The present invention relates a loudspeaker membrane with a suspension path along which to suspend the membrane in a loudspeaker and with an excitation path along which to excite the membrane to produce sound when suspended and excited, the membrane having an outward face for radiating sound and opposite an inward face for facing towards a volume of a loudspeaker, the membrane having a plurality of structure paths each single structure path substantially extending between the excitation path and the suspension path and along each individual structure path being non- flush structures to the otherwise flush outward face wherein the projection of the suspension path and the excitation path on the outward face are symmetric about a symmetry point or a symmetry line and wherein the projection of the structure paths are asymmetric.

The present invention relates a loudspeaker being a low-profile loudspeaker having an enclosure volume defined between a bottom and an outer wall with an outer periphery. The loudspeaker may comprise a magnet cup forming the bottom. The magnet cup may be and arranged to support a chassis configured to form a centrally placed inner support with an inner support periphery facing the outer periphery of the outer wall and to form an opening between the inner support periphery and the outer periphery. Along the inner support periphery there may be a suspender to suspend a membrane. The membrane may have an aperture and a shape configured to essentially cover the opening and with a suspension path along which to suspend the membrane via the suspender from the chassis. The membrane has with an excitation path to excite the membrane to produce sound when suspended and excited. The membrane has an outward face for radiating sound and opposite an inward face facing the bottom. The membrane may have a voice coil rigidly connected to the excitation path and extending towards and for magnetic interaction with a pole piece. The pole piece may be configured in the magnet cup and to form a pole from a magnet in the magnet cup. Background of the Invention

Loudspeakers have undergone a century of development, but room for improvements under constraints are still needed.

In particular spatial constraints combined with sound quality characteristics demand novel concepts. Also integration in units and stand-alone loudspeaker units impose constraints that would otherwise impact sound quality. Prior art loudspeakers that are compact or shallow can be improved. In particular digital loudspeakers characterised in receiving a digital signal to be transformed to sound.

Modern digital or wirelessly connected loudspeakers may also benefit from prolonged play times when powered by e.g. batteries.

Improved or reasonable sound characteristics may vary in acceptance levels, but generally the scope of the loudspeaker disclosed herein relates to a loudspeaker unit capable of producing an improved, reasonable, or even HI-FI quality frequency spectrum in the frequency range between e.g. 100 Hz to 10 kHz and/or the range between e.g. 100 Hz to 20 kHz.

Object of the Invention

It is an object of the present invention to overcome shortcomings of existing loudspeaker designs and/or membrane designs.

It is an object of the present invention to provide design aspects that will allow for the design of a membrane and/or loudspeaker that has a desirable frequency response that is generally flat over a wide frequency range and at the same time a low or shallow- profile.

It is an object of the present invention to provide design aspects that can provide a membrane that is structurally stiff whilst providing desirable vibration and acoustic properties over a wide frequency range to allow for improvements in the design of a loudspeaker.

It is an object of the present invention to provide design aspects of a membrane that can be easily manufactured.

Description of the Invention

An object of the invention is achieved by a loudspeaker membrane with a suspension path along which to suspend the membrane in a loudspeaker and with an excitation path along which to excite the membrane to produce sound when suspended and excited, the membrane having an outward face for radiating sound and opposite an inward face for facing towards a volume of a loudspeaker, the membrane having a plurality of structure paths each single structure path substantially extending between the excitation path and the suspension path and along each individual structure path being non- flush structures to the otherwise flush outward face wherein the projection of the suspension path and the excitation path on the outward face are symmetric about a symmetry point or a symmetry line and wherein the projection of the structure paths are asymmetric. The symmetries of the suspension and the excitation paths may be about a common point or a common line.

Such membrane will provide a generally stiff membrane that can be suspended and excited to produce a sound with a wide frequency range whilst the membrane is sen- sitive and structurally stable so as to produce a high or power output or a power output higher than what is normally produced.

Furthermore the membrane is easy to manufacture. In particular the membrane reduces or eliminates break-up modes and resonance, thus allowing for a membrane to be used in low-profile loudspeakers whilst maintaining the vibration and acoustic properties of otherwise non-low-profile loudspeakers. In an embodiment, each single structure path has the shape of a curve section of one or more curves or approximations thereto and chosen amongst:

a Fibonacci spiral,

a golden spiral,

an Archimedean spiral,

a Euler spiral,

a Fermat's spiral,

a hyperbolic spiral,

a logarithmic spiral,

or combinations thereof.

Structure paths with specific geometries have shown to provide a particularly well suited structural stability providing a membrane capable of functioning over a wide frequency range. Such geometries have been found amongst curve sections of a spe- cial class of curves.

The Fibonacci curve is generated geometrically from a spiral of squares with a side length according to the Fibonacci sequence F _n =F _n- i + F _n-2 , with Fi=F ₂ =l or F ₀ =0, Fi=l . The Fibonacci spiral may be an approximation of the golden spiral created by drawing circular arcs connecting the opposite corners of squares in the Fibonacci tiling. The squares may have sizes of 1, 1, 2, 3, 5, 8, 13, 21, and 34.

A golden spiral may be generated from a logarithmic formula recited in polar coordinates as r=ae ^be . When Θ is in radians, the golden spiral may be for b=0.3063489...

As for the construction of the Euler spiral, Fermat's spiral, hyperbolic spiral or other further details, the person skilled in the art will find similar formulas for the respective variants of a logarithmic spiral. The class of curves have shown to provide asymmetric structures that prevent or reduce resonance modes and to provide additional stiffness to obtain a frequency response over a wide range of frequencies including the range from 100 Hz to 10 kHz. Furthermore the class of curves have shown to allow for suspension and/or excitation points or paths that are symmetric which then allow for simple geometries in respect of suspension and excitation thereby allowing for simple design of the suspension and/or excitation means.

When incorporate in the otherwise flush membrane, the structure paths shaped from segments of curves as the Fibonacci spiral or approximations thereto and/or the golden spiral have shown to provide sufficient structural stability to provide strength and stiffness. At the same time, they allow the membrane to be excited and to provide the frequency response according to the intended acoustic design without undesired vibration and/or acoustic disharmonic modes.

In particular structural paths with the Fibonacci curve or golden spiral allow for exci- tation of the whole membrane at low frequencies, such as about 50-200 Hz or around 100 Hz. At the same time excitation at higher frequencies in the middle region, such as 2000-8000 Hz or around 5000 Hz has allowed the essential parts of the membrane to excite without undesired resonances or modes caused by undesired deformation of the membrane. Furthermore at the same time, excitation at high frequencies, such as 10k Hz to 20k Hz, has allowed parts of the membrane to excite sufficiently to generate sound at the corresponding high frequencies.

In an embodiment, the membrane is essentially a stiff membrane. Ideally a loudspeaker membrane should work as a piston providing the same sound pressure level for all audible frequencies (20 Hz to 20 kHz).

The membrane may be a flat membrane with a typical thickness of less than 1 mm. The thickness may be 0.2-0.3 mm, but also 0.1-0.2 mm.

In an embodiment, the membrane is made of a metal. The metal may be a nonmagnetic material such as Al (Aluminium) or Ti (Titanium) or an alloy. The advantage of such materials is that they are easy to form. In particular Al has appeared to be sufficiently stiff at a thickness of about 0.2 mm and a diameter of e.g. 30 to 200 mm, such as 120 to 160 mm.

Alternative materials may be composite materials. The composite material may be a carbon-based composite material (C). A fibre-rich material may also be used. In an alternative embodiment the membrane is made of a ceramic material. The membrane material may be reinforced by a coating or by further processing.

In particular a metal may be anodized, which may increase resistance against corrosion and tear and wear. Also, anodized surfaces may provide additional strength or stiffness to the membrane.

Anodized aluminium may provide additional advantages in terms of durability since the anodized aluminium prides an additional protective layer.

Anodized aluminium may provide additional corrosion resistance along with addition- al sealing providing long-term stability by maintaining the same vibration and/or acoustic properties as originally designed for.

Anodized aluminium provides a harder surface than does pure aluminium due to the crystalline structure thereby providing further strength and stiffness to the membrane.

Anodized aluminium allows for the membrane to be a front-end surface that can be cleaned and handled and thus eliminates the need for a protective cover of the membrane. Likewise other metals, including Titanium, may be anodized to achieve similar advantages. Similarly any other materials such as composites may benefit from a coating that is a hardening coating. A person skilled in the art may explore suitable materials and bracing/anodization to obtain a stiffness or strength to sufficiently control/ avoid / minimize the effect of resonances without increasing the thickness of the membrane. In an embodiment, the loudspeaker membrane further comprises one or more flanges along one or more of the excitation paths or suspension paths. One or more flanges may be essentially perpendicular to the inward face.

A flange may be along the suspension path, along the excitation path, or along both. The flange may provide further stability to the membrane and at the same time an and area to connect suspension means and/or excitation means, i.e. a voice coil, to the membrane.

Preferably the flange is of the same material as the membrane.

In an embodiment, the membrane is a monolith. This particular embodiment is advantageous in providing a single piece membrane that will react to environmental changes uniformly. This may either be short-term temperature variations or long-term wear- and-tear.

In an embodiment, the membrane has an aperture surrounded by the suspension path and the excitation path.

This embodiment defines an annularly shaped membrane with an outer perimeter and an aperture perimeter or an inner perimeter. The suspension path may be at the aperture perimeter and the excitation path may be at the outer perimeter. Or the paths may be arranged vice versa.

In an embodiment, the curve origin of the generic curve is placed at the symmetry point, at the periphery of aperture, or at the suspension path and the curve section is, from the curve origin, the first curve section that essentially extends between the suspension path and to the excitation path without crossing the suspension path. This arrangement of curve sections have shown to provide a sufficient stiffness to the membrane whilst maintaining the lightness and desired acoustic properties of the membrane when suspended and excited. In particular this arrangement has shown to dampen or eliminate un-desired break up modes over a wide range of frequencies when the membrane is suspended and exited.

In an embodiment, the excitation path surrounds the suspension path.

This allows for the membrane to be suspended centrally and excited at the outer pe- riphery thereby allowing for placing the voice coil at the outer periphery in a loudspeaker.

Furthermore the arrangement controls the outer periphery and allows for un-desired modes to be dampened centrally by not having the suspended area or uncontrolled path or periphery at the outer periphery.

In an embodiment, the shape of the excitation path is substantially identical in shape to the shape of the suspension path, but uniformly scaled shape. This particular embodiment allows for a simple design and layout of the membrane to ease design to achieve specific or desired acoustic properties as ideal properties.

In an embodiment, the excitation path may be in the outer periphery of the membrane. This may further eliminate free or uncontrolled areas of the membrane and thereby and mitigate undesired break-up modes.

In an embodiment, the outward face of the membrane is convex.

This allows for further stiffening of the membrane as wells as improving the far field characteristics of the sound. In particular when the membrane is excited at the outer periphery, the convex membrane will transmit the mid and higher frequencies outwardly thus improving the far field of mid and high frequency perception of infor- mation in this frequency range. Higher frequencies being directive may be directed in a line of sight or with a field profile that is broader than hereto.

This allows for better dispersion of high and directive frequency from the edge instead of centrally driven standard drivers or excited membranes. The convex membrane also gives more volume to the enclosure volume and further gives more space to allow a spider to be attached advantageously or with a degree of freedom in view of the attachment of a voice coil. The direction of the non- flush structures may alternate between outward from the outward face and inward from the inward face of the membrane. The distance from an aperture periphery or from the suspension path to the starting point of a single structure path may differ and alternate. An object is achieved by a loudspeaker membrane that is annularly shaped with an aperture and with the excitation path at the outer periphery and with the suspension path at the aperture periphery and with a plurality of structure paths extending essentially from the aperture periphery to essentially the outer periphery where each single structure path is formed as a curve section of a Fibonacci curve a golden spiral curve and along each single structure path being non-flush structures that are an embossing in the membrane .

These combined features have shown to provide an overall balanced membrane that shows overall desirable frequency response over a wide range of frequencies ranging from 10 Hz to 10 kHz. Such combined features can be provided in a membrane that is easy to manufacture and easy to integrate in a loudspeaker.

In an embodiment, the embossing alternates between outward and inward directions in the respective structure paths. The counting may be in the annular direction.

Such alternation further dampens undesired modes whilst maintaining the overall stiffness. According to an embodiment, the distance from the aperture periphery or from the suspension path to the starting point of a single structure path is different and alternates. The counting may be in the annular direction. Thereby further asymmetry is introduced in the membrane without compromising the overall stiffness or strength of the membrane.

An object of the invention is achieved by a low-profile loudspeaker having an enclosure volume defined between a bottom and an outer wall with an outer periphery. The loudspeaker may comprise a magnet cup forming the bottom. The magnet cup may be and arranged to support a chassis configured to form a centrally placed inner support with an inner support periphery facing the outer periphery of the outer wall and to form an opening between the inner support periphery and the outer periphery. Along the inner support periphery there may be a suspender to suspend a membrane. The membrane may have a shape configured to essentially cover the opening and with a suspension path along which to suspend the membrane via the suspender from the chassis. The membrane has with an excitation path to excite the membrane to produce sound when suspended and excited. The membrane has an outward face for radiating sound and opposite an inward face facing the bottom. The membrane may have a voice coil rigidly connected to the excitation path and extending towards and for magnetic interaction with a pole piece. The pole piece may be configured in the magnet cup and to form a pole from a magnet in the magnet cup.

The membrane may have an aperture. The suspension path may surround such aper- ture or be essentially along the periphery of such aperture.

The membrane may have the suspension path surrounding the excitation path in the outer periphery of the membrane to freely move relatively to the pole piece as a function of a signal applied to the voice coil. The membrane may be a substantially stiff membrane.

Thereby a low-profile loudspeaker is achieved allowing for a particular shallow form factor that can be self-contained and thus eliminates the need for an additional cabinet. The arrangement increases enclosure volume or air volume, which is otherwise required to be provided by other means such as a cabinet, and provides more space, which allows for the incorporation of battery-powered digital signal processing and/or amplification. Thus signals to the loudspeaker can be provided wirelessly.

Such low-profile loudspeaker has been found to yield a substantially linear frequency spectrum over a wide range of frequencies. The wide range may be the range from 100 Hz to 10 kHz and even 100 Hz to 20 kHz with tweeter integration.

Furthermore the arrangement provides for coaxial design and for digital loudspeaker applications.

The arrangement furthermore provides a high sensitivity speaker with increased space for power sources such as batteries to increase playtime in wireless configurations.

The arrangement also allows for integration of the loudspeaker in space limited environments such as automotive settings. In particular it allows for the loudspeaker to function as a satellite coaxial driver for shallow mounting on- wall, in-wall, in ceiling, even in the frequency range of 100-20k Hz, since there is no need for additional enclosure when used as a satellite.

The arrangement also allows for the magnet system to be contained in the required enclosure, which is desirable when used as a satellite

The sensitivity and far field properties of in the mid-range to high-range of frequencies also makes the speaker ideal for conference call devices. Even thus included the overall arrangement makes it possible to omit the tweeter whilst maintain the frequency response between 100 Hz to 10 kHz The arrangement with the outer peripherally excited membrane gives more freedom to the magnet design and allows to reduce use of materials/resources and also to minimize cost. The arrangement also allows for the suspension, such as a rubber suspension, to function as wave guide for the tweeter.

In an embodiment, the low-profile loudspeaker is configured with a membrane configured as previously outlined and wherein the chassis and the pole piece are config- ured complementarily to the membrane to suspend and excite the membrane.

Thus a person skilled in the art will be able to configure a chassis and/or pole piece according to the layout of the membrane and achieve the benefits of the wide frequency range of 100 Hz to 10 kHz of the membrane without optional tweeter.

According to an embodiment, the low-profile loudspeaker may further comprise a tweeter covering a tweeter cavity in the central inner support and being interactively connected to the suspender. Furthermore, making use of the membrane with the aperture will allow for inclusion and interaction with a tweeter to achieve benefits in the high frequency range and thus increase the frequency range to about 20 kHz.

According to an embodiment, the pole piece may be arranged in the magnetic cup towards the outer wall to form a gap between the outer wall and the pole piece for the voice coil be exited and formed with an radially outward pole face and with a bottom pole face facing the magnetic cup with decreasing extend from the outer wall towards the inner support. Thereby the air volume or enclosure volume may further be increased and/or use of sparse magnetic materials may be reduced without compromising the overall functioning of the loudspeaker. According to an embodiment, the pole piece has a copper cap at the radially outward pole face for facing the voice coil.

The larger area of the outward pole face achieved by the arrangement of the pole piece for excitement at the outer region gives a larger area and thus reduces the effect of or increases the design options to reduce eddy currents.

The arrangement provides a larger than otherwise area and allows for electromagnetic coupling between the magnet and the voice coil thus improving the transfer of signals.

According to an embodiment, a permanent magnet is connected to the pole piece only at the bottom pole face, which thereby reduces the complexity of the magnetic field and provides more space in the housing. The magnet may be a standard magnet or a Neodymium type magnet.

According to an embodiment, the low-profile loudspeaker further comprises a spider connecting the voice coil to the chassis, preferably to an outwardly extending part of the chassis. The spider may provide more stability to the membrane when the membrane is excited, and the area of excitement is counterbalanced and thereby providing a more uniform excitement of the membrane. This is particular advantageous when the membrane is excited at the outer periphery, the spider further mitigates or dampens unde- sired modes.

The low-profile loudspeaker may further comprise a diffuser being essentially flat and extending into the enclosure volume and formed to reflect sound waves in the enclosure and to direct sound waves outwardly. The arrangement provides space for a diffuser to be embedded in a loudspeaker in a protective fashion. Part of the increased air volume may thus allow for increased design options of the diffuser to further enhance the near or far field characteristics of the speaker according particular circumstances. In an embodiment, the loudspeaker may further comprise a rear housing essentially covering the bottom of the chassis forming a rear chamber and/or configured with one or more electronics chambers and terminals.

The arrangement allows for the rear chamber to be an integral part of the loudspeaker unit without affecting the overall acoustic properties of the speaker and thus allows for electronics including processing electronics and power electronics to be integrated according to circumstances.

The low-profile loudspeaker has one or more sound canals connecting the enclosure volume and/or the tweeter cavity and/or the rear chamber.

Thus the rear housing adds further air volume to the loudspeaker.

An object is achieved by a low-profile loudspeaker wherein the chassis is configured with an annularly shaped pole piece interacting with and a coaxial circular inner support supporting an annularly shaped membrane as recited previously. Such a special embodiment has been found to provide a balanced low-profile loudspeaker having a frequency response that is generally flat over a wide range of frequencies.

In particular the loudspeaker may have a less than 100 mm, preferably less than 75 mm, and more preferably less than 60 mm and an essentially flat frequency response spectrum in the range of 100 Hz to 10 kHz.

The loudspeaker may have a coaxial tweeter and a height of less than 100 mm, preferably less than 75 mm, and more preferably less than 60 mm and an essentially flat frequency response spectrum in the range of 100 Hz to 20 kHz.

The height may be as low as 30 mm. The before recited heights are for a diameter of about 100 - 140 mm, but may be scaled to diameters of about 50 - 200 mm. Description of the Drawing

Embodiments of the invention will be described in the figures, where:

Fig. 1 illustrates symmetric form shapes of a loudspeaker membrane along with suspension and excitation paths;

Fig. 2 illustrates further symmetric form shapes of a loudspeaker membrane;

Fig. 3 illustrates structure paths and embossing of a membrane;

Fig. 4 illustrates a generic curve and curve section to form a structure path that is asymmetric;

Fig. 5 illustrates the construction of a Fibonacci curve;

Fig. 6 illustrates a membrane with symmetric suspension and excitation paths and structure paths formed by asymmetric curve sections; here sections from a Fibonacci curve;

Fig. 7 illustrates an annularly formed membrane with structure paths of curve sections distributed annularly in an asymmetric fashion, the curve sections are sections of a golden spiral/Fibonacci curve;

Fig. 8 illustrates further introduction of asymmetry by varying the extent of the curve sections;

Fig. 9 illustrates an elliptic form factor of a membrane with structure paths from curve sections as disclosed;

Fig. 10 illustrates a particular embodiment of a membrane with asymmetric structure paths formed as segments of a Fibonacci curve/golden spiral as embossings in an otherwise flush and convex membrane;

Fig. 11 illustrates an embodiment of a low-profile loudspeaker;

Fig. 12 illustrates a top and perspective view of the loudspeaker from figure 11 and with a membrane from figure 10; and

Fig. 13 illustrates a frequency response of the low-profile loudspeaker illustrated in figures 11 and 12.

Detailed Description of the Invention

Item No

Loudspeaker membrane 10 Outward face 12

Inward face 14

Flush face 16

Suspension path 20

Excitation path 22

Structure path 24

Non-flush structures 26

Embossing 27

Outer periphery 30

Aperture 32

Aperture periphery 34

Annular 36

Symmetry point 40

Symmetry line 42

Curve 50

Curve Origin 52

Curve form 53

Curve section 54

Rotation Angle 56

Flange 60

Loudspeaker 100

Enclosure volume 102

Bottom 104

Outer wall 106

Wall periphery 108

Gap 110

Height 112

Diameter 114

Magnet cup 120

Magnet 122

Chassis 130

Inner support 132 Inner support periphery 133

Suspender 140

Voice coil 150

Pole piece 160

Pole 162

Outward pole face 164

Bottom pole face 165

Copper cap 166

Tweeter 170

Tweeter cavity 172

Spider 180

Rear housing 200

Rear chamber 202

Electronics chamber 204

Terminals 206

Sound canal (Cable canal) 208

Frequency response spectrum 500

Frequency response spectrum SPL 510

Frequency response spectrum Tweeter 520

Figure 1 illustrates the form of a loudspeaker membrane 10 with a suspension path 20 along which to suspend the membrane 10 in a loudspeaker (not shown) and with an excitation path 22 along which to excite the membrane 10 to produce sound when suspended and excited.

The suspension path 20 may be at the inner region of the membrane 10 and the excitation path may be at the outer region of the membrane 10. The suspension path 20 may be at the outer region of the membrane 10, and the excitation path may be at the inner region of the membrane 10.

The membrane 10 has an outward face 12 for radiating sound and opposite an inward face 14 for facing towards a volume of a loudspeaker (not shown), the membrane 10 has a plurality of structure paths 24, each single structure path 24 substantially extending between the excitation path 22 and the suspension path 20.

The membrane 10 has a symmetry point 40 about which the suspension path 20 is symmetric. The excitation path 22 is symmetric about the symmetry point 40. In this embodiment the membrane has a symmetry line 42 about which the suspension path 20 is symmetric. The excitation path 22 is symmetric about the symmetry line 42.

In other embodiments the symmetry may only be about the symmetry line 42.

In the shown embodiment the suspension path 20 is a circle and the excitation path 22 is a circle. In this embodiment the suspension path 20 and the excitation path 22 are coaxial circles. Figure IB illustrates an embodiment where a membrane 10 has an aperture 32. In this case the aperture is coaxial with a centre at the symmetry point 40. The membrane 10 has a suspension path 20 at or near to an aperture periphery 34 of the aperture 32. The shown embodiment is where the membrane has an annular shape 36 (circular) with an outer periphery 30 and an excitation path 22 close to the outer periphery 30.

For both embodiments in figures 1 A and IB, the otherwise outward face 12 is generally flush and the symmetries are generally understood as the projection of the suspension path 20 and the excitation path 22 on the outward face 12. The suspension path 20 and the excitation path 22 are understood to be symmetric about the common symmetry point 40 or the common symmetry line 42, which may be through the common symmetry point (40) and wherein the projection of the structure paths (24) are asymmetric.

Figure 2 illustrates embodiments of membranes 10 having different types of symmet- ric shapes. Figure 2 A illustrates a circular membrane 10A shape. Figure 2B illustrates an elliptic membrane shape 10B or oval shape. Figure 2C illustrates a square membrane IOC shape, and figure 2D illustrates a rectangular membrane 10D shape. The membranes 10A-D are shown with suspension paths 20 and excitation paths 22 having the symmetric shapes of a circle, an ellipse, a square and a rectangle. The membranes are illustrated without an aperture, but embodiments could be with a central aperture similar to that shown in figure IB.

Figure 3 is an exemplary embodiment of a membrane from the previous membranes 10 and membranes sharing the stated symmetry properties. In this embodiment, the shown membrane 10 is circular and has coaxial suspension path 20 and excitation path 22.

On the outward face 12 of the membrane 10 there are structure paths 24 along which paths there are stiffness-adding structures. Each structure path 24 extends essentially between the suspension path 20 and the excitation path 22. For illustrative purposes there is a structure extending continuously along the whole structure path 24A and there are multiple disjunct, multiple discrete, structures along a structure path 24B. Such structure paths are asymmetric with respect to the symmetry of the suspension path 20 and the symmetry of the excitation path 22.

In this embodiment, and along each individual structure path 24, the structure is a non- flush structure 26 to the otherwise flush outward face 12. The non-flush structures 26 provide stability and stiffness to the membrane 10.

The illustrated individual structure paths 24 and structures such as the non-flush structure 26 may be distributed along each individual structure path 24 being non-flush structures 26 to the otherwise flush outward face 12. It is understood that it is the projection of the suspension path 20 and the excitation path 22 on the outward face 12 that are symmetric about a common symmetry point 40 or a common symmetry line 42 and wherein the projection of the structure paths 24 are asymmetric. In each individual structure path 24 there are non-flush structures 26 such as an embossing 27 in a plate and distributed on the surface of the membrane 10. Figure 4 illustrates a generic curve 50 with a curve origin 52 and a particular curve form 53. Along the curve 50 there is a curve section 54. Such curve 50 may be chosen amongst several curve forms 53 and generated as for example a Fibonacci spiral, a golden spiral, an Archimedean spiral, a Euler spiral, a Fermat's spiral, a hyperbolic spiral, a logarithmic spiral, or combinations thereof.

Figure 5 illustrates the generation of a Fibonacci curve 50 or Fibonacci spiral where the curve form 53 is generated by squares according to the Fibonacci sequences added in a spiral form from an curve origin 52 so that in this case, the curve form 53 is gen- erated by spiralling squares 53A, 53B, 53C, ...

The actual curve 50 may be an approximation to the Fibonacci curve form 53 such as the golden spiral. Figure 6 illustrates a membrane 10 with symmetric suspension 20 and excitation 22 paths, where the suspension path 20 is towards the centre and the excitation path 22 at the outer periphery of the membrane 10. The structure paths 24A, 24B are formed by asymmetric curve sections 54 A, 54B. Here the curve sections 54 are from a Fibonacci curve 50 originating 52 from the symmetry point 40. The structure paths 24 may ex- tend from the suspension path 20 or from the curve origin 52 to or close to the excitation path 22.

Thus the curve origin 52 of the generic curve 50 is placed at the symmetry point 40 or the periphery of aperture 34 and the curve section 54 is, from the curve origin 52, the first curve section 54 that essentially extends between and without crossing the suspension path 20 and the excitation path 22.

Figure 7 illustrates an annularly 36 formed membrane 10 with an aperture 32 having an aperture periphery 34. The suspension path 20 is at the aperture periphery 34 the excitation path 22 is at the outer periphery 30 of the membrane 10. The suspension path 20 and the excitation paths 22 are symmetric about the symmetry point 40. Structure paths 24 (A,B, and not shown C, D . ) of curve sections 54 (A,B, and not shown C, D, ...) are distributed annularly in an asymmetric fashion. The curve sections 54 are sections of a golden spiral/Fibonacci curve 50. The curve sections 54 are separated or distributed by shifting the curve origin 52 placed on the aperture periphery 34 or suspension path 20 according to an rotation angle 56, which here is 60 degrees. Figure 8 illustrates in continuation of figure 7 the introduction of further asymmetry by varying the extent of the curve sections 54. Here the curve sections 54 extend only close to the suspension path 20 at the outer periphery 30. Notably curve sections 54 may start from different distances from the suspension path 20. Alternatively the origin 52 of the curve 50 may be located at different distances from the aperture pe- riphery 34 or suspension path 20. In a particular realisation the distance may alternate from one curve section to a subsequent curve section.

Figure 9 illustrates in continuation of the previous figures an elliptic form factor of a membrane 10 and thus a membrane 10 with a symmetry about a symmetry line 42 with structure paths from curve sections 54 that may be generated in line with the previously disclosed principles.

Figure 10 illustrates a particular embodiment of a membrane 10 with construction elements in continuation of figures 7 and 8. The lower figure shows the membrane 10 seen towards the outward face 12 and the upper figure shows a cross section (A) of the membrane 10.

The figure shows a circularly symmetrical membrane 10 with a coaxial aperture 32 with an aperture periphery 34. The suspension path 20 is along the aperture periphery 34 and the excitation path 22 is at the outer periphery. The membrane 10 has an annular 36 form. The membrane 10 has a number of non-flush structure 26 distributed on the outward face 12. The non- flush structures 26 are also on the inward face 14.

The non-flush structures 26 are numbered A,B ...F and each non-flush structure 26 is an embossing 27 in an otherwise flush face 16 being the outer face 12 or the inner face 14. The embossings 27 forming the non-flush structures 26 alternate outwardly and inwardly as seen on the upper figure. The form of the non-flush structures 26 follows structure paths 24 that are curve sections 54 of a Fibonacci curve/golden spiral. Furthermore the starting point of a structure path 24 has an alternating and different distance from the aperture periphery 34. The aperture periphery 34 has a flange 60, which here is directed inwardly. The outer periphery has a flange 60, which here is directed inwardly.

The membrane 10 may be a monolith and the flange 60 as well as non- flush structures 27 allows for the membrane to essentially have the same thickness between the outer face 12 and the inner face 14.

The form factor of the membrane 10 is overall convex.

Figure 11 illustrates a loudspeaker 100 being a low-profile loudspeaker 100 having an enclosure volume 102 defined between a bottom 104 and an outer wall 106 with an wall face 108 facing towards the enclosure volume 102. The loudspeaker 100 has a magnet cup 120 forming the bottom 104. The magnetic cup 120 anchors a chassis 130 that forms a centrally placed inner support 132 with an inner support periphery 133 facing the wall face 108 of the outer wall 106 and to form an opening between the inner support periphery 133 and the wall face 108. Along the inner support periphery 133 there is a suspender 140 to suspend a membrane 10. The suspension is at an aperture 32 in the membrane 10 along suspension path 20 and via the suspender 140 from the chassis 130. The membrane 10 has a shape to essentially cover the opening and an excitation path 22 to excite the membrane 10 to produce sound when suspended and excited.

The membrane 10 has an outward face 12 for radiating sound and opposite an inward face 14 facing the bottom 104. The membrane 10 has a voice coil 150 rigidly connect- ed to the excitation path 22. The voice coil 150 extends for magnetic interaction with a pole piece 160 that is configured in the magnet cup 120. The to form a pole 162 of a pole pair 162N, 162S coming from a magnet 122 in the magnet cup 120. The pole piece 160 is arranged in the magnetic cup 120 towards the outer wall 106 so as to form a gap 110 between the outer wall 106 and the pole piece 160 for the voice coil 150 to excite the voice coil 150 attached to the excitation path 22. The pole piece 160 is formed with a radially outward pole face 164 and with a bottom pole face 165 facing the magnetic cup 120. In this case with decreasing extend or height from the outer wall 106 towards the inner support 132.

Furthermore the pole piece 160 has a copper cap 166 at the radially outward pole face 164 and for facing the voice coil 150.

It is noted that membrane 10 has the suspension path 20 at the aperture periphery 34 and the excitation path 22 in the outer periphery 30 of the membrane 10 to move freely relatively to the pole piece 160 as a function of a signal applied to the voice coil 150. The membrane 10 is a substantially stiff membrane 10 and may be of aluminium.

The shown membrane 10 shares features of the membrane 10 illustrated in figure 10 and the chassis 130 and the pole piece 160 are configured complementarily to the membrane 10 to suspend and excite the membrane 10; or vice versa.

The loudspeaker 100 has a tweeter 170 covering a tweeter cavity 172 in the central inner support 132 and interactively connected to the suspender 140.

The low-profile loudspeaker 100 is characterised in having a low height 112 either absolutely or relative to a diameter 114.

The loudspeaker 100 is where shown with a rear housing 200 essentially covering the bottom 104 of the chassis forming a rear chamber 202 and/or configured with one or more electronics chambers 204 and terminals 206.

The rear housing 200 has one or more cable canal or sound canals 208 connecting the enclosure volume 102 with the tweeter cavity 172 and the rear chamber 202. Figure 12 illustrates perspective views of the loudspeaker 100 from figure 11 and the membrane from figure 10. The loudspeaker has a form factor essentially described by a height 112 and a diameter 114 and the loudspeaker is shown to be a unit having a self-containing enclosure and a shallow design with no need of an additional cabinet.

For the unit shown, the height is 29 mm, approximately 30 mm, and the diameter 88 mm, approximately 90 mm.

Figure 13 illustrates a frequency response 500 of the low-profile loudspeaker illustrated in figures 11 and 12. Frequency response spectrum SPL 510 is seen to be essentially flat from below 100 Hz to about 10 kHz. Frequency response spectrum Tweeter 520 extends the low flatness to about 20 kHz. Thus the overall frequency response is generally flat between 100 Hz and 20 kHz and thus over a wide frequency range.

ITEMS

In the following certain aspect of a membrane or a loudspeaker is disclosed in terms of ITEMS or any combination of ITEMS. ITEM 1. A loudspeaker membrane (10) with a suspension path (20) along which to suspend the membrane (10) in a loudspeaker and with an excitation path (22) along which to excite the membrane (10) to produce sound when suspended and excited, the membrane (10) having an outward face (12) for radiating sound and opposite an inward face (14) for facing towards a volume of a loudspeaker, the membrane (10) hav- ing a plurality of structure paths (24) each single structure path (24) substantially extending between the excitation path (22) and the suspension path (20) and along each individual structure path (24) being non-flush structures (26) to the otherwise flush outward face (12) wherein the projections of the suspension path (20) and the excitation path (22) on the outward face (12) are symmetric about a symmetry point (40) or a symmetry line (42) and wherein the projection of the structure paths (24) are asymmetric.

ITEM 2. The loudspeaker membrane (10) according to ITEM 1, wherein each single structure path (24) has the shape of a curve section (54) of one or more curves (50) or approximations thereto and chosen amongst:

a Fibonacci spiral,

a golden spiral,

an Archimedean spiral,

a Euler spiral,

a Fermat's spiral,

a hyperbolic spiral,

a logarithmic spiral,

or combinations thereof. ITEM 3. The loudspeaker membrane (10) according to any preceding ITEM, wherein the curve section (54) is divided into subsections. ITEM 4. The loudspeaker membrane (10) according to any preceding ITEM, wherein the membrane (10) is essentially a stiff membrane (10). ITEM 5. The loudspeaker membrane (10) according to any preceding ITEM, wherein the membrane (10) is made of a metal.

ITEM 6. The loudspeaker membrane (10) according to any preceding ITEM, further comprising one or more flanges (160) along one or more of the excitation path (22) or suspension path (20).

ITEM 7. The loudspeaker membrane (10) according to any preceding ITEM, wherein the membrane (10) is a monolith. ITEM 8. The loudspeaker membrane (10) according to any preceding ITEM, the membrane (10) having an aperture (32) surrounded by the suspension path (20) and the excitation path (22).

ITEM 9. The loudspeaker membrane (10) according to ITEM 8, wherein the curve origin (52) of the generic curve (50) is placed at a symmetry point (40) or the periphery of aperture (34) and the curve section (54) is, from the curve origin (52), the first curve section (54) that essentially extends between and without crossing the suspension path (20) and the excitation path (22).

ITEM 10. The loudspeaker membrane (10) according to any preceding ITEM, wherein the excitation path (22) surrounds the suspension path (20). ITEM 1 1. The loudspeaker membrane (10) according to any preceding ITEM, wherein the shape of the excitation path (22) substantially is identical in shape to, but a scaled shape of the suspension path (20).

ITEM 12. The loudspeaker membrane (10) according to any preceding ITEM, wherein the excitation path (22) is in the outer periphery (30) of the membrane (10).

ITEM 13. A loudspeaker membrane (10) according to any preceding ITEM, wherein the outward face (12) of the membrane (10) is convex.

ITEM 14. A loudspeaker membrane (10) according to any preceding ITEM, wherein the membrane (10) is annularly shaped with an aperture (32) and with the excitation path (22) at the outer periphery (30) and with the suspension path (20) at the aperture periphery (34) and with a plurality of structure paths (24) extending essentially from the aperture periphery (34) to essentially the outer periphery (30) where each single structure path (24) is formed as curve section (54) of a Fibonacci curve (50) or a golden spiral curve (50) and along each single structure path (24) being non-flush structures (26) that are an embossing (27) in the membrane (10).

ITEM 15. The loudspeaker membrane (10) according to ITEM 14, wherein the direction of the embossing (27) alternates between outward and inward directions in the structure paths (24). ITEM 16. The loudspeaker membrane (10) according to ITEM 14 or 15, wherein the distance from the aperture periphery (34) or from the suspension path (20) to the starting point of a single structure path (24) is different and alternates.

ITEM 17. The loudspeaker membrane (10) according to any of the ITEMS 14 to 16, wherein the curve section (54) alternates for the structure paths (24) counting radially of the annular (36) shape. ITEM 18. A low-profile loudspeaker (100) having an enclosure volume (102) defined between a bottom (104) and an outer wall (106) with an wall face (108) and comprising:

a magnet cup (120) forming the bottom (104) and arranged to support

- a chassis (130) configured to form a centrally placed inner support (132) with an inner support periphery (133) facing the wall face (108) of the outer wall (106) and to form an opening between the inner support periphery (133) and the wall face (108) and along the inner support periphery (133)

a suspender (140) to suspend

- a membrane (10) with an aperture (32) and a shape configured to essentially cover the opening and with a suspension path (20) to suspend the membrane (10) via the suspender (140) from the chassis (130) and with an excitation path (22) to excite the membrane (10) to produce sound when suspended and excited, the membrane (10) having an outward face (12) for radiating sound and opposite an inward face (14) facing the bottom (104), the membrane (10) having a voice coil (150) rigidly connected to the excitation path (22) and extending towards and for magnetic interaction with

a pole piece (160) configured in the magnet cup (120) and to form a pole (162) from a magnet (122) in the magnet cup (120)

wherein

the membrane (10) has the suspension path (20) at the aperture periphery (34) and the excitation path (22) in the outer periphery (30) of the membrane (10) to move freely relatively to the pole piece (160) as a function of a signal applied to the voice coil (150) and wherein the membrane (10) is a substantially stiff membrane (10).

ITEM 19. The low-profile loudspeaker (100) according to ITEM 18, wherein the membrane (10) is according to any of the ITEMS 1 to 17 and wherein the chassis (130) and the pole piece (160) are configured complementarily to the membrane (10) to suspend and excite the membrane (10). ITEM 20. The low-profile loudspeaker (100) according to ITEM 19 further comprising a tweeter (170) covering a tweeter cavity (172) in the central inner support (132) and interactively connected to the suspender (140). ITEM 21. The low-profile loudspeaker (100) according to any of ITEMS 18 to 20, wherein the pole piece (160) is arranged in the magnetic cup (120) towards the outer wall (106) to form a gap (110) between the outer wall (106) and the pole piece (160) for the voice coil (150) to be excited and formed with a radially outward pole face (164) and with a bottom pole face (165) facing the magnetic cup (120) with decreas- ing extend from the outer wall (106) towards the inner support (132).

ITEM 22. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 21, wherein the pole piece (160) has a copper cap (166) at the radially outward pole face (164) for facing the voice coil (150).

ITEM 23. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 22, wherein a permanent magnet (122), preferably a Neodymium type magnet, is connected to the pole piece (120) only at the bottom pole face (165). ITEM 24. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 23, further comprising a spider (180) connecting the voice coil (150) to the chassis (130), preferably to an outwardly extending part of the chassis (130).

ITEM 25. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 24, further comprising a diffuser being essentially flat and extending into the enclosure volume (102) and formed to reflect sound waves and to direct sound waves outwardly.

ITEM 26. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 25, further comprising a rear housing (200) essentially covering the bottom (104) of the chassis forming a rear chamber (202) and/or configured with one or more electronics chambers (204) and terminals (206). ITEM 27. The low-profile loudspeaker (100) according to any of the ITEMS 18 to

26, where the rear housing (200) has one or more sound canals (208) connecting the enclosure volume (102) and/or the tweeter cavity (172) and/or the rear chamber (202).

ITEM 28. The low-profile loudspeaker (100) according to any of the ITEMS 18 to

27, wherein the loudspeaker (100) is configured with an annularly shaped pole piece (160) interaction with and a coaxial circular inner support (132) supporting an annularly shaped membrane (10) according to any of the ITEMS 14 to 17.

ITEM 29. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 28 wherein the loudspeaker has a height (112) of less than 100 mm, preferably less than 75 mm, and more preferably less than 55 mm and an essentially flat frequency response spectrum (510) in the range of 100 Hz to 10 kHz.

ITEM 30. The low-profile loudspeaker (100) according to any of the ITEMS 18 to 29 wherein the loudspeaker has a height (112) of less than 100 mm, preferably less than 75 mm, and more preferably less than 55 mm and a coaxial tweeter (170) and an essentially flat frequency response spectrum (500) in the range of 100 Hz to 20 kHz.