RU2454824C2 - Composite dynamic head of loud speaker - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: dynamic head (22) of a loud speaker suitable for use as a composite head comprises a rigid frame (11, 13, 15, 19, 8) of a loud speaker, to which a permanent magnet (13) is attached. A winding (9) of a voice call is designed for interaction with this magnet by means of electromagnetic forces. The winding is made with the possibility to drive a membrane unit (21) along the axis, and the unit comprises an elastic external section (2), attached with its outer edge (5) to the external part (11) of the loud speaker frame. The membrane unit (21) comprises substantially a rigid main vibrating membrane (4) fixed between the elastic external section (2) and the elastic inner section (3). The inner edge (10) of the membrane is attached to the inner part (8) of the loud speaker frame. The winding (9) of the voice coil is fixed relative to the main vibrating membrane (4) via the frame (6) of the voice coil, arranged as capable of membrane unit (21) displacement.

EFFECT: reduced sound distortions.

16 cl, 5 dwg

Description

Technical field

The invention relates to loudspeakers. More specifically, it relates to a new type of dynamic head, which, according to one of the preferred options, can be a composite dynamic head, especially effective in applications with medium-frequency and high-frequency sound reproduction.

State of the art

Combined speakers usually contain at least two dynamic heads that provide reproduction in the respective low-frequency and high-frequency bands. Low-frequency and high-frequency dynamic heads have traditionally been implemented as separate units. Moreover, to ensure high-quality reproduction, without emission in intensity and direction, the dynamic heads were installed more or less coaxially. Such improved composite speaker loudspeakers are typically low- or mid-frequency nodes integrated with high-frequency loudspeakers. In addition, each high-frequency head is mounted separately, in front of or in the immediate vicinity of a relatively low-frequency voice coil in the system. No. 5,548,657 describes examples of such devices in which a high-frequency dynamic head was integrated into a low-frequency voice coil and separated from the coil of this coil by a gap sufficient to allow non-contact axial movement of the voice coil.

Other known from the prior art examples of composite or coaxial dynamic heads can be found in the following publications: US 6493452; US 5604815; US 6356640; US 6,745,867.

The quality of known constructions usually suffers from an acoustic mismatch between the high-frequency diaphragm and adjacent acoustic surfaces, mainly the low-frequency cone and its surroundings. If the high-frequency diaphragm is advanced forward relative to the neck of the low-frequency cone (see US 6493452 and US 6356640), part of the radiation from the high-frequency diaphragm will be directed back to the low-frequency cone, and then reflected back from it, i.e. forward. As a result, interference will occur with the radiation of the high-frequency diaphragm propagating forward. This will degrade the high-frequency parameters of the high-frequency diaphragm due to the comb filter effect in the acoustic frequency response of the system.

US 5,548,657 describes another type of acoustic mismatch between the cone (21) and the high-frequency diaphragm (27) when a circular gap is left between the cone and the annular screen (44) of the high-frequency dynamic head to allow axial movement of the low-frequency cone. The presence of such a gap creates a mismatch in the acoustic conjugation of the high-frequency diaphragm. As a result, due to the circular shape of this diaphragm and the radial nature of the wavefront emitted by it, as a rule, there is significant diffraction on the axis of the radiation emitted by the system. The frequency interval for such diffraction, depending on the used geometry of the dynamic head, usually corresponds to 2-20 kHz. A similar phenomenon can also be caused by the presence of a flexible female external component (22), which leads to acoustic mismatch, the result of which, as in the described case with a voice coil, is radial diffraction, but at different frequencies. US 6,745,867 describes an attempt to eliminate this problem by improving the smoothness of said external component.

In general, the known attempts to create a loudspeaker with a composite head are characterized by disadvantages consisting in the complexity of mechanical structures and in diffraction problems caused by geometric irregularities of the diaphragm. Diffraction problems usually lead to a deterioration in the frequency response and directivity control.

Disclosure of invention

The problem solved by the invention is to create a low- or mid-frequency dynamic head, which can be used in loudspeakers with a composite head and which overcomes at least one of the considered disadvantages. To solve this problem, a new principle is proposed for constructing a mid-frequency dynamic head, on the basis of which acoustic coupling is realized through double radial suspension of the diaphragm using the push-pull principle of linearization of axial displacement in order to reduce acoustic distortion for the mid-frequency dynamic head.

Another problem solved by the invention is to implement the principle that the acoustic coupling of a high-frequency diaphragm with the air is as continuous as possible, i.e. the geometry of the parts directly restricting the diaphragm on the front side is free from sharp transitions and ruptures, especially of the radial type, which could cause secondary acoustic radiation, which would lead to acoustic interference between the radiation emitted directly by the diaphragm and this secondary radiation. The result is an improvement in the frequency response of the high-frequency dynamic system head in the axial and off-axis directions.

The invention is based on the use of a new type of dynamic loudspeaker head, comprising a substantially rigid chassis and substantially flexible suspension elements that are driven by a substantially rigid primary (i.e., sound-emitting) vibrating diaphragm.

More specifically, the device according to the invention is characterized by features included in an independent claim.

The use of the invention provides significant advantages. Compared with the known structures, the invention provides a weakening of the diffraction components in the composition of the acoustic radiation, which leads to a smoother frequency response and to improved directional control. Thanks to the improved linearity of the suspension, the invention provides a reduction in non-linear acoustic distortion. In addition, since the invention provides a simple mechanical structure, known components and technologies can be used in its manufacture, which will ensure the economic efficiency of the invention.

Brief Description of the Drawings

Below will be described in detail, with reference to the accompanying drawings, some embodiments of the invention are described.

Figure 1 in section shows a dynamic head with a single diaphragm, used in the coaxial version.

Figure 2 in section shows a dynamic head with a divided diaphragm, used in the coaxial version.

In Fig.3, a composite dynamic head is shown with a spatial separation of its parts.

4 is a graph illustrating the relationship between axial displacement and stiffness of the diaphragm suspension.

Figure 5 illustrates the effect of using an internal radial clearance of 1 mm wide on the frequency response of a small speaker for reproducing higher sound frequencies (tweeters) using a dome with a diameter of 25 mm and installed inside the voice coil frame with a diameter of 40 mm.

The implementation of the invention

In the context of the invention, the term rigid refers to structural elements that do not experience significant vibrations as a result of the application of electromechanical forces generated by any voice coil within the system, while the term elastic corresponds to structural elements that are subject to the application of electromechanical forces to them, generated by any voice coil in the system, bend, compress or expand. Further, the term forward direction (forward direction) means the direction in which sound waves generated by the loudspeaker begin to propagate, i.e. the direction in which the diaphragm moves closer to the intended sound receiver. Conversely, the term backward direction (reverse direction) means the direction opposite to the forward direction. Accordingly, the terms front and rear correspond to the sides of the speaker, which are located in the forward or backward directions. The term "voice coil frame" is used in relation to any structural element capable of providing mechanical coupling of the voice coil and the vibrating diaphragm, although it is understood that there may be a direct connection between these components.

As shown in FIG. 1, according to one embodiment of the invention, the loudspeaker is formed by a rigid frame comprising the following components: a rigid outer part 11 and a rigid inner part 8, as well as the following additional components: mating element 12 (for a high-frequency dynamic head), magnetic pole piece 19, as well as the front and rear flanges 14, 15 of the magnetic circuit, which will be discussed later. A rigid frame is attached to or forms at least a portion of the speaker housing. Inside the frame is a rigid inner part 8 and sound-emitting, i.e. vibrating parts that are located either between the outer and inner hard parts 11, 8, or within the rigid inner part 8. Hereinafter, these outer and inner hard parts 11, 8 will be referred to as the chassis 11 of the head assembly and the chassis 8 of the high-frequency dynamic head, respectively.

More specifically, the head assembly 22 (i.e., the composite dynamic head) has a composite structure mounted on the chassis 11 of the head assembly. In other words, a mid-frequency dynamic head and a high-frequency dynamic head are installed on the chassis 11 of the head assembly, which is integrated in the voice coil frame 6 as part of the mid-frequency dynamic head, shown in Figs. 1 and 2. In these figures, corresponding to sectional views, a vertical dashed line corresponds to imaginary axes of rotational symmetry. The axis of symmetry of the frame 6 of the voice coil of the mid-frequency dynamic head does not necessarily coincide with the axis of the voice coil 20 of the high-frequency dynamic head, although this implementation seems to be the most practical. The voice coil 20 of the high-frequency head is always small: its diameter is usually 10-55 mm. The chassis 11 of the head assembly is connected by its rear wall to the flange 14 of the magnetic circuit. The specified flange 14 is also attached to the rear flange 15 of the magnetic circuit. Between these two flanges there is a permanent magnet 13, which creates a constant magnetic field in the air gap 23. According to one embodiment, the permanent magnet 13 is in the form of a ring of ferrite material (for example, the brand "Ferroxdure 300") with an outer diameter of 134 mm and a height of 20 mm. The magnetic flux density B in the air gap 23, which should preferably be 1.4 T, is ensured by selecting a height and a width of the gap of 6 mm and 1.35 mm, respectively.

The flanges 14 and 15, the central pole piece 19 and the permanent magnet 13 form a magnetic system relative to which the voice coils of the dynamic heads move. The central pole piece 19 of the magnetic system is also attached to the mating element 12 (for the high-frequency head), which connects the chassis 11 of the head assembly to the chassis 8 of the high-frequency dynamic head. The chassis 8 of the high-frequency dynamic head can be used to place on it the diaphragm 7 of the high-frequency dynamic head containing, as shown in Fig. 1, a magnet and a winding of the voice coil 20 of this head. The chassis 8 of the high-frequency dynamic head can also be considered as a mounting component for the diaphragm block 21. The chassis 8 of the high-frequency dynamic head can preferably have an opening angle between 30 ° and 80 ° (this angle is measured as the angle between the axis of movement of the voice coil 20 and the tangent to the specified chassis 8 in the radial direction). The voice coil unit - containing its winding 9 and the frame 6 - moves under the action of electromagnetic forces resulting from the interaction of the permanent magnet 13 and the winding 9 of the voice coil when current flows through it. An acceptable diameter of this winding can be selected between 15 mm and 110 mm.

The diaphragm block 21 is attached along its outer edge 5 to the chassis 11 of the head assembly, and along its inner edge 10 to the chassis 8 of the high-frequency dynamic head. This block contains a substantially rigid main vibrating diaphragm 4 attached to its surface. In typical embodiments, this attachment is carried out by gluing, thermolamination, welding or casting of the diaphragms 1 and 4 in the form of a single part, the main vibrating diaphragm 4 can be located on the front or rear side of the elastic diaphragm 1 or form an integral part with it. The elastic diaphragm 1 itself is preferably made of elastic foam rubber, in particular EPDM-NR-SBR rubber with closed pores, the acceptable layer thickness of which can be 0.1-6 mm, preferably about 2 mm, the hardness of which is 20-50 Shore units and the diameter is about 120 mm. The diaphragm 1 and the main vibrating diaphragm 4 can be connected by means of a neoprene adhesive. In any case, it is necessary to ensure a strong connection with the main vibrating diaphragm 4, an acceptable diameter of which can be 35-250 mm, and an acceptable thickness of 0.05-5 mm. In a specific embodiment, the main vibrating diaphragm 4 is preferably made of a 0.2 mm thick deep-drawn aluminum sheet and has a diameter of 100 mm. In this case, the main vibrating diaphragm 4 may have an opening angle between 30 ° and 80 ° (this node is measured as the angle between the axis of movement of the voice coil 20 and tangent to the diaphragm 1 in the radial direction). In a preferred embodiment, the angle is 63 °.

A gap is left between the main vibrating diaphragm 4 and the chassis 11 of the head assembly so that the elastic diaphragm 1 can function as a flexible suspension element allowing axial movement of the main vibrating diaphragm 4. This gap is hereinafter referred to as the outer radial clearance. The outer radial clearance is completely covered by the outer radial section 2 of the elastic diaphragm 1. In order for the elastic diaphragm 1 to function as a flexible suspension element allowing axial movement of the main vibrating diaphragm 4, a gap is also left between the main vibrating diaphragm 4 and the chassis 8 of the high-frequency dynamic head. This gap, hereinafter referred to as the inner radial gap, is completely covered by the inner radial section 3 of the elastic diaphragm 1. The joint between the flexible diaphragm and the chassis 11 of the head assembly, i.e. the interface between the outer edge 5 of the diaphragm assembly and the chassis 11 is smooth and continuous in order to minimize acoustic diffraction and improve acoustic communication with the diaphragm 7 of the high-frequency dynamic head, especially with a coaxial arrangement. In general, the acceptable smoothness (continuity) of the radial profile can be characterized by an axial displacement between the diaphragm 1 and the chassis 11 of the head assembly (measured at the outer edge 5) less than 2 mm, and an axial displacement between the diaphragm 1 and the high-frequency chassis 8 (measured at the inner edge 18 ), also less than 2 mm.

The main vibrating diaphragm 4 is attached to the frame 6 of the voice coil, at the other end of which is the winding 9 of the voice coil. The voice coil frame 6 can be made of rolled aluminum sheet with a thickness of 0.1 mm and have a diameter of 51 mm and a length of 30 mm. In this case, the winding 9 of the voice coil can be made of aluminum wire with a diameter of 0.3 mm, clad with copper, and the winding can be two-layer and can be wound over a length of 7 mm. The coil 9 of the voice coil interacts with the permanent magnet 13 by means of induced electromagnetic forces. The axial movement of the coil 9 of the voice coil is transmitted by its frame 6 to the main vibrating diaphragm 4. Since the main vibrating diaphragm 4 is connected to the winding 9 of the voice coil through the frame 6 of this coil, and the diaphragm block 21 is connected to the chassis 8 of the high-frequency dynamic head, as a rule, there is no need the use of traditional axial suspension type crosses.

When the main vibrating diaphragm 4 is axially moved, its movement is transmitted to the diaphragm block 21. This axial movement forces the outer and inner radial sections 2, 3 to be deformed in the axial and radial directions depending on the indicated movement. The relationship between the stiffness of the radial jumpers and the axial displacement of the diaphragm block 21 is illustrated in Fig.4. The geometry of this deformation for the outer and inner flexible radial bridges is symmetrical in relation to positive and negative (i.e., forward and reverse) displacements. The combination of the outer radial section 2, the main vibrating diaphragm 4 and the inner radial section 3 can be considered as the equivalent of the combination of a spring element - a rigid component - a spring element, in which each of the spring elements has a non-linear characteristic graph of stiffness - displacement, and the graphs for both elements essentially mutually symmetric with respect to displacement. This characteristic provides a linearity increase (linearization) of the total stiffness of the axial suspension of the diaphragm block 21. This, in turn, provides a significant attenuation of the acoustic distortions generated by the dynamic head in the form of even harmonics compared to using a single flexible radial section.

As shown in FIG. 2, the main vibrating diaphragm 4 can be attached to the diaphragm block 21 in such a way that it forms a radial section between the outer and inner radial sections 2, 3. In this embodiment, there is no flexible diaphragm 1 overlapping the main vibrating diaphragm 4. as was the case in the embodiment of figure 1. Indeed, when looking at the dynamic head from the front, the diaphragm block 21 will be divided into three coaxial annular sections, with the main vibrating diaphragm 4 forming the middle radial section performing axial movement. The main vibrating diaphragm 4 is attached to the inner and outer radial sections 3, 2 with its protruding connecting flanges. This attachment is usually carried out by gluing, thermolamination or co-molding. The inner radial section 3 is attached to the chassis 8 of the high-frequency dynamic head along its inner edge 10, similarly to what was done in the embodiment of FIG. 1. This also applies to attaching the outer radial section 2 to the chassis 11 of the head assembly. The attachment of the inner radial section 3 to the chassis 8 of the high-frequency dynamic head is critical because it is necessary to form an interface that should be as smooth as possible in order to minimize acoustic diffraction and improve acoustic communication with the diaphragm 7 of the high-frequency dynamic head, especially with a coaxial arrangement. This requirement, as noted above, applies to the connection between the outer edge 5 of the diaphragm block and the chassis 11 of the head assembly. If there was a gap between the inner radial section 3 and the high-frequency chassis 8, this would lead (as shown in FIG. 5) to a degradation of the frequency response. In the construction according to the invention, the high-frequency band typically corresponds to an interval of 3-20 kHz with an average sensitivity of 88 dB / W / m. The mid-frequency band typically corresponds to an interval from 450 Hz to 3 kHz with an average sensitivity of 94 dB / W / m.

As in the embodiment described with reference to Fig. 1, the main vibrating diaphragm 4 is additionally connected to the coil 9 of the voice coil, which is connected to the inner protruding connecting flange of the diaphragm 4 through the frame 6 of the voice coil. The outer and inner radial sections 2, 3 respond to the axial movement of the main vibrating diaphragm 4 by a corresponding deformation, as described in relation to the embodiment of FIG. 1. This deformation corresponds to the model shown in figure 4.

In Fig. 3, the embodiment of Fig. 1 is shown with a spatial separation of the parts and in assembled form, in order to better illustrate the parts of the structure.

The outer mounting ring 31 has a supporting surface 17 (see FIGS. 1 and 2) that is inclined inward and which is formed with high precision to receive the outer edge 5 of the diaphragm block 21. FIG. 3 shows two flexible leads 32 of the voice coil, which depart from its winding 9. A power amplifier or similar component can be connected to the winding 9 of the voice coil (to its flexible terminals 32) through passive isolation filters (not shown). These filters can be replaced by active electronic filters in front of the power amplifiers, each of which drives its voice coil 9, 20 with signals in the corresponding frequency band with the possible use of frequency correction in addition to dynamic heads.

The described options represent only two possible preferred alternatives. There are, of course, many ways of carrying out the invention described in the attached claims. For example, the main vibrating diaphragm 4 can be made similarly to the outer and inner radial sections 2, 3, forming together with them a single structure, the corresponding parts of which have rigid and flexible properties. Such properties can be, at least theoretically, realized in the manufacture of a diaphragm from a homogeneous material having different thicknesses or stiffness values in different sections.

Claims (16)

1. The dynamic head (22) of the speaker, containing:
- a rigid frame, to which a permanent magnet (13) is attached, capable of interacting, by means of electromagnetic forces, with the winding (9) of the voice coil configured to transmit axial motion to the diaphragm block (21), the front side of which sets the primary direction for reproduced sound, and the back side is designed to connect a voice coil to the winding (9), and the diaphragm block (21) has an elastic outer section (2), the outer edge (5) of which is attached to the outer part (11) of the frame la, characterized in that
- the diaphragm block (21) contains a rigid main vibrating diaphragm (4) fixed between the elastic outer section (2) and the elastic inner section (3), the inner edge (10) of which is attached to the inner part (8) of the loudspeaker frame; wherein
- the front side of the diaphragm block (21) and the specified inner edge (10) have a substantially continuous radial profile, so that the diaphragm block (21) and the area of its attachment to the inner part (8) of the loudspeaker frame do not form sharp transitions or gaps. 2. The loudspeaker head (22) according to claim 1, characterized in that the main vibrating diaphragm (4) is attached to the diaphragm block (21) so that it is blocked from the front side of the head by an elastic diaphragm (1). 3. The loudspeaker head (22) according to claim 1, characterized in that the main vibrating diaphragm (4) is fixed to the diaphragm block (21) so that it is open from the front side of the head. 4. The loudspeaker head (22) according to claim 1, characterized in that it is a composite dynamic head containing, together with the diaphragm block (21), a high-frequency diaphragm (7). 5. The head (22) of the loudspeaker according to claim 4, characterized in that the high-frequency diaphragm (7) is located in the rigid inner part (8) of the loudspeaker frame. 6. The loudspeaker head (22) according to claim 1, characterized in that the diaphragm block (21) has a substantially constant opening angle. 7. The loudspeaker head (22) according to claim 1, characterized in that the diaphragm block (21) has a progressively increasing opening angle. 8. The speaker head (22) according to claim 6, characterized in that the opening angle is 30-80 °. 9. The loudspeaker head (22) according to claim 6, characterized in that the rigid inner part (8) of the loudspeaker frame and the diaphragm block (21) have the same opening angle. 10. The loudspeaker head (22) according to claim 9, characterized in that the rigid inner part (8) of the loudspeaker frame has an opening angle, measured as the angle between the axis of movement of the voice coil (20) and tangent to the specified inner part (8) in the radial direction is 30-80 °. 11. The loudspeaker head (22) according to claim 1, characterized in that the axial displacement between the diaphragm block (21) and said outer part (11), measured at the outer edge (5), is less than 2 mm. 12. The loudspeaker head (22) according to claim 1, characterized in that the axial displacement between the diaphragm block (21) and the rigid inner part (8) of the loudspeaker frame, measured at the inner edge (18), is less than 2 mm. 13. The head (22) of the speaker according to claim 1, characterized in that the diameter of the voice coil (20) of the high-frequency diaphragm (7) is 10-55 mm. 14. The loudspeaker head (22) according to claim 1, characterized in that the diameter of the winding (9) of the voice coil is 15-110 mm. 15. The head (22) of the speaker according to any one of the preceding paragraphs, characterized in that the diameter of the main vibrating diaphragm (4) is 35-250 mm. 16. The head (22) of the loudspeaker according to 14, characterized in that the diameter of the main vibrating diaphragm (4) is 100 mm.

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