DE2003950B2 - ACOUSTIC CONVERTER - Google Patents

Description

The lirlindimg deceives an acoustic transducer, preferably an electroacoustic transducer, with a Membranunordiuing, the several at least partially has vibratory membrane parts, which are adjacent between them, opposite to each other Forming recesses that fill the sides. she In a more specific sense, it deals with the design of the membrane arrangement and its use for sound windows, Microphones, headphones, loudspeakers, etc.

If sound is to get from one room into a separate room, a sound window must be used to be used; a light, thin membrane does this best.

The aim is to convert sound in a microphone into electrical currents or from electrical currents are reproduced in a loudspeaker, so result in the lightest membrane arrangements the most faithful and performing renditions.

Air has a specific density of 1.2 mg / cm ³ and is therefore 1,000 to 1,000 times lighter than solid bodies. This is the reason why, in the aforementioned four devices, membranes can hardly be made thin enough to reduce the effective specific mass of the membrane.

The simplest way of making this problem clear is to make a comparison: Do you want a cherry pit Throwing with the hand like a ball results in a very low efficiency. The reason this is due to the relatively low weight of the core compared to the weight of the hand, which is estimated 100 times harder.

The process is similar with one of the usual loudspeakers. These move the air - like the hand ^{moves the K:} rschkern - by direct pushing, which results in a very low level of efficiency.

Thus, the French patent 670 386 shows a rigid diaphragm with a single acoustic excited point from which an elastic wave propagates across the membrane. This elastic wave creates complicated vibration patterns, especially at higher frequencies, similar to those in the air reproduce a very poor sound image.

A similar arrangement is shown in US Pat. No. 1,566,337. Here, a folded elastic Membrane is excited at one point of its edge, and from this point an elastic one spreads Wave out over the membrane. Here, too, there are the same disadvantages as in the case of the one mentioned at the beginning French patent specification.

It is therefore an object of the invention to provide a To create membrane for use in sound windows, microphones or loudspeakers in which the effective specific mass of the membrane (grams per square centimeter) at hearing frequency around one can be reduced by a considerable factor without reducing the membrane thickness, in particular the reproduction of the sound should be extremely true to the original.

According to the invention, this is achieved in an acoustic transducer mentioned at the outset in that the recesses are designed as narrow air pockets that the vibratory membrane parts so are interconnected that adjacent air pockets alternate at the opposite ends are closed and open, and that the opposite parts of the membrane are in phase opposition are drivable. This allows a reduction in the effective specific mass dei Easily realize membrane by a factor of 10 in the frequency range mentioned. If mar again the above-mentioned picture of the cherry pit; as a help, it is easy to see that there is a there is a very clever way of accelerating the cherry stone: you squeeze it between thumbs and index finger. If there is enough pressure, the egg shoots

jo off at great speed. Here is the kinetic energy of the thumb and forefinger is much smaller than the kinetic energy of the hand Throwing the core by hand. In a similar way, in the converter according to the invention, the air squeezed out between them by the opposite phase movement of the opposite membrane parts, and the kinetic energy of the membrane parts is only a fraction of the kinetic energy the air.

The sound transducer according to the invention is advantageously designed in such a way that the vibratory Membrane parts are in operative connection with a suitable device, the sound waves converts vibrations applied to the membrane parts into electrical energy, and vice versa. In this case, at least one conductor with the vibratory membrane parts is expedient connected, and a cooperating with this conductor device for generating a strong magnetic odec electrostatic field is provided to help with the application of auditory frequencies Alternating current signals generate oscillations in the membrane parts, and vice versa.

The air spaces or pockets, which alternately open to opposite sides, can thereby be formed by bending a thin membrane into a maroon shape; here the vibratory membrane parts: of essentially parallel, spaced apart

Parts of the tape formed. The vibratory membrane parts can also consist of several separate ones thin sheet-like elements be formed, which are spaced from one another and approximately parallel to one another are held, namely by spacers connected to them, which open ends have, which alternately point in opposite directions.

In the case of electroacoustic converters, in which sound waves are converted into electrical signals, or vice versa, the vibratable parts of the diaphragm assembly can be direct or indirect are driven. In the first case, as mentioned above, there is at least one conductor on the vibratory Parts of the membrane supported, and this conductor is arranged so that it is in a magnetic or moving electrostatic field; in the second case is a separate electromagnetic device, z. B. one or two loudspeaker coils are provided, which are mechanically connected to the vibration

capable parts of the membrane assembly connected

is to cause them to move when the loudspeaker coils (sound coils) vibrate and move away from each other.

Further details and advantageous developments of the invention emerge from the im The following exemplary embodiments described and shown in the drawing as well as from the Subclaims. It shows

Pig. I cine a schematic, explanatory representation a membrane according to the state of the art,

F i and 2 are a schematic, explanatory representation a membrane according to the invention,

F i g. 3 is a schematic, three-dimensional representation of an embodiment of an inventive concept Membrane,

Fig. 4 is a schematic, three-dimensional representation of a modification of the membrane arrangement of F i g. 3,

F i g. 5 shows a schematic, three-dimensional representation of a further modification of an inventive Membrane,

Fig.fi is a schematic side view showing a membrane structure according to FIG Shows device for generating an electrostatic field,

F i g. 7 a schematic plan view of a loudspeaker according to the invention;

7a shows a partially enlarged illustration similar to FIG. 7,

Fig. 8 is a side view of the loudspeaker shown in Fig. 7,

Fig. 9 is a section, seen along the line IX-IX of Fig. 8,

FIG. 10 shows a cross section, seen along the line X-X in FIG. 11, through another exemplary embodiment of a loudspeaker according to the invention.

Figure 11 is a cross-section as seen along the line XI-XI of Fig. 10,

12a and 12b three-dimensional representations to explain the manufacturing process of the im Loudspeaker according to FIGS. 10 and 11 used membrane,

13a is a partial plan view of a thin one Tape of plastic material with attached wires, before this tape is deformed into one Meander shape, as z. B. is shown in Fig. 11,

Figure 13b is a partial illustration showing the tape the F i g. 13 shows a in the folded state,

14 shows a cross section through a further exemplary embodiment a loudspeaker according to the invention, seen along the line XIV-XIV of Fig. 15,

Figure 15 is a partial plan view of the loudspeaker the F i g. 14,

16 shows a partial cross-section through a Modification of the arrangement according to FIG. 14,

17 shows a sciiematic cross section through an indirectly driven loudspeaker according to the invention,

Fig. 18 is an exploded view of the Loudspeaker of FIG. 17 in a simplified representation and

19 shows a simplified, exploded view of a headphone or microphone according to FIG the invention.

As explained at the outset, the present invention relates to membranes in which the effective specific Mass (grams per square centimeter) for acoustic frequencies by at least one factor 10 can be reduced without reducing the membrane thickness; it also concerns application such a membrane for sound windows, microphones and loudspeakers.

The principle of the membrane according to the invention with reduced effective mass is illustrated below with reference to FIGS. 1 and 2 explained. Fig. 1 shows schematically a Hache membrane / J, which is connected along its circumferential edges with walls W which define an opening of width 2 na , so that the membrane separates the air space on its left .Seite from the Lurtraum on its right side. Fig. 2 shows schematically a membrane according to the invention, which also extends over an opening of width 2/1, in which, however, the membrane / -) 'is folded into a meander shape. In Fig. 2 is the

ίο The width of each fold is designated with α and its depth with b . The ratio of width to depth of the folded membrane represents the effective mass reduction factor /.

Are sound waves in the direction of arrow A

is (Fig. 1) supplied, the membrane D is deflected by an amount c in the direction of the arrow; For the sake of simplicity, it is assumed that the membrane D moves parallel to itself over its full width.

In the case of the folded membrane according to FIG. 2, assuming that the membrane sections α remain rigid without any movement, the membrane sections b are displaced in directions which run in the direction of arrow A by the distance d; here too, for the sake of simplicity, it is assumed that the membrane sections b shift over their entire width. These assumptions facilitate the evaluation without significantly affecting the end result.

Although the total mass of the in F i g. 2 is the folded membrane shown by a factor of 1 // greater than the total mass of the in F i g. 1, it can be shown that the total kinetic energy of the moving membrane mass, which is necessary to cause a certain air displacement per unit of time across the membrane, in the case of the in FIG. 2 is smaller by the reduction factor / than that of the flat membrane of FIG. 1. It is assumed that the thickness of both membranes Z? and D 'is the same and the width of the two is 2 na . The relative displaced air volumes are represented in the two figures by the two areas 2 nac and 2 nbd . For the same air movement, these surfaces must be the same, ie

2 nac = 2 nbd

from which it follows that

ad ,, d

- = ■ = /, or c = -.
be f

In the case of the air displacements taking place in the same unit of time, the displacement velocities V ₁ and V ₂ must have the same ratio, ie

- = / · ¹

The mass ratio of the moving parts both Membranes is

2 na _ _ m, ■ I

2nb

provided that both membranes are equally thick.

The ratio of the kinetic energies of the two membranes is

OT,

ι /

With electroacoustic! Transducers can vibrate the parts of the membrane - these can e.g. B. from a metal foil carrying the currents of the audio frequency or from an insulating one Foil be formed on the parallel, the audio-frequency currents are attached metal strips or wires - be arranged in two different ways, as shown in Figs. 3 and 5, respectively are. The two types shown in these figures

Factor / is reduced. The effective mass is

2naf or 2 / i

The actual mass of the membrane folded in I is

i g. 2 shown

The relationship between actual mass and effective mass is therefore

Ah

For the same kinetic energy of the air, the folded membrane according to FIG. 2 one around the factor / lower kinetic energy than that in

Fig. 1 shown flat membrane, or with andeto orders differ mainly by In other words, the folded membrane corresponds to a direction from one another in which the sound is flattened membrane, whose thickness or mass radiates around the. Elci of the arrangement according to FIG. 3 is

the inventive membrane from a thinner one Metal foil 2 is formed, which is bent into a meander shape. as shown in FIG. around several narrow, adjacent air pockets that are closed alternately at the top and bottom are. Thin plastic films 4 are connected in a suitable manner to the front and rear edges of the meandering film 2 in order to close the aforementioned air pockets at the front and back. The membrane or metal foil is placed in a strong magnetic field. For the sake of clarity, these are the magnetic poles generating the magnetic field are not established in FIG. 3, but only the direction of this magnetic field is shown by the arrows 6. With this arrangement, the passage of an audible current through the membrane or metal foil 2 are essentially parallel

Wrinkles on the order of 10 is easily made from 30 parts of the membrane 2 to each other and feasible and gives a ratio of actually swinging away from each other, and sound is in to an effective mass of 110: 1. This makes one of the direction indicated by the arrows 8 of the Sound window very strong in its physical structure. Air pockets radiated, d. h .. be sound waves With electroacoustic transducers, a supply makes practically perpendicular to the direction of the magnetic would take the actual mass of the current-carrying field radiated.

Parts stronger, the ohmic losses relatively low. In the arrangement according to FIG

but still maintains a good match with or metal foil 10 to that shown in this figure the air mass. At a ratio of b: a = 10 wave-shaped arrangement bent to form a honeycomb corresponds to the actual mass of a 0.025 mm or zelien-like structure, and neighboring Aluminum membrane of a loudspeaker of this type 40 parts of the band are mechanically connected to one another in an effective air equivalent of 5.7 mm thick, the. z. B. by gluing, but at the points 10 '. WC what is low enough for the highest audible fre- they are against each other, isolated from each other. In sequence. The air that is moved in this way becomes several rows of air pockets The opposing forces exerted by the membrane have formed differently, alternating above and below on the other hand, a very small movement effect on the 45 thin plastic sheets 12 are closed, the ir Membrane, suitably with the upper and lower because of the high ratio

A ratio between the length and width of the

th of the film 10 are connected. In Fig. 5 only the upper webs 12 are shown, but of course the air tabs shown open at the top in Fig. 5 are on their underside by correspondingi. Lanes 12 closed.

The direction of the magnetic field is through in FIG the arrow 14 indicated, d. It .. the magnetic field is perpendicular to the direction in which an audible

membranes described above can be used. 55 cross-currents through the film strip 10 skillfully reach a new active uni wheel. namely will. With this arrangement, when sans through:

from effective to actual mass of 1: 110. The membrane therefore does not need any mechanical support for its acoustic stiffness. In the case of microphones, air equivalents of 1 mm can easily be achieved, since only low powers have to be converted and thinner membranes can be used.

For electroacoustic converters in which the

for two reasons:

effective membrane mass

of an audible-frequency current through the film 10, the sound is radiated in the direction of arrow 16, ie the sound is radiated in the direction of the inacne-

The diminished

(Air equivalent of 1... 5 mm) guarantees _{6o t} ; ^ h ^ n '"Fdds. ΛιιοϊΓίη ΐ'Γε.'ϋ simfdie"the' macne small blind energies (positive and negative acceleration of the mass), and the kinetic
Energy from the membrane is converted directly into air vibrations, or vice versa: and

the actual total mass of the actuator diaphragm can be relatively large. Since this mass corresponds to the mass of the conductive metal, the ohmic losses low.

tables field-generating magnetic poles not shown these must be made of divided iron laminates; perforated sheets are made in order for the Sound to be transparent.

The depth of the air pockets formed by the membrane parts is related to the highest frequencies that can be effectively transmitted. A depth of 10 to 15 mm results in a perfect

Works up to 10 to 15 kHz. The membrane can create adjacent air pockets that take turns

formed from a thin metal ribbon; Ban- opened on opposite sides and

made of aluminum, magnesium, copper or silver, and oppositely charged electrical

0.05 to 0.005 mm (0.002 to 22 mm thick) extending from opposite sides

0.0002 inches) result in perfect work up to 5 in the air pockets, like the one in FIG. 6 schematically

to the highest listening frequencies. Is shown in place of Me-. For example, when arranging

Tallbäncfc / n can also thin Mylar ribbons according to Fig. 6 the electrodes 22, from the left

that protrude into the air pockets with one of the metals mentioned, be positively charged, and

are coated. the electrical appliances protruding from the right into the air pockets

A disadvantage of the io shown in FIGS. 3 and 5 can be negatively charged, so that the

Arrangements in which thin plastic sheets, the essential parallel parts of the folded membranes

Each extending in a plane, with the edges in the strong electrostatic fields that lie

Hes metal band are connected, is that the parts are formed by the oppositely charged electrodes.

This metal band close to its edges, which are firmly det. Is now in a manner known per se

fn are connected to the plastic foils, an auditory-frequency current through the membrane 20 is generated at the swing 1.5.

{are hindered, so that in these parts a low sends, so are the parallel parts of the membrane

residual tension is built up and a larger one, which is made to vibrate in order to remove sound from the open

Current increasing thermal losses through the air created by the membrane

and flows. bags, or, if sound waves hit the

Different arrangements are possible, around 20 diaphragm impinge to vibrate their par-

At least partially to remedy the huge disadvantage. To stimulate all parts, a high-frequency electrical

Y / 'nd z. B. metal-coated plastic tape for her- tric signal is generated in the membrane. Instead of the

! Division of the membrane related, so can longitudinal F i g, 3 corresponding meander-shaped training

strip this tape along its opposite membrane 20 of FIG. 6 can do this by yourself

the longitudinal edges are left uncoated, at 25 hourly also in the manner shown in FIG

the band can be formed in the area of its opposite. The distance between the F.lck

Longitudinal edges with which the air pockets move 22 can be very small. z. B. in sizes

There are also 12 connected plastic foils, larger order 0.5 mm. A bias from elwt

Flexibility to \ allow. On the other hand, at Λ 1000 V can be used. For the depth of the

an arrangement according to Fig. 5 essentially cup folds are the same frequency considerations

Shaped phistic parts on the slope of the parallel path parts limit valid as for the magnetic device

12 to Vj: -chücßcn the air pockets between the and a depth of 10 to 15 mm results in an impeccable

interconnected band parts 10 '\ used freit s work. The arrangement can be used for elekiro

will. static loudspeakers are also used \\ i (

A particularly advantageous arrangement is in FIG. 35 for electrostatic microphones.

Fig. 4 shows a modification of the in Fig. 3 Figs. 7 to 9 show schematically a flat «

represents the arrangement shown. When arranging loudspeaker arrangement in which a erfindungsge

according to FIG. 4 are in the of the meander-shaped membrane in an electromagnetic fault

Metal band 2 formed air pockets not as is arranged in FIG. This arrangement has several flat «

3 by thin strips of permanent magnetic ferrites 24 with which 40 strips extend in the longitudinal direction

extending opposite edges of the tape which are arranged parallel and spaced from one another

Connected thin plastic foils are closed, as are two sets of soft pole pieces 26

the sleeve-like cylindrical parts 18 (in the manner of each of which several subdivided strips into one

Tubing sections) made of thin plastic film. Has arrangement, as best shown in Fig. '

z. B. Mylar, are formed in the in F i g. 4 shows 45 and each against the opposite

In each case, the poles of the permanent magnets 24 which are lowing from the metal mouth 2 are in contact with each other

formed air pockets arranged, these being partially in the space between the permanent

Sleeves 18 essentially extend the air pockets on counter magnets 24 in order to open spaces with them

Complete iiherliegenden ropes and to form Sicli case in which each _^d:; e membranes aneeord

fciwas about the opposite edges of the band 50 are not. The conductive membrane strips are in de

des 2: these sleeves 18 can be attached to in FIG. 5 illustrated manner in the aforementioned;

their .außenkanten 18 'with a (in Fig. 4 not arranged spaces to rows of air pockets

shown) carrying arrangement are connected. to form between the corrugated strip parts, dii

in order to keep the metal band 2 elastic, but in the longitudinal direction of the permanent magnets 2

a correct swinging essentially extends in its own right and is shown in a simplified manner in FIG. 7

Velvets allow width if it are put by one, with these air pockets alternating

audible current is flowing through it. Self-as described in Fig. 5, by thin plastic sheet

Of course, the metal strip 2 of FIG. 4 is also alternated with 12 on the top and bottom!

placed in a magnetic field as it are closed by. The conductive membrane strips 1 (1

the arrow 6 of FIG. 3 is indicated. 60 each in the spaces between adjacent egg

The membrane according to the invention are arranged with less effective permanent magnets 24 can ai

Breaded earth can also be connected in series or in parallel with clektro ends

acoustic energy converters are used when an audible current flows through the conductive]

which instead of a magnetic, in particular strip 10, are sent to Schwin

electromagnetic field brought an electrostatic field 65 gene, and sound waves are caused by di

Is used. Such an arrangement is schematic spaces between the divided, strips

lisch shown in Fig. 6. The conductive membrane 20 shaped soft iron Polbicchpaketen 26 radiated

is shown folded into a meander shape so as to d. H. in the direction of the generated magnetic field?

The in the F i g. 7 to 9 shown arrangement can be placed in a horn that extends beyond the speaker and the Separates sound radiation at the front and rear of the speaker.

A rotationally symmetrical loudspeaker arrangement with a folded membrane according to the invention is shown in FIGS. The advantages of this arrangement are its simple construction, the ability to use an elongated membrane in a confined space, and the adaptability of the arrangement for use an acoustic horn to extend the frequency range down to the lowest frequencies.

In the arrangement shown in FIGS. 10 and 11, between two permanent magnets Ferrite rings 28 and 30, which are arranged coaxially and at a distance from one another, generate a circular magnetic field; any of these magnets can be attached its side opposite the other ring with a pole piece 28 'or 30' made of soft iron be provided. The folded membrane arranged in the space between the pole pieces 28 'and 30' preferably has the above in connection with FIG. 4 illustrated shape, and the arrangement can comprise a meandering conductive foil 2, the parallel parts of which extend substantially radially, as best shown in FIG. 11, in order to form adjacent air pockets between them alternately open radially outwards and inwards. Mylar sleeves 18 are here too, as well as above, in connection with FIG. 4 shown and described, arranged in the air pockets, wherein These Mylar sleeves extend somewhat in the axial direction beyond the conductive film 2 and the essentially close off air pockets formed between the parallel foil parts against the pole pieces 28 'and 30'. As explained above, provides this arrangement ensures greater flexibility of the radially extending parts of the membrane.

The bellows-like structure thus formed can easily be bent into an annular shape, with an equal distance between the substantially parallel parts of the folded membrane being maintained in each case. The membrane may be between the pole pieces 28 ', 30' of the magnets are supported by coaxial Rinee 34 which are formed from rubber or plastic material, each in a suitable manner with the pole pieces 28 'and 30' and connected with the end faces against the radially innermost and outermost parts of the folded membrane 2 rest and at the same time close the small remaining openings of the folded membrane which extend beyond the Mylar sleeves 18. The magnetic circuit can be closed magnetically by ice bridges (not shown) on the inside or outside of the ring arrangement in order to increase the field strength. However, this is not necessary because of the high coercive force of the ferrite material from which the magnets are made.

The ends of the band 2 are connected to a device (not shown) for generating a liörfre- (luent current) in order to generate an oscillation between essentially parallel parts of the membrane and thus radiate sound waves radially inwards and inwards 32 in the opening of the magnetic ring 30 and arranged coaxially to this in order to deflect the sound waves emerging radially inward from the air pockets formed by the membrane 2 in the axial direction; a corresponding, outwardly protruding horn 36 can be connected to the magnetic ring 28.

Instead of a membrane formed from a thin metal band, as mentioned above, a Find thin plastic tape use to which narrow metal bands or wires are attached, the

ίο are connected in series with one another. Such a Series connection is obtained z. B. by putting a narrow metal band or wire 40 in a tight Spiral is braced around a band ring 38, as shown in Fig. 12a, and then this ring 38 folds into a meander shape 38 ', as shown in FIG. 12b is shown. To facilitate the folding of the ring 38 shown in FIG. 12: a into a meander shape of Fig. 12b, recesses 39 (Fig. 13a) at longitudinally spaced locations

so along, opposite longitudinal edges of the plastic tape 38 and at the points are formed where the plastic tape is to be bent into a meander shape, as shown in a development of this tape in Fig. 13a is shown, and the wires 40 can be flattened in the area between the opposing recesses 39, as shown in FIG. 13 a is shown at 40 'so as to facilitate bending of the wires 40 in these areas. The wires 40 can either be used in a suitable manner with the tra lowing plastic tape 38 are connected, or they can be stored between two thin plastic strips that are heat-sealed together get connected. After, as shown in Fig. 12b, the tape 38 is folded into a meander shape has been. the edge pieces 38a (FIG. 13a) between the recesses 39 in the in FIG. 13b bent over to close the cells at opposite ends.

Instead of, as shown in Fig. 12a, a wire in

In a continuous, narrow spiral on the ring-shaped plastic tape, it is also possible to apply several parallel wires or parallel narrow metal tapes closely spaced to a carrier tape made of plastic, before this tape, as shown in FIG. 12 a shown, is formed into a ring, then bend the ends of the plastic tape out of the plane of the ring and then connect these ends, slightly offset from one another, so that one end of a wire on one of the tape ends connected to the corresponding end of the adjacent wire is connected at the other end of the tape, so that the parallel wires at the interconnected ends of the plastic tape are connected to form a continuous spiral.

The ring thus formed with the serially connected pieces of wire arranged thereon is then further brought into the meander shape shown in FIG. 12b. This arrangement is particularly advantageous when the conductive parts of the membrane ah ^r hmaie. parallel, spaced apart conductive parts are formed, which were applied to the strap by vapor deposition. 14 and 15 show a further loudspeaker arrangement according to the invention. Here the meandering membrane parts are held in a direction running transversely to their longitudinal direction under a mechanical tension, as will be described in detail below. The arrival

" ?

The arrangement according to FIGS. 14 and 15 has two bars spaced apart from one another.

manentniagnete 42 on the parallel and spaced bungs 52 provided to the magnetic flux between

are spaced apart, as best seen from the plate 50 and the pole pieces 54 'in the area

14 and a pair of Eud plates 46 focus on the lower ends thereof and

and 50, each transversely to the longitudinal direction of FIG.

Magnets 42 extend to keep them spaced from one another against opposite ends,

which the permanent magnets 42 abut and with the A modification is shown in Fig. 16, where the

sen are connected in a suitable manner. These end pole piece laminates 54, each formed identically

Plates 46 and 50 are made of soft iron: Plates are, as is described for FIGS. 14 and 15,

44 made of non-magnetic material are each on io at their upper and lower ends with the

the opposite sides of the Perma end plates 46 and 50 are connected. the

nentmagnete 42 arranged and connected with these membrane is in turn made of a plastic strap

suitably connected to be molded between their inner 60 'which, as described above, into a

ropes and the insides of the end plates 46 and 50 meander shape is curved, but the parallel parts

to form a prismatic space. Each of the ends 15 of the meander-shaped lanyard 60 'are, as in FIG

plates has several approximately rectangular openings, shown in Fig. 16, corrugated. Longitudinally

gen 48 on. how best the plate 46 of the extending metal strips 62 'are with the im \ ve-

15 shows, and through these openings 48, essential flat parts of these shafts are connected,

the mentioned prismatic space in connection with and these strips 62 'can be in series with one another

the outside of the loudspeaker assembly. Two zo or be connected in parallel.

Rows of spaced poles The membrane parts in Figs. 14 and 15 are in the

Piece laminates 54 and 54 'each protrude from the illustrated substantially parallel to one another. One

Inner sides of the end plates 46 and 50 deviate from each other from parallelism in such a way that

before, and each of the pole piece laminates 54 is of two the membrane portions at their open ends one

outer flat iron strips 56 and an iron strip as further and one at their closed ends

fen 58 formed, which the latter is thinner but wider have a smaller spacing, facilitates a lighter one

than the outer strip 6 pounds to get over the inner and smoother movement of air into the pockets

Ends of the latter protrude inward. Which and from these, especially at high sound

the flattened poles forming the flat iron strips energy levels.

can be connected to one another in a suitable manner The meander-shaped membrane is in the space ringer membrane amplitude, z. B. microphones and between the peeled pole pieces 54 and 54 'on headphones, you can use thinner orderly. It has a thin lanyard 60 made of ferromagnetic layers on the very membranes Plastic that is curved in a meander shape and has narrow, parallel membrane spaces. In the along longitudinal edges, e.g. B. by gluing, with the 35 these layers by the permanent magnetic outer strip 56 of the pole pieces is connected so-called fields induced magnetic polarization directs the such as a central conductive part 62, e.g. B. of membranes parallel to each other in the direction of a thin metal foil that acts on the lines of force and holds them through the uniform Plastic lanyard 60 is applied or from a repulsive forces induced between the same Metal layer z. B. by vapor deposition on the 40 poles in adjacent layers ir the same transfer tape is upset. The inner ends of the stands from each other. Will these be ferromagnetic thin pole piece laminates 58 extend to layers asymmetrically between the permanent maggots Longitudinal edges of the conductive part 62 of the mem- gnets arranged by being closer to the one bran. The laminates 58 must be thin enough to lie pole than the other, so one sided when the membrane vibrates, the effort does not make the effort to direct it ζυ the nearer pole the parts 68 to come into contact. How to pull in. Will the membrane on the other ^ side 14, when the pole piece laminates 54 are held in place, it is subject to a constant deflin Transverse direction with respect to the pole piece laminates 54 'ned force stretched which never diminishes. This( Staggered so that the laminates 54 and 54 'are each up- force is more reliable than the force in an elastic * consecutive, between the parallel parts of the 5 ° elongated membrane, exposed to fatigue Meander-shaped membrane is formed by air pockets. This one-sided magnetic force is a result close their upper and lower ends. How nis the inhomogeneity of the magnetic field close to the 14, the laminates 54 lie on pole pieces. The through the ferromagnetic materia with their upper ends against the inside of the additional mass added to the membrane is small Plate 46 and are connected to this in a suitable manner 55 loudspeakers with membranes of the described Connected while the laminates 54 'have their un- kind at the sound radiation opening in the front a small distance from the inward and backward direction an actual! Side of the plate 50 have to be between the lower air cross section, which is half of the cross section de Ends of the laminates 54 'and the inside of the membrane packing is because half the cross ! Plate 50 to form an air gap 53. Those in this 60 section are open and half are closed The magnetic force generated by the air gap attracts the laminated air pockets. The gradual increase lated pole pieces 54 'towards plate 50 of this half cross-section to its full white tind generated in this way in the lanyard 68 a continuous can be achieved by the fact that the closure mechanical tension in a transverse to its longitudinal elements of the pockets in the form of wedges in de direction running direction, so that a post-65 airspace extends. At the ends of these parts et Leaving the tension of the belt in the transverse direction keeps the full air cross-section. This practice is safely prevented. The end plate 50 is gear is easier to achieve with a smaller to preferably, as shown in FIG. 14, with a number of larger wedges, which are connected to the air pockets in the at

was not coordinated and preferably arranged perpendicular to the pockets. An even more practical one The way to achieve this transition is characterized by curved lobe-shaped parts of constant thickness, forming wedge-shaped curved air spaces resembling the same The purpose of this is to gradually increase the air cross-section. The curved (flat-shaped Parts are very rigid. The arrangement requires less space and is shorter than the one with the wedges.

The continuous transition described here is important. If it is missing, the converter shows an air response at the frequency at which the depth of the air space between the membranes equals one Quarter of the wavelength of the emitted sound.

The loudspeakers described so far are directly driven; i.e., the ladder through which a high frequency of hearing Electricity is sent and subjected to the influence of a magnetic or electrostatic field are either formed by the membrane itself or by conductors that elongate extend the membrane and are attached to this. However, the membrane according to the invention can also find use in a sound transducer in which the membrane parts are driven indirectly, d. H. at an ano. young at the ladder, through which a hearing-stimulated current is sent, to prevent its oscillation to effect in a magnetic field, not attached to the Mcmbranteile itself, but mechanically are connected to the membrane parts in order to cause oscillation of the same.

Such a loudspeaker arrangement is shown in section and in a simplified exploded view in FIGS. As shown in these two figures, the indirectly powered loudspeaker comprises a pair of conventional, permanent magnet sonic coil drive units 64 which are arranged coaxially with one another and axially spaced from one another and each have a permanent magnet 66 and a pair of pole pieces 68 and 70 which between them form an annular gap 72 in which a sound coil 74 of conventional construction is arranged so that it can vibrate when an audible current is sent through it. Non-magnetic spacers 76 bear against the pole pieces 70 and are connected to them, and in the axial space between the spacers 76 a plurality of membrane discs 78 are arranged, which preferably have a shape as best shown in Pig. 18, as well as several approximately U-shaped spacers, which are best shown in FIG. 18 and which are arranged between edge parts of the membrane disks 78 and connected to them in a suitable manner. z. B. by gluing. The U-shaped spacers 80 are arranged so that their open ends point alternately in opposite directions to form, with the membrane disks 78 connected to them, air pockets which open alternately to opposite sides of the loudspeaker.

The sound coils 74 are each alternately connected to successive membrane disks 78 via a plurality of drive rods 82, ie the upper sound coil 74 (with reference to FIG. 17) can e.g. B. be connected by several rods 82 with the uppermost membrane disk 78, and these rods then go through openings 84 of the second membrane disk from top to bottom and are again connected to the third membrane disk, etc., while the lower sound coil 74 via corresponding rods 82 is connected to the membrane disks not driven by the upper sound coil. The sound coils are arranged in a manner known per se in such a way that they vibrate towards and away from one another when an audio-frequency current passes through them, so that the respective upper and lower ones

ίο sound coil 74 connected membrane disks 78 when an auditory-frequency current passes through the sound coils towards and away from one another vibrate in order to generate sound waves that emanate from the air pockets between adjacent Mcmbranplatten emerge through the olTenen ends 81 of the U-shaped spacer element 80, as shown in FIG. 1 8 is indicated by the arrows 86. In Fig. 18, only two U-shapes are shown for the sake of clarity Spacers 80 and two membranes 78 are shown.

If desired, a horn can be attached to one of the sound-emitting openings of the device shown in FIG. 17 shown Gchallwandlers are arranged.

It is also possible to provide only a single sound coil 74, the rods 82 with every second Membrane disk is connected, while the other membrane disks are not mechanically driven will. These non-rubbed sets of washers can be difficult to form in this case, so that it remains practically stationary. Instead of each of the membranes as shown in Figs. 17 and 18, designed as a double cone, it is also possible to use differently shaped membrane disks, and these membrane disks can have hemispherical or otherwise curved surfaces exhibit.

19 shows schematically in an exploded view a headphone or a microphone with a membrane according to the invention. As shown in the illustration of FIG. 19, the microphone shown there can have a pair of circular cover plates 88 made of soft iron, which are provided at a central point with several parallel sound radiation slots 90, as well as a permanent magnet ring 92, which in the finished arrangement with its upper - and the underside lies between the cover plates and is connected to them in a suitable manner. A sound diaphragm 94 made of non-magnetic material with a cylindrical outer surface, the diameter of which corresponds approximately to the inner diameter of the magnetic ring 92, is arranged in its interior and has a central opening of square cross-section, which forms a prismatic space 94 'inside the sound diaphragm. In this space 94 'two sets of pole pieces 96 are arranged, which extend transversely through this space at a distance from one another and are each in abutment with the upper and lower cover plates 88 and connected to them in a suitable manner. A meandering membrane, which can have a thin carrying strap 98 and wires 100 connected to it in the manner described above, forms a plurality of air pockets between the parallel parts of the meandering band, which are alternately closed at the top and bottom by the pole pieces 96; this membrane is arranged between the pole pieces 96. The meandering strap 98 is, for. B. by gluing, connected on its upper and lower longitudinal edges with the respective padding.

the. Instead of a meander Trugebancl to use isi us also possible to have multiple Hache sleeves (on the type of tube sections) to use Clie are arranged parallel and at a distance from each other and provided with a tightly wound wire spiral are each. The wire spirals on each sleeve are then connected in series or in parallel with one another, and a pair of conductors are connected in a known manner, not shown in FIG. 19, to a device for generating an audible current. Elei such an arrangement, the pole pieces 96 of the upper set can close the upper linden of the sleeves, while the pole mosquito of the lower set 96 can be arranged so that they open up the spaces between benachbarlcn sleeves at the lower ends thereof \. When an audio-frequency current passes through the conductors carried by the membrane, the parallel parts of the meander-shaped membranes or the parallel parts of the flat sleeves vibrate towards and away from one another, so that sound waves are radiated through the slots 90 in the upper and lower cover plates 88.

Of course, the converter constructions described above and their various Features, individually or in combination, also for other types of loudspeakers, microphones Od. The like. Find use with advantage.

Claims (35)

30 claims: 1. Acoustic transducer, preferably an electroacoustic transducer, with a membrane arrangement, which has a plurality of at least partially oscillatable membrane parts which between adjacent recesses that open on opposite sides are formed, characterized in that the recesses are designed as narrow air pockets that the vibratable membrane parts so are interconnected that adjacent air pockets at opposite ends are alternately closed and open, and that the opposite membrane parts are driven in phase opposition. 2. Converter according to claim 1, characterized in that the membrane arrangement is a single one Has membrane in which the vibratable parts at a distance from each other approximately parallel planes are arranged and each on an edge with the vibratable part on one side and on the other edge with the vibrating part on the other Side are fully connected by arcuate connectors so that they form a meandering membrane. 3. Converter according to claim 2, characterized in that the arcuate connecting parts are essentially in two parallel Planes are arranged which extend approximately perpendicular to the vibratable parts. 4. Converter according to claim 2 or 3, characterized in that the arcuate connecting parts are arranged essentially in two concentric circles. 5. Converter according to one of the preceding claims, characterized in that the air pockets are closed in a suitable manner on opposite longitudinal edges of the membrane. fi. Converter according to one of the preceding claims, characterized in that the Diaphragm arrangement has a plurality of vibratory diaphragms (78) spaced from one another and are arranged at least almost parallel to one another, and that each spacer pieces (80) are arranged between the membranes and are connected to edge parts thereof in such a way that adjacent, between adjacent membranes (78) formed air pockets and the associated with them Spacers (80) alternate on opposite sides of the membrane assembly to open. 7. Converter according to claim 6, characterized in that the spacers (80) are approximately U-shaped are formed and that the open ends (81) of adjacent U-shaped spacers in point in opposite directions. 8. Converter according to one of the preceding claims, characterized in that the Membrane assembly has endless membrane members, the a pair of elongated, approximately parallel and have vibrating parts arranged at a distance from one another, which over short connectors are fully interconnected to form one inside each link These air pockets form that the links are spaced apart in a row are in order to have a different one of these air pockets between each pair of adjacent links form, and that one air pockets at one end of each link and the other air pockets at the other end of each adjacent pair of links in a suitable manner are locked. 9. Converter according to one of the preceding claims, characterized in that the vibrating membrane parts with a suitable device (e.g. 72, 74) in operative connection stand that the vibrations acted upon by sound waves in the membrane parts converts electrical energy, and vice versa. in. Transducer according to claim 9, characterized in that the device has at least one iciter (40. 40 ': 74) which is connected to the vibratable membrane parts, as well as a device cooperating with the conductor to generate a flux in order to of alternating current signals to this conductor to generate sound wave-generating vibrations of these membrane parts and vice versa. 11. Converter according to claim in, characterized in that the device for generating a flux is designed as a device (24, 26; 28, 30; 42, 46, 50; 64, 66, 68; 92) for generating a magnetic field, so that when an audible current is sent through the conductor, sound wave-generating vibrations are generated by the vibratory membrane parts, and vice versa. 12. Converter according to claim 10, characterized in that the device for generating a flow as a device (22) for generating an electrostatic oil ^; e | cles is designed so that when a hearing frequency voltage is applied to the conductor (20), sound wave-generating vibrations are generated by the vibratable memhran elements, and vice versa. 13. Converter according to one of claims H) to 12, characterized in that the conductor uls wires (40) are formed extending along the membrane disorder and from these are worn. 14. Converter according to claim 13, characterized in that that the wires (40) are connected together to form a coil. 15. Converter according to claim 13 or 14, characterized in that the wires for formation several coils (74) connected in series are connected to one another. 16. Converter according to one of claims 10 to 12, characterized in that the conductor a thin base made of electrically conductive material has, which at least partially with the vibratable parts of the membrane assembly connected is. 17. Converter according to one of claims 10 to 12, characterized in that the membrane arrangement comprises a thin band formed from electrically conductive material which forms the conductor. 18. Converter according to one of claims 10 to 12, characterized in that the membrane arrangement is formed from plastic material and that the conductor is a layer applied to at least part of the plastic material made of electrically conductive material. \ '). Transducer according to one of the preceding claims, characterized in that a device connected to the vibratable membrane parts is provided in order to make them vibrate and thus to generate sound waves emerging from the open ends of the air pocket. 20. Converter according to claim 19, characterized in that said device for generating vibrations has an electromagnetic arrangement which is mechanically connected to ikn vibratable parts. 21. Converter according to claim 20, characterized in that that the electromagnetic arrangement is movable in a magnetic field (66; 92) Has Sehallspule (74; 100). 22. Converter according to one of the preceding claims, characterized in that a permanent magnet arrangement is provided for generating a magnetic field which defines a space in communication with the outside atmosphere, that the membrane arrangement is arranged in this space and has adjacent, at least partially vibrating parts which form between them narrow, adjacent air pockets which are open on opposite sides, that the vibrating parts are connected in a suitable manner so that adjacent air pockets at opposite ends are alternately closed and left open, and that at least one conductor in the magnetic Field is arranged and at least connected to the vibratory parts in order to cause the vibratory parts to vibrate when an audible-frequency current passes through this conductor to generate sound waves radiated through the open ends of the air pockets, and vice versa rt. 23. Converter according to claim 22, characterized in that the conductor extends along the Membrane assembly extends and is supported by this. 24. Converter according to claim 23, characterized in that the diaphragm arrangement is the Has the shape of an elongated, meandering band. 25. Converter according to claim 23 or 24, characterized in that at least two elongated Permanent magnets (24) are provided, which are at least almost parallel and at a distance are arranged from each other that two sets of pole pieces (26) are also provided which are at least almost parallel and at a distance from one another transversely between opposite ones Sides of the permanent magnets (24) extend and form a space between the latter, in Your is the membrane assembly (10, 12), and that this space with the outside atmosphere relating to the spaces between the pole pieces of each set of pole pieces dung stands. 26. Converter according to claim 24, characterized in that that two ring-shaped permanent magnets (28, 30) are provided, which are spaced are arranged from each other along a common axis that the membrane assembly forming meander-shaped band (2) in a coaxial with the ring magnets (28, 30) Ring is arranged in the space between these magnets and that an arrangement (34) for elastic Mounting of the membrane arrangement (2) on the mutually facing sides of the permanent magnets (28, 30) and to close the between the vibrating parts of the Membrane assembly located air pockets in the direction of these sides is provided. 27. Converter according to claim 26, characterized in that that a sound-reflecting cone (32) is provided in one of the ring magnets (30) is and protrudes with its tip in the direction of the other ring magnet (28), and that a Horn (36) extends outwardly from this other magnet (28). 28. Converter according to claim 24, characterized in that two permanent magnets (42) are arranged at least almost parallel and at a distance from one another and each have two opposite end surfaces and a side surface, the latter opposite the other of the two magnets (42), that two non-magnetic Plates (44) are provided and bear against one or the other of the side surfaces of the magnets (42) that two end plates ?! (46, 50) made of magnetizable material rest against one or the other of the two end faces of the two magnets, extend between the latter and are each provided with sound passage openings (48) so that two sets of buttock laminates (54, 54 ') move into the space between the non-magnetic plates (44) from the end plates (46, 50) towards one another te , 003 stretch so that the meander-shaped band forming the membrane arrangement (60) is connected to the sets of pole piece laminates (54, 54 ') on opposite long edge parts and that the pole piece laminates of one set are offset with respect to those of the other set, in order to alternately close the air pockets formed between the vibrating parts of the membrane arrangement at their edges facing the end plates (46, 50). 29. Converter according to claim 28, characterized in that the diaphragm arrangement is a Has carrying strap (60) made of plastic, which at the edges with the pole piece laminates (54, 54 ') is connected, and that a thin metal band (62) is provided as a conductor, which is connected to a middle The longitudinal part of the lanyard (60) is connected, and that the pole piece laminates (54, 54 '), respectively two outer plates (56) with inner ends ending shortly before the metal band (62) as well one arranged between these two plates (56) and compared to them you imere Have middle plate (58) extending beyond the outer plates (56) in the area of the respective Edge of the metal band (62) extends. 30. Converter according to claim 28 or 29, characterized in that the pole piece laminates (54) of a set rest at their outer ends against one of the end plates (46) and with this are connected, while the outer ends of the pole piece laminates (54 ') of the other set are separated from the other end plate (50) by a small air gap (53) so that they be pulled magnetically against this, causing the plastic lanyard (60) in a transverse to its The longitudinal direction is spanned. 31. Converter according to claim 30, characterized in that the other end plate (50) zwisehen the pole piece laminates (54 ') of the other set are provided with notches (52). 32. Converter according to claim 22, characterized in that that two permanent magnet arrangements (64) are provided and coaxial with one another are arranged and each form an annular air gap (72) in which a magnetic field is generated is that the membrane assembly is a plurality of spaced apart, at least has nearly parallel diaphragms (78) which form the vibratable parts and are coaxial are arranged with the permanent magnet arrangements between these that U-I'-shaped Uisianzstüeke (80) arranged between adjacent membranes (78) and with peripheral parts thereof are connected to connect the schwingungsiühigen parts together that the U-shaped Spacers (80) each have an ollen linden tree so that the spacers (80) are arranged in such a way are that the olive ends (81) are consecutive Spacers point in opposite directions, and that sound coils as conductors (74) are provided, one of which in each case in one of the two of the permanent niagnet arrangements (64) formed air gap (72) is arranged, and that rigid members (82) for alternating Connection of the sound coils (74) with successive membranes (78) is provided are. 33. Converter according to claim 32, characterized in that the membranes (78) each an approximately conical-.! Have middle part. 34. Converter according to Anspiach 24, characterized in that that the permanent magnet arrangement has an annular permanent magnet (92) with opposite end faces, that a cover plate (88) made of magnetizable material against one of these end faces rests and is provided with openings (90) which communicate with the space inside the ring magnet (92) communicating, and that two sets of pole pieces (96) from one and the other, respectively Cover plate (88) protrude into this space so that the meander-like shape forming the membrane arrangement Band (98) with the conductor arrangement (100) carried by it on opposite sides Longitudinal edge parts connected to the inner ends of the pole pieces, and that the pole pieces of one set are offset from those of the other set so that the pole pieces of each Set alternately the open ends of the cover plates (88) facing from the meander-shaped Close the air pockets formed by tape (98). 35. Converter according to claim 34, characterized in that the ring magnet (92) is cylindrical Has inner surface in which a sound diaphragm (94) made of non-magnetic material is arranged, which in turn has a central opening (94 ') of approximately square cross-section and that the two sets of pole pieces (96) with the one in between meandering band (98) are arranged in this central opening (94 '). For this purpose 3 sheets of drawings