CN1319320A - Loudspeaker - Google Patents

Abstract

A mid/high frequency loudspeaker drive unit comprising a stiff lightweight resonant panel form member, a housing in which the panel form member is mounted, a resilient suspension connected between the edges of the panel form member and the housing, the arrangement being such that the housing and the panel form member together define a sealed enclosure, and an electrodynamic exciter for applying bending wave energy to the panel form member to cause it to resonate to produce an acoustic output, the exciter comprising a magnet assembly rigidly fixed to the housing and defining an annular gap and a voice coil disposed in the annular gap and rigidly fixed to the panel form member near to the geometric centre thereof, the location of the voice coil in the annular gap being provided by the said resilient suspension.

Description

speaker

The present invention relates to loudspeakers, in particular to loudspeakers in the form of a resonant plate, such as that described in International Patent Application WO 97/09842, so-called distribution mode loudspeakers.

Previously, it was difficult to provide speakers covering the mid- and high-frequency audio range with high quality. For a mid-range driver alone, the directivity changes in this range are very large, and it is very difficult to extend to even high frequencies. Typically, two drivers are used, with a frequency selective network dividing the frequency range between them, adding cost and complexity. The junction frequency is generally about 3 kHz, which is the most sensitive of human hearing, which increases the difficulty.

The idea of the present invention is to design a mid/tweeter driver, replacing the two conventional drivers previously used, which does not overlap in the critical area and has a consistent directivity of the desired width throughout its operating range.

Distribution mode loudspeakers can be designed to operate over certain octaves of the audio band, although for applications such as hi-fi this is not always the best solution. It is conceivable that distribution mode loudspeakers are sometimes suitable for use with subwoofers at low frequencies that cross over, for example, around 100 to 200 Hz.

Therefore, there is a need for a speaker or at least one speaker drive unit, which does not necessarily work on the 8th octave, but can work on the 6th to 7th octave. The material selection range is wide, and various structures can be used, which is helpful in The loudspeaker is optimized over its entire operating range. An example of this is a hi-fi mid/treble driver operating on the distributed mode principle. By designing the junction point away from the critical 3kHz region to the 1kHz range, typically 300-500Hz, it can bring significant benefits to box-type traditional loudspeaker systems, and can also benefit from the excellent radiation characteristics associated with distributed mode loudspeakers. benefit.

In multimedia and computer peripherals, there is an ever-expanding market for small speakers that require high performance, and traditional TVs, monitors, and flat-panel TVs have been demanding better sound and more compact structures.

Therefore, there is a need for a structure that is very compact and has multiple features to enhance performance, versatility of application and save cost.

The present invention provides a cost-effective concept for all these applications, enabling manufacturers to optimize tool configuration and production processes.

The basic concept of the invention revolves around the simple construction of a loudspeaker "engine" or driver unit, allowing for ease of production assembly and consistency.

According to the invention, there is provided a mid/high frequency loudspeaker drive unit, comprising: a rigid, lightweight resonant plate-shaped element; a housing containing the plate-shaped element; an elastic suspension connected between the plate-shaped element and the shell. Bearing, such a layout makes the shell and the plate-shaped element together form a sealed housing; an electrodynamic vibration exciter, which applies bending wave energy to the plate-shaped element, causing it to resonate to produce sound output, the exciter includes a firmly mounted to the housing and form an annular gap magnet assembly, and a voice coil located in the annular gap fixedly mounted on the plate-shaped element close to its geometric center, the positioning of the voice coil in the annular gap is determined by the Elastic suspension is provided.

The bending stiffness of the plate-shaped element can be between 0.15 Nm and 24 Nm, preferably between 2 Nm and 9 Nm.

The vibration exciter may be bonded to the plate-shaped member (hereinafter "plate") and/or to the housing by injection molding or using an adhesive. The voice coil of the vibration exciter can be bonded directly to the resonant plate during the injection molding process of the plate. Alternatively, the voice coil of the exciter can be bonded to a pre-formed opening molded into the resonant plate during assembly. In this way, a separate voice coil carrier is no longer required.

The plate can be co-molded with the suspension. The suspension can be of elastic material, such as plastic.

The plates can be injection molded as a one-piece body, or foamed. The plate can be flat or curved and can vary in thickness or cross-section.

The housing can embed conductive inserts to efficiently carry electrical signals from connectors on the housing edge to the vibration exciter. In this way, the assembly and connection of the drive unit can be automatically completed.

For example, for aesthetic reasons, the drive unit could be encased in other moldings to suit the application. Appropriate trim would make it suitable for surface mounting on a hi-fi speaker cabinet, for example. Conversely, an appropriate overmolding will convert the speaker into a multimedia speaker. Further, the speaker can be installed in other structures such as a TV sound box.

The invention is illustrated by way of example in the accompanying drawings. in:

Figure 1 is a perspective view of a loudspeaker drive unit partially cut away to reveal its internal details;

FIG. 2 is a cutaway side view of the speaker drive unit of FIG. 1;

FIG. 3 is a representative frequency response curve of the drive unit shown in FIG. 1 and FIG. 2 .

A loudspeaker drive unit 1 is shown, used as a mid/high frequency driver, which can also be used as a component in a loudspeaker system that also includes a low frequency driver, in which case the mid/high frequency and low frequency drivers can be assembled In a common loudspeaker, or as a single driver for small speakers in eg multimedia or computers or cars.

The drive unit 1 includes a substantially rectangular housing 2, the housing 2 has a disc-shaped body 11, the body 11 is surrounded by a fixed flange 3 extending outwards, and holes 12 are formed at certain intervals on the flange, so that The housing is positioned on a sound box, eg a loudspeaker, by suitable fasteners (not shown). The housing 2 can be made of plastics such as injection molding, and the cross partition flange 13 is formed inside to increase the rigidity of the housing while maintaining its light weight.

An inner, substantially circular dimple 4 is formed at the base 14 of the housing 2 . The recess 4 has a central through hole 16 . The recess is adapted to neatly receive a circular back plate 6 to which the magnet assembly is securely mounted with bolts 20 . The driver 5 includes said magnet assembly forming an annular gap 19 , and a voice coil and cylindrical shaper assembly 8 . The assembly 8 is arranged in the annular gap and can move axially according to the electrical signal applied to the voice coil.

The back plate 6 can be secured to the housing in any convenient manner. Therefore, the back plate 6 can be fixed together with the casing by fasteners or adhesive method or integral molding method.

Adjacent to the edge flange 3 , a generally rectangular, rigid, lightweight resonant plate-shaped element 9 is resiliently mounted on the housing 2 by flexible foam suspensions 10 extending around the perimeter of the plate 9 . The housing and the plate then form a closed cavity 15 . The suspension 10 can be mounted on the plate 9 and the housing 2 by bonding. Plate 9 is a distributed mode plate according to the teaching of WO97/09842. The voice coil/shaper assembly 8 of the exciter 5, as taught in WO 97/09842, is rigidly mounted on the plate 9 at a suitable near-centre drive location, to introduce bending waves into the plate, causing the plate to resonate and produce sound output. The voice coil and coil former assembly 8 has an annular mounting member or foot 21, such as plastic, mounted securely on one end of the assembly adjacent the plate 9, to facilitate mounting the assembly to the plate, possibly by means of an adhesive . Note that it is not common for the exciter 5 to be attached directly to the housing 2, and no suspension is included between the voice coil and the magnet assembly, so that the centering of the voice coil in the annular gap of the magnet assembly is only supported by the plate edge suspension 10 to achieve. In this way, the moving mass of the exciter is reduced and its high frequency response is improved. The magnet assembly can be thermally coupled to the voice coil to improve its power handling, heat radiating from the exposed backside of the backplate 6 .

Optional, localized small masses 17, for example from 2 grams to 12 grams, are bonded to the plate to tune the bonded resonance situation in an optimal manner so that the overall response can be properly tailored. This technique has the particular advantage of extending the low frequency range of the device. The high frequency response is extended through the opening 18 of the plate 9 coaxial with the voice coil. Some sound absorbing material (not shown) within the chamber 15 may help reduce the magnitude of higher order standing waves within the chamber and may further improve the frequency response.

The above drive unit can have the following specifications:

Board size=210×148.5mm (A5 standard size)

Core = 3mm polycarbonate honeycomb structure, 3.5mm cell diameter

Skin = 100 micron woven glass reinforced polycarbonate skin (0°/90° skin direction) 50% glass by weight

Bending stiffness = 5.6 Nm

Surface density μ=0.7 kg/square meter

Zm=16 Newton seconds/meter

Voice coil diameter=26mm

The voice coil is placed in the standard distribution mode position (ratio is 4/9,3/7)

Large ferrite ring magnet for improved BL and power handling.

As discussed, there is no suspension between the magnet and voice coil, the plate is held in place by foam suspensions around its edges. The holes in the inner plate of the voice coil allow for alignment and precise mounting of the plate, helping to align the voice coil in the annular gap. It is also possible to establish positioning pins near the edge of the upper plate of the housing to prevent the plate from moving sideways. Figure 3 shows the frequency response of such a board.

Conceivably, small modifications to the drive unit with high quality piezo actuators could extend the response into the ultrasonic range, which would be useful for interfacing with newer audio formats at 50kHz or 100kHz. This performance is beyond the range of conventional piston technology.

The present invention provides a new type of mid- and high-frequency loudspeaker drive unit that solves the outstanding problems of known structures related to frequency overlap and divergence.

Claims (9)

1. A mid/high frequency loudspeaker drive unit comprising: a rigid, lightweight resonant plate-shaped element; an enclosure housing the plate-shaped element; an elastic suspension connected between the plate-shaped element and the enclosure, such layout such that the housing and the plate-shaped element together form a sealed enclosure; an electrodynamic vibration exciter, which applies bending wave energy to the plate-shaped element to cause it to resonate to produce an acoustic output, includes a motor firmly mounted to the housing and A magnet assembly constituting an annular gap, and a voice coil fixedly mounted in the annular gap to the plate-shaped element close to its geometric center, the positioning of the voice coil in the annular gap is determined by said elastic suspension supply. 2. 2. A loudspeaker drive unit as claimed in claim 1, wherein said housing comprises a disc-shaped body surrounded by securing flanges. 3. The loudspeaker drive unit of claim 2, wherein said disc-shaped body includes a through hole, wherein the magnet assembly of the vibration exciter is securely mounted on the disc-shaped body, a portion of its surface enclosing the through hole in the body. hole. 4. 3. The loudspeaker driving unit according to claim 3, comprising a recess in the disc-shaped body, the magnet assembly including a back plate mounted in the disc-shaped body, said through hole being formed in the recess. 5. 3. A loudspeaker drive unit as claimed in any one of the preceding claims, characterized in that the resilient suspension is of foam material. 6. 3. Loudspeaker drive unit according to any one of the preceding claims, characterized in that the plate-shaped element comprises a core of honeycomb material sandwiched between skins, having a bending stiffness of 0.15 to 24 Nm. 7. 6. Loudspeaker drive unit according to claim 6, characterized in that the bending stiffness is 2 to 9 Newton meters. 8. A loudspeaker drive unit as claimed in any one of the preceding claims, comprising an opening through the plate-shaped element, coaxial with the voice coil and having a smaller radius than the voice coil. 9. 3. A loudspeaker drive unit as claimed in any one of the preceding claims, comprising at least one discrete mass mounted on the plate-shaped element and positioned to damp the low frequency response.

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