WO2023072781A1

WO2023072781A1 - Loudspeaker

Info

Publication number: WO2023072781A1
Application number: PCT/EP2022/079471
Authority: WO
Inventors: Jozef A.F. BAETEN; David Corynen
Original assignee: Pss Belgium Nv
Priority date: 2021-10-25
Filing date: 2022-10-21
Publication date: 2023-05-04
Also published as: EP4424026A1; GB202115322D0

Abstract

A loudspeaker including: a chassis: a diaphragm; at least one suspension. The diaphragm is suspended from the chassis by the at least one suspension, wherein the at least one suspension includes a damper having multiple corrugations. The loudspeaker also includes: a drive unit configured to move the diaphragm along a movement axis, wherein the diaphragm has a front face that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis; a voice coil former, attached to the diaphragm; a voice coil mounted on the voice coil former, wherein the voice coil forms part of the drive unit; at least one loudspeaker terminal; at least one lead wire which electrically connects the voice coil to the at least one loudspeaker terminal. The/each lead wire is integrated with the damper and, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviates substantially from a straight line.

Description

LOUDSPEAKER

Field of the Invention

The present invention relates to loudspeakers.

Background

In the field of loudspeakers, the term “lead wire” is typically used to describe a flexible wire which electrically connects a voice coil of a loudspeaker (e.g. via connectors, such as solder pads, on the voice coil) to a loudspeaker terminal (e.g. a connection tab or other terminal). Typically, a pair of (i.e. two) lead wires are used to connect a voice coil of a loudspeaker to a pair of loudspeaker terminals, but other numbers of lead wires are possible. The/each loudspeaker terminal might conveniently be located on a chassis of the loudspeaker. By connecting external audio circuitry (e.g. an amplifier) to the loudspeaker terminal(s), the external audio circuitry can be used to drive the loudspeaker. In a typical loudspeaker arrangement, the voice coil moves relative to the loudspeaker terminals), which can apply mechanical stresses and frictions to the lead wire(s). In time, this can cause the lead wire(s) to become damaged, potentially even broken, which can cause intermittent interruptions or even a permanent interruption in the electrical connection between the voice coil and the loudspeaker terminal(s) provided by the lead wire(s).

In the loudspeaker design process, damage to or breaking of a lead wire may be detected, for example, during a validation run, in which a loudspeaker under development is operated for a long period of time.

The problem of lead wire damage/breakage can be exacerbated if a loudspeaker is driven at large mechanical excursions (“mechanical excursion”, sometimes referred to as “stroke”, typically refers to a distance by which a diaphragm of the loudspeaker is moved along a movement axis of the loudspeaker, whilst the loudspeaker is in use) for a long period of time.

It is known in the prior art to integrate a flexible lead wire with a damper of a loudspeaker. A damper (sometimes referred to as a “spider”) is typically an annular suspension, extending from an outer perimeter to an inner perimeter, which is used to suspend a diaphragm from a chassis of a loudspeaker, and which includes a plurality of corrugations.

Traditionally, dampers are formed from woven fibrous material, e.g. Nomex®. But more recently, some dampers have been made from other materials, e.g. rubbers.

One reason for integrating the lead wire(s) with the damper is, for example, where the loudspeaker must have a low profile, i.e. be relatively flat in the direction of the movement axis, and particularly where there is inadequate space available for the lead wire(s) between the damper and the diaphragm (e.g. cone) of the loudspeaker without the lead wire(s) causing rattling/ticking sounds when the loudspeaker is in use. Such rattling/ticking sounds can be caused by the free curved lead wire(s) between the damper and diaphragm touching the damper and/or diaphragm at certain frequencies or mechanical excursions of the loudspeaker.

Another reason for integrating the lead wire(s) with the damper relates to the mass production capabilities of the loudspeaker. In particular, if the lead wire(s) is(are) integrated with the damper, then production lines do not have to be equipped with complex and expensive units to guide and correctly curve the free hanging lead wires to avoid the lead wire(s) touching other movable parts (such as the diaphragm and damper) in the loudspeaker.

Also integrating the lead wire(s) with the damper can help to avoid a short circuit between two or more “free moving” lead wires, especially if the voice coil contains multiple different windings, with a corresponding increase in the number of individual lead wires.

Prior art has been published on the subject of integrating lead wires with a damper. This is perhaps not surprising given that all engineers and designers in the field of loudspeakers are confronted with the same problems and challenges. For examples, see: US2526836, DE892145, US3014996US3925626, JPS61137498, JPS64897, US5008945, JPH01295599, EP0369434, US5125473, JPH02241297, JPH0710120, US5091958, JP2673026, EP0479317, US5191697, US5249236, EP0720415, US5850462, JPH116948, US6940991 , EP0753238, US6269167, US7082667, EP2028876, US8295538, US2003123693, US7346183, US2004008860, US2010046788, WO9526616A, US2008075318.

After analyzing all the above-mentioned prior art documents, the present inventor has observed that most of these prior art documents focus on the following issues, relating to integrating lead wires with a damper:

• General principles associated with integrating lead wires with a damper.

• Different ways to integrate the lead wire with a damper such as stitching, sewing, weaving, or sandwiching.

• Different forms of lead wire to improve the durability of a lead wire integrated with a damper (e.g. based on novel principles, properties, and compositions). This may involve round/flat flexible conductive lead wires, different forms, or otherwise more durable lead wire forms.

• Alternatives which avoid use of flexible lead wires, such as molding & gluing electrical conductors, solderable flexible strips principles.

• New solutions for automatically soldering lead wires

• Reducing material cost for production of dampers with integrated lead wires.

The present inventor has performed validation runs involving a number of designs implementing solutions based on some of the principles discussed in the prior art for integrating lead wire(s) with dampers, and has found that even following the teaching of the prior art known to the inventor, the lead wires could still become damaged or broken, particularly when the loudspeaker is driven at large mechanical excursions for a long period of time. Moreover, in relation to those solutions that seek to solve the problem of lead wire damage/breakage by increasing the durability of the lead wire(s), the present inventor found that the lead wires can cause damage to the damper due to friction.

The present invention has been devised in light of the above considerations.

Summary of the Invention

In a first aspect, the present invention may provide:

A loudspeaker including: a chassis: a diaphragm; at least one suspension, wherein the diaphragm is suspended from the chassis by the at least one suspension, and wherein the at least one suspension includes a damper having multiple corrugations; a drive unit configured to move the diaphragm along a movement axis, wherein the diaphragm has a front face that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis; a voice coil former, attached to the diaphragm; a voice coil mounted on the voice coil former, wherein the voice coil forms part of the drive unit; at least one loudspeaker terminal; at least one lead wire which electrically connects the voice coil to the at least one loudspeaker terminal; wherein the/each lead wire is integrated with the damper and, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviates substantially from a straight line.

By having the/each lead wire, when projected onto a plane perpendicular to the movement axis, trace a path across the damper which deviates substantially from a straight line, the present inventor has found that damage/breakage of the/each lead wire can be reduced substantially, compared with equivalent designs where the lead wire(s) trace(s) a straight line path in the plane perpendicular to the movement axis.

Without wishing to be bound by theory, the present inventor believes that a problem caused by having a lead wire which traces a straight line path across the damper is that the damper is locally weakened along the straight line, which over time, results in a damper that can bend easily along the weakened line, which over yet more time can lead to tearing of the damper along the straight line. This issue is described in more detail below.

In contrast, having the/each lead wire, when projected onto a plane perpendicular to the movement axis, trace a path across the damper which deviates substantially from a straight line, the damper is not weakened along the straight line, which results in a damper that is less prone to bending/damage over time.

The damper may be an annular suspension which extends from an outer (typically circular) perimeter to an inner (typically circular) perimeter, and includes a plurality of corrugations.

The plurality of corrugations may each extend circumferentially around the annular suspension element, e.g. with the/each corrugation having a cross-section which is uniform in a circumferential direction.

The damper may be formed from a woven fibrous material such as Nomex®. But the damper may in other examples be formed from a non-woven or a non-fibrous material, e.g. rubber.

For the purposes of this disclosure, a substantial deviation from a straight line may, in some examples, be a deviation from a straight line that is at least 5mm, more preferably at least 10mm, more preferably at least 15mm, in a direction perpendicular to the straight line.

The/each lead wire may be attached to the damper at a plurality of attachment locations on the damper.

Preferably, for the/each lead wire, the attachment locations are arranged such that they, when projected onto a plane perpendicular to the movement axis, lie on the path which deviates substantially from a straight line, and include at least two attachment locations which deviate substantially from the straight line (as above, this substantial deviation may, in some examples, be at least at least 5mm, more preferably at least 10mm, more preferably at least 15mm, in a direction perpendicular to the straight line). This is one way of ensuring that the/each lead wire, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviates substantially from a straight line.

The/each lead wire may be integrated with the damper in a number of ways.

Preferably, for the/each lead wire, the lead wire is integrated with the damper by the lead wire passing through a hole in the damper at each of a plurality of attachment locations, i.e. such that the lead wire passes from one side to the other of the damper at each attachment location. Preferably, for the/each lead wire, the lead wire is preferably adhered (e.g. by glue) to the damper at each attachment location (though in some examples, the lead wire could be attached to the damper simply by being passed through multiple holes in the damper).

In other examples, for the/each lead wire, the lead wire may be integrated with the damper in other ways, for example by:

• stitching the lead wires to the damper at a plurality of attachment locations

• integrating the lead wire into a precursor material used to form the damper, e.g. by sewing or weaving the lead wire into a precursor material used to form the damper, and then heat forming the damper from the precursor material (which may be a woven fibrous material, such as Nomex®) sandwiching the lead wire between two or more layers of precursor material which form the damper, and then heat forming the damper from the layers of precursor material. The loudspeaker may include at least two lead wires. It is normal for a loudspeaker to have two lead wires. More than two lead wires is also possible.

As such, the loudspeaker may include: a first lead wire integrated with the damper that, when projected onto a plane perpendicular to the movement axis, traces a first path across the damper which deviates substantially from a straight line; a second lead wire integrated with the damper that, when projected onto the plane perpendicular to the movement axis, traces a second path across the damper which deviates substantially from a straight line.

Preferably, the first and the second paths lie on opposite sides of a radial axis of the damper, wherein the radial axis lies in a plane perpendicular to the movement axis.

Preferably the first and/or second path bulge outwardly with respect to the radial axis. In this way, a portion of damper enclosed by the first and second paths may have a non-rectangular shape.

The/each bulge preferably follows a curved path.

Preferably, the first and second paths are the mirror image of each other with respect to the radial axis.

The/each lead wire may electrically connect to the voice coil via a connector on the voice coil. The/each connector on the voice coil may be a solder pad.

The/each loudspeaker terminal may be a connection tab, or other terminal.

The/each loudspeaker terminal may be configured to be connected to external audio circuitry (e.g. an amplifier), so as to allow the loudspeaker to be driven by the external audio circuitry.

The loudspeaker terminals may, for example, be located on the chassis of the loudspeaker, e.g. rigidly attached to the chassis of the loudspeaker.

The drive unit may be an electromagnetic drive unit that includes a magnet unit configured to produce a magnetic field in an air gap, and the voice coil, wherein the voice coil is configured to sit in the air gap when the diaphragm is at rest. When the loudspeaker is in use, the voice coil may be energized (have an electric current passed through it) to produce a magnetic field which interacts with the magnetic field produced by the magnet unit and which causes the voice coil (and therefore the diaphragm) to move relative to the magnet unit along the movement axis. Such drive units are well known.

The/each lead wire will typically be a flexible wire.

The loudspeaker is preferably configured to, in use, displace the diaphragm by at least 10mm from its rest position in a direction parallel to the movement axis (i.e. at least 20mm peak to peak).

In a second aspect, the present invention may provide a method of making a damper suitable for use in a loudspeaker according to the first aspect of the invention.

The method may include: integrating at least one lead wire with a damper such that, when projected onto a plane perpendicular to a movement axis of the damper, the/each lead wire traces a path across the damper which deviates substantially from a straight line.

A movement axis of a damper may be an axis along which part of the damper is configured to be moved when the damper is in use. This movement axis may thus be the same as a movement axis of a loudspeaker in which the damper is included.

The method, and/or damper produced by the method, may include any feature discussed above with reference to the first aspect of the invention.

The method may include forming the damper from at least one portion of precursor material.

Forming the damper may include: heat forming the damper from at least one portion of precursor material; and forming an inner and outer perimeter for the damper, e.g. using a punching tool which punches the damper out from the precursor material.

The terms “heat forming” and “thermoforming” may be used interchangeably herein.

Heat forming the damper from at least one portion of precursor material may include heat forming the damper from a plurality of portions of precursor material (e.g. layered together). For avoidance of any doubt, each layer may be a different precursor material in some examples

Preferably, for simplicity, heat forming is performed before the forming of the inner and outer perimeter for the damper.

However, in some examples, an inner and outer perimeter for the damper may be formed prior to heat forming the damper.

Preferably, integrating the at least one lead wire with the damper includes, for the/each lead wire: forming a plurality of holes in the damper at a plurality of attachment locations on the damper after heat forming the damper; passing the lead wire through each of the plurality of holes; optionally, adhering the lead wire to the damper at each hole it is passed through (e.g. with glue).

The/each lead wire may be adhered to the damper at each hole by glue.

Preferably the glue has a high temperature resistance (e.g. temperature resistant across at least the range -30°C to +100°C, or even -40°C to +125°C).

Preferably the glue has a low elastic modulus (e.g. <250N/mm²).

The glue may be a UV glue, i.e. a glue that is cured using UV light.

Preferably, the glue is applied on only one side of the damper at each hole.

Preferably, the forming of the plurality of holes (for the/each lead wire) is done using a punching tool.

More preferably, the forming of the plurality of holes (for the/each lead wire) is done using the same punching tool as a punching tool used to form an inner and outer perimeter for the damper (by punching the damper out from the precursor material). Here, the plurality of holes and the inner and outer perimeter are preferably formed using the same punching tool at the same time.

The precursor material is preferably a woven fibrous material, e.g. Nomex®.

In other examples, integrating the least one lead wire with the damper may include: forthe/each lead wire, sewing or weaving the lead wire into a woven fibrous material; heat forming the damper from the woven fibrous material into which the lead wire(s) have been sewn or woven.

In other examples, integrating the at least one lead wire with the damper may include: forthe/each lead wire, stitching the lead wire to the damper at each of a plurality of attachment locations.

In other examples, integrating the at least one lead wire with the damper may include: forthe/each lead wire, sandwiching the lead wire between two or more layers of precursor material used to form the damper; heat forming the damper from the two or more layers or precursor material.

The method may further include, after integrating the at least one lead wire with the damper: making a loudspeaker using the damper.

The resulting loudspeaker may be a loudspeaker according to the first aspect of the invention.

Making a loudspeaker using the damper may include: connecting the/each lead wire to the voice coil; connecting the/each lead wire to a respective loudspeaker terminal.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Fig. 1 shows an example arrangement for incorporating a lead wire into a loudspeaker without integrating the lead wire with a damper, in accordance with known principles.

Fig. 2 shows an example of two lead wires integrated with a damper, in accordance with known principles.

Fig. 3 is a sketch showing how a fibrous material is typically composed in a woven fibrous material from which a damper may be formed.

Figs. 4a-c shows an example damper in which two lead wires have been integrated in accordance with the present invention. Fig. 4d shows alternative paths that could be traced by the first and second lead wires shown in Figs. 4a-c.

Fig. 5 is a photo of an example damper which implements the principles discussed in relation to Figs. 4a-c.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

In high-power, high-excursion applications, loudspeakers are expected to be driven at large mechanical excursions (i.e. large mechanical strokes). When loudspeakers intended for such applications have lead wires integrated with a damper of the loudspeaker, the present inventor has observed the following problems, both in isolation and in combination:

• lead wire breakage

• electrical interruptions of the lead wires

• tearing of the damper

Without wishing to be bound by theory, the present inventors believe these problems are at least in part caused by long time exposure of stresses in and/or friction between materials caused by the integration of the lead wires with the damper.

The examples that follow seek to improve the durability and reliability of a loudspeaker suspension arrangement in which one or more lead wires are integrated with a damper of a loudspeaker, particularly where that damper is to be used in high-power, high-excursion applications, with a view to reducing the likelihood of loudspeaker failure over its lifetime in such applications.

In the drawings shown herein, alike features have been given alike reference numerals.

Fig. 1 shows an example arrangement for incorporating a lead wire 30 into a loudspeaker 1 without integrating the lead wire 30 with a damper 20, in accordance with known principles.

Note that in Fig. 1 , the lead wire 30 has not been integrated with the damper 20, but instead the lead wire 30 is provided as a free curved flexible wire positioned between a conical diaphragm 10 and the damper 20. The damper 20 is here assumed to be a woven fibrous material such as Nomex®.

In this example, the lead wire 30 connects to a connector (solder pad) 32 on the a voice coil (not shown) and a loudspeaker terminal 34 is provided here as a connection tab. In this way, the lead wire 30 electrically connects the voice coil to the loudspeaker terminal 34, i.e. such that an electrical signal applied to the loudspeaker terminal is electrically guided by the lead wire 30 to the voice coil where it can drive the loudspeaker 1 . The arrangement shown in Fig. 1 suffices for many audio applications.

However, in some cases, e.g. where the loudspeaker must have a low profile and/or large mechanical excursions in use, a loudspeaker designer may not have adequate mechanical space available in between the diaphragm 10 and damper 20 in which to locate free hanging lead wires 30 that avoid contact with the diaphragm 10 and/or damper 20 in use . In such cases, the distances X1 , X2 shown in Fig.1 will be small and the free hanging curved lead wires will start to touch the diaphragm 10 or the damper 20 during the axial movements of the diaphragm driven by force (F) along a movement axis 2 of the loudspeaker. This touching can cause unwanted audible sounds as well unwanted harmonic distortions.

For this reason it is known in “flat” loudspeaker designs for lead wires to be integrated with the damper.

Fig. 2 shows an example of two lead wires 130, 130’ integrated with a damper 120, in accordance with known principles.

In Fig. 2, the damper 120 is shown in a plane perpendicular to the movement axis of the damper 120 (which may be the same as the movement axis of a loudspeaker in which the damper is installed).

The lead wires 130, 130’ extend between connectors (e.g. solder pads) 132, 132’ on the voice coil (not shown) to loudspeaker terminals 134, 134’ which in this example are connection tags located on a frame of the loudspeaker (not shown). The lead wires 130, 130’ may be pre-tinned for the soldering to the solder pads 132, 132’ on the voice coil.

In this example, each lead wire is integrated with the damper and, when projected onto a plane perpendicular to the movement axis, traces a straight line path across the damper, as is conventional in the art.

Each lead wire 130, 130’ may be integrated with the damper 120 at a number of attachment locations, e.g. as depicted as stiches on the first (upper) lead wire 130 shown in Fig. 2, or as circles on the second (lower) lead wire 130’ shown in Fig. 2. Here the stiches and circles represent different manners or techniques for integrating the lead wires 130, 130’ with the damper. Such techniques may e.g. be in accordance with one of solutions 1-3 discussed below.

In use, an electrical signal from external audio circuitry, e.g. an amplifier, may be presented on the loudspeaker terminals 134, 134’ and, via the lead wires 130, 130’ transferred to the voice coil, where it drives the loudspeaker (in which the damper 120 is integrated) by a force F along the movement axis, e.g. in accordance with the known equation F=B*L*i.

Once the loudspeaker or transducer is driven in axial direction by the force F force the damper 120 will be caused to move. Due to the integration of the flexible lead wires 130, 130’ into the damper, the flexible lead wires 130, 130’ will be forced to follow movement of the damper 120 along the movement axis (perpendicular to the damper 120 as shown in Fig. 2). This will cause mechanical stresses in the lead wires 130, 130’ and will also mechanically impact the material of the damper as a result of friction between the lead wires 130, 130’ and the damper 120. With arrangements with lead wires 130, 130’ tracing a straight line as shown in Fig. 2, breaking of lead wires 130 and tearing of the damper 120 was observed by the inventor when operating a loudspeaker incorporating such an arrangement with signals corresponding to high-power, high-excursion applications.

At least three different solutions exist for potentially integrating lead wires into a damper, such as for the arrangement shown in Fig. 2. These solutions are referred to as solutions 1-3 herein for brevity, and can be understood as follows:

Solution 1 : Stitching the lead wires to an already heat formed damper at one or more attachment locations on the damper.

Solution 2: Integrating the lead wires into a precursor material used to form the damper (e.g. by sewing the flexible lead wires to a woven fibrous material used to form the damper, or weaving in the lead wires in a woven fibrous material used to form the damper) prior to thermoforming the damper from the precursor material. If the lead wires are woven into a woven precursor material prior to heat forming the damper, they are generally known as “in woven lead wires”.

Solution 3: Sandwiching the flexible lead wires (3.b) between two or more layers of precursor material (which may be fibrous or non-fibrous materials) prior to heat forming the damper from the two or more layers or precursor material.

Combinations of solutions 1-3 are also known.

In the context of this disclosure, materials which may be used for a damper may include, for example:

• Cotton [fibrous]

• Polycotton [fibrous]

• Su perpoly cotton [fibrous] (3.a)Pure aramids, such as pure Nomex® and pure Conex® [fibrous]

• Cotton-Nomex® combinations [fibrous]

• Cotton-Conex® combinations [fibrous]

• Polyesters [fibrous]

• Flexible polymers [non-fibrous]

• Rubbers [non-fibrous]

• combinations of the above-listed materials

In the context of this disclosure, a lead wire will typically be flexible, and may have a variety of forms such as those currently used in the loudspeaker industry, such as:

• flat lead wires

• round lead wires

The present inventor has found that no matter which material or combinations of materials are used for the damper 120 and lead wires 130, 130’ in the arrangement shown in Fig. 2, and no matter which of solutions 1-3 is used for integration of the flexible lead wires 130, 130’ with the damper 120, the inventor has faced technical durability issues at higher excursions. Without wishing to be bound by theory, the present inventor believes this is caused at least in part by the process of integrating the flexible lead wire(s) with the damper causing damage to the lead wire(s) and/or damper.

In more detail, the present inventor observes that a flexible lead wire is typically composed out of multiple strands of wire twisted around a flexible polymer, aramid, or other flexible core material.

Thus, the inventor observes that for solutions 1 and 2, stitching the lead wires to an already formed damper, or integrating the lead wires into a precursor material prior to heat forming the damper (e.g. in an open-close tooling), will typically cause damage to the lead wires and/or damper at the locations at which the lead wires are attached to the damper (attachment locations) prior to the loudspeaker being used. It is thought this is because during the process of stitching the lead wires to the damper, or sewing/weaving the lead wire with the raw material used to heat form the damper, will cause some damage to some strands present in the flexible lead wire.

For example, for solution 2, heat forming a damper from a precursor material in which the lead wires 130, 130’ have already been integrated will cause damage to the lead wires. It is thought this is because, during the open-close tooling used to heat form the damper, the flexible lead wires 130, 130’ will be forced to follow the waves or curves from the damper 120. Moreover, the pressing forces of the heat forming process will cause additional damage to occur in the lead wires 130, 130’. Also, bad tooling maintenance and/or so-called tool wearing will further increase the amount of damage on the strands present in the flexible lead wires 130, 130’ prior to the loudspeaker being used.

Fig. 3 is a sketch showing how a fibrous material is typically configured in a woven fibrous material from which a damper may be formed (e.g. Nomex®). The weaving of the threads is done in two directions called “warp & weft”. During the heat forming of the damper with “woven in" lead wires this constant weaving pattern of the fibrous material will be locally disturbed. The individual threads will be displaced and can be damaged in (and by) the tool.

For solution 3 (sandwiching), the heat forming process used to form the damper can also risk damaging the different strands in the flexible lead wires prior to the loudspeaker being used. This is mainly caused by tool wearing and/or bad maintenance of the open-close toolings.

Damage as described above happens prior to the damper being used in a loudspeaker, and may be referred to as “zero hour” damage herein. We might say that the damper or spider we purchase is already statically damaged in the production process before we expose it to dynamic loads or forces coming from validation (test signals such as sinus, IEC & Pink noises) or in the application of the loudspeaker, (music signals)

Once a damper starts to move at high excursions in the loudspeaker, all the individual strands present in the lead wire will be continuously mechanically stretched. If “zero hour” damage exists prior to the damper even being used, then in the long run more and more strands break or start to interrupt the electrical conductivity. During validation runs performed by the present inventor with high mechanical excursions, the present inventor has observed sparkling lights in a complete dark room caused by these effects, and subsequent loudspeaker failure.

The “zero hour” damage as described above may be described as a first source of damage that may cause damage/breakage to lead wires and/or a damper. The dynamic forces generating high excursions in an axial direction caused by using a loudspeaker with such “zero hour” damage just accelerates the damaging of the lead wires or the damper in which the lead wires are integrated.

After further research the present inventor detected a second source of damage that may cause damage/breakage to the lead wires and/or a damper into which the lead wires are integrated. This second source of damage relates to the path the lead wire traces across the damper.

Referring back to Fig. 2. we see that the flexible lead wires 130, 130’ integrated into the damper 120 trace a path in one straight line from the loudspeaker terminals 134, 134’ to the solder pads 132, 132’ on the voice coil. Thus, the lead wires, when projected onto a plane perpendicular to the movement axis, trace a straight line path across the damper.This straight line is approximately radial with respect to the movement axis (not exactly radial). After a search in the prior art, the present inventor found the integration of the lead wires in a damper is consistently done in a straight line, with the straight line typically extending from the loudspeaker terminals to the voice coil solder pads. The present inventor believes this is the case for reasons of mass production feasibility.

With reference to Fig. 2, the present inventor has observed that a lead wire 130, 130’ which traces a straight line path across a damper 120 causes the damper 120 to be locally weakened along the straight line and results in a damper 120 that bends easily along the weakened line due the decreased mechanical strength present in that line when the damper 120 is exposed to high axial excursions over a long time. Over time this effect amplifies, and the damper 120 may start to tear along the weakened line.

Fig. 4a-c shows an example damper 220 in which two lead wires 230, 230’ have been integrated in accordance with the present invention.

In particular, the damper 220 includes: a first lead wire 230 that, when projected onto a plane perpendicular to the movement axis 202, traces a first path across the damper 220 which deviates substantially from a straight line; a second lead wire 230’ of the two lead wires that, when projected onto the plane perpendicular to the movement axis 202, traces a second path across the damper 220 which deviates substantially from a straight line.

In this example, the deviation of the first path from the straight line (in a direction perpendicular to the straight line) is indicated by Y1 , and the deviation of the second path from a straight line (in a direction perpendicular to the straight line)Y1 ’. Y1 and Y1 ’ are preferably at least 10mm, more preferably at least 15mm.

In this example, the first and the second paths lie on opposite sides of a radial axis 203 of the damper 220, wherein the radial axis 203 lies in a plane perpendicular to the movement axis 201. As shown in Fig. 4a, the first and second paths bulge outwardly (i.e. in opposite directions) with respect to the radial axis 203. In this way, a portion A’ of damper 120 enclosed by the first and second paths has a non-rectangular shape (whereas the equivalent portion would be substantially rectangular, for the example shown in Fig. 2), which broadens towards an intermediate region of the damper 120. As shown in Fig. 4, each bulge follows a curved path.

Due to the non-straight line path traced by the lead wires, an untouched non-square region A’ of damper material is formed in which all mechanical properties of the damper are substantially the same as the mechanical properties of the material from which the damper is formed. The weakening effect of the damper at high excursions will no longer occur in this region, and there is no straight line along which the damper is weakened. Consequently, the lifetime of the spider with the undamaged strands in the integrated lead wires can be significantly extended.

These factors are believed to help inhibit the formation of a weakened line in the damper 220 which could, overtime, lead to a failure of the damper for reasons already discussed.

Fig. 4b shows a cross-section through the damper, to better show the integration of the first lead wire 230 into the damper 220.

In Fig. 4b, it can be seen that the first lead wire 230 is integrated with the damper 220 by the lead wire passing through a hole in the damper at each of a plurality of attachment locations 224 on the damper, i.e. such that the first lead wire 230 passes from one side to the other of the damper 220, at each attachment location 224. In this example, the lead wire 230 is adhered (e.g. by glue) to the damper 220 at each attachment location 224.

In more detail, Fig. 4b shows that a curving of the first lead wire 230 is in the opposite direction of the curving of the corrugations in the damper 220. The first lead wire 220 will therefore face reduced stress because it is not forced to closely follow the curves present in the damper 220, as would have been the case had the first lead wire 220 been integrated into the damper prior to the thermoforming process. This can be achieved by punching the holes in the damper, prior to passing the first lead wire 230 through the holes (and gluing in the first lead wire). Through hole-punching, a loudspeaker designer has the freedom to validate the speaker with different curve heights of the flexible lead wires 230, 230’, e.g. so as to achieve an optimal curving of the lead wires 230, 230’. More height of the curving of the lead wires 230, 230’ means less mechanical load on the flexible lead wires 230, 230’ because more length is available for the higher excursions in axial direction coming from the axial applied force F.

Once the exact attachment locations at which the flexible lead wires 230, 230’ are to pass through the holes in the damper 220, as well the exact curving height of the lead wires 230, 230’ and so thus the length of the lead wires 230, 230’ are known, the loudspeaker designer can adhere the flexible lead wires 230, 230’ on the different attachment locations at which the flexible lead wires 230, 230’ go through the damper 220, e.g. by means of glue relief drops. These relief glue drops are preferably configured to avoid mechanical friction between the flexible lead wires 230, 230’ and the damper 220 during high mechanical excursions or axial applied forces F. Depending on the different variables of the damper design such as shape (e.g. curve height) of the damper 220, the selected material for the damper 220, the type of flexible lead wire 230, 230’ used, the curve height & shape of the flexible lead wires 230, 230’ and the applied axial forces F on the damper 220 in use, the designer can choose to use relief drops with a “hard glue” or a “soft” flexible glue as applicable.

Currently the present inventor prefers to use, for the glue relief drops, a glue with very low elastic modulus and high temperature resistance to successfully pass the high excursion validations with high environmental temperatures and high powers applied to the transducer. Also, the application of UV-glues with high temperature resistance will result in it being easier to produce the part. It becomes very easy to manipulate the part and the glue will be dry after the UV light is applied. It can realize a significant cost reduction to produce the part and the production process can be controlled much better.

The punching of holes in the damper 220 through which the lead wires 230, 230’ can be passed and then glued helps to avoid ’’zero hour” damage to lead wires 230, 230’ which, as discussed above, is a problem in many processes for integrating lead wires into a damper.

Moreover, the lead wire holes in the damper 220 may conveniently be formed by the same tool that punches an inner diameter (ID) and outer diameter (OD) for the damper 220. This helps to simplify the manufacturing process since the lead wires 230, 230’ can be pulled through the punched holes after the holes have been punched out from the heat formed damper 220. Due the fact that the lead wires 230, 230’ are not present during the heat forming step they cannot be damaged.

Fig. 4c shows the example damper 220 of Fig. 4a implemented in a loudspeaker.

In this example, the straight line path (from which the path traced by the first path deviates) in the plane perpendicular to the movement axis is indicated by the reference numeral 231 . As shown, the straight line path 231 extends in a straight line from a solder pad on the voice coil to a loudspeaker terminal on the frame.

Fig. 4d shows alternative paths that could be traced by the first and second lead wires 230, 231 shown in Figs. 4a-c. As shown here, a wide variety of paths, symmetrical or non-symmetrical, bulging inwards and outwards are possible.

Fig. 5 is a photo of an example damper 320 which implements the principles discussed in relation to Figs. 4a-c.

In this photo, the lead wires 330, 330’ are passed through holes in the damper, and are glued to those holes by glue relief drops, in the manner described above with reference to Figs. 4a-c.

Here, a UV glue is used to provide the glue relief drops 321 , with glue being applied on only one side of the damper (which was found to still be very effective). The speaker shown here was able to pass a 100 hour validation test in which the loudspeaker was exposed to a high temperature and high excursions (±18mm, so 36mm peak to peak), which the present inventor found to be a very good performance compared with more conventional arrangements in which lead wires are integrated into a damper. Loudspeakers incorporating the present invention may, for example, include loudspeakers for use in home audio or consumer audio systems, PA systems (loudspeakers for professional sound reproduction outdoor & indoor) and automotive loudspeaker systems, particularly where loudspeakers are expected to have a high excursion when in use, e.g. with mechanical excursions of 10mm or more from rest position (i.e. 20mm or more peak to peak).

Various modifications may be made to the above described examples, to create yet further examples of the present invention.

For example, instead of punching holes and guiding the lead wires in a non-straight radial way from the connector tags towards the voice coil soldering pads through these punched holes (as described above in relation to Figs. 4a-d), we must also consider solutions such as:

• Stitching or gluing the lead wires on certain wave positions on one side (top or bottom side) of the damper in a non-straight line from the loudspeaker terminals to the solder pads on the voice coil. In this case, the lead wires may stay on a same side (e.g. top or bottom side) of the damper, without passing through holes in damper. This may reduce cost compared with a solution in which the lead wires are threaded through punched holes.

• In Figs. 4a-c, we described lead wires 230, 230’ whose paths had mirror symmetry about the radial axis 203, but non-mirrored or asymmetrical integration of the lead wires in the fibrous or non-fibrous material are also possible (see Fig. 4d) to achieve the same effect (avoiding locally weakening of the damper in one straight line from the loudspeaker terminals to connectors on the voice coil).

***

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/- 10%.

References

A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein.

US2526836, DE892145, US3014996US3925626, JPS61137498, JPS64897, US5008945, JPH01295599, EP0369434, US5125473, JPH02241297, JPH0710120, US5091958, JP2673026, EP0479317, US5191697, US5249236, EP0720415, US5850462, JPH116948, US6940991 , EP0753238, US6269167, US7082667, EP2028876, US8295538, US2003123693, US7346183, US2004008860, US2010046788, WO9526616A, US2008075318.

Claims

Claims:

1. A loudspeaker including: a chassis; a diaphragm; at least one suspension, wherein the diaphragm is suspended from the chassis by the at least one suspension, and wherein the at least one suspension includes a damper having multiple corrugations; a drive unit configured to move the diaphragm along a movement axis, wherein the diaphragm has a front face that faces in a forwards direction parallel to the movement axis and a rear face that faces in a rearwards direction parallel to the movement axis; a voice coil former, attached to the diaphragm; a voice coil mounted on the voice coil former, wherein the voice coil forms part of the drive unit; at least one loudspeaker terminal; at least one lead wire which electrically connects the voice coil to the at least one loudspeaker terminal; wherein the/each lead wire is integrated with the damper and, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviates substantially from a straight line.

2. A loudspeaker according to claim 1 , wherein the/each lead wire, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviates from a straight line by at least 10mm in a direction perpendicular to the straight line.

3. A loudspeaker according to claim 1 or 2, wherein the/each lead wire is attached to the damper at a plurality of attachment locations on the damper, wherein for the/each lead wire, the attachment locations are arranged such that they, when projected onto a plane perpendicular to the movement axis, lie on the path which deviates substantially from a straight line, and include at least two attachment locations which deviate from the straight line. This is one way of ensuring that the/each lead wire, when projected onto a plane perpendicular to the movement axis, traces a path across the damper which deviate substantially from a straight line.

4. A loudspeaker according to any previous claim wherein, for the/each lead wire, the lead wire is integrated with the damper by the lead wire passing through a hole in the damper at each of a plurality of attachment locations.

5. A loudspeaker according to claim 4, wherein for the/each lead wire, the lead wire is adhered to the damper at each attachment location.

6. A loudspeaker according to any previous claim wherein, the loudspeaker includes: a first lead wire integrated with the damper that, when projected onto a plane perpendicular to the movement axis, traces a first path across the damper which deviates substantially from a straight line; a second lead wire integrated with the damper that, when projected onto the plane perpendicular to the movement axis, traces a second path across the damper which deviates substantially from a straight line.

7. A loudspeaker according to claim 6, wherein: the first and the second paths lie on opposite sides of a radial axis of the damper, wherein the radial axis lies in a plane perpendicular to the movement axis; wherein the first and second paths bulge outwardly with respect to the radial axis.

8. A loudspeaker according to claim 7, wherein each bulge follows a curved path.

9. A loudspeaker according to any previous claim wherein the damper is formed from a woven fibrous material.

10. A loudspeaker according to any previous claim wherein the loudspeaker is configured to, in use, displace the diaphragm by at least 10mm from its rest position in a direction parallel to the movement axis.

11. A method of making a damper suitable for use in a loudspeaker, wherein the method includes: integrating at least one lead wire with a damper such that, when projected onto a plane perpendicular to a movement axis of the damper, the/each lead wire traces a path across the damper which deviates substantially from a straight line.

12. A method according to claim 11 , wherein the method includes: heat forming the damper from at least one portion of precursor material; and forming an inner and outer perimeter for the damper using a punching tool which punches the damper out from the precursor material.

13. A method according to claim 11 or 12, wherein integrating the at least one lead wire with the damper includes, for the/each lead wire: forming a plurality of holes in the damper at a plurality of attachment locations on the damper after heat forming the damper; passing the lead wire through each of the plurality of holes

14. A method according to claim 13, wherein the integrating the at least one lead wire with the damper further includes, for the/each lead wire: adhering the lead wire to the damper at each hole it is passed through.

15. A method according to claim 13 or 14, wherein the forming of the plurality of holes for the/each lead wire is done at the same time as forming an inner and outer perimeter for the damper, using the same punching tool.