Patent Application
20230403512
This patent application claims priority from Austrian patent application No. A50411/2022, filed Jun. 10, 2022, the disclosure of which is incorporated herein, in its entirety, by reference.
The invention relates to a speaker, which comprises a coil arrangement with at least two voice coils, a magnet system and a membrane. Each of the voice coils has an electrical conductor in the shape of loops running around a coil axis in a loop section. The voice coils are annular when viewed in a direction parallel to the coil axis, each have an inner circumference and an outer circumference and are arranged over one another in said direction. The magnet system is designed to generate a magnetic field transverse to the conductors of the voice coils in the loop section. The membrane is fixed to the coil arrangement and directly or indirectly to the magnet system. The membrane forms a first connector between the coil arrangement and the magnet system with a first compliance, and the membrane together with the coil arrangement causes a first resonance frequency for an oscillation of the membrane in a direction parallel to the coil axis.
Moreover, the invention relates to an electronic sound signal circuit, which comprises a sound input, which is designed to receive a sound input signal, and at least two sound outputs, which each are designed to feed a coil signal to one of the voice coils of a coil arrangement of a speaker.
Additionally, the invention relates to a sound system, which comprises an electronic sound signal circuit and a speaker of the above kind, wherein the sound outputs of the electronic sound signal circuit each are connected with a voice coil of the coil arrangement.
Finally, the invention relates to a method of manufacturing a coil arrangement, which comprises the steps of:
A speaker, an electronic sound signal circuit, a sound system and a manufacturing method of the above kinds are generally known in prior art.
An electrical sound input signal fed to the voice coil generates a force in the magnetic field of the magnet system and causes a movement between the coil arrangement and the magnet system. In turn the membrane moves according to the electric sound input signal. As a consequence, sound corresponding to the electric sound input signal is emanated from the membrane.
There is a general ambition to reduce power consumption and to improve efficiency of technical devices. This is particularly true for mobile devices, the operating time of which substantially depend on the efficiency of the inbuilt systems. So, there is also an ambition to reduce power consumption and to improve efficiency of sound systems in general and in particular of sound systems of mobile devices.
Thus, it is an object of the invention to provide a better speaker, a better electronic sound signal circuit, a better sound system and a better manufacturing method. In particular, the efficiency of the sound system shall be improved.
The object of the invention is solved by a speaker as defined in the opening paragraph, wherein the speaker in addition comprises a second connector with a second compliance, wherein the second connector connects the voice coils of the coil arrangement, wherein the second connector together with the voice coils of the coil arrangement causes a second resonance frequency for the oscillation of the membrane in a direction parallel to the coil axis and wherein the second resonance frequency is above the first resonance frequency.
Moreover, the object of the invention is solved by an electronic sound signal circuit as defined in the opening paragraph, wherein the electronic sound signal circuit is designed to output coil signals corresponding to the sound input signal in terms of their time course but being phase shifted to each other, wherein the phase shift depends on the frequency of the sound input signal.
In addition, the object of the invention is solved by a sound system, which comprises an electronic sound signal circuit and a speaker of the above kind, wherein the sound outputs of the electronic sound signal circuit each are connected with a voice coil of the coil arrangement.
Finally, the object of the invention is solved by a manufacturing method as defined in the opening paragraph, wherein the voice coils are moved to each other until a desired gap between the same is obtained, wherein the glue layer or glue pads reach(es) to the inner circumferences of the voice coils at each position of a desired glue bead arranged on the inner circumferences of the voice coils and to the outer circumferences of the voice coils at each position of a desired glue bead arranged on the outer circumferences of the voice coils and wherein additionally the voice coils of the coil arrangement are connected by applying glue beads to the voice coils at the aforementioned positions.
By the above measures, the speaker provides a second resonance frequency, by which the frequency response of the speaker can be influenced and improved. The second resonance frequency is above the first resonance frequency and hence the frequency response of the speaker can be improved at higher frequencies. To achieve that, the voice coils receive coil phase shifted coil signals. By doing so, the sound system can be tuned or designed in a way that the frequency response gets a peak at the second resonance frequency. At the same time, the power consumption of the sound system is reduced at this second resonance frequency. Accordingly, overall efficiency can be improved by the proposed measures. In addition, the proposed method allows for provision of an advantageous coil arrangement for a speaker or sound system of the above kind. In detail, the glue layer or glue pads hinder the glue beads from reaching into the gap between the voice coils what could deteriorate the quality of the output sound.
Generally, the first resonance frequency results from a common movement of the voice coils, whereas the second resonance frequency results from a movement of the voice coils relative to each other or with different speeds respectively. The membrane oscillation in question refers to its piston movement. It should also be noted that additional factors, which influence the first resonance frequency and the second resonance frequency shall not be excluded, but anyway the first resonance frequency is mainly caused by the membrane together with the coil arrangement and the second resonance frequency is mainly caused by the second connector together with the voice coils.
The proposed measures apply to speakers in general and particularly to micro speakers, whose membrane area is smaller than 600 mm2 and/or whose back volume is in a range from 200 mm3 to 2 cm3. Such micro speakers are used in all kinds of mobile devices such as mobile phones, mobile music devices, laptops and/or in headphones. It should be noted at this point, that a micro speaker does not necessarily comprise its own back volume but can use a space of a device, which the speaker is built into, as a back volume. That means, the speaker does not necessarily comprise its own (closed) housing but can comprise just an (open) frame. The back volume of the devices, which such speakers are built into, typically is smaller than 10 cm3.
The electrical conductor of the voice coils can have a circular cross section and form a coil wire or can be flat and form a coil foil. A diameter of a coil wire of micro speakers beneficially is ≤110 μm. The electrical conductor can also comprise a (electrically insulating) coating on the metal core as the case may be. The coil foil can be stacked with a glue layer in-between to form a voice coil. The second connector may also comprise a plurality of wires electrically connecting the voice coils of the coil arrangement.
Beneficially a distance or gap between adjacent voice coils in their idle position is in range of 5 to 150 μm when measured in a direction parallel to the coil axis. In this way, the efficiency of the speaker at high frequencies can be improved in a good way.
The proposed measures in particular apply to speakers, wherein the coil arrangement comprises a first voice coil, which is mounted to the membrane, and a second voice coil, which is connected to the first voice coil by the second connector. In other words, the proposed measures in particular apply to speakers with just two voice coils where the coil arrangement forms a two-mass spring system. However, the proposed measures also apply to more complex systems with more than two voice coils oscillating to each other. Such a system then has more than a second resonance frequency. Accordingly, the frequency response of a speaker can be influenced even more then.
Further details and advantages of the proposed speaker, the proposed electronic sound signal circuit, the proposed sound system and the proposed manufacturing method will become apparent in the following description and the accompanying drawings.
Beneficially, the second resonance frequency is below 30 kHz. In this way, the peak of the frequency response of the speaker at the second resonance frequency, considered it is broad enough, can reach into the region of audible sound and improve the efficiency of the speaker at very high frequencies. To improve said effect, the second resonance frequency may also be below 25 kHz and even below 20 kHz. However, one should note that the proposed speaker, the proposed electronic sound signal circuit, the proposed sound system and the proposed manufacturing method in principle also apply to ultrasonic systems.
Beneficially, the second resonance frequency is at least three times higher than the first resonance frequency, in particular at least ten times higher than the first resonance frequency. In this way, the first resonance frequency and the second resonance frequency and their associated peaks in the frequency response of the speaker are considerably spaced from each other.
Beneficially, a variable K1 in the equation
K
1
=c
1·(m1+m2+m3)
Furthermore, it is beneficial if a variable K2 in the equation
Beneficially, a stiffness or spring constant of the second connector can be set in a range of 0.01 N/μm to 0.1 N/μm or a compliance of the second connector can be set in a range of 10 μm/N to 100 μm/N respectively. These measures also support a peak of the frequency response of the speaker in a useful range.
Beneficially, a quality factor of the second resonance frequency caused by the second connector is in a range of 1 to 20. These measures support a peak of the frequency response of the speaker with an advantageous width and avoid distortions of the output sound respectively.
In one embodiment of the speaker, the second connector is embodied as or comprises a glue layer between the voice coils of the coil arrangement. Here, the glue layer fully covers connection areas of the voice coils, which connection areas face each other and are oriented perpendicular to the coil axis. By the proposed measures, a long lasting connection of the voice coils is obtained.
Alternatively, the second connector can comprise a plurality of sub parts, which each is embodied as or comprises a glue pad connecting the voice coils of the coil arrangement. The glue pads partly cover connection areas of the voice coils, which connection areas face each other and are oriented perpendicular to the coil axis. By the proposed measures, a long lasting connection of the voice coils is obtained, too. However, the spring constant of the second connector can be decreased in view of a glue layer of the same material, which fully covers connection areas of the voice coils.
Advantageously, the glue layer or glue pads is/are made of plastics having a Shore hardness from 00-5 to A-20 and/or an elongation at tear of more than 100%. Shore hardness is a measure indicating how soft or how rigid the material is. The Shore 00 scale is used for extra soft materials, the Shore A scale is used for soft materials and the Shore D scale is used for semi-rigid and hard materials. Accordingly, a comparable soft material is proposed for the glue layer or glue pads, which does not contribute much to a spring constant of the second connector.
It should be noted that a “glue layer” or a “glue pad” in the context of this disclosure in particular includes glues, which are applied on the voice coils in the liquid or pasty form, as well as strips or pads with an adhesive layer on one or both sides. Said strips or pads can be made of a continuous or foamed material. Accordingly, a “glue layer” or a “glue pad” in the context of this disclosure also includes “gaskets” (whose sealing function is not in the focus here).
In another embodiment, the second connector comprises a plurality of sub parts, which each is embodied as or comprises a glue bead connecting the voice coils of the coil arrangement at their inner circumferences or outer circumferences. In particular, the glue beads can run in a direction parallel to the coil axis. In this way, the voice coils are connected to each other by a kind of “glue posts”. By variation of a count, a cross section and a material of the glue beads, the spring constant of the second connector can be influenced in a very good way.
Advantageously, the glue beads are made of plastics having a Shore hardness from A-20 to D-50 and/or an elongation at tear of more than 200%. In this way, the glue beads can considerably contribute to the spring constant of the second connector despite a comparably small cross sectional area of the same.
In yet another embodiment, the second connector comprises a plurality of sub parts, which each is embodied as a strip connecting the voice coils of the coil arrangement and which runs along the inner circumferences or outer circumferences of the connected voice coils and is attached thereto. A “strip” is a body, which has a thickness extending in a first orthogonal direction, a width extending in a second orthogonal direction and a length extending in a third orthogonal direction, wherein the width and the length of the strip are substantially larger than its thickness. The length may be substantially larger than the width in case of that the strip is long, but the length may also be the same as the width in case of that the strip is short. It should be noted that the strip running along the inner circumferences or outer circumferences of the connected voice coils may get a more complex spatial shape with different total extensions, e.g. when it does not run straight but along roundings or corners. However, within small sections the above stays true. In particular, the strip can have an adhesive layer, by which the same is attached to the voice coils. By variation of a count, a cross section and a material of the strips, the spring constant of the second connector can be influenced in a very good way, too.
Advantageously, the strip can comprise one or more corrugations. In this way, the compliance of the strip can be influenced by giving the same a special shape. In particular a corrugation can run along a gap between the voice coils of the coil arrangement. In this way, similar spring characteristics both for tension (i.e. when the voice coils move away from each other) and compression (i.e. when the voice coils move towards each other) can be obtained.
Beneficially, the thickness of a strip can be in a range of 5 μm to 50 μm. in particular in a range of 5 μm to 20 μm. By these measures, the strip has enough long term stability and provides spring characteristics in a useful range.
Advantageously, the strip can be made of or comprise a thermoplastic elastomer with a Young's Modulus of 2 MPa to 2 Gpa or a thermoplastic with a Young's Modulus of 100 MPa to 12 Gpa. By these measures, the strip has enough long term stability and provides spring characteristics in a useful range as well.
“Plastic” in the given context in particular can be: (a) any member of the group of thermoplastics; (b) any combination of one or more of thermoplastic layers with one or more layers of acrylate, urethane, rubber, silicone or silane-modified polymer; (c) any member of the group of thermoplastic elastomers (TPE) or thermoplastic rubbers respectively; (d) any combination of one or more of thermoplastic elastomer layers with one or more layers of acrylate, urethane, rubber, silicone or silane-modified polymer; (e) any blend of thermoplastic elastomers; (f) any member of the group of rubbers and in particular silicone rubbers; (g) any combination of one or more layers of silicone rubbers with one or more layers of acrylate, urethane, rubber, silicone or silane-modified polymer; or (h) any combination of thermoplastics layers and/or thermoplastic elastomers and/or silicone rubbers and/or acrylate, urethane, rubber, silicone or silane-modified polymer layers.
“Thermoplastics” in the above context in particular can be Polyether ether ketone (PEEK, PEAK), Polycarbonate (PC), Polyetherimide (PEI), Polyethylene terephthalate (PET), Polyethylene naphthalate (PEN) or Polybutylene terephthalate (PBT).
“Thermoplastic elastomers” or “thermoplastic rubbers” in the above context in particular can be thermoplastic polyurethanes (TPU) or thermoplastic copolyester (TPC, TPE-E).
In case of silicone rubbers, the same may be provided as silicone sheets or can be sprayed.
In yet another embodiment, the second connector can comprise a plurality of sub parts, which each is embodied as a first spring arm connecting or coupling the voice coils of the coil arrangement and which together form a first spring arrangement. In particular, the first spring arms can be made of or comprise a metal. “Metals” in the given context in particular can be aluminum and its alloys, copper, and its alloys and stainless steel. In this way, very good spring characteristics can be obtained for the second connector.
Beneficially, the speaker can additionally comprise an arrangement of second spring arms each having a first end and a second end, wherein each of the second spring arms at its first end connects to the second voice coil, at its second end connects to a frame of the speaker and at a connecting point displaced from both end points connects to a first spring arm of the first spring arrangement. In this way, the movement of the coil arrangement can be stabilized and the first and second resonance frequency can be influenced. In particular, the second spring arms can act as a suspension system. The second spring arms can also be seen as a third connector between the coil arrangement and the common frame, which increases the first resonance frequency for the oscillation of the membrane in a direction parallel to the coil axis without further measures. To keep the first resonance frequency low, the first connector should be made softer in accordance with the added stiffness of the third connector. In particular, the second spring arm can be made of or comprise a metal. “Metals” in the given context in particular again can be aluminum and its alloys, copper, and its alloys and stainless steel.
In a very advantageous embodiment, the voice coils can be shaped like a polygon when viewed in a direction parallel to the coil axis, wherein the sub parts are arranged in the corners of the polygon, in particular exclusively arranged in the corners of the polygon. That means one or more glue pads, one or more glue beads, one or more stripes and/or one or more first spring arms can be arranged in a corner of a polygonal coil. In this way the sub parts are arranged in a region where the magnetic flux usually is not very high and hence does not contribute to a movement of the voice coils much anyway.
In another advantageous embodiment, the voice coils are shaped like a polygon when viewed in a direction parallel to the coil axis, wherein the sub parts are arranged at the longitudinal sides of the polygon, in particular exclusively arranged at the longitudinal sides. That means one or more glue pads, one or more glue beads, one or more stripes and/or one or more first spring arms can be arranged at the longitudinal sides of a polygonal coil. In this way, in particular lengthy sub parts like stripes can be used for connecting the voice coils.
Generally, a glue layer or glue pads, glue beads, strips and first spring arms may be used alone in any desired combination. For example, in very advantageous solution, the second connector comprises a glue layer or glue pads between the voice coils of the coil arrangement and the second connector in addition comprises glue beads, which connect the voice coils of the coil arrangement at their inner circumferences or outer circumferences. By these measures, the advantageous features of a glue layer or glue pads and glue beads are combined. For example, the glue layer or glue pads can consist of a very soft material, whereas the glue beads can be formed by a stronger material.
It is very advantageous in the above context if the glue layer or the glue pads reach to the inner circumferences of the voice coils at each of the glue beads being arranged on said inner circumferences, and reach to the outer circumferences of the voice coils at each of the glue beads being arranged on said outer circumferences.
In this embodiment, glue layer or glue pads hinder the glue beads from reaching into the gap between the voice coils what could deteriorate the quality of the output sound. At this point, reference is also made to the proposed manufacturing method.
Beneficially, the voice coils are shaped like a polygon when viewed in a direction parallel to the coil axis and the glue pads and the glue beads are arranged in the corners of the polygon. In other words the voice coils are shaped like a polygon when viewed in a direction parallel to the coil axis, wherein the second connector comprises a glue layer or glue pads between the voice coils of the coil arrangement arranged in the corners of the polygon, and wherein the second connector in addition comprises glue beads, which connect the voice coils of the coil arrangement at their inner circumferences or outer circumferences and which are arranged in the corners of the polygon, too. In this way the given sub parts are arranged in a region where the magnetic flux usually is not very high and hence does not contribute to a movement of the voice coils much anyway.
In yet another beneficial embodiment, the second connector in addition can comprise a plurality of strips connecting the voice coils of the coil arrangement which run along the inner circumferences or outer circumferences of the connected voice coils at the longitudinal sides of the polygon and which are attached thereto. In this way, the stability of the coil arrangement can be improved. In particular, corrugated strips can be used so that the same provide similar characteristics both for tension and compression.
In another advantageous embodiment, the voice coils are shaped like a polygon when viewed in a direction parallel to the coil axis, the second connector comprises a glue layer or glue pads between the voice coils of the coil arrangement arranged in the corners of the polygon, and the second connector in addition comprises a plurality of strips connecting the voice coils of the coil arrangement which run along the inner circumferences or outer circumferences of the connected voice coils at the longitudinal sides of the polygon and which are attached thereto. By these measures, the advantageous features of a glue layer or glue pads and strips are combined. For example, the glue layer or glue pads can consist of a very soft material, whereas the strips can be formed by a stronger material.
Generally, the voice coils can be identical or can be different. If they are identical, the manufacturing of the coil arrangement can be eased. If they are different, the frequency response of the speaker can further be influenced. For example, the voice coils may be made of different materials, may have different numbers of windings, may have different mass and/or may have different height.
Beneficially, the phase shift in an electronic sound signal circuit can be <5° below a threshold frequency and then can rise above the threshold frequency. In that, the generation of a considerable peak in the frequency response of the speaker at the second resonance frequency is supported.
Furthermore it is beneficial if the threshold frequency is between the first resonance frequency and the second resonance frequency. In that, the generation of a considerable peak in the frequency response of the speaker at the second resonance frequency is supported as well. For example, the threshold frequency can be in a range from 3 kHz to 6 kHz.
Beneficially, the electronic sound signal circuit can comprise an electronic phase shifter, which is provided to perform the phase shifting of the coil signals. In this way, proven means are used to perform the desired phase shifting. For example, the electronic phase shifter can be embodied as an allpass filter, which can be realized by passive or active analog circuits as well as by digital circuits. The non phase shifted coil signal may be delayed by a delay circuit to consider a phase-independent delay of the electronic phase shifter (i.e. a delay, which is also existent at a phase shift of 0°).
In an advantageous embodiment of the electronic sound signal circuit, the maximum coil signals output by the electronic sound signal circuit are smaller than coil signals, which cause a body contact between the voice coils of the coil arrangement. By these measures, quality of output sound is not deteriorated by body contact of the voice coils.
In one embodiment, the at least two sound outputs of the electronic sound signal circuit each can be formed by two wires per voice coil. In detail, a first amplifier of the electronic sound signal circuit can be connected to the first voice coil by means of two wires, and a second amplifier of the electronic sound signal circuit can be connected to the second voice coil by means of further two wires.
In another very advantageous embodiment of the electronic sound signal circuit, the at least two sound outputs each are formed by a first single wire per voice coil and a second common wire, which is shared between two voice coils. So, in view of the aforementioned embodiment, one sound output and one wire can be saved. For example, three half bridges each having two serial transistors can be connected to the sound outputs of the electronic sound signal circuit. It should be noted in this context that load or current carried by the half bridge connected to the common sound output or common wire may reach twice the load or current carried by the other half bridges. Accordingly, the common half bridge can be made with transistors, which allow for a higher current than the transistors of the other half bridges. It is also possible to use the same transistors for all half bridges and to double the common half bridge. That means that there are two parallel common half bridges then. In that, production of the electronic sound signal circuit can be eased. One another possibility for using the same transistors is to overdimension the transistors of the half bridges connected to the single outputs or wires.
These and other aspects, features, details, utilities, and advantages of the invention will become more fully apparent from the following detailed description, appended claims, and accompanying drawings, wherein the drawings illustrate features in accordance with exemplary embodiments of the invention, and wherein:
Like reference numbers refer to like or equivalent parts in the several views.
Various embodiments are described herein to various apparatuses. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims.
Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment,” or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment,” or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional.
It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the content clearly dictates otherwise.
The terms “first,” “second,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
All directional references (e.g., “plus”, “minus”, “upper”, “lower”, “upward”, “downward”, “left”, “right”, “leftward”, “rightward”, “front”, “rear”, “top”, “bottom”, “over”, “under”, “above”, “below”, “vertical”, “horizontal”, “clockwise”, and “counterclockwise”) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the any aspect of the disclosure. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.
As used herein, the phrased “configured to,” “configured for,” and similar phrases indicate that the subject device, apparatus, or system is designed and/or constructed (e.g., through appropriate hardware, software, and/or components) to fulfill one or more specific object purposes, not that the subject device, apparatus, or system is merely capable of performing the object purpose.
Joinder references (e.g., “attached”, “coupled”, “connected”, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.
All numbers expressing measurements and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about” or “substantially”, which particularly means a deviation of ±10% from a reference value.
An example of a speaker 1 is disclosed by use of the
The speaker 1 comprises a coil arrangement 2 with at least two voice coils 3a, 3b, wherein each of the voice coils 3a, 3b has an electrical conductor in the shape of loops running around a coil axis A in a loop section, wherein the voice coils 3a, 3b are annular when viewed in a direction parallel to the coil axis A, wherein the voice coils 3a, 3b each have an inner circumference and an outer circumference and wherein the voice coils 3a, 3b are arranged over one another in said direction. For example, a diameter of a metal core of the electrical conductor of the voice coils 3a, 3b can be ≤110 μm and/or the electrical conductor can also comprise an (electrically insulating) coating on the metal core. Alternatively, also a metal foil may be used for the electrical conductor. In this example, the voice coils 3a, 3b are shaped like a polygon when viewed in a direction parallel to the coil axis A. In particular, the voice coils 3a, 3b are rectangular. However, other shapes are possible as well. For example, the voice coils 3a, 3b may be oval or circular or may have a different number of corners.
Furthermore, the speaker 1 comprises a magnet system 4, which is designed to generate a magnetic field B transverse to the conductors of the voice coils 3a, 3b in the loop section. The magnet system 4 in this example comprises a center magnet 5 and outer magnets 6 as well as a center top plate 7 from soft iron, an outer top plate 8 from soft iron and a bottom plate 9 from soft iron. The center magnet 5 is mounted to the bottom plate 9 and to the center top plate 7, and the outer magnets 6 are mounted to the bottom plate 9 and to the outer top plate 8.
Moreover, the speaker 1 comprises a membrane 10, which in this example comprises a flexible membrane part 11 and a rigid membrane part 12 in the shape of a plate. However, the rigid membrane part 12 is just optionally and may be omitted. In this case, the membrane 10 comprises only a flexible membrane part 11 or is flexible as whole respectively. The membrane 10 is fixed to the coil arrangement 2 and to the magnet system 4. Accordingly, the membrane 10 forms a first connector between the coil arrangement 2 and the magnet system 4 and has a first compliance based on its flexible membrane part 11. In more detail, the membrane 10 is fixed to the coil arrangement 2 and to the magnet system 4 at its backside. At the backside of the membrane 10 an optional back volume F may be formed like this is the case in the example of
In this example, the speaker 1 comprises an optional frame 13, via which the membrane 10 (concretely its flexible membrane part 11) is fixed to the magnet system 4. Hence, the membrane 10 is indirectly fixed to the magnet system 4 in this example. However, the membrane 10 may also directly be fixed to the magnet system 4 in an alternative embodiment. In the latter case, a frame 13 may be omitted.
In addition, the speaker 1 comprises a second connector 14a, which connects the voice coils 3a, 3b of the coil arrangement 2 and which has a second compliance. Because of its compliance, the second connector 14a allows a relative movement of the voice coils 3a, 3b to each other in an excursion direction C parallel to the coil axis A.
In this embodiment, the second connector 14a is embodied as a flexible glue layer between the voice coils 3a, 3b of the coil arrangement 2. However, there are various possibilities to embody the second connector 14a which are disclosed later in detail. For example, a second connector in general may be embodied by or may comprise glue pads, strips, glue beads and first spring arms, which connect or couple the voice coils 3a, 3b and which form a first spring arm arrangement.
Finally, the speaker 1 comprises an optional second spring arm arrangement 15, which comprises a plurality of second spring arms (or legs or levers) 16 connecting the coil arrangement 2 and the magnet system 4 and which like the flexible membrane part 11 allows a relative movement between the coil arrangement 2 and said magnet system 4 in the excursion direction C parallel to the coil axis A. In this example, the second spring arm arrangement 15 comprises two spring arm sub arrangements each having two second spring arms 16. Alternatively, single second spring arms 16 or a spring arm sub arrangement with even more (e.g. four) second spring arms 16 can be used. In particular, the second spring arms 16 can act as a suspension system.
In this example, the membrane 10 (in detail its flexible membrane part 11), the outer magnets 6, the outer top plate 8 and the bottom plate 9 are mounted to the frame 13. However, the frame 13 may be shaped different than depicted and may hold together a different set of parts. For example, it may be connected only to the outer magnets 6 or to the outer top plate 8. It should also be noted that the second spring arm arrangement 15 does not necessarily connect the coil arrangement 2 and the magnet system 4 directly, but it may also connect them (indirectly) via the frame 13 for example.
The membrane 10 (in detail its flexible membrane part 11) together with the coil arrangement 2 causes a first resonance frequency fres1 for an oscillation of (inter alia) the membrane 10 in a direction parallel to the coil axis A. The second connector 14a, 17a together with the voice coils 3a, 3b of the coil arrangement 2 causes a second resonance frequency fres2 for the oscillation of (inter alia) the membrane 10 in a direction parallel to the coil axis A (do also see
The first resonance frequency fres1 results from a common movement of the voice coils 3a, 3b, whereas the second resonance frequency fres2 results from a movement of the voice coils 3a, 3b relative to each other. The membrane oscillation in question refers to its piston movement and hence mainly to the oscillation of the rigid membrane part or dome 12.
Beneficially, the compliance c2 of the second connector 14a, 17a is in a range of 10 μm/N to 100 μm/N or its stiffness or spring constant is in a range of 0.01 N/μm to 0.1 N/μm or respectively.
The electronic sound signal circuit 18 is designed to output coil signals SO1, SO2 corresponding to the sound input signal SI in terms of their time course which are phase shifted to each other. That means that the first coil signal SO1 equals the second coil signal SO2 with regard to its shape or time course, but the first coil signal SO1 and the second coil signal SO2 are phase shifted to each other. In detail, the phase shift between the first coil signal SO1 and the second coil signal SO2 depends on the frequency of the sound input signal SI.
In this embodiment, the sound input 19 is connected to a delay circuit 21 and a downstream first amplifier 22a and to an electronic phase shifter 23 and a downstream second amplifier 22b. The phase shifter 23 provides said phase shift between the first coil signal SO1 and the second coil signal SO2, i.e. it delays the second coil signal SO2 with respect to the first coil signal SO1. For example, the phase shifter 23 can be embodied as an allpass filter, which can be realized by passive or active analog circuits as well as by digital circuits.
The delay circuit 21 provides a constant delay to take into consideration a phase independent delay of the phase shifter 23. In other words, the phase shifter 23 delays the second coil signal SO2 even at a phase shift of φ=0°. This delay is the delay provided by the delay circuit 21. The amplifiers 22a, 22b just amplify the sound input signal SI and if at all cause the same delay for the first coil signal SO1 and the second coil signal SO2. So, the amplifiers 22a, 22b have no influence on the phase shift p.
Generally, the maximum coil signals SO1, SO2 output by the electronic sound signal circuit 18 shall be smaller than coil signals SO1, SO2, which cause a body contact between the voice coils 3a, 3b of the coil arrangement 2. Otherwise the acoustic performance of the speaker 1 may be deteriorated. In particular, a distance or gap g between the adjacent voice coils 3a, 3b in their idle position can be in a range of 5 to 150 μm when measured in a direction parallel to the coil axis A. In this way, the speaker 1 is not only usable for audible sound but also for ultrasonic applications.
Finally,
The impedances Z1 and Z2 and the total impedance Z can be calculated as follows:
Accordingly, the first resonance frequency fres1 and the second resonance frequency fres2 can be approximately calculated as follows:
Based on the equivalent circuit of
Beneficially, a variable K1 in the equation
K
1
=c
1·(m1+m2+m3)
A quality factor of the second resonance frequency fres2 caused by the second connector 14a, 17a in particular by the damping of the second connector 14a, 17a or second resistor D2′ respectively beneficially can be in a range of 1 to 20.
When designing a sound system, in particular the following steps can be taken:
It should be noted that although the above description refers to strips 17, the technical disclosure equally applies to glue beads 24. That means that one or more glue beads 24 can be provided instead of a strip 17 in the arrangements of
Mixed embodiments of strips 17 and glue beads 24 are possible as well. In addition, a glue layer 14s or glue pads 14b can be provided. It should also be noted that glue pads 14b can also be provided on the longitudinal sides of the polygonal voice coils 3a, 3b (not only in the corners).
Moreover, the arrangement of
Generally, the second spring arms 16 can be seen as a third connector between the coil arrangement 2 and the common frame 13, which increases the first resonance frequency fres1 without further measures. To keep the first resonance frequency fres1 low, the first connector or membrane 10 can be made softer in accordance with the stiffness added by the third connector. Similar considerations apply if the speaker 1 has a back volume F (see
To “connect” the voice coils 3a, 3b in the context of the first spring arms 25a, 25b means that the voice coils 3a, 3b are directly interconnected like this is the case in the example shown in
Generally, the first spring arm 25a, 25b and/or second spring arms 16 can be made of or comprise a metal. “Metals” in the given context in particular can be aluminum and its alloys, copper, and its alloys and stainless steel.
The second spring arms 16 are meander-like with two bows each. However, the second spring arms 16 can look differently. For example, the second spring arms 16 may have a different number of bows and may be formed by straight concatenated segments, too. Similar considerations apply to the first spring arms 25a of
It should be noted that the wires 26 bridge just a small distance between the voice coils 3a, 3b and the first ends E1 of the second spring arms 16. So, the second spring arms 16 electrically connect the wires 26 and the two sound outputs 20a, 20b of the sound signal circuit 18 (see
Reference is now made to the sound signal circuit 18 again. In one embodiment, the at least two sound outputs 20a, 20b (see
However, this is not the only possibility.
By connecting or coupling the phase shifter 23 and the delay circuit 21 to the control inputs of the transistors Ta1 . . . Tc2, the coil signals SO1, SO2 can be generated. Controlling the output power of the amplifier 22 and in turn overload protection of the amplifier 22 can be done by measuring the currents Ia and Ic and the voltages Va . . . Vc. The third current Ib can be measured, too, or can be calculated by the formula Ib=Ic−Ia.
Note that in the above disclosure just the wires 26, 26a, 26b have been taken into consideration to connect the sound outputs 20a, 20b and the voice coils 3a, 3b. However, as noted hereinbefore, the second spring arms 16 can have an electrical function, too, as the case may be.
It should also be noted that load or current Ia carried by the first half bridge BRa may reach twice the load or current Ib, Ic carried by the second and third half bridge BRb, BRc. Accordingly, the first half bridge BRa can be made with transistors Ta1, Ta2 which allow for a higher current than the transistors Tb1 . . . Tc2 of the second and third half bridge BRb, BRc. It is also possible to use the same transistors Ta1 . . . Tc2 for the half bridges BRa . . . BRc and to double the first half bridge BRa. That means that there are two parallel first half bridges BRa then. In that, production of the amplifier 22 can be eased. One another possibility for using the same transistors Ta1 . . . Tc2 is to overdimension the transistors Tb1 . . . Tc2 of the second and third half bridge BRb, BRc.
Generally, the second connector 14, 17, 17a, 17b, 24, 25a, 25b and its sub parts may have different second compliances c2 and different second damping factors D2. In this way, the vibration characteristics can be influenced widely. Although compliance and damping appear as a pair in real materials, the second connector 14, 17, 17a, 17b, 24, 25a, 25b and its sub parts can be more on the spring side or more on the damping side.
Beneficially, a glue layer 14a or glue pads 14b can be made of plastics having a Shore hardness from 00-5 to A-20 and/or an elongation at tear of more than 100%. Accordingly, the glue layer 14a or glue pads 14b are very soft and do not have a considerable spring constant. The reason is that the glue layer 14a or the glue pads 14b because of their comparably large active area have a comparably great influence on the vibration characteristics.
Glue beads 24 beneficially are made of plastics having a Shore hardness from A-20 to D-50 and/or an elongation at tear of more than 200%. Accordingly, the glue beads 24 have a considerable spring constant.
The same counts for strips 17a, 17b, which are beneficially made of or comprise a thermoplastic elastomer with a Young's Modulus of 2 MPa to 2 Gpa or a thermoplastic with a Young's Modulus of 100 MPa to 12 Gpa and thus mainly act as a spring. Preferably, the thickness of a strip 17a, 17b is in a range of 5 μm to 50 μm. in particular in a range of 5 μm to 20 μm.
Similarly, the first spring arms 25a, 25b, mainly act as a spring as well.
In a very advantageous embodiment of the speaker 1, the glue layer 14a or the glue pads 14b reach to the inner circumferences of the voice coils 3a, 3b at each of the glue beads 24 arranged on said inner circumferences, and reach to the outer circumferences of the voice coils 3a, 3b at each of the glue beads 24 arranged on said outer circumferences.
In this context, it is very advantageous if a method of manufacturing a coil arrangement 2, comprises the following steps:
By the above measures, the risk that the comparably hard glue beads 24 reach into the gap g between the voice coils 3a, 3b and hinder or even block a relative movement between the same is avoided. Instead, the glue layer 14a or glue pads 14b fill the gap g where the glue beads 4 are later applied.
An additional possibility to influence the vibration characteristics of the oscillating system is variation of the mass m1, m2 of the voice coils 3a, 3b and the mass m3 of the rigid membrane part or dome 12. In the above examples, the voice coils 3a, 3b were considered to be identical and thus were considered to have identical masses m1, m2. However, this is no mandatory condition and the voice coils 3a, 3b can also be designed differently. In particular, the voice coils 3a, 3b may be made of different materials, may have different numbers of windings, may have different height and/or may have different masses m1, m2.
In the above disclosure, a two-mass spring system based on a coil arrangement 2, comprising a first voice coil 3a, which is mounted to the membrane 10, and a second voice coil 3b, which is connected to the first voice coil 3a by the second connector 14, 17, 17a, 17b, 24, 25a, 25b is described. However, the above considerations also apply to more complex systems with more than two voice coils 3a, 3b oscillating to each other. Such a system then has more than a second resonance frequency fres2. Accordingly, the frequency response of a speaker 1 can be influenced even more then.
The technical disclosure in particular applies to small speakers 1 with a membrane 10, which has an area of less than 600 mm2 when viewed in a direction parallel to the coil axis A and/or speakers 1 with a back volume F, which is in a range from 200 mm3 to 2 cm3. The back volume F generally is the volume “behind” the membrane 10 and may be the volume enclosed by a housing of the speaker 1.
It should be noted that the invention is not limited to the above-mentioned embodiments and exemplary working examples. Further developments, modifications and combinations are also within the scope of the patent claims and are placed in the possession of the person skilled in the art from the above disclosure. Accordingly, the techniques and structures described and illustrated herein should be understood to be illustrative and exemplary, and not limiting upon the scope of the present invention. The scope of the present invention is defined by the appended claims, including known equivalents and unforeseeable equivalents at the time of filing of this application. Although numerous embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure.
It should also be noted that the FIGS. are not necessarily drawn to scale and the depicted parts may be larger or smaller in reality.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 50411/2022 | Jun 2022 | AT | national |
