which has two surfaces (28, 29), with a drive arrangement (14) which drives at least the first membrane (15) and which is arranged at an axial distance from the latter, with fastening means (13) for the mutual connection of the first membrane (15) and the drive arrangement (14), with two displacement volumes (37, 37 ') which are arranged upstream of the two surfaces (28, 29), and with a closed damping volume (30), which is formed by walls of a housing (12) and the first membrane (15),
characterized, that the displacement volume (37; 37 ') which connects to that surface (28, 29) of the first membrane (15) which faces away from the damping volume is closed except for at least one opening (35), that the cross-sectional area of all openings (35) is significantly smaller than the cross-sectional area (35) of the first membrane (15) and that each opening (35) is followed by an open sound guide channel (34), the cross section of which essentially corresponds to the cross-sectional area of the opening (35) to which it is connected. A sound display device according to claim 1,
characterized, that the displacement volume (37, 37 ') with one-sided deflection of the first membrane (15) is calculated according to the following formula: Displacement volume <= effective diaphragm diameter 3rd x 0.06 A sound display device according to claim 1 or claim 2,
characterized, that the length of the sound guide channel 34 ≤ λ / 8 of the desired upper limit frequency. Sound reproduction arrangement according to one of Claims 1 to 3,
characterized,
that a further membrane (15 ') is present, that the further membrane (15 ') is arranged at an axial distance from the first membrane (15) and that the drive arrangement (14), which also drives the further membrane (15 '), is placed between the two membranes (15, 15'). A sound display device according to claim 4,
characterized, that a further closed damping volume (30 ') is present, which is formed by walls (40, 41) of a further housing and the further membrane (15'). A sound display device according to claim 5,
characterized, that the sound guide channel (s) (34) are at least partially formed by the walls (40, 41) of the further housing. Sound reproduction arrangement according to one of Claims 1-6,
characterized, that the drive arrangement (14) has wall surfaces which are in exchange with a gas volume of a listening room (38). Sound reproduction arrangement according to one of Claims 4 - 7,
characterized, that the drive arrangement (14) for each of the two membranes (15, 15 ') has an independent and a permanent magnet (23; 23') and a yoke (22) having magnet system (21, 21 ') and that both magnet systems (21, 21 ') are connected to each other back to back.

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