GB2595318A

GB2595318A - Loudspeaker arrangement

Info

Publication number: GB2595318A
Application number: GB2016832.4A
Authority: GB
Inventors: Corynen David; Haelvoet Tom; Van Den Keybus Thomas; Vuine Fabian
Original assignee: PSS Belgium NV
Current assignee: PSS Belgium NV
Priority date: 2020-10-23
Filing date: 2020-10-23
Publication date: 2021-11-24
Also published as: DE202021105667U1; GB202016832D0

Abstract

The arrangement includes a plurality of seat assemblies 120 located in the enclosed space and at least one shared mid-high frequency loudspeaker 130 to project sound into the enclosed space. Each seat assembly includes a personal bass loudspeaker 140 and at least one personal mid-high frequency loudspeaker 150, 155 positioned within 50cm of the listening position. The loudspeaker arrangement may operate in a shared mode in which the at least one shared mid-high frequency loudspeaker projects sound into the enclosed space, at least one seat assembly is operational, and for each operational seat assembly the personal bass loudspeaker produces supplementary sound that supplements the sound from the at least one shared mid-high frequency loudspeaker. The loudspeaker arrangement may also operate in a personal mode in which the at least one shared mid-high frequency loudspeaker is muted, at least one seat assembly is operational and for each operational seat assembly the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker produce sound.

Description

LOUDSPEAKER ARRANGEMENT

Field of the Invention

The present invention relates to a loudspeaker arrangement for use in an enclosed space, e.g. a car.

S

Background

Among the frequencies in the audible spectrum, lower frequencies are the ones that tend to carry most over large distances and are the ones difficult to keep inside a room. For example, nuisance from neighbouring loud music has mostly a low frequency spectrum. "Low" frequencies can also be referred to as "bass" frequencies and these terms may be used interchangeably throughout this document.

Many cars today are equipped with a main audio system, which typically consists of a central user interface console with internal or external audio amplifiers, and one or more loudspeakers placed in the doors. This type of audio system is used to ensure enough loudness of the same content (e.g. radio) for all passengers.

Some cares include personal entertainment systems (music, games & television) which are typically equipped with headphones to ensure individual passengers receive personalised sound, without disturbing (or being disturbed by) other passengers who are enjoying a different audio-visual content.

However, although the usage of headphones ensures a good sound quality and a very effective personal sound cocoon (little sound leakage), the use of headphones has safety, ergonomic and comfort problems.

Similar considerations apply in other environments such as home, studio, and public areas where individual entertainment is needed without disturbing neighbours.

Some cars include loudspeakers placed very close to an individual passenger, so that sound having an adequately high sound pressure level ("SPL") can be obtained at the ears of that individual passenger, whilst having a much lower SPL at the positions of other passengers.

The present inventors have observed that the concept of a personal sound cocoon is a useful way to understand the approach of having a loudspeaker placed close to a user, wherein the personal sound cocoon is a region in which a user is able to experience sound having an SPL deemed to be acceptably high for their enjoyment, whereas outside the personal sound cocoon the sound is deemed to have an SPL which is lower than it is within the personal sound cocoon.

It is known that the use of a highly directive loudspeaker positioned close to an individual passenger! user can bring an effective solution for medium and high frequencies. However, it is generally impractical in most situations to make a loudspeaker directive at bass frequencies, since in order to provide a highly directive loudspeaker for bass frequencies, the dimensions of the radiating surface must be of the same order as the wavelength, and wavelengths are typically very long for bass frequency content (e.g. A =3.4m for f = 100Hz). Loudspeakers with radiating surfaces of this scale for producing bass frequency content are impractical in many situations, such as in a car. Nonetheless, bass frequency content is a very important part of the audio spectrum and in most music this spectrum represents half or more of the total sound power.

It is known from W02019/121266A1 that dipole loudspeakers can provide an effective personal sound cocoon at bass frequencies, thereby effectively providing a personal subwoofer. This disclosure also suggests combining the disclosed dipole loudspeakers with high directivity loudspeakers for mid and high frequencies (see page 30 lines 28-30).

Further developments and refinements relating to this concept are also disclosed in: * W02019/192808 * W02019/192816 * W02020/126847 * GB2008724.3 * GB2009203.7 * G82014020.8 * GB2015053.8 The present inventors have observed that where these disclosures describe examples in which mid-high frequency loudspeakers are incorporated into a headrest of a seat, these examples lack frontal stereo imaging, due to the position of the loudspeakers behind or at most next to a user's ear.

The present inventors have observed that a typical car audio system today plays back one audio source (same audio content) for all passengers. The audio system is typically optimized to achieve equal performance at every seat.

A typical loudspeaker arrangement for a car involves having large 16.5cm (6.5 inch) loudspeakers mounted in each door, in order to achieve good SPL at low frequencies. This is expensive for the car manufacturer to implement, as it requires the car doors to include sound insulation, construction, water proving, wiring harness, grilles, which leads to added weight and permits less room for safety features. Also, at louder listening levels, sound can leak out of the enclosed space within the car and into the environment.

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

Summary of the Invention

A first aspect of the present invention may provide: A loudspeaker arrangement including: an enclosed space; a plurality of seat assemblies located in the enclosed space; and at least one shared mid-high frequency loudspeaker configured to project sound into the enclosed space; wherein each seat assembly includes: a seat, for a user to sit on; a personal bass loudspeaker positioned so as to be within 50cm of a listening position corresponding to the head of a user sat on the seat: at least one personal mid-high frequency loudspeaker positioned so as to be within 50cm of the listening position; wherein the loudspeaker arrangement is configured to operate in a shared mode in which: the at least one shared mid-high frequency loudspeaker projects sound into the enclosed space; at least one seat assembly is operational, wherein for the/each operational seat assembly, the personal bass loudspeaker produces supplementary sound that is configured to supplement the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker; wherein the loudspeaker arrangement is configured to operate in a personal mode in which: the at least one shared mid-high frequency loudspeaker is muted; at least one seat assembly is operational, wherein for the/each operational seat assembly, the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker produce sound whose audio content is adjustable independently of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in at least one other seat assembly.

In this way, users sat in the seat assemblies can (in shared mode) enjoy a shared experience in which the personal bass loudspeaker allows for an enhanced bass experience (preferably also at mid-high frequencies) for each user, but can also enjoy a personal sound experience in which different users enjoy different audio content at the same time, without the sound produced by one operational seat assembly distracting users in other seat assemblies, and without the need for headphones.

Advantageously, the shared mode allows for a shared experience that is familiar for a listener, since in existing loudspeaker arrangements employed with a plurality of seat assemblies (e.g. in a car), listeners are more familiar with a full range spatial sound reproduction that originates from a location that is distant from the user. Although the experience of a listener in personal mode can be enjoyable, some people may find it comfortable to switch when possible to a more familiar "distant" sound. By having the bass portion of the sound provided from a location close to the listener in the shared mode, it is possible that only one or more small (mid-high frequency) loudspeakers are needed to enable this distant sound experience, thereby saving a lot of complexity (e.g. by avoiding the need for installation of large woofers, e.g. as might otherwise be needed in car doors, where the enclosed space is in a car).

The term "operational" seat assembly is used to identify a seat assembly in which at least one personal loudspeaker is operating. An "operational" seat assembly is thus distinguished from a "non-operational" seat assembly in which no personal loudspeakers are operating. It is thus to be understood that not all seat assemblies need to be operating at once.

A bass loudspeaker can be understood as a loudspeaker configured to operate at frequencies in the range 50-150Hz.

A mid-high frequency loudspeaker can be understood as a loudspeaker configured to operate at frequencies in the range 500-20kHz (a mid-high frequency loudspeaker operating in this range could of course additionally operate at frequencies above or below this range). Thus, a tweeter configured to operate only at frequencies in the range 2kHz-20kHz can still be viewed as a mid-high frequency loudspeaker, a mid-range loudspeaker configured to operate at frequencies only in the range 500Hz-4Hz can still be viewed as mid-high frequency loudspeaker, as can a loudspeaker configured to operate at frequencies in the range 150Hz-20kHz.

For avoidance of any doubt, a seat assembly that includes a single, full-range loudspeaker, configured to produce bass frequencies On the range 50-150Hz) and also configured to produce frequencies extending into a mid-high frequency range (e.g. 150Hz-20kHz) can be viewed as including a personal bass loudspeaker and a personal mid-high frequency loudspeaker, with the single, full-range loudspeaker, serving as both the personal bass loudspeaker and a personal mid-high frequency loudspeaker in that seat assembly. However, it is preferred for the personal bass loudspeaker and the personal mid-high frequency loudspeaker included in each seat assembly to be separate loudspeakers.

When the at least one shared mid-high frequency loudspeaker is described as being muted in the personal mode, it is preferably meant that the/each shared mid-high frequency loudspeaker produces substantially no sound (e.g. is silent) in the shared mode. This may be achieved by the/each shared mid-high frequency loudspeaker producing no sound at all, or by he/each shared mid-high frequency loudspeaker producing so little sound that the sound produced by the/each shared mid-high frequency loudspeaker cannot be heard by a user sat on a seat of an operational seat assembly. Thus, the SPL of sound that is produced by the/each shared mid-high frequency loudspeaker in the shared mode Of any sound is produced at all by the/each shared mid-high frequency loudspeaker in the shared mode) should be substantially less (preferably at least 10dB less, more preferably at least 20dB less) than the SPL of sound produced by the personal loudspeakers included in an operational seat assembly at a listening position corresponding to the head of a user sat on the seat of that seat assembly in the shared mode at the same time.

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Herein, an audio source can be understood as an audio device configured to provide an audio signal (e.g. an electrical signal) which carries a representation of sound that can be replicated by a loudspeaker. An audio source may provide a digital audio signal (e.g. CD player, streaming service) or an analogue audio signal (e.g. record player, tape player). If the audio source provides a digital audio signal, then typically a digital-to-analogue converter (DAC) is used to convert the digital audio signal into an electrical analogue audio that is amplified before being received by a loudspeaker (which then replicates the representation of sound carried by the digital audio signal). Typically digital audio sources are used in most vehicles.

When reference is made herein to the audio content of sound produced by a loudspeaker, it is intended to mean the underlying audio content (a digital or analogue representation of sound, e.g. as carried to the loudspeaker by an audio signal) replicated by the loudspeaker. Thus, when the audio content of sound produced by a first set of loudspeakers (e.g. the personal bass loudspeaker and the at least one personal mid-high loudspeaker in a first seat assembly) is said to be "adjustable independently" of sound produced by a second set of loudspeakers (e.g. the personal bass loudspeaker and the at least one personal mid-high loudspeaker in a second seat assembly), it is intended to mean that the sound produced by the first set of loudspeakers replicates audio content that can be adjusted independently of the audio content replicated by the second set of speakers, e.g. so that the sound produced by the first set of loudspeakers replicates different audio content from that replicated by the second set of loudspeakers (e.g. different sound recordings, different radio stations).

For avoidance of any doubt, two sets of loudspeakers producing sound that replicate different channels (e.g. left and right channels) of the same audio content are considered to replicate the same audio content.

For avoidance of any doubt, two sets of loudspeakers producing sound that replicate the same audio content but whose relative volumes (the volume of one set of loudspeakers relative to the other) can be controlled independently are considered to replicate the same audio content.

For avoidance of any doubt, two sets of loudspeakers producing sound that replicate the same audio content except for there being a small (less than 1 second) time delay between the sound produced by one set of loudspeaker compared with the other, are considered to replicate the same audio content.

For avoidance of any doubt, there may be modes other than the shared mode and personal mode, e.g. an announcement mode in which the shared mid-high frequency loudspeaker interrupts the personal mode to deliver sound that needs to be heard by all users seated on a seat in the loudspeaker arrangement.

Herein, a principal radiating axis of a radiating surface may be understood as an axis along which the radiating surface produces direct sound at maximum amplitude (sound pressure level). Typically, the principal radiating axis will extend outwardly from a central location on the radiating surface. The principal radiating axes of the first and second radiating surfaces will in general extend in opposite directions, since they are located on opposite faces of the diaphragm.

Preferably, the loudspeaker arrangement may be configured operate in the personal mode such that: the at least one shared mid-high frequency loudspeaker is muted; at least two seat assemblies are operational, wherein for each operational seat assembly, the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker produce sound whose audio content is adjustable independently of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in at least one other operational seat assembly. This clarifies that in the personal mode, two users can listen to different audio content at the same time from their personal loudspeakers, though of course the personal mode may additionally allow for just one seat assembly to be operational.

In some implementations, in the shared mode, for each operational seat assembly, the at least one personal mid-high frequency loudspeaker (in addition to the personal bass loudspeaker) produces supplementary sound that is configured to supplement the sound projected into the enclosed space by the mid-high frequency loudspeaker. However, it is possible in the shared mode, for each operational seat assembly, for only the personal bass loudspeaker to produce supplementary sound, i.e. with the at least one personal mid-high frequency loudspeaker not producing sound (since mid-high frequency sound might instead only be produced by the shared mid-high frequency loudspeaker, in the shared mode).

Preferably, in the shared mode, for each operational seat assembly, if the at least one personal mid-high frequency loudspeaker produces sound in the shared mode, the loudspeaker arrangement is configured to apply an attenuation to supplementary sound produced by the at least one personal mid-high frequency loudspeaker (e.g. by applying an attenuation to an audio signal supplied to the at least one personal mid-high frequency loudspeaker), preferably such that the sound is perceived by a user sat on the seat of the seat assembly as being produced by the at least one shared mid-high frequency loudspeaker. The attenuation applied to the supplementary sound may result in the supplementary sound produced by the at least one personal mid-high frequency loudspeaker having an SPL that is at least 5dB lower than the SPL of the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker at the listening position corresponding to a head of a user sat in the seat of the operational seat assembly. This may help a user sat on the seat perceive the sound as being produced by the at least one shared mid-high frequency loudspeaker.

Preferably, in the shared mode, for each operational seat assembly, the supplementary sound produced by the personal bass loudspeaker (optionally also the supplementary sound produced by the at least one personal mid-high frequency loudspeaker) derives from the same audio source as the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker. For example, the audio content of the supplementary sound may be the same as that of the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker. Or the audio content of an audio signal deriving from the same audio source may be processed in some way to provide a particular supplementary effect (e.g. reverb, e.g. 3D sound).

Preferably, in the shared mode, for each operational seat assembly, the loudspeaker arrangement is configured to apply a time delay to the audio content of supplementary sound produced by the personal bass loudspeaker (and to the audio content of supplementary sound produced by the at least one personal mid-high frequency loudspeaker, if the at least one personal mid-high frequency loudspeaker produces sound in the shared mode) compared with the audio content of sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker, wherein the time delay is configured to compensate for a delay in sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker reaching the listening position corresponding to the head of a user sat on the seat of the operational seat assembly (due to a distance between the shared mid-high frequency loudspeaker and the listening position). The time delay may be applied by applying a time delay to an audio signal supplied to the at least one personal bass loudspeaker (and to an audio signal supplied to the at least one personal mid-high frequency loudspeaker, if the at least one personal mid-high frequency loudspeaker produces sound in the shared mode). The time delay may be different for some/all operational seat assemblies, e.g. due to different positions of the operational seat assemblies relative to the position of the shared mid-high frequency loudspeaker. Thus, for a car interior, the time delay may be larger for rear seats compared with front seats, if the shared mid-high frequency loudspeaker is mounted in the front (e.g. dashboard) of the car. For a vehicle interior, this delay may be in the range 1-10ms, or even 2-5ms, depending on the size of the vehicle.

Preferably, the loudspeaker arrangement is configured to, for each operational seat assembly, operate the personal bass loudspeaker across a first bass frequency range in the personal mode, and across a second bass frequency range in the shared mode, wherein the first frequency range includes a lower upper frequency limit than the second frequency range. The upper frequency limit of the first frequency range may be lower than 180Hz, more preferably lower than 160Hz, or even 150Hz or lower, so as to achieve a good "cocooning" effect (see e.g. W02019/121266A1), whereas the upper frequency limit of the second frequency range may be higher than this (e.g. 180Hz or higher), in order to provide a better experience in the shared mode.

Preferably, the loudspeaker arrangement is configured to operate the shared mid-high frequency loudspeaker across a frequency range that at least includes frequencies across the range 500Hz-4Hz, more preferably across the range 200Hz-20kHz.

Preferably, the loudspeaker arrangement is configured to, for each operational seat assembly, operate the at least one personal mid-high frequency loudspeaker across a frequency range that at least includes frequencies across the range 500Hz-4Hz, more preferably across the range 200Hz-20kHz.

In the shared mode, the shared mid-high frequency loudspeaker, and for each operational seat assembly, the personal bass loudspeaker and optionally the at least one personal mid-high frequency loudspeaker, may be configured to receive audio signals deriving from the same audio source. The loudspeaker arrangement may be configured to, in the shared mode, process an audio signal deriving from the audio source differently according to whether it is to be received (and converted into sound) by the shared mid-high frequency loudspeaker, by the personal bass loudspeaker in an operational seat assembly, or optionally by the at least one personal mid-high frequency loudspeaker in that operational seat assembly. For example, a different gain, delay and/or highpass/lowpass filter may (or may not) be applied differently to an audio signal deriving from the audio source, depending on whether it is to be received (and converted into sound) by the shared mid-high frequency loudspeaker, by the personal bass loudspeaker in an operational seat assembly, or optionally by the at least one personal mid-high frequency loudspeaker in that operational seat assembly, see e.g. Fig. 2A.

In the personal mode, for each operational seat assembly, the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker in that seat assembly, may be configured to receive audio signals deriving from the same audio source. The loudspeaker arrangement may be configured to, in the personal mode, process an audio signal deriving from the audio source differently according to whether it is to be received (and converted into sound) by the personal bass loudspeaker in an operational seat assembly, or by the at least one personal mid-high frequency loudspeaker in that operational seat assembly. For example, a different gain, delay and/or highpass/lowpass filter may (or may not) be applied differently to an audio signal deriving from the audio source, depending on whether it is to be received (and converted into sound) by the personal bass loudspeaker in an operational seat assembly, or by the at least one personal mid-high frequency loudspeaker in that operational seat assembly, see e.g. Fig. 2B.

Preferably, for each seat assembly, the seat is configured to position a user who is sat down in the seat such that the head of the user (e.g. a centre of the head of the user) is located at the listening position corresponding to the head of a user sat on the seat. The listening position corresponding to the head of a user sat on the seat may be a distance of 50cm or less (more preferably 30cm or less, more preferably 25cm or less, more preferably 20cm or less, more preferably 15cm or less) from (e.g. a first radiating surface of) the personal bass loudspeaker. The listening position corresponding to the head of a user sat on the seat is preferably 50cm or less (more preferably 30cm or less, more preferably 25cm or less, more preferably 20cm or less, more preferably 15cm or less) from (e.g. a first radiating surface of) the/each personal mid-high frequency loudspeaker.

This can conveniently be achieved by mounting the loudspeaker in a headrest of the seat, since a typical headrest is configured to be a small distance (e.g. 30cm or less) from the head of a user who is sat down in a seat.

Preferably, for each seat assembly, the personal bass loudspeaker is mounted in a headrest of the seat.

This is a particularly convenient way of positioning the personal bass loudspeaker to be near to the listening position corresponding to the head of a user sat on the seat of the seat assembly, especially if the bass loudspeaker is a dipole loudspeaker (though other ways are possible, e.g. the personal bass loudspeaker could be positioned just above the head of a user sat in the seat). With the personal bass loudspeaker mounted in headrests of the seats, the number of bass loudspeakers needed in other areas of the enclosed space (e.g. woofers in car doors, if the enclosed space is in a car) can be reduced or eliminated altogether.

Preferably, for each seat assembly, the at least one personal mid-high frequency loudspeaker is mounted in a headrest of the seat. This is a convenient way of positioning the personal bass loudspeaker to be near to the listening position corresponding to the head of a user sat on the seat of the seat assembly. However, it is more practical to locate mid-high frequency loudspeakers elsewhere in an enclosed space (e.g. in a walls of an enclosure which enclose the enclosed space), since they are generally much smaller than bass loudspeakers.

In other examples, for each seat assembly, the at least one personal mid-high frequency loudspeaker may be included in a wearable device configured to be worn by a user seat on a seat of the seat assembly. The/each wearable device preferably does not occlude an ear of the user and could, for example take the form of an open headphone that does not occlude an ear of a user, e.g. as in the audio eyeglasses disclosed in W02020/028529. The low frequency performance of using mid-high frequency loudspeaker(s) included in a wearable device in addition to the personal bass loudspeaker would be much improved compared with using the wearable device alone (when any bass sound that is produced would quickly be masked in a noisy environment, e.g. a car). By pairing such wearable devices to an audio system of the enclosed pace (e.g. a car entertainment system), the wearable devices can become pad of the audio system, which can allow for delay, gain, cross-over settings being implemented as described elsewhere in this disclosure in personal and/or shared modes.

A seat headrest typically has a front surface configured to face towards the head of a user sat in the seat, and a back surface configured to face away from the head of a user sat in the seat.

Each headrest may include mounting pins which are part of the rigid frame of the seat On which the headrest is included), but are configured to allow the headrest to be detached from the remainder of a rigid frame of the seat (such mounting pins are common in most cars). Alternatively, each headrest may be integral with the remainder of the seat On which the headrest is included).

For each seat assembly, the personal bass loudspeaker is preferably mounted within a headrest of the seat with a first radiating surface of a diaphragm (or of each diaphragm, if the personal bass loudspeaker includes more than one diaphragm) of the personal bass loudspeaker facing towards the listening position corresponding to the head of a user sat on the seat.

For each seat assembly, there are preferably two personal mid-high frequency loudspeakers, wherein a first ("right ear") personal mid-high frequency loudspeaker is mounted within a headrest of the seat with a first radiating surface of a diaphragm of the first ("right ear") personal mid-high frequency loudspeaker facing towards a position corresponding to a right ear of a user sat on the seat, and wherein a second ("left ear") personal mid-high frequency loudspeaker is mounted within the headrest with a first radiating surface of a diaphragm of the second ("left ear") personal mid-high frequency loudspeaker facing towards a position corresponding to a left ear of the user sat on the seat. In this way, the two personal mid-high frequency loudspeakers may be configured to deliver personal stereo sound to the user sat in the seat.

The first and second personal mid-high frequency loudspeakers may be mounted in forward-protruding wings of the headrest to achieve this.

Each loudspeaker in the loudspeaker arrangement may have a diaphragm, and a drive unit configured to move the diaphragm along a movement axis so as to produce sound. Each diaphragm may have a first radiating surface and a second radiating surface. Usually, herein the "first radiating surface" of a diaphragm belonging to a loudspeaker in a headrest of a seat is assumed to be the radiating surface of the diaphragm which faces towards a listening position corresponding to the head of a user sat on the seat (but this need not always be the case, e.g. for mulfipole embodiments based on the teaching of W02019/192808).

Each drive unit may be an electromagnetic drive unit that includes a magnet unit configured to produce a magnetic field, and a voice coil attached to the diaphragm. When each loudspeaker is in use, the voice coil may be energized (have a 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. Such drive units are well known.

Each personal bass loudspeaker is preferably a dipole loudspeaker. For example, each personal bass loudspeaker may be a dipole loudspeaker having at least one diaphragm that includes a first radiating surface and a second radiating surface, wherein at least one drive unit of the personal bass loudspeaker is configured to move the/each diaphragm along a movement axis at bass frequencies such that the first and second radiating surfaces produce sound at bass frequencies, wherein the sound produced by the first radiating surface is in antiphase with sound produced by the second radiating surface; wherein the loudspeaker arrangement is configured to allow sound produced by the first and second radiating surfaces to project into the enclosed space. If each personal bass loudspeaker is mounted in a headrest, the headrest may include one or more acoustically transparent regions (e.g. acoustically transparent foam) to allow sounds from both first and second radiating surfaces to project into the enclosed space.

Preferably, each personal bass loudspeaker is a dipole loudspeaker, and the effective radiating area of the first radiating surface of the diaphragm (or the combined effective radiating areas of the first radiating surfaces, if there is more than one diaphragm included in the personal bass loudspeaker) may be 60cm2 or more, more preferably 80cm2 or more, more preferably 100 cm2 or more. For reasons that can be understood from W02019/121266A1, an effective radiating area in this range can provide an effective personal sound cocoon at bass frequencies.

As is known in the art, for a diaphragm having a circular perimeter which is suspended from a loudspeaker support structure by a roll suspension having an outer diameter do and an inner diameter di, the effective radiating surface area of the diaphragm may be estimated as 53 = , where d is the half-diameter of the roll suspension, (d. + d1)/2.

Alternatively, or for more complex diaphragm geometries, the effective radiating area of the diaphragm So 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_Radi ation_ Area.pdf).

To avoid complex calculations regarding effective radiating area, for each personal bass loudspeaker that is a dipole loudspeaker, the surface area of the first radiating surface of the diaphragm (or the combined surface area of the first radiating surfaces, if there is more than one diaphragm included in the personal bass loudspeaker) may be 50cm2 or more, 60cm2 or more, more preferably 80cm2 or more, more preferably 90 cm2 or more. With surface areas in these ranges, an effective personal sound cocoon at bass frequencies can be achieved for reasons that can be understood from W02019/121266A1 (noting that the effective radiating area is generally only a few % larger than the actual surface area).

The/each personal mid-high frequency loudspeaker may be a cardioid loudspeaker, e.g. as described in GB2004076.2, since cardioid loudspeakers are particularly directional, although other forms of directional loudspeaker are of course possible. For example, the/each personal mid-high frequency loudspeaker may instead be a monopole loudspeaker.

In some examples, the/each shared mid-high frequency loudspeaker may be a mounted at the boundary of the enclosed space, and thus might typically be a monopole loudspeaker (with one side of the mid-high frequency loudspeaker not radiating into the enclosed space, so that sound produced by a first radiating surface is prevented from interacting with sound produced by a second radiating surface). But the/each shared mid-high frequency loudspeaker could be a cardioid loudspeaker, if it were mounted within the enclosed space, away from the boundary of the enclosed space (for a cardioid to work in the enclosed space, it must be positioned away from the boundary of the enclosed space so it can radiate freely on both sides). For avoidance of any doubt, in yet other examples, the/each shared mid-high frequency loudspeaker could be located outside of the enclosed space, with a waveguide being used to guide sound produced by the shared mid-high frequency loudspeaker so as to project into the enclosed space.

The loudspeaker arrangement preferably includes a user interface configured to permit at least one user to change the mode in which the loudspeaker arrangement operates, between the shared mode and the personal mode, based on user input at the user interface.

The user interface may include one or more elements located on one or more seat assemblies (e.g. on an armrest or headrest of a seat assembly) and/or may include one or more elements located other than on one or more seat assemblies (e.g. on a dashboard).

The user interface may include a graphical user interface, which may be displayed by a display of an entertainment system of the loudspeaker arrangement (the entertainment system may e.g. be part of a vehicle including the loudspeaker arrangement).

The user interface may include one or more mechanical elements, e.g. a mechanical switch.

The user interface may include, for each seat assembly, a personal user interface configured to allow a user sat in the seat of that seat assembly to adjust the audio content of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in that seat assembly when the loudspeaker arrangement is operating in the personal mode.

The personal user interface for each seat assembly may be configured to allow a user sat in the seat to adjust the volume of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in that seat assembly.

Each personal user interface may include a graphical user interface, which may be displayed by a display of an entertainment system of the loudspeaker arrangement (the entertainment system may e.g. be part of a vehicle including the loudspeaker arrangement).

Each personal bass loudspeaker may include: a drive unit frame, wherein the/each diaphragm of the personal bass loudspeaker is suspended from the drive unit frame via at least one drive unit suspension, and a mounting frame, wherein the drive unit frame is suspended from a mounting frame via a mounting frame suspension system that includes at least one mounting frame suspension. Bass loudspeakers having such a configuration is taught in W02019/121266A1, for example. If the personal bass loudspeakers have such a configuration, the loudspeaker arrangement preferably includes an adjustment mechanism configured to adjust the mounting frame suspension system of each personal bass loudspeaker so as to change the extent to which vibrations generated by the personal bass loudspeaker reach the mounting frame via the mounting frame suspension system when the loudspeaker is in use. For each personal bass loudspeaker, the mounting frame is preferably a frame of the seat included in the seat assembly in which the personal bass loudspeaker is included. The adjustment mechanism thus permits a user to adjust the extent to which vibrations generated naturally by the action-reaction forces of the personal bass loudspeaker, when the loudspeaker is in use, are passed on to a seat which incorporates the loudspeaker. Suitable adjustment mechanisms are discussed for example in GB2015053.8.

The loudspeaker arrangement may include a user interface, configured to permit at least one user sat in an operational seat assembly to change the the extent to which vibrations generated by the personal bass loudspeaker in that seat assembly reach the seat of that seat assembly.

A personal user interface for each seat assembly may be configured to allow a user change the extent to which vibrations generated by the personal bass loudspeaker included in that seat assembly reach the seat of that seat assembly. For example, each personal user interface may include a mechanical element, e.g. a rotatable knob, configured to a change the extent to which vibrations generated by the personal bass loudspeaker included in that seat assembly reach the seat of the seat assembly. The mechanical element may e.g. be located on a headrest of the seat assembly that includes the personal bass loudspeaker.

The loudspeaker arrangement may include an enclosure which encloses the enclosed space. The enclosure may include walls. For the purposes of this disclosure, a floor and a roof which enclose an enclosed space can be viewed as "walls".

The enclosure may be a cabin of the vehicle, e.g. a cabin of a car or plane.

The enclosure may be a room.

A second aspect of the present invention may provide a vehicle including a loudspeaker arrangement according to the first aspect of the invention, wherein (e.g. a cabin of) the vehicle encloses the enclosed space.

The vehicle may be a road vehicle (e.g. car, bus), a train, or an aeroplane, for example.

If the vehicle is a car, then preferably doors of the car do not include a dedicated bass loudspeaker (e.g. woofer), since woofers in car doors are not necessary if personal bass loudspeakers are mounted in the headrests of the seats (as taught above). Thus, the construction of the car is considerably simplified. For similar reasons, preferably the car does not include a dedicated bass loudspeaker under any of the seat assemblies. The word "dedicated" in this context is intended to signify a bass loudspeaker dedicated to producing sound only at bass frequencies. In some examples, the car may include no dedicated bass loudspeakers (e.g. woofers) other than the personal bass loudspeakers. Again, this can simplify the construction of the car.

If the vehicle is a car, then preferably at least one shared mid-high frequency loudspeaker is mounted in a dashboard of the car. This may be done as a single shared mid-high frequency loudspeaker (e.g. mounted centrally in the dashboard), or as multiple shared mid-high frequency loudspeakers (e.g. two shared mid-high frequency loudspeakers located on opposite sides of the dashboard, e.g. for stereo sound). Additional shared mid-high frequency loudspeakers may be mounted elsewhere in the car, e.g in one or more doors of the car.

A fourth aspect of the present invention may provide a kit of parts for forming a loudspeaker arrangement in an enclosed space, wherein the kit of parts is configured to form a loudspeaker arrangement according to the first aspect of the invention in the enclosed space.

The kit of parts may include any parts described herein suitable for forming a loudspeaker arrangement according to the first aspect of the invention, e.g. as discussed above, but preferably doesn't include the enclosed space or seats (or enclosure). Thus, the kit of parts may be supplied to, for example, a manufacturer who forms the loudspeaker arrangement in an enclosed space (e.g. a cabin of a vehicle, e.g. a cabin of a car), using the kit of parts.

The kit of parts may include: at least one shared mid-high frequency loudspeaker, and for each of a plurality of seat assemblies to be located in the enclosed space, a personal bass loudspeaker and at least one personal mid-high frequency loudspeaker.

A fifth aspect of the present invention may provide a method of forming a loudspeaker arrangement in an enclosed space using a kit of parts according to the fourth aspect of the invention.

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: Figs. 1A and 1B show a loudspeaker arrangement operating in a shared mode and a personal mode.

Figs. 1C and 1D show an alternative loudspeaker arrangement.

Figs. 2A and 2B show the provision of audio signals to the loudspeakers of the loudspeaker arrangement of Figs. 1A and 1B when the loudspeaker arrangement is operating in the shared mode and the personal mode.

Fig. 2C shows figuratively how SPL varies with frequency for the loudspeaker arrangement of Figs. 1A and 1B.

Fig. 3 shows a user interface configured to permit at least one user to change the mode in which the loudspeaker arrangement of Figs. 1A and 1B operates.

Figs. 4A and 4B show an example loudspeaker assembly suitable for use in the loudspeaker arrangement of Figs. 1A-B.

Figs. 5A-C show an example loudspeaker assembly suitable for use in the loudspeaker arrangement of Figs. 1A-B.

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.

Fig. 1A shows a loudspeaker arrangement 101 including an enclosed space 110; four seat assemblies 120a-d located in the enclosed space; and two shared mid-high frequency loudspeakers 130a-b configured to project sound into the enclosed space 110.

Here, the enclosed space is a cabin of a car, which is enclosed by walls of the car.

In this example, the two shared mid-high frequency loudspeakers 130a-b are monopole loudspeakers mounted in a dashboard of the car, and configured to project sound into the enclosed space 110. Optionally, additional shared (monopole) mid-high frequency loudspeakers 130c-d may be mounted in the sides of the car.

Each seat assembly 120a-d includes: a seat for a user to sit on; a personal bass loudspeaker 140 mounted in a headrest 122 of the seat so as to be within 50cm of a listening position 124a-d corresponding to the head of a user sat on the seat two personal mid-high frequency loudspeakers 150, 155 mounted in the headrest of the seat so as to be within 50cm of the listening position. In Fig. 1A, only the loudspeakers 140, 150, 155 of the seat assembly 120c are labelled, but it should be apparent that the same arrangement is replicated in the other seat assemblies 120a-b, 120d.

Each personal bass loudspeaker 140 is preferably a dipole loudspeaker having a diaphragm that includes a first radiating surface and a second radiating surface, wherein at least one drive unit of the personal bass loudspeaker is configured to move the diaphragm along a movement axis at bass frequencies such that the first and second radiating surfaces produce sound at bass frequencies, wherein the sound produced by the first radiating surface is in antiphase with sound produced by the second radiating surface; wherein the loudspeaker arrangement is configured to allow sound produced by the first and second radiating surfaces to project into the enclosed space (e.g. through one or more acoustically transparent regions in the headrest). An effective radiating area of the first and second radiating surfaces of the diaphragm are preferably 60cm2 or more, more preferably 100 cm2 or more. For reasons that can be understood from W02019/121266A1, an effective radiating area in this range can provide an effective personal sound cocoon at bass frequencies.

An example dipole loudspeaker suitable for use in the headrests of the seat assemblies 120a-d is discussed below with reference to Figs. 4A-B.

Each personal mid-high frequency loudspeaker 150, 155 may be a small cardioid loudspeaker, since cardioid loudspeakers are able to provide high directionality, e.g. similar to those described in GB2004076.2.

An effective personal sound cocoon can be provided by the two personal mid-high frequency loudspeakers 150, 155 by means of their directivity, owing to their operating at mid-high frequencies (and not bass frequencies).

The loudspeaker arrangement 101 is configured to operate in a shared mode, illustrated by Fig. 1A, in which: the two shared mid-high frequency loudspeakers 130a, 130b (optionally also the additional shared mid-high frequency loudspeakers 130c-d) project sound 131a, 131b into the enclosed space at least one seat assembly is operational On Fig. 1B, both front seat assemblies 120a-b and one rear seat assembly 120d are shown as operational), wherein for the/each operational seat assembly 120a-b, 120d, the personal bass loudspeaker 140 produces supplementary sound 141 that is configured to supplement the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker 130a, 130b.

The supplementary sound produced (in the shared mode) by the personal bass loudspeaker 140 in an operational seat assembly 120d is depicted in Fig. 2A by the label 141. Note that this sound is produced on both sides of the personal bass loudspeaker 140 because this loudspeaker is a dipole loudspeaker.

Optionally, the personal mid-high frequency loudspeakers 150, 155 may produce supplementary sound in the shared mode, though this is not depicted in Fig. 1B.

The loudspeaker arrangement 101 is also configured to operate in a personal mode, illustrated by Fig. 1B, in which: the two shared mid-high frequency loudspeakers 130a, 130b (also the additional shared mid-high frequency loudspeakers 130c-d, if present) are muted; at least two seat assemblies are operational On Fig. 1B, both front seat assemblies 120a-b are shown as operational), wherein for each operational seat assembly 120a-b, the personal bass loudspeaker 140 and the the personal mid-high frequency loudspeakers 150, 155 produce sound 142, 152, 157 whose audio content is adjustable independently of sound produced by the personal bass loudspeaker 140 and the personal mid-high frequency loudspeakers 150, 155 included in at least one other operational seat assembly.

The sound produced (in the personal mode) by the personal bass loudspeaker 140 in an operational seat assembly 120b is depicted in Fig. 2A by the label 142. Note that this sound is produced on both sides of the personal bass loudspeaker 140 because this loudspeaker is a dipole loudspeaker.

The sound produced (in the personal mode) by the personal mid-high frequency loudspeakers 150, 155 in an operational seat assembly 120a is depicted in Fig. 2A by the labels 152, 157. Note that this sound is predominantly produced on one side of the personal mid-high frequency loudspeakers 140 (by a radiating surface configured to face towards the head of a user sat in the seat of a seat assembly that includes the personal mid-high frequency loudspeaker), though some sound will likely be produced at the opposite side of the personal mid-high frequency loudspeakers 140. Monopole loudspeakers could be used instead of cardioid loudspeakers for the personal mid-high frequency loudspeakers 150, 155, but monopole loudspeakers tend to be less directional and also tend to radiate more sound to the rear.

In the example of Fig. 1B, the users sat on the seats of seat assemblies 120a-b are listening to different audio content, e.g. different music, but because of the cocooning effects referred to above, the users can enjoy their own audio content without being distracted by the audio content that the other user is listening to.

Fig. 10 shows an alternative loudspeaker arrangement, which is structurally the same as the loudspeaker arrangement of Figs. 1A and 1B, except there is only one shared mid-high frequency loudspeaker 130, located in the centre of the car dashboard. As shown in Fig. 1C, the loudspeaker arrangement is operating in the shared mode, the two front seat assemblies 120a, 120b are operational, and for each operational seat assembly, both the personal bass loudspeaker 140 and the personal mid-high frequency loudspeakers 150, 155 produce supplementary sound 141, 151, 156 that is configured to supplement the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker 130.

Fig. 1D shows the shared mid-high frequency loudspeaker of Fig. 1C positioned so as to project sound into the enclosed space via reflections off a windscreen of the car. In this example, the sound produced by the personal mid-high frequency loudspeakers 150, 155 is not depicted, for clarity.

Fig. 1D also shows the personal (bass and mid-high frequency) loudspeakers mounted in a headrest of a seat.

Fig. 2A shows the provision of audio signals to the shared mid-high frequency loudspeakers 130a, 130b, the personal mid-high loudspeakers 150, 155 and the personal bass loudspeaker 140 in the loudspeaker arrangement 101 of Figs. 1A-B, when the loudspeaker arrangement 101 is operating in the shared mode.

As can be seen from Fig. 2A, the loudspeaker arrangement 101 is configured to, in the shared mode, process an audio signal deriving from an audio source 160 differently according to whether it is to be received (and converted into sound) by the shared mid-high frequency loudspeakers 130a, 130b, by the personal bass loudspeaker 140, or by the at least one personal mid-high frequency loudspeakers 150, 155.

In the example of Fig. 2A, the sound produced by the personal mid-high frequency loudspeakers 150, 155 is preferably attenuated (using the "Gain" unit) by more than 5dB as compared to the sound produced by the shared mid-high frequency loudspeakers 130a, 130b at a listening position corresponding to the head of a user sat on the seat in which the personal mid-high frequency loudspeakers 150, 155 are mounted (for reasons discussed above). In other examples (not shown), the personal mid-high frequency loudspeakers 150, 155 could be muted (e.g. turned off) in the shared mode, or could be further processed to enhance the spatialization of sound perceived by a user sat in the seat in which the personal mid-high frequency loudspeaker is mounted (e.g. reverb, or "3D" sound effects).

In the example of Fig. 2A, the loudspeaker arrangement is configured to apply a time delay (using the "Delay" unit) to the audio content of supplementary sound produced by the personal bass loudspeaker 140 and the personal mid-high frequency loudspeakers 150, 155 compared with the audio content of sound projected into the enclosed space by the shared mid-high frequency loudspeakers 130a, 130b.

The time delay is configured to compensate for a delay in sound projected into the enclosed space by the shared mid-high frequency loudspeakers 130a, 130b reaching a listening position corresponding to the head of a user sat on the seat of the seat in which the personal bass loudspeaker 140 and personal mid-high frequency loudspeakers 150, 155 are mounted (due to a distance between the shared mid-high frequency loudspeaker and the listening position for that seat), thereby ensuring that the sound produced by these different sources is synchronized at the listening position. For a typical car, the delay might be in the range 2-5ms.

If the loudspeaker arrangement includes additional shared (monopole) mid-high frequency loudspeakers 130c, 130d mounted in the sides of the car, then a time delay may be applied to the audio content of sound produced by those additional loudspeakers to compensate for their different location compared with the shared mid-high frequency loudspeakers 130a, 130b.

In the shared mode, the shared mid-high frequency loudspeakers 130a, 130b and personal mid-high frequency loudspeakers 150, 155 are configured to operate at mid-high frequencies through use of highpass filters.

In the shared mode, the personal bass loudspeaker 140 is configured to operate at bass frequencies though use of a lowpass filter.

Fig. 2B shows the provision of audio signals to the shared mid-high frequency loudspeakers 130a, 130b, the personal mid-high loudspeakers 150, 155 and the personal bass loudspeaker 140 in the loudspeaker arrangement 101 of Figs. 1A-B, when the loudspeaker arrangement 101 is operating in the personal mode.

As can be seen from Fig. 2B, the loudspeaker arrangement 101 is configured to, in the personal mode, mute the shared mid-high frequency loudspeaker (e.g. using the "Gain" unit, or simply by not providing an audio signal thereto), and to process an audio signal deriving from the audio source 160 differently according to whether it is to be received (and converted into sound) by the personal bass loudspeaker 140, or by the personal mid-high frequency loudspeakers 150, 155.

A time delay may not be needed in personal mode (time delay = Oms), e.g. if the shared mid-high frequency loudspeakers are located at a same distance along the rear-front axis of the car, e.g. in a dashboard at the front of the car.

In the personal mode, the personal mid-high frequency loudspeakers 150, 155 are configured to operate at mid-high frequencies though use of highpass filters.

In the personal mode, the personal bass loudspeaker 140 is configured to operate at bass frequencies though use of a lowpass filter.

Fig. 2C shows figuratively how sound pressure level ("SPL") produced by a personal bass loudspeaker 140 relates to frequency, in comparison to how SPL produced by shared mid-high frequency loudspeakers 130a, 130b and personal mid-high frequency loudspeakers 150, 155 for the loudspeaker arrangement 101 of Figs. 1A-B.

As shown here, the SPL produced by the bass loudspeaker 140 (marked 'X') drops off with increasing frequency, as the SPL produced by the shared mid-high frequency loudspeakers 130a, 130b and the personal mid-high frequency loudspeakers 150, 155 (marked 'Y') instead become dominant.

Preferably, the loudspeaker arrangement 101 is configured to, for each operational seat assembly 120a-d, operate the personal bass loudspeaker 140 across a first bass frequency range in the personal mode, and across a second bass frequency range in the shared mode, wherein the first frequency range includes a lower upper frequency limit than the second frequency range. In this example, the first frequency range across which the personal bass loudspeaker operates in the personal mode is 50Hz150Hz (upper limit = 150Hz) and the second frequency range across which the personal bass loudspeaker operates in the shared mode is 50Hz-200Hz (upper limit = 200Hz).

The frequency range across which the personal mid-high frequency loudspeakers 150, 155 and the shared mid-high frequency loudspeakers 130a, 130b operate, may be the same, and could for example be 200Hz-20kHz.

To summarise: * In the shared mode, the occupants can listen to the same audio content via the shared mid-high frequency loudspeakers 130a-b, but with at least the bass frequencies provided by their headrest (optionally supplementary mid-high frequencies from the headrest). Even if a driver is alone in their car, they may appreciate improved frontal stereo imaging. A delay applied to the bass sound provided by the headrest can provide time alignment at the listening position between the acoustic output from the personal bass loudspeaker and the shared mid-high frequency loudspeaker(s) located at greater distance. Whilst in shared mode, one can still receive personal content (e.g. phone calls, messages). All seat assemblies or only an occupied seat assembly may be operational during this mode. A separate (non-headrest mounted) subwoofer may still be used in shared mode.

* In the personal mode, occupants can listen to personal audio content at their preferred listening level via their headrest loudspeakers. All seat assemblies or only an occupied seat assembly may be operational during this mode.

Fig. 3 shows a user interface configured to permit at least one user to change the mode in which the loudspeaker arrangement 101 of Figs. 1A and 1B operates, between the shared mode and the personal mode, based on user input at the user interface.

In this example, the user interface includes a graphical user interface 170, which is displayed by a display of an entertainment system of a car, and permits the driver to change the mode in which the loudspeaker arrangement operates by pressing the display (which is a touch screen -"together" = shared mode; "individual" = personal mode).

In this example, the user interface also includes a rotatable knob 175 mounted on a headrest of a seat assembly 120a, wherein the rotatable knob 175 is configured to a change the extent to which vibrations generated by the personal bass loudspeaker in the seat reach the seat.

Fig. 4A is a cross-sectional view of an example loudspeaker assembly 200 for producing sound at bass frequencies suitable for use in the loudspeaker arrangement 101 of Figs. 1A-B.

The loudspeaker assembly 200 comprises a bass loudspeaker 201, the loudspeaker 201 including diaphragm 210, a drive unit 220, a drive unit frame 230. The loudspeaker also includes a mounting frame 240, wherein the drive unit frame 230 of the loudspeaker 201 is suspended from the mounting frame 240 via a mounting frame suspension system that includes at least one mounting frame suspension.

The diaphragm 210 has a first radiating surface 212 and a second radiating surface 214, wherein the first radiating surface 112 and the second radiating surface 214 are located on opposite faces of the diaphragm 210.

The drive unit 220 is configured to move the diaphragm 210 along a movement axis 202 at bass frequencies such that the first and second radiating surfaces 212, 214 produce sound at bass frequencies. The sound produced by the first radiating surface 212 is in antiphase with sound produced by the second radiating surface 214.

In this example, the loudspeaker 201 is a dipole loudspeaker wherein the loudspeaker 201 is configured to, in use, allow sound produced by the first radiating surface 212 of the diaphragm 210 to propagate out from a first side of the dipole loudspeaker 201 and to allow sound produced by the second radiating surface 214 to propagate out from a second side of the dipole loudspeaker 201.

The diaphragm 210 is suspended from the drive unit frame 230 via On this example) two drive unit suspensions 232,233.

The first drive unit suspension 232 is a roll suspension extending substantially continuously around the periphery (outer edge) of the diaphragm 110. The second drive unit suspension 233 is a spider.

In the example shown in Fig. 4A, the diaphragm 210 has a folded paper structure, explained in more detail below.

The drive unit frame 230 is suspended from the mounting frame 240 via a mounting frame suspension system that (in this example) includes a single mounting frame suspension 242 formed in a gap between the drive unit frame 230 and the mounting frame 240.

The mounting frame 240 defines a waveguide (in the form of an aperture in the mounting frame) which surrounds the diaphragm 210 and is configured to guide sound produced by the first and/or second radiating surface of the diaphragm out of opposite sides of the loudspeaker 200.

The mounting frame suspension 242, as projected onto a plane perpendicular to the movement axis 202, at least partially overlaps with the at least one drive unit suspension 232 as projected onto the same plane.

The mounting frame 240 includes a supplementary frame 246. The supplementary frame 246 of the mounting frame 240 is configured to snap-fit to the remainder of the mounting frame 240 via snap-fit feature(s) 248 on the remainder of the mounting frame. This may help simplify assembly of the loudspeaker 200.

In this example, the mounting frame suspension 242 is a portion of elastic material that forms a hollow band, which includes a hollow region that extends continuously around the drive unit frame 230.

The mounting frame suspension 242 is attached to the supplementary frame 246 of the mounting frame 240 (e.g. by an adhesive), and is also attached to the drive unit frame 230 (e.g. by an adhesive).

A gap 250 is provided between the drive unit frame 230 and the mounting frame 240 in order to allow the drive unit 220 to move the diaphragm 210 along the movement axis 202, whilst having the drive unit frame 230 suspended from the mounting frame 240 by the mounting frame suspension 242. However, the gap 250 is preferably minimized in order to maximise the effective radiating surface area 254 of the first radiating surface 212 within the mounting frame 240. Accordingly, the gap 250 is preferably 2mm or less, as measured in a plane perpendicular to the movement axis, at one or more locations (and preferably for substantially the entirety of a path which extends around the drive unit frame) at a periphery of the drive unit frame 230.

The effective radiating surface area 254 of the first radiating surface 212 is preferably 60cm2 or more.

Ideally, a shape of the diaphragm 210 is chosen to closely match the shape of the space provided by the mounting frame 240. In this example, the diaphragm 210 has an oval or racetrack shape. This is shown figuratively in the cross-section view of Fig. 4A, by the diaphragm 210 having different dimensions to the right and left of the drive unit 220.

However, the shape of the diaphragm 210 may not completely correspond to the shape of the space provided by the mounting frame 240. As such, the gap 250 between the drive unit frame 230 and the mounting frame 240 may have a different size, as measured in a plane perpendicular to the movement axis, at different locations around the periphery of the drive unit frame 230.

In this example, the diaphragm 210 is a paper diaphragm which comprises a pattern of folds 260 similar to those described in W02005/015950A1. When viewed in a circumferential direction, each fold 260 radially extends between the inner circumferential edge and the outer circumferential edge of the diaphragm 210, and has a depth that increases from the outer circumferential edge, and the inner circumferential edge of the diaphragm 210, towards a base region 262. A maximum depth of each fold 260 is located at the base region 262 and the folds 260 are provided with faces at the base region 262 (these faces are part of the second radiating surface 214).

The spider 233 is secured (e.g. by an adhesive) at its inner rim to the drive unit frame 230, and at its outer rim to the faces of the folds 260 at the base region 262 of the diaphragm 210.

Attached to the outer rim of the spider 233 is a stiffening element 268 with a corrugation, similar to that described in W02008/135857A1, which extends around a magnet unit of the drive unit 220, and which stiffens the diaphragm at the base region 262 of the diaphragm 210, so as to reinforce the diaphragm 210 against deformation in the base region 262. The stiffening element 268 may be made from a material selected from paper, aluminium, titanium, polypropylene, polycarbonate, acrylonitrile butadiene styrene or KevlarTM, for example.

The mounting frame 240 is only partly shown in Fig. 4A, and is a support foam region of a car headrest.

The complete headrest is not shown in Fig. 4A, but may be similar to that shown in Fig. 5A, below.

The drive unit 220 is an electromagnetic drive unit including a magnet unit 270 and a voice coil 222. The voice coil 222 is attached to the inner circumferential edge of the diaphragm 210 by a tubular element 224 of a voice coil coupler. In particular the voice coil 222 is wrapped around the tubular element 224 and is configured to be energized by having a current passed through it (via lead wires 282).

A dustcap 280 is attached to the tubular element 224 of the voice coil coupler.

The magnet unit 270 is located in front of the second radiating surface 214 of the diaphragm 210.

As shown most clearly in Fig. 4B, the magnet unit 270 comprises a permanent magnet 272, a top part 273, and a U-yoke 274 (e.g. of steel). The top pad 273 is formed here by a first (bottom) washer 273a (e.g. of steel) and a second (top) washer 273b (e.g. of steel). The magnet unit 270 provides an air gap 228 in which the voice coil 222 is configured to sit when the diaphragm 210 is at rest. In particular, the air gap 228 is between the top part 273 and the U-yoke 274.

The top part 273 comprises a cut-out at a location along a direction parallel to the movement axis 202, adjacent to the voice coil 222 when the diaphragm 210 is at rest. A shorting ring 278 is positioned in the cut-out. The shorting ring 278 may comprise copper, for example.

In use, the voice coil 222 may be energized (have a current passed through it) to produce a magnetic field that interacts with a magnetic field produced by the magnet unit 270 in the air gap 228, and which causes the voice coil 222 (and therefore the diaphragm 210) to move relative to the magnet unit 270.

The permanent magnet 272, top part and the U-yoke 274 are configured such that the magnetic flux density in the air gap 228 reaches a first local maximum peak location along a direction parallel to the movement axis 202 and a second local maximum peak location along a direction parallel to the movement axis 202. The first peak and the second peak location are separated spatially in a direction parallel to the movement axis 202 by a valley region in which the magnetic flux density is lower than both the first local maximum and the second local maximum. The voice coil 222 is configured to be positioned in the valley region when the diaphragm 210 is at rest. The shorting ring 278 described above may help to achieve such a magnetic flux density. Analogous examples are provided in PCT/EP2020/064577.

In use, the drive unit 220 may be configured to move the diaphragm 210 at bass frequencies across the range 40-100Hz, for example.

The loudspeaker 200 additionally includes an adjustment mechanism 285 configured to adjust the mounting frame suspension 242 (which in this example is the only element included in the mounting frame suspension system) so as to change the extent to which vibrations generated by the loudspeaker reach the mounting frame via the mounting frame suspension system when the loudspeaker is in use.

In this example, the adjustment mechanism 285 is an air pressure control unit (which may be referred to as a pneumatic control unit) configured to adjust the air pressure inside the hollow band mounting frame suspension 242 so as to ("pneumatically") adjust the mounting frame suspension system so as to change the extent to which vibrations generated by the loudspeaker reach the mounting frame suspension system.

In particular, by inflating the hollow band, both the stiffness and resistance of the mounting frame suspension system will be increased, which will in turn affect the extent to which vibrations from the moving diaphragm 210 reach the mounting frame 240.

The mounting frame suspension system may be configured to have a first (e.g. "low vibration") configuration in which the mounting frame suspension system has a resonant frequency in the range 10Hz-30Hz (inclusive), more preferably in the range 10Hz-20Hz (inclusive). In a first configuration having such a resonant frequency, relatively little of the vibrations produced by a moving diaphragm 210 of the loudspeaker 201 will reach the mounting frame 240 via the mounting frame suspension 242, when the loudspeaker 201 is in use to produce sound at bass frequencies.

The adjustment mechanism may be configured to adjust the mounting frame suspension system so that the mounting frame suspension system changes from the first configuration to a second (e.g. "high vibration") configuration.

Preferably, the mounting frame suspension system, in the second configuration, has a resonant frequency that is in the range 20Hz-60Fz (inclusive), more preferably in the range 30Hz-60Fz (inclusive).

In this way, the extent to which vibrations generated by the loudspeaker reach the mounting frame via the mounting frame suspension system, when the loudspeaker is operated at typical bass frequencies in the range 30-60Hz, is increased for the second configuration compared with the first configuration.

In the second configuration, the mounting frame suspension 242 may be more inflated than it is in the first configuration, thereby increasing the stiffness and resistance of the mounting frame suspension system (and therefore increasing the frequency at which the mounting frame 240 of the loudspeaker assembly 200 is caused to resonate, and therefore increasing the extent to which vibrations generated by the loudspeaker reach the mounting frame via the mounting frame suspension system when the loudspeaker is in use).

Of course, there may be yet further (e.g. intervening) configurations in which the stiffness and resistance of the mounting frame suspension system is different from that in the first and second configurations.

A skilled person would appreciate that the adjustment mechanism shown in Fig. 4A is just one example of how an adjustment mechanism may be configured to adjust the stiffness and/or resistance of a mounting frame suspension system Figs. 5A-C show a loudspeaker assembly 300 in which a bass loudspeaker 301 has been mounted in the headrest 390 of a seat, suitable for use in each of the four seat assemblies of the loudspeaker arrangement 101 shown in Figs. 1A-B.

The bass loudspeaker 301 is essentially the same as the bass loudspeaker 201 of Fig. 4A, except that it uses an alternative mounting frame suspension system and adjustment mechanism. Corresponding features have been given corresponding reference numerals.

In the adjustment mechanism of Figs. 5A-C, the mounting frame suspension system includes two roll suspensions 342, 343, wherein a drive unit frame 330 of the loudspeaker 301 is suspended from this mounting frame by the roll suspensions 342, 343.

The mounting frame suspension system further includes a portion of elastic material 344 that defines a hollow region and is attached to the mounting frame 340. In this example the portion of elastic material 344 does not extend continuously around the drive unit frame 330 (but could in other embodiments). The adjustment mechanism is an air pressure control unit (not shown). In use, the air pressure control unit adjusts the air pressure in the hollow region defined by the portion of elastic material 344 thereby inflating or deflating the portion of elastic material 344, and which brings the portion of elastic material 344 into contact with a friction pad 345 (e.g. of foam, felt, textile or rubbed) on the drive unit frame 330, so as to increase the resistance of the mounting frame suspension system, and thus increasing the extent to which vibrations generated by the loudspeaker reach the mounting frame via the mounting frame suspension system when the loudspeaker is in use.

The seat (not shown) of a seat assembly which incorporates the headrest 390 is configured to position a user who is sat on the seat such that the head of a user is located at a listening position that is 50cm or less (more preferably 30cm or less, more preferably 25cm or less, more preferably 20cm or less, more preferably 15cm or less) from the first radiating surface of the diaphragm 310 of the loudspeaker 300.

The headrest 390 includes two personal mid-high frequency loudspeakers 391 configured to operate over a frequency band that includes 300Fz-3kHz, more preferably 200Hz-20kHz. The one or more personal mid-high frequency loudspeakers may be cardioid loudspeakers, e.g. as described in GB2004076.2, although other forms of directional loudspeaker are of course possible (e.g. monopole loudspeakers tend to be directional at such frequencies).

The headrest 390 comprises rigid mounting pins 392 and rigid framework 392a, support foam 393 (which may be acoustically opaque) and acoustically transparent foam 393a.

The support foam 393 forms a waveguide which surrounds the diaphragm of the loudspeaker 301 On a place perpendicular to the movement axis) and is configured to guide sound produced by the first and/or second radiating surface of the diaphragm out of opposite sides of the headrest 390.

The regions of acoustically transparent foam 393a are positioned in front of the first and second radiating surfaces of the loudspeaker 300, as well as in front of the mid-high frequency loudspeakers 391, to allow sound produced thereby to reach positioned as shown in Figs. 5B-C.

The rigid mounting pins 392 and rigid framework 392a form part of a rigid seat frame of a seat assembly (not shown) of which the headrest 390 is a part. The rigid seat frame permits vibrations generated by the moving diaphragm 210 of the bass loudspeaker 301 to propagate into the body of a user sat on the seat.

In this example, the entire rigid seat frame can be viewed as the mounting frame of the loudspeaker assembly 300.

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.

* W02005/015950A1 * W02008/135857A1 * W02019/121266A1 * W02019/192808 * W02019/192816 * W02020/126847 * RCT/ER2020/064003 * G82004076.2 * GB2008724.3 * G82009203.7 * G82014020.8 * GB2015053.8 * W02020/028529 * "Dynamical Measurement of the Effective Radiating area SD", Klippel GmbH (littps://www.ktpel.delfiescirninikiippe IF iles/Knowilow/Application_NotesiAN_32_Effective_Ra ation*Area.pcl:

Claims

Claims: 1. A loudspeaker arrangement including: an enclosed space; a plurality of seat assemblies located in the enclosed space; and at least one shared mid-high frequency loudspeaker configured to project sound into the enclosed space; wherein each seat assembly includes: a seat, for a user to sit on; a personal bass loudspeaker positioned so as to be within 50cm of a listening position corresponding to the head of a user sat on the seat; at least one personal mid-high frequency loudspeaker positioned so as to be within 50cm of the listening position; wherein the loudspeaker arrangement is configured to operate in a shared mode in which: the at least one shared mid-high frequency loudspeaker projects sound into the enclosed space; at least one seat assembly is operational, wherein for the/each operational seat assembly, the personal bass loudspeaker produces supplementary sound that is configured to supplement the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker; wherein the loudspeaker arrangement is configured to operate in a personal mode in which: the at least one shared mid-high frequency loudspeaker is muted; at least one seat assembly is operational, wherein for the/each operational seat assembly, the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker produce sound whose audio content is adjustable independently of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in at least one other seat assembly.
2. A loudspeaker arrangement according to claim 1, wherein the loudspeaker arrangement is configured operate in the personal mode such that: the at least one shared mid-high frequency loudspeaker is muted; at least two seat assemblies are operational, wherein for each operational seat assembly, the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker produce sound whose audio content is adjustable independently of sound produced by the personal bass loudspeaker and the at least one personal mid-high frequency loudspeaker included in at least one other operational seat assembly.
3. A loudspeaker arrangement according to any previous claim, wherein in the shared mode, for each operational seat assembly, the at least one personal mid-high frequency loudspeaker produces supplementary sound that is configured to supplement the sound projected into the enclosed space by the mid-high frequency loudspeaker.
4. A loudspeaker arrangement according to claim 3, wherein in the shared mode, for each operational seat assembly, the loudspeaker arrangement is configured to apply an attenuation to supplementary sound produced by the at least one personal mid-high frequency loudspeaker, preferably such that the sound is perceived by a user sat on the seat of the seat assembly as being produced by the at least one shared mid-high frequency loudspeaker.
5. A loudspeaker arrangement according to any previous claim, wherein in the shared mode, for each operational seat assembly, the supplementary sound produced by the personal bass loudspeaker derives from the same audio source as the sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker.
6. A loudspeaker arrangement according to any previous claim, wherein in the shared mode, for each operational seat assembly, the loudspeaker arrangement is configured to apply a time delay to the audio content of supplementary sound produced by the personal bass loudspeaker compared with the audio content of sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker, wherein the time delay is configured to compensate for a delay in sound projected into the enclosed space by the at least one shared mid-high frequency loudspeaker reaching the listening position corresponding to the head of a user sat on the seat of the operational seat assembly.
7. A loudspeaker arrangement according to any previous claim, wherein the loudspeaker arrangement is configured to, for each operational seat assembly, operate the personal bass loudspeaker across a first bass frequency range in the personal mode, and across a second bass frequency range in the shared mode, wherein the first frequency range includes a lower upper frequency limit than the second frequency range, wherein the upper frequency limit of the first frequency range is lower than 180Hz.
8. A loudspeaker arrangement according to any previous claim, wherein the loudspeaker arrangement is configured to operate the shared mid-high frequency loudspeaker across a frequency range that at least includes frequencies across the range 500Hz-4Hz.
9. A loudspeaker arrangement according to any previous claim, wherein, for each seat assembly, the personal bass loudspeaker is mounted in a headrest of the seat.
10. A loudspeaker arrangement according to claim 9, wherein, for each seat assembly, the at least one personal mid-high frequency loudspeaker is mounted in a headrest of the seat.
11. A loudspeaker arrangement according to any previous claim, wherein, for each seat assembly, the personal bass loudspeaker is a dipole loudspeaker.
12. A loudspeaker arrangement according to any previous claim, wherein each personal bass loudspeaker is a dipole loudspeaker, and the effective radiating area of a first radiating surface of the diaphragm, or if there is more than one diaphragm included in the personal bass loudspeaker, the combined effective radiating areas of a first radiating surface of each diaphragm, is 60cm2 or more.
13. A loudspeaker arrangement according to any previous claim, wherein the loudspeaker arrangement preferably includes a user interface configured to permit at least one user to change the mode in which the loudspeaker arrangement operates, between the shared mode and the personal mode, based on user input at the user interface.
14. A loudspeaker arrangement according to any previous claim, wherein the loudspeaker arrangement includes a user interface, configured to permit at least one user sat in an operational seat assembly to change the the extent to which vibrations generated by the personal bass loudspeaker in that seat assembly reach the seat of that seat assembly.
15. A vehicle including a loudspeaker arrangement, wherein the loudspeaker arrangement is as set out in any previous claim, wherein the vehicle encloses the enclosed space.
16. A vehicle according to claim 15, wherein the vehicle is a car, and doors of the car do not include a dedicated bass loudspeaker.
17. A kit of parts for forming a loudspeaker arrangement in an enclosed space, wherein the kit of parts includes: at least one shared mid-high frequency loudspeaker; and for each of a plurality of seat assemblies to be located in the enclosed space, a personal bass loudspeaker and at least one personal mid-high frequency loudspeaker; wherein the kit of parts is configured to form a loudspeaker arrangement according to any one of claims 1-14 in the enclosed space.