Method of manufacturing a vehicle, a loudspeaker and a vehicle

Abstract

There is provided a method of manufacturing a vehicle including: providing a precursor vehicle; the precursor vehicle includes a body having a weight of at least 100kg; the body includes an airtight surface configured to face into an interior of the vehicle manufactured from the precursor vehicle; providing a loudspeaker module for producing sound at bass frequencies; the loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; the loudspeaker frame has a rear opening; a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening. The method further includes attaching the loudspeaker module to the body so as to form a sealed volume bounded by the airtight surface of the body, the loudspeaker frame and the diaphragm; the partially-enclosed volume forms at least a majority of the sealed volume.

Description

[0001] METHOD OF MANUFACTURING A VEHICLE, A LOUDSPEAKER AND A VEHICLE

[0002] Field of the Invention

[0003] The present invention relates to a method of manufacturing a vehicle, a loudspeaker module for use with the method of manufacturing, and a vehicle.

[0004] Background

[0005] A typical conventional loudspeaker has a frame, a diaphragm and a drive unit for the reproduction of sound. In use, the drive unit causes the diaphragm, which acts as a piston, to move backwards and forwards to generate pressure waves, i.e. sound.

[0006] For audio reproduction in automobiles, conventionally low frequency sound is generated by woofers mounted in the doors of the automobile. This approach may have some advantages, such as a sufficiently large acoustic back volume to allow for an efficient woofer design with a large radiating surface and a low resonance frequency. Moreover, most automobiles have two or four doors and in typical cases an equal number of woofers may be foreseen. With these different sources spatial differences in sound pressure levels may be equalised by means of gains, filters and delays to realise an evenly distributed bass among multiple listening positions. However, integrating low frequency loudspeakers in doors may also cause problems. For example, sound proofing of the doors might be compromised, which may reduce passenger comfort. Also, vibrations may result in audible artefacts or discomfort to an occupant in contact with the door.

[0007] Some manufacturers have sought solutions where the generation of low frequency sound is done with loudspeakers positioned in other locations where sufficient acoustic back volume is available.

[0008] W02007036245 describes a speaker system for a motor vehicle. The speaker system is mounted on a support structure and utilises cavities formed in the support structure as acoustic back volume.

[0009] The present invention has been devised in light of the above considerations.

[0010] Summary of the Invention

[0011] W02007036245 (‘245) describes a loudspeaker system for motor vehicles utilizing cavities formed by supporting structures. According to ‘245, loudspeakers for low frequency reproduction require a relatively large acoustic volume. The loudspeakers described in ‘245 are therefore mounted onto cavities formed in the supporting structure in order to expand the acoustic volume available to the loudspeakers. As such, ‘245 reflects what is believed to be a common teaching, i.e. that a large volume is needed for reproducing low frequency sound, and provides a solution by adding suitable cavities to the motor vehicle. The inventors of the present invention observed that, contrary to this common teaching, a large cavity to expand the acoustic volume is not always needed for low frequency reproduction, provided that the loudspeaker is attached to a sufficiently heavy body of the vehicle for absorbing vibrations caused by the loudspeaker in operation.

[0012] According to a first aspect of the invention, there is provided a method for use in manufacturing a vehicle. The method includes: providing a precursor vehicle, wherein the precursor vehicle includes a body having a weight of at least 100kg, wherein the body includes an airtight surface which is configured to face into an interior of the vehicle manufactured from the precursor vehicle; providing a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the loudspeaker frame has a rear opening, wherein a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening, wherein the method includes: attaching the loudspeaker module to the body so as to form a sealed volume bounded by the airtight surface of the body, the loudspeaker frame and the diaphragm; wherein the partially-enclosed volume forms at least a majority of the sealed volume.

[0013] The loudspeaker module may be operable to energise the drive unit to cause movement of the diaphragm relative to the loudspeaker frame along a movement axis of the loudspeaker module to produce sound.

[0014] The drive unit may include a moveable part attached to the diaphragm and a stationary part attached to the loudspeaker frame. The loudspeaker module may be operable to energise the drive unit in order to cause movement of the moveable part relative to the stationary part of the drive unit. A moveable assembly, which may include the moveable part of the drive unit and the diaphragm, may thus be caused to move along the movement axis of the loudspeaker module to produce sound. The moveable assembly may also be referred to as a “moving” assembly.

[0015] The terms “stationary” and “moveable” are relative terms and in principle dependent on the particular frame of reference. In this context, the terms “stationary” and “moveable” are intended to refer to a conventional frame of reference according to which the diaphragm is considered to be moveable, and in use to be moving, whereas other parts of the loudspeaker module are considered to be stationary. As such those parts of the loudspeaker module which in use move with the diaphragm, such as the moveable part of the drive unit, are referred to as moveable, while other parts of the loudspeaker module, which in use do not move with the diaphragm (and which may be stationary with respect to an external apparatus to which the loudspeaker module is attached), are referred to as stationary, e.g. the stationary part of the drive unit. Those parts of the loudspeaker module which are moveable, i.e. the diaphragm and parts that in use move with the diaphragm, may collectively be referred to as the moveable assembly.

[0016] The drive unit may include a magnet unit and a voice coil. The magnet unit may be included in one of the stationary part and the moveable part, and the voice coil may be included in the other of the stationary part and the moveable part. When the drive unit is energised (e.g. by supplying a time-varying electric current to the voice coil), the moveable part of the drive unit and the stationary part of the drive unit may magnetically interact to cause the movement of the moveable part relative to the stationary part.

[0017] In some examples (referred to herein as “moveable voice coil” examples), the moveable part of the drive unit may be the voice coil and the stationary part of the drive unit may be the magnet unit. In such examples, when the drive unit is energised, magnetic flux generated by the flow of electric current in the (moveable) voice coil may interact with magnetic flux generated by the (stationary) magnet unit of the drive unit to cause the movement of the moveable part, which is the voice coil, relative to the stationary part, which is the magnet unit.

[0018] In other examples (referred to herein as “moveable magnet unit” examples), the moveable part of the drive unit may be the magnet unit and the stationary part of the drive unit may be the voice coil. In such examples, when the drive unit is energised, magnetic flux generated by the flow of electric current in the (stationary) voice coil may interact with magnetic flux generated by the (moveable) magnet unit of the drive unit to cause the movement of the moveable part, which is the magnet unit, relative to the stationary part, which is the voice coil.

[0019] The loudspeaker module, when attached to the body (so as to form the sealed volume), may have a resonant frequency in a range of 30-100Hz (Hertz), optionally 40-80Hz. The resonant frequency of the loudspeaker module, when attached to the body (so as to form the sealed volume) may be referred to as the “in-box” resonant frequency of the loudspeaker module.

[0020] The loudspeaker module may be a subwoofer configured to produce sound with frequencies in a bass frequency range. The bass frequency range may include 60-80Hz, more preferably include 40-100Hz. By way of example, the bass frequency range may be 20Hz-100Hz.

[0021] In some examples, the rear opening may be taken to correspond to a geometric plane which passes through at least three points on the loudspeaker frame at which the loudspeaker frame (when attached to the body) forms a junction with the body. The geometric plane so defined divides the sealed volume into two portions, i.e. the partially-enclosed volume which is proximal to the diaphragm and the additional volume distal to the diaphragm. In this case, the partially enclosed volume may be taken to be the portion of the sealed volume formed between the diaphragm, the loudspeaker frame and the geometric plane; the additional volume may be taken to be the portion of the sealed volume formed between the geometric plane and the body.

[0022] In other examples, the rear opening may be taken to correspond to a geometric surface defined in that it is smooth and is bounded by the inner edge and has minimal surface area, zero mean curvature, and does not intersect the airtight surface.

[0023] The sealed volume may be a structural volume. In particular, the structural volume may be the volume of space that is sealed by the loudspeaker module and the airtight surface.

[0024] The sealed volume, i.e. the structural volume, may define an acoustic volume VB. The acoustic volume

[0025] VB, which is known in the art (see, for example, L.L. Beranek, Acoustics, McGraw-Hill, 1954), may be different from the structural volume. It is known that the acoustic volume VB is not a purely structural volume, but that the acoustic volume VB can be increased by stuffing the structural volume, e.g. with wool, by typically up to 20 percent, in some cases up to 40 percent.

[0026] The partially-enclosed volume forms at least a majority of the sealed volume, such that at least 50% (percent) of the sealed volume correspond to the partially-enclosed volume. In some examples, the partially-enclosed volume may form at least 75% of the sealed volume. In some examples, the partially- enclosed volume may form at least 85% of the sealed volume.

[0027] The sealed volume may be substantially equal to the partially-enclosed volume. In other words, the partially-enclosed volume may form substantially the entirety of the sealed volume. For example, the airtight surface of the body may be substantially flat such that the partially-enclosed volume of the loudspeaker module may form substantially the entirety of the sealed volume.

[0028] Attaching the loudspeaker module to the body may use a plurality of fastening members which attach the loudspeaker module to the body. Any suitable type of fastening member may be used, e.g. bolts. The fastening members may be permanently or non-permanently attachable to the body. In some examples, attaching the loudspeaker module to the body using a plurality of fastening members may include locating the fastening members in a corresponding plurality of blind holes in the body. The blind holes may be tapped holes configured to receive corresponding threaded shafts of bolts. Alternatively, the plurality of fastening members may be permanently attached to and extend from the airtight surface. For example, the plurality of fastening members may include threaded shafts permanently attached, e.g. welded, to the airtight surface. Attaching the loudspeaker frame to the body may include receiving the plurality of fastening members into the loudspeaker frame and suitably fastening thereof, e.g. using matching nuts.

[0029] Attaching the loudspeaker module to the body may include attaching a portion or portions of the loudspeaker frame to the body.

[0030] The loudspeaker frame may include an outer frame portion which bounds the rear opening. Attaching the loudspeaker module to the body may include attaching the outer frame portion to the body.

[0031] The loudspeaker frame may include an inner frame portion. The inner frame portion may be attached to the drive unit.

[0032] Attaching the loudspeaker module to the body may include attaching the inner frame portion to the body.

[0033] Attaching the loudspeaker module to the body may include attaching the drive unit to the body, and may in particular include attaching the stationary part of the drive unit to the body.

[0034] The body of the precursor vehicle may be a frame, body or unibody structure on which other components of the vehicle are to be added during manufacture of the vehicle.

[0035] The body of the precursor vehicle may be a “body-in-white”.

[0036] The method may include forming the cabin of the vehicle. The method may further include making an opening into the cabin for sound produced by the diaphragm to propagate into the cabin. The precursor vehicle may be a precursor road vehicle, and the vehicle may be a road vehicle.

[0037] The method may further include further manufacturing steps in order to complete manufacture of the vehicle. Such steps are well known and do not need to be described herein.

[0038] The mass of the moveable part of the drive unit may be at least 60%, more preferably 70%, of the mass of the moveable assembly. That is to say, the moveable part of the drive unit may have a first mass, the moveable assembly may have a second mass, and the first mass may be at least 60% (preferably 70%) of the second mass.

[0039] In this context, the moveable part of the drive unit may be taken to include only the parts of the moveable assembly which magnetically interact with the stationary part of the drive unit, when the drive unit is energised. Thus, in a “moveable voice coil” example (see above), the moveable part of the drive unit may include only the voice coil (and may in some examples be taken as including only the metal wire of the voice coil). Similarly, in a “moveable magnet unit” example (see above), the moveable part of the drive unit may include only the magnet unit (e.g. only a permanent magnet and flux guiding elements of the magnet unit).

[0040] Having the mass of the moveable part of the drive unit be at least 60%, more preferably 70%, of the mass of the moveable assembly, may mean that an unusually large proportion of the mass of the moveable assembly is due to the moveable part of the drive unit.

[0041] The present inventors have observed that such forces can be absorbed by the heavy (100kg+) body of the precursor vehicle, leading to good sound performance.

[0042] A ratio of the mass of the moveable assembly to the effective radiating area Sd of the diaphragm may be at least 5 kilograms per square-metre, optionally at least 7 kilograms per square-metre. The ratio of the mass of the moveable assembly to the effective radiating area Sd of the diaphragm may be at most 20 kilograms per square-metre, optionally at most 15 kilograms per square-metre, optionally at most 12 kilograms per square-metre. For example, the ratio of the mass of the moveable assembly to the effective radiating area Sd of the diaphragm may be in a range of 5 to 20 kilograms per square-metre, optionally in a range of 5 to 15 kilograms per square-metre, optionally in a range of 7 to 12 kilograms per squaremetre.

[0043] Such a ratio, particularly when combined with the mass of the moveable part of the drive unit being at least 60%, more preferably 70%, of the mass of the moveable assembly, may represent a compact yet heavy moveable assembly. Such a moveable assembly may in use generate large forces, but the present inventor has observed that such forces can be absorbed by the heavy (100kg+) body of the precursor vehicle, leading to good sound performance (despite the significant forces).

[0044] The effective radiating area Sd is a concept known in the art. For a round diaphragm, the effective radiating area Sd is quantified using the half-roll-to-half-roll diameter and hence the suspension contributes to the effective radiating area Sd. Particularly for a loudspeaker with a comparatively small diaphragm, the contribution of the suspension to the effective radiating area Sd may not be negligible. For a diaphragm having a circular perimeter which is suspended from the loudspeaker frame by a roll suspension having an outer diameter do (“d_o”) and an inner diameter di (“dj”), the effective radiating surface area of that diaphragm may be estimated as Sd Sd equals pi times the square of d over the square of 2”) where d is the half-diameter of the roll suspension, (do + d) / 2, (“d_o d_i over 2”).

[0045] In other examples, the effective radiating surface area of the diaphragm Sd may be measured using known techniques, see e.g. “Dynamical Measurement of the Effective Radiating area SD”, Klippel GmbH (https: / / www.klippel.de / fileadmin / klippel / Files / Know How / Application Notes / AN 32 Effective Radiation Area.pdf).

[0046] The sealed volume may be in the range 0.25 litres to 8 litres, preferably in the range of 0.5 litres to 3 litres, and more preferably in the range of 0.5 litres to 1 .5 litres. Such volumes are relatively small for subwoofers, but the present inventors have found that they are adequate with a powerful loudspeaker (see above) mounted to the heavy (100kg+) body of the precursor vehicle.

[0047] The loudspeaker module may be operable to cause displacement of a volume VD of air by the diaphragm. The volume VD displaced by the diaphragm may be defined as the volume of air displaced by the diaphragm as it moves from its rest position in the air gap to a position of maximum displacement. As such, twice the volume VD is displaced by the diaphragm when the diaphragm is moved from nominal maximum displacement inwards to nominal maximum displacement outwards or vice versa, i.e. a peak- to-peak stroke.

[0048] The volume VD of air displaced by the diaphragm may be at least 0.05 times the sealed volume (5 percent of the sealed volume). This may result in a loudspeaker module having a comparatively large diaphragm and enclosing a comparatively small sealed volume.

[0049] A ratio of the sealed volume over the effective radiating surface Sd may be in a range of 0.01 to 0.5 metres. This ratio of the sealed volume over Sd may provide an alternative parametrisation of a comparatively large diaphragm and a comparatively small sealed volume.

[0050] A ratio of the acoustic volume VB, which is defined by the sealed volume, over the effective radiating surface Sd may be in a range of 0.01 to 0.5 metres. This ratio of the acoustic volume VB over Sd may provide an alternative parametrisation of a comparatively large diaphragm and a comparatively small sealed volume.

[0051] The loudspeaker module may include one or more suspension elements, wherein the diaphragm is suspended from the loudspeaker frame by the one or more suspension elements. Preferably, the loudspeaker module includes at least two suspension elements.

[0052] The one or more suspension elements may include a first suspension element, e.g. a surround (which may also be referred to as the roll suspension), which attaches to the loudspeaker frame at a first landing surface on the loudspeaker frame. The first suspension element may be attached directly or indirectly to the diaphragm. In some examples, the first suspension element may attach (directly) to an outer edge of the diaphragm. In other examples, the first suspension element may be attached to another element of the moveable assembly.

[0053] The one or more suspension elements may include a second suspension element, e.g. a damper, which attaches to the loudspeaker frame at a second landing surface on the loudspeaker frame. The second suspension element may be attached directly or indirectly to the diaphragm. In some examples, the second suspension element may be attached (directly) to the diaphragm at a location inwardly located with respect to the outer edge of the diaphragm. In other examples, the second suspension element may be attached to another element of the moveable assembly (e.g. the moveable part of the drive unit, particularly where the moveable part is the magnet unit).

[0054] The centre of gravity of the moveable part of the drive unit may have a position along the movement axis that is between the first landing surface and the second landing surface.

[0055] By locating the centre of gravity of the magnet unit between the first landing surface and the second landing surface, rocking of the moveable assembly may be inhibited. More particularly, the rocking modes of the loudspeaker module may be pushed outside of the working frequency range of the loudspeaker module.

[0056] The magnet unit may include a permanent magnet and one or more flux guiding elements for guiding magnet flux produced by the permanent magnet in a magnetic circuit and across an air gap, wherein the voice coil is configured to be located in the air gap when the moveable part of the drive unit is at rest.

[0057] Herein, a reference to the moveable part of the drive unit being at rest, or the diaphragm being at rest, may be taken to correspond to a state in which the drive unit is not energised (e.g. an electric current is not being supplied to a voice coil of the drive unit) with the moveable part of the drive unit and the diaphragm having been given time to reach a state of rest.

[0058] The magnet unit may include at least two flux guiding elements. The at least two flux guiding elements may be configured to guide magnet flux produced by the permanent magnet across the air gap. The air gap may be formed between the at least two flux guiding elements.

[0059] The at least two flux guiding elements may include a washer and a yoke. The permanent magnet may be located between the washer and the yoke. The washer and the yoke may be arranged to define the air gap between the washer and the yoke.

[0060] The yoke may include a base and an upright portion extending from the base. In some examples, the yoke may be a U-yoke wherein the upright portion is an annular sidewall. In some examples, the yoke may be a T-yoke wherein the upright portion is a central post.

[0061] The magnet unit may form a magnetic circuit. The magnetic circuit may provide a substantially closed circuit (or loop) for the magnetic flux. The magnetic circuit may have a comparatively high magnetic reluctance. For example, the magnetic reluctance of the magnetic circuit may be at least 2.5 x 10A6 [1 / H] or even 3 x 10A6 [1 / H], where “H” represents the physical unit “Henry”. The majority of the magnetic reluctance of the magnetic circuit may be attributed to the air gap. For example, the air gap may have a magnetic reluctance of at least 2 x 10A6 [1 / H].

[0062] Further detail relating to high-reluctance magnetic circuits in the context of loudspeakers is described in GB 2209544.2 and PCT / EP2023 / 067426.

[0063] The voice coil may have a first perimeter and a second perimeter. The first perimeter may be an outer perimeter or an inner perimeter of the voice coil, and the second perimeter may corresponding be the inner perimeter or the outer perimeter.

[0064] The distance between the first perimeter and the second perimeter may be referred to as a winding thickness of the voice coil. Accordingly, the magnetic flux density permeating the voice coil may drop over the winding thickness of the voice coil as specified above.

[0065] If the voice coil is generally circular, the inner perimeter of the voice coil may be referred to as the inner diameter of the voice coil, and the outer perimeter of the voice coil may be referred to as the outer diameter of the voice coil.

[0066] When the voice coil is located in the air gap, i.e. the moveable part of the drive unit is at rest, a magnetic flux density at the first perimeter of the voice coil may be 50% or less of a magnetic flux density at the second perimeter of the voice coil.

[0067] In an arrangement in which the at least two flux guiding elements include a U-yoke, the magnetic flux density at the outer perimeter of the voice coil may be 50% or less of the magnetic flux density at the inner perimeter of the voice coil.

[0068] In an arrangement in which the at least two flux guiding elements include a T-yoke, the magnetic flux density at the inside perimeter of the voice coil may be 50% or less of the magnetic flux density at the outside perimeter of the voice coil.

[0069] An extent of the voice coil as measured in direction parallel to the movement axis (which may be referred to as the ‘height’ of the voice coil) may be in a range of 85% and 100% of the separation between the first and second landing surfaces as measured in direction parallel to the movement axis. This configuration may enable large linear displacement of the voice coil while effectively inhibit rocking motion.

[0070] According to a second aspect of the invention, there is provided a loudspeaker module configured for use in the method as described above. The loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit. A partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening.

[0071] The loudspeaker module according to the second aspect may have any one or more features as described above with reference to the first aspect of the invention.

[0072] According to a third aspect of the invention, there provided a vehicle comprising: a body having a weight of at least 100kg, wherein the body includes an airtight surface which faces into an interior of the vehicle; a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the loudspeaker frame has a rear opening and a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening; wherein the loudspeaker frame is attached to the body to form a sealed volume between the airtight surface of the body, the loudspeaker frame and the diaphragm; wherein the partially-enclosed volume forms at least a majority of the sealed volume.

[0073] The vehicle according to the third aspect may include any one or more features as described in relation to the first aspect of the invention.

[0074] The loudspeaker module of the vehicle according to the third aspect may be as the loudspeaker module described above with reference to the first aspect of the invention.

[0075] According to a fourth aspect of the invention, there is provided a method for use in manufacturing a vehicle, the method includes: providing a precursor vehicle, wherein the precursor vehicle includes a body having a weight of at least 100kg, wherein the body includes an airtight surface which is configured to face into an interior of the vehicle manufactured from the precursor vehicle; providing a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the method includes: attaching the loudspeaker module to the body so as to form a sealed volume between the airtight surface of the body and a rear face of the diaphragm; wherein the sealed volume includes a loudspeaker-enclosed volume which is defined by the loudspeaker frame and a geometric plane which passes through at least three points at which the loudspeaker frame forms a junction with the body, wherein the loudspeaker-enclosed volume forms at least the majority of the sealed volume.

[0076] The method according to the fourth aspect may include any one or more features as described in relation to the first aspect of the invention.

[0077] According to a fifth aspect of the invention, there is provided a method for use in manufacturing a vehicle, the method includes: providing a precursor vehicle, wherein the precursor vehicle includes a body having a weight of at least 100kg, wherein the body includes an airtight surface which is configured to face into an interior of the vehicle manufactured from the precursor vehicle; providing a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes: a loudspeaker frame which includes a rear opening bounded by an inner edge of the loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the method includes: attaching the loudspeaker module to the body so as to form a sealed volume between the airtight surface of the body and a rear face of the diaphragm; wherein the sealed volume includes a loudspeaker-enclosed volume which is defined by the loudspeaker frame and a geometric surface; wherein the geometric surface is defined in that it is smooth and is bounded by the inner edge and has minimal surface area, zero mean curvature, and does not intersect the airtight surface; wherein the loudspeaker-enclosed volume forms at least the majority of the sealed volume.

[0078] The method according to the fifth aspect may include any one or more features as described in relation to the first aspect of the invention.

[0079] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0080] Summary of the Figures

[0081] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0082] Figure 1 is a cross-sectional view of a loudspeaker module.

[0083] Figure 2 is an enlarged view of a portion of Figure 1 .

[0084] Figure 3 is another cross-sectional view of the loudspeaker module, with some components not shown.

[0085] Figure 4 is a cross-sectional view of the loudspeaker module attached to a body.

[0086] Figure 5 is a graph showing relating the mass Mms of a moveable assembly of the loudspeaker module, an acoustic volume VB enclosed by the loudspeaker module, and the resonant frequency fc of the loudspeaker module.

[0087] Figure 6 illustrates a method of manufacturing a vehicle including the loudspeaker module.

[0088] Figure 7 is a schematic view of a precursor vehicle with the loudspeaker module.

[0089] Figure 8 is a schematic view of a vehicle with the loudspeaker module.

[0090] Figure 9 is a graph recording frequency against force for the loudspeaker module and a conventional loudspeaker module.

[0091] Figure 10 is a graph recording frequency against volume displacement for the loudspeaker module and a conventional loudspeaker module.

[0092] Figure 11 is a graph recording frequency against acceleration for the loudspeaker module and a conventional loudspeaker module.

[0093] Figure 12 is a cross-sectional view of the loudspeaker module attached to the body in another configuration in addition to what is shown in Figure 4.

[0094] Figure 13 is a cross-sectional view of the loudspeaker module attached to a curved portion of the body. Detailed Description of the Invention

[0095] 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.

[0096] Figure 1 shows an exemplary loudspeaker module 200. In particular, Figure 1 is a cross-sectional view of the loudspeaker module 200. The loudspeaker module 200 includes a loudspeaker frame 210, a diaphragm 220, and a drive unit 230. The drive unit 230 includes a moveable part 240, which is attached to the diaphragm 220, and a stationary part 250, which is attached to the frame 210.

[0097] The loudspeaker module 200 is operable to energise the drive unit 230 to cause displacement of the moveable part 240 relative to the stationary part 250. In particular, the moveable part 240 and the stationary part 250 magnetically interact with each other to effect displacement of the moveable part 240.

[0098] The diaphragm 220 and the moveable part 240 of the drive unit 230 are joined together to define a moveable assembly 260, such that in use they move together ‘as a unit’ when the moveable part 240 is caused to move. When causing the moveable assembly 260 to move along the movement axis 202, the diaphragm 220 acts as a piston and produces sound.

[0099] The moveable assembly 260 is suspended from the frame 210 by at least a first suspension element 262 and a second suspension element 264. The first suspension element 262 is attached to the frame 210 at a first landing surface 211 on the frame 210 and the second suspension element 264 is attached to the frame 210 at a second landing surface 212 on the frame 210.

[0100] The first suspension element 262 and the second suspension element 264 are secured to the moveable assembly 260 such that the centre of gravity of the moveable part 240 of the drive unit 230 is located between the first landing surface 211 and the second landing surface 212 when the moveable assembly 260 is at rest. More particularly, the centre of gravity of the moveable part 240 has a position along the movement axis 202 that is between the first landing surface 211 and the second landing surface 212.

[0101] The diaphragm 220 has a first sound radiating surface 221 and a second sound radiating surface 222. The first sound radiating surface 221 faces in a forward direction (away from the frame 210) and in use is utilised for producing sound. The second sound radiating surface 222 faces in a rearward direction, i.e. into the frame 210. The forward direction and the rearward direction are opposite directions parallel to the movement axis 202.

[0102] As shown in Figure 1 , the moveable part 240 of the drive unit 230 is a voice coil 242 while the stationary part 250 includes a magnet unit 252.

[0103] The magnet unit 252 is configured to generate magnetic flux and to guide the magnetic flux across an air gap 253. Suitably, the magnet unit 252 includes a permanent magnet 254 to generate the magnetic flux and at least two flux guiding elements 255, 256 to guide the magnetic flux across the air gap 253. The permanent magnet 254 is a rare earth magnet and may comprise more than one structural element. The flux guiding elements 255, 256 are provided as a (magnetic) yoke 255 and a (magnetic) washer 256. In Figure 1 , the yoke 255 is a U-yoke which has a base and a wall, which extends from the base, arranged about the movement axis 202.

[0104] In some examples, the permanent magnet 254 and the flux guiding elements 255, 256 are axially symmetric about the movement axis 202, though other arrangements are possible.

[0105] The magnet unit 252 and the air gap 253 form a magnetic circuit. The magnetic circuit provides a closed loop for the magnetic flux generated by the permanent magnet 254 and guided across the air gap 253 by the two flux guiding elements 255, 256. In some examples, the air gap 253 has a magnetic reluctance of 5.3 x 10A6 [1 / Henry] and the magnetic circuit has a total magnetic reluctance slightly greater than the magnetic reluctance of the air gap 253.

[0106] The loudspeaker module 200 makes use of a comparatively large voice coil 242 using many layers in the magnetic circuit. In some examples, the mass of the voice coil 242 is 60% or more of the total mass of the moveable assembly 260. In view of the large mass of the voice coil 242, the connection between the voice coil 242 and the diaphragm 220 is improved to prevent forces acting on the moveable assembly during operation from damaging the moveable assembly 260.

[0107] Figures 2 and 3 are further views of the loudspeaker module 200. Figure 2 is an enlarged view of a particular section of Figure 1 (indicated by a dotted circle in Figure 1). Figure 3 shows the loudspeaker 200 with the moveable part 240 of the drive unit 230 removed.

[0108] The voice coil 242 has a first perimeter 243 and a second perimeter 244. The distance between the first perimeter 243 and the second perimeter 244 is a winding thickness 245 of the voice coil 242.

[0109] Here, the voice coil 242 is a substantially circular coil such that the first perimeter is an inner radial boundary of the voice coil 242, and the second perimeter 244 is an outer radial boundary of the voice coil 242.

[0110] The diaphragm 220 includes a neck portion 223 forming a diaphragm aperture 224 (shown in Figure 3). The neck portion 223 is (when viewed in cross-section) a straight segment of the diaphragm 220. The diaphragm 220 further includes an inner diaphragm portion 225 and a curved portion 226 (or ‘curved segment’). The inner diaphragm portion 225 is another segment of the diaphragm 220 which (in crosssection) is straight. The curved portion 226 is located between and connects the neck portion 223 and the inner diaphragm portion 225, and (in cross-section) is curved.

[0111] The moveable assembly 260 also includes a voice coil former 290 which carries the voice coil 242. The voice coil former 290 extends through the diaphragm aperture 224 such that a first gap 266 is formed between the voice coil former 290 and the neck portion 223 of the diaphragm 220. Also, a second gap 268 is formed between the neck portion 223 and the voice coil 242. An adhesive body 269 of hardened adhesive occupies the first gap 266 between the voice coil former 290 and the neck portion 223 of the diaphragm 220 and the second gap 268 between the neck portion 223 and the voice coil 242 so as to attach the neck portion 223 of the diaphragm 220 to the voice coil former 290. The adhesive body 269 may occupy the entire first gap 266 and / or the entire second gap 268, i.e. fill either or both gaps 256, 258. In some examples, the adhesive body 269 may not be bonded to the voice coil 242, which in use may get very hot such that a bond between the adhesive body 269 and the voice coil 242 may be damaged. Nevertheless, the bond between the diaphragm 220 and the voice coil former 290 may be improved over a traditional loudspeaker.

[0112] The adhesive body 269 of hardened adhesive, e.g. a monolithic body of hardened / cured adhesive, occupies a volume of space both above and below the neck portion 223. More particularly, the adhesive body 269 of hardened adhesive extends all the way to the voice coil 242 (even if in use not bonded to the voice coil 242). As such, a greater volume of adhesive is provided than may be present in a traditional loudspeaker. Moreover, the volume of adhesive is both above and below the neck portion 223, whereas in the case of a traditional loudspeaker the adhesive may be exclusively on the diaphragm.

[0113] As illustrated in Figure 3, the loudspeaker frame 210 has a rear opening 213. The rear opening 213 is formed in a rear face 214 of the loudspeaker frame 210. The rear face 214 is in use attached to an airtight surface 310 of the body 300, such that the first radiating surface 221 of the diaphragm 220 faces away from the airtight surface 310. The airtight surface 310 is a structural surface of the body 300 (as opposed to a geometric surface).

[0114] The rear opening 213 is bounded by an inner edge 215, which faces towards the movement axis 202. The inner edge 215 is formed in the rear face 214 of the loudspeaker frame 210.

[0115] A partially-enclosed volume 270 is formed between the diaphragm 220, the loudspeaker frame 210 and the rear opening 213. That is to say, the partially-enclosed volume 270 is bounded by the loudspeaker module 200, and in particular the diaphragm 220 and the loudspeaker frame 210, and is open at the rear opening 213.

[0116] The rear opening 213 is the only opening of the loudspeaker module 200. That is to say, the loudspeaker module 200 has no other openings such that the partially-enclosed volume 270 of the loudspeaker module 200 is otherwise closed. Further components of the loudspeaker module 200 may also bound the partially-enclosed volume 270. For example, the first suspension element 262 by which the diaphragm 220 is suspended from the loudspeaker frame 210 also bounds the partially-enclosed volume 270. Similarly, a dust cap 280 also bounds the partially-enclosed volume 270. Also, the adhesive body 269 of hardened adhesive also bounds the partially-enclosed volume 270.

[0117] In use, the rear opening 213 is sealed, as is now described with reference to Figure 4, such that sound produced by the second sound radiating surface 222 of the diaphragm 220 is radiated into the loudspeaker module 200 inhibited from reaching the user.

[0118] Figure 4 is another cross-sectional view showing the loudspeaker module 200 and also showing a body 300 to which the loudspeaker module 200 has been mounted. The body 300 is a comparatively heavy structural element of a vehicle; as opposed to a comparatively lightweight structural element of the vehicle, such as a door. As such, the body 300 is heavier than a door. The body 300 has a weight of at least 100 kilograms. In some examples, the body corresponds to a unibody of a road vehicle, such as an automobile.

[0119] The body 300 includes an airtight surface 310. The loudspeaker module 200 is attached to the airtight surface 310 such that the rear opening 213 is sealed and the partially-enclosed volume 270 fully sealed.

[0120] A sealed volume 400 is formed between the loudspeaker module 200 and the airtight surface 310 of the body 300. According to the example of Figure 4, the sealed volume 400 is substantially identical to the partially-enclosed volume 270, since the loudspeaker module 200 is attached to a portion of the airtight surface 310 which is generally flat. The sealed volume 400, which is the acoustic volume inside the loudspeaker module 200, may in other examples be larger than the partially-enclosed volume.

[0121] At least one of the loudspeaker frame 210 and the stationary part 250 of the drive unit 240 is attached to the airtight surface 310 of the body 300.

[0122] The loudspeaker frame 210 includes, when viewed in cross-section through the movement axis 202, an outer portion 216 and inner portion 217.

[0123] An arch portion 218 which extends between the outer portion 216 and the inner portion 217. The outer frame portion 216 bounds the rear aperture 215.

[0124] At least one of the outer portion 216 and the inner portion 217 of the loudspeaker frame 210 may be attached to the airtight surface 310 of the body 300.

[0125] In Figure 4, the outer portion 216 of the loudspeaker frame 210 is attached to the body 300. In particular, a plurality of fastening members 510 are fitted to the outer portion 216 and inserted into corresponding blind holes 520 in the body 300. The blind holes 520 extend into the body 300 but do not extend through the body 300.

[0126] In some examples, the fastening members 510 are bolts and the blind holes 520 are matching tapped holes to receive the threaded shafts of the bolts.

[0127] In Figure 4, the stationary part 250 of the drive unit 230 to the body 300. Suitably, hardened adhesive 530 bonds the stationary part 250 to the body 300. As shown in Figure 4, the adhesive 530 bonds one of the flux guiding elements 255, which is provided the yoke, to the airtight surface 310 of the body 300.

[0128] The airtight surface 310 faces into an interior (or “cabin”) of the vehicle and in use, sound produced by first sound radiating surface 221 of the loudspeaker module 200 is radiated into the interior of the vehicle.

[0129] Figure 5 is a graph illustrating parameter ranges applicable to loudspeaker modules according to the present disclosure, such as the loudspeaker module 20. As such, Figure 5 may be used to estimate parameters during the design process.

[0130] The horizontal axis represents a normalised moving mass Mms / Sd, which corresponds to the mass Mms of the moveable assembly over the effective radiating surface Sd and ranges from 0 to 20 [kg / m2]. The vertical axis represents a normalised in-box acoustic volume VB of the enclosure, which corresponds to the volume VB over the effective radiating surface Sd and ranges from 0 to 1 [m3 / m2]. Accordingly, Figure 5 is Sd normalised; and Kms / Kb is equal to 0.5.

[0131] A set of frequency curve (solid lines) corresponds to different in-box resonant frequencies of 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz and 80Hz, respectively. As such, Figure 5 relates the mass Mms of the moveable assembly, the volume VB of the loudspeaker module, and the resonant frequency fc.

[0132] The grey area indicates preferred parameter ranges, with darker areas being more preferred. Thus, Mms / Sd is preferably in a range of 5 to 15 [kg / m2], and more preferably in a range from 7 to 12 [kg / m2]. VB / Sd is preferably greater than 0 and up to 0.5 [m], and more preferably in a range from 0.03 to 0.3 [mJ. The in-box resonant frequency is preferably in a range from 30Hz to 80Hz, and more preferably in a range of 40Hz to 80Hz.

[0133] The top left corner of Figure 5 may be considered to represent conventional loudspeaker design where either the moving mass is small, or the volume VB is large, or both are small. The lower right corner is a preferred area, and relates to comparatively high masses Mms, such as 180g, in an acoustic volume VB such as 6 litres. These parameters may not be preferred for music reproduction but may be preferred for cinema applications.

[0134] As an example, when choosing a volume VB of 1 .5 litres, then in order to achieve a target in-box resonant frequency fc of 60Hz, according to Figure 5 the normalised moving mass Mms / Sd is estimated at approximately 8.5 Mms / Sd. For an effective radiating surface Sd of 110cm2, this would correspond to a moving mass of approximately 93.5g.

[0135] Such estimation may give a first indication of approximate parameter values during the design process. It is noted that effects of the mechanical suspension contribution may in practice not be negligible and have been taken into account in Figure 5 (Kms / KB=0.5).

[0136] Figures 6, 7, 8 illustrate a method of manufacturing a vehicle 1000 including the loudspeaker module 200. In Figure 6, the steps of the method of manufacturing are illustrated. Figure 7 is a schematic illustration of a part-assembled vehicle or “precursor vehicle”. Figure 8 is a schematic illustration of the fully assembled vehicle 1000.

[0137] The method includes a step S110 of providing a precursor vehicle 500. The precursor vehicle 600 is a structure which ultimately is assembled into the vehicle 1000. In some examples, the precursor vehicle 600 corresponds to a so-called body-in-white. The body-in-white is an incomplete structure which is ultimately assembled into a vehicle. The body-in-white typically lacks moveable structural features, such as doors.

[0138] In the example of Figure 9, the precursor vehicle 600 is a unibody which corresponds to the body 300 and has a weight of at least 100 kilograms.

[0139] The body 300 includes the airtight surface 310 which is configured to face into an interior 1010 (or ‘cabin’) of the vehicle 1000. The method includes a step S120 of providing the loudspeaker module 200 as described above.

[0140] The method includes a step S130 of attaching the loudspeaker module 200 to form the sealed volume 400. The loudspeaker module 200 is attached to the airtight surface 310 of the body 300 so as to form the sealed volume 400 bounded by the airtight surface 310 of the body 300, the loudspeaker frame 210 and the diaphragm 220. In particular, the loudspeaker module 200 is directly attached to the body 300, as opposed to an intermediary structure, e.g. a decorative panel, attached to the body 300.

[0141] The method includes a step S140 of completing the manufacturing of the vehicle. Step 140 may include installation of the engine, windscreen, doors, seats, electronics and other conventional components. In some examples, the method of manufacturing the vehicle 1000 concludes with installation of the loudspeaker module 200, i.e. attaching the loudspeaker module 200 and suitably connecting the loudspeaker module 200 to the electronics of the vehicle 1000.

[0142] An example of the loudspeaker module 200 mounted the airtight surface 310 was prototyped, with the following parameters:

[0143] • voice coil resistance of 2.1 Ohm;

[0144] • BL of 6.3 Tm (Tesla-metres);

[0145] • mass of moveable assembly of 82g;

[0146] • mechanical resistance of 2.7Ns / m (Newtons times seconds over metres);

[0147] • stiffness of 4.2 N / mm (Newtons over millimetres);

[0148] • effective radiating surface of 110 cm2(square-centimetres);

[0149] • mechanical stroke of 11 mm;

[0150] • a motor and suspension linearity enabling more than 8mm peak displacement at resonance when powered with 100W and mounted in the box described below;

[0151] • an Acrylonitrile Butadiene Styrene module with integrated loudspeaker frame offering an acoustic back volume of 1 .5 litres, 4 mounting holes and an acoustic sealing;

[0152] • an in-box resonance frequency of 67Hz and a total quality factor of 1 .6 when mounted on a flat airtight barrier.

[0153] For purposes comparison, a modified loudspeaker module with the same parameters but including an integrated rear wall, sealing off the back volume, was also prototyped. Strong acceleration was observed when this modified loudspeaker module while driven with a sine wave of 100W (Watts) nominal power at 70Hz, a strong acceleration was observed. The inventors believe the observed vibration may be strong enough to create many undesired artefacts if used for audio reproduction when attached to a traditional mounting position in an automobile, such as an interior panel or door trim. Vibrations of a conventional 6.5inch-door woofer having a moving mass of 15 grams and a power handling capability of 35W were also observed. However, the acceleration on the conventional 6.5inch- door woofer was an order of magnitude smaller compared to the example above relating to the modified loudspeaker module. Nevertheless, it is known that these conventional solutions already create many issues related to vibrations induced in the door structures. As such, it may not be desirable to increase the forces acting on the door structure even further.

[0154] A lumped element analysis was performed to compare the modified loudspeaker module and the conventional 6.5inch-door woofer. Figure 9 displays the result of the lumped element analysis. The solid line corresponds to the forces generated by the modified loudspeaker module running at 100W in function of frequency. The dotted line corresponds to the forces generated by the conventional 6.5inch-door woofer running at 35W. The simulation shows that the forces generated by the modified loudspeaker module are approximately 10 times larger when compared to the forces generated by the traditional door loudspeaker.

[0155] To estimate the acoustic output, the volume displacement of the modified loudspeaker and the conventional 6.5inch-door woofer were calculated using lumped element analysis. Figure 10 displays the results of the analysis. The solid line corresponds to the volume displacement of the modified loudspeaker module running at 100W in function of frequency. The dotted line plots the volume displacement of the conventional 6.5inch-door woofer running at 35W in function of frequency. The graph shows that the output between 50Hz and 100Hz of both options is comparable.

[0156] Figure 11 illustrates the measured acceleration caused by the loudspeaker module 200 mounted in a vehicle. The horizontal axis of the graph corresponds to frequency, the vertical axis to the measured acceleration. The solid line represents the measured acceleration on a mounting feature to which the loudspeaker module 200 was attached. The dashed line corresponds to the acceleration measured at a foot step of the vehicle (in particular a screw on the portion of the floor intended for the feet of the occupant).

[0157] The vehicle in this example was an Audi A8 vehicle MY2000 (with a unibody predominantly made from aluminium). The loudspeaker module 200 was mounted to the lower right side of the firewall behind the front right wheel and arranged to be facing into the cabin.

[0158] The loudspeaker module 200 was driven with a 100W sine wave. As can be seen in Figure 11 , the solid line indicates a rather high inertia from the application, especially below 100Hz. The dashed line indicates an even more reduced acceleration due to the high inertia of the application.

[0159] While evaluating the example of the loudspeaker module 200 with music while driven with a 100W rated amplifier, no disturbing vibrations were observed anywhere in the automobile. Moreover, no disturbing rub and buzz sounds were observed. The overall subjective quality was estimated higher than a conventional loudspeaker in a door. Without wishing to be bound by theory, it is believed that this may be linked to the absence of acoustic resonances in the doors, the absence of acoustic short circuits linked to floppy door panels and separation between the dry and wet zone inside the door structure, the absence of vibrations and the absence of rub, buzz, and other rattling sounds liked to this.

[0160] While measuring the module on different locations it was observed that the cabin boost on the evaluated position was higher compared to the cabin boost associated to a door position over a wide frequency range from 40Hz to 200Hz. Without wishing to be bound by theory, it is believed that this may be contributed to the alignment of the direct sound from the mounting feature at the firewall and the reflected sound from the three boundaries around the evaluated position: the floor, front firewall and right side of the car. This arrangement may lead to a higher achieved sound pressure level in the cabin compared to other positions.

[0161] The loudspeaker module 200 as described above has the voice coil 242 included in the moveable part 240 and the magnet unit 252 included in the stationary part 250. In some examples, the voice coil 242 is included in the stationary part 250 and the magnet unit 252 is included in the moveable part 240.

[0162] Figure 12 is another view of the loudspeaker module 200 attached to the body 300. The loudspeaker module 200 and the body 300 are as in Figure 4, and the corresponding description applies also to Figure 12. The example of Figure 12 differs from that of Figure 4 in that the inner frame portion 217 is attached to the body 300, whereas in Figure 4 it is the stationary part 250 of the drive unit 230 that is attached to the body 300. Suitably, the hardened adhesive 530 bonds the inner frame portion 217 to the body 300. In other examples, the hardened adhesive 530 is replaced by, for example, compressed foam or thermoplastic elastomer.

[0163] In some examples, both the stationary part 250 of the drive unit 230 and the inner frame portion 217 may be attached to the body 300.

[0164] The loudspeaker frame 210 of the loudspeaker module 200 described above forms a flat rear opening 213 which is perpendicular to the movement axis 202, matching the correspondingly flat airtight surface 310 of the body 300. In some examples, the loudspeaker frame 210 may have a rear opening that is not flat, not perpendicular to the movement axis 202, or neither flat nor perpendicular to the movement axis 202. In some examples, the sealed volume may include additional (acoustic) volume outside of the loudspeaker module 200. The inside volume of the loudspeaker module 200, i.e. the partially-enclosed volume 270, and the outside volume of the loudspeaker module 200 may be separated with reference to a (geometric) surface which has minimal surface area. The rear opening 213 may correspond to such a plane, bounded by the inner edge 215 of the rear face 214. For example, in the example of Figure 1 the flat rear opening 213 corresponds to a geometric surface of minimal surface area.

[0165] Figure 13 shows an example wherein the rear opening 213 of the loudspeaker frame 210 is neither flat nor perpendicular to the movement axis 202. In particular, the rear face 214 of the loudspeaker frame 210 is slanted with respect to the movement axis 202, and the loudspeaker module 200 is attached to a curved portion of the airtight surface 310. The resulting sealed volume 400 includes the partially-enclosed volume 270 defined by the loudspeaker module 200 as well as an additional volume 410 defined by the body 300.

[0166] The rear opening 213, which provides a (virtual) boundary between the partially-enclosed volume 270 and the additional volume 410, may be defined as corresponding to a geometric surface bounded by the inner edge 214 and which, when the loudspeaker module 200 is attached to the body 300, does not intersect the airtight (structural) surface 310 of the body 300, is smooth, has minimal surface area and zero mean curvature. The geometric surface so defined and shown in Figure 13 is curved along a portion of the airtight surface 310 since the geometric surface is not to intersect the airtight surface 310.

[0167] In Figure 13, a geometric plane 219 which may alternatively be used to define the rear opening is also shown. The geometric plane 219 passes through at least three points on the loudspeaker frame 210 at which the loudspeaker frame 210 (when attached to the body 300) forms a junction with the body 300. As can be seen in Figure 13, the geometric plane 219 intersects the body 300. As such, when using this definition, the partially enclosed volume 270 is taken to be the portion of the sealed volume which is forward of the geometric plane 219 (i.e. proximal to the diaphragm) whereas the additional volume 410 is taken to be the portion of the sealed volume which is behind the geometric plane 219 (i.e. distal to the diaphragm). As such, the actual sealed volume is divided by the geometric plane 219 in that any portion of the sealed volume forward of the geometric plane 219 is the partially-enclosed volume 270, while any portion of the sealed volume behind the geometric plane 219 is the additional volume 410. Thus, the portion of the body 300 which is intersected by the geometric plane 219 is accounted for insofar as it reduces the partially-enclosed volume 270.

[0168] As can be seen in Figure 13, the partially-enclosed volume 270 is larger than the additional volume 410 irrespective of whether the rear opening is defined by way of the geometric surface 213 or the geometric plane 219. Indeed, it is noted that both definitions divide the sealed volume 400 into approximately the same portions. Notably, the geometric plane 219 attributes more volume to the partially-enclosed volume 270 towards the left-hand side of Figure 13, and attributes less volume to the partially-enclosed volume 270 towards the right-hand side of Figure 13, so that in combination both contributions approximately cancel to yield a result similar that obtained when using the geometric surface 213.

[0169] 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.

[0170] 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.

[0171] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0172] 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.

[0173] 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%.

[0174] References

[0175] 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.

[0176] 1. L.L. Beranek, Acoustics, McGraw-Hill, 1954

Claims

Claims:1 . A method for use in manufacturing a vehicle, the method includes: providing a precursor vehicle, wherein the precursor vehicle includes a body having a weight of at least 100kg, wherein the body includes an airtight surface which is configured to face into an interior of the vehicle manufactured from the precursor vehicle; providing a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the loudspeaker frame has a rear opening, wherein a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening, wherein the method includes: attaching the loudspeaker module to the body so as to form a sealed volume bounded by the airtight surface of the body, the loudspeaker frame and the diaphragm; wherein the partially-enclosed volume forms at least a majority of the sealed volume.

2. The method according to claim 1 , wherein attaching the loudspeaker module to the body includes using a plurality of fastening members to attach the loudspeaker module to the loudspeaker frame.

3. The method according to claim 2, wherein attaching the loudspeaker module to the body using the plurality of fastening members includes locating the fastening members in a corresponding plurality of blind holes in the body.

4. The method according to claim 2, wherein the plurality of fastening members is permanently attached to and extends from the airtight surface, and attaching the loudspeaker module to the body includes receiving the plurality of fastening members into the loudspeaker frame.

5. The method according to any preceding claim, wherein the loudspeaker frame includes an outer frame portion which bounds the rear opening; and attaching the loudspeaker module to the body includes attaching the outer frame portion to the body.

6. The method according to any preceding claim, wherein the loudspeaker frame includes an inner frame portion which is attached to the drive unit; and attaching the loudspeaker module to the body includes attaching the inner frame portion to the body.

7. The method according to any preceding claim, wherein attaching the loudspeaker module to the body includes attaching the drive unit to the body.

8. The method according to any preceding claim, wherein the airtight surface is substantially flat and the partially-enclosed volume of the loudspeaker module forms substantially the entirety of the sealed volume.

9. The method according to any preceding claim, wherein wherein the body is included in a unibody structure.

10. The method according to any preceding claim, wherein the loudspeaker module includes a moveable assembly which includes the diaphragm and a moveable part of the drive unit; and the mass of the moveable part of the drive unit may be at least 60% of the mass of the moveable assembly.

11. The method according to claim 10, wherein the loudspeaker module is operable to cause the moveable part of the drive unit to magnetically cooperate with a stationary part of the drive unit to cause the moveable assembly to move along the movement axis to produce sound; and a ratio of the mass of the moveable part of the drive unit and an effective sound radiating area Sd of the diaphragm is at least 5 kilograms per square-metre, optionally at least 7 kilograms per square-metre.

12. The method according to any preceding claim, wherein the ratio of the sealed volume over an effective sound radiating area Sd of the diaphragm is in a range of 0.01 to 0.5 metres.

13. The method according to any preceding claim, wherein the loudspeaker module is a subwoofer configured to produce sound with frequencies in a bass frequency range, the bass frequency range including 60-80Hz.

14. A loudspeaker module configured for use in the method according to any preceding claim, wherein the loudspeaker module includes: a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit; wherein a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening.

15. A vehicle comprising: a body having a weight of at least 100kg, wherein the body includes an airtight surface which faces into an interior of the vehicle; a loudspeaker module for producing sound at bass frequencies, wherein the loudspeaker module includes a loudspeaker frame, a diaphragm suspended from the loudspeaker frame, and a drive unit configured to move the diaphragm to produce sound; wherein the loudspeaker frame has a rear opening and a partially-enclosed volume is formed between the diaphragm, the loudspeaker frame and the rear opening; wherein the loudspeaker frame is attached to the body to form a sealed volume between the airtight surface of the body, the loudspeaker frame and the diaphragm; wherein the partially-enclosed volume forms at least a majority of the sealed volume.

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