JPH02161895A - Sound reproducer and method - Google Patents

Abstract

PURPOSE: To make it possible to largely displace a movable coil without generating dangerousness accidentally bringing a diaphragm into contact with a mouth part by forming the diaphragm as a part of an wall of a horn in an input area. CONSTITUTION: In a 1st part of an input area 23, the displacement of the diaphragm 20 includes air of small capacity and pressure is substantially changed as the result of a narrow interval up to the wall. In a final output area 26, the displacement of the diaphragm 20 includes air of large capacity and pressure is slightly changed because the interval between the diaphragm 20 and the wall arranged so as to be mutually opposed is sufficiently large. When a distance from the input area is increased, the accumulated impedance of a preceding capacity part is made larger than the impedance of a succeeding capacity part. Consequently the movable coil can be extremely largely displaced without generating dangerousness accidentally bringing the diaphragm 20 into contact with the mouth part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to the field of electro-acoustic devices and more particularly to devices and methods for producing high fidelity sound.

' the. Electro-acoustic devices or speakers emit variable acoustic pressure as a function of changes in the electrical signals supplied to them. Such a device is formed in two main parts. 1st
The part is a transducer having electrical input terminals for transmitting electrical signals and movable output components whose displacement is linked to changes in the electrical signal. The second part is a movable component in the form of a plate or diaphragm mechanically coupled to a movable transducer component that ensures the emission of acoustic radiation waves corresponding to the electrical signals supplied into the device. .

Although devices of this type have been widely used, they usually present significant problems arising from the power obtained from the conversion of the applied energy to produce a displacement of the movable diaphragm. In practice, acoustic coupling of a directly protruding diaphragm and air produces a low level output because the respective acoustic impedances of the diaphragm (high impedance) and air (low impedance) are quite different.

For this reason, loudspeakers have been constructed using acoustic impedance transformers, generally conically shaped hollow funnels or horns with curved generatrixes. Most advantageously, this curve will be an exponential curve. Acoustic impedance transformation is achieved through a small section or "throat" of the horn, which accommodates high impedance levels and is fitted with a movable diaphragm, and a small section or "throat" of the horn, which accommodates low impedance levels and is connected directly to the outside world. It is carried out within a region located between the main part of the

However, given the mouth surface, high conversion ratios are obtained when the throat area is made very small. This therefore also reduces the surface area of the speaker diaphragm, which severely limits the output power available from the speaker.

To overcome this limitation, it has been proposed to place a cavity or intermediate chamber between the movable diaphragm and the entrance to the throat. In this way, it became possible to make the surface area of the diaphragm larger than the surface area of the throat. The transmission of acoustic energy between the diaphragm and the throat will take place by compressing the air trapped within the chamber.

However, this compression chamber type speaker has serious drawbacks. The transmission of acoustic energy between the diaphragm and the throat and thus the proper functioning of the loudspeaker takes place only within a frequency range or band that is restricted in the direction of high frequency frequencies. The compression chamber produces true damping in this region.

Reducing the spacing between the diaphragm and the throat increases the frequency of new frequencies, but introduces the risk of accidental contact between the diaphragm and the mouth during high amplitude excursions in the bass range. Therefore, in this case as well, the output obtained from the speaker is similarly limited. Furthermore, it should be noted that the acoustic emission from this type of loudspeaker is very directional, with the emission taking place in the axial direction of the horn. To provide this, multiple horns or multiple horns juxtaposed with each other must be used.

FIG. 1 shows a horn-equipped speaker according to the prior art.

It consists of an electro-acoustic transducer and a device for acoustic coupling with air. First of all, the transducer includes a coil 1 of electrically conductive wire with two terminals 2 and 3. The coil is enclosed within the magnetic field created by the magnet 4. Second
Second, the transducer includes a movable diaphragm 5 to which a coil is attached. The air coupling device is a hollow horn 7
a cavity or chamber 6 connected to and having a small input opening 8 or "throat" and a large output opening 9 or "mouth".

This type of speaker operates as follows.

When an alternating current voltage is supplied to the input terminals 2 and 3, the moving coil 1 is displaced by the action of the magnetic field formed by the magnet 4, thereby displacing the converter diaphragm 5. The acoustic energy thus created is propagated across the chamber 6 in the direction of the output throat 8 of the horn, from which the acoustic energy is finally emitted to the outside through the mouth 9.

The surface area of the throat 8 must be small in order to ensure an effective coupling or acoustic impedance match with the large surface area of the mouth 9. However, in order to generate high levels of acoustic output, the diaphragm 50 surface area must be large; these mutually contradictory requirements are reconciled by the presence of the chamber or cavity 6, which reduces the air volume inside the chamber or cavity 6. transmits acoustic energy as a result of the compression increase and pressure drop that takes place there, which results in an acoustic impedance match between the diaphragm 5 and the throat 8.

However, the use of the compression chamber 6 constitutes a serious drawback, as mentioned above, in that it limits the transmission of high frequency frequencies and raises the "breakdown frequency" beyond which no more acoustic energy can be transmitted.

The speaker of the present invention improves the above-mentioned drawbacks of prior art speakers.

One of the objects of the present invention is to provide a horn-equipped speaker that includes a movable diaphragm whose dimensions are significantly larger than the dimensions of the horn throat without requiring reliance on a compression chamber.

Another object of the invention is to create a horn-equipped speaker which allows very large displacements of the moving coil without the risk of accidental contact between the diaphragm and the mouth.

Yet another object of the invention is to provide a horn-equipped speaker that ensures sound emission within an angle extending up to 360 degrees.

In the horn-equipped loudspeaker according to the invention, a portion of the horn wall made of a diaphragm, which is located in the region of the throat and serves to emit acoustic radiation waves, is movable. More particularly, the speaker of the invention comprises an electro-acoustic transducer for converting an electrical signal into an acoustic signal, a coil with an input terminal for supplying the electrical signal, and at least one coil for emitting the acoustic signal. A hollow horn is also provided with a conically shaped wall forming a small input area or throat and a large output area or mouth formed by a movable diaphragm. The speaker diaphragm is formed by a portion of the wall of the input area of the horn.

The invention will be better understood from the following description based on the accompanying drawings.

Figure 2 shows a first embodiment of a horn-equipped speaker according to the present invention. It includes an electro-acoustic transducer and a device ensuring acoustic coupling with air. The electro-acoustic transducer includes a conductive coil 1 with two terminals 2, 3;
The conductive coil l is enclosed within the magnetic field formed by the magnet 4.

It also includes a movable diaphragm 20, the edges of which are supported by flexible spring suspensions such as 21, to which a coil is fastened.

The air coupling device is formed by a hollow horn 22 with a throat or input region 23 and an output region 24 or mouth. The movable diaphragm of the electro-acoustic transducer is formed by a portion of the wall of the input area of the horn.

A speaker constructed as described above creates a sequentially converging acoustic impedance between the diaphragm and the horn without the need for intermediate compression chambers. As a result, it has no limitations on the transmission of high frequency frequencies between the diaphragm and the horn, and there is no rise in the "new frequency".

According to the invention, the operation of acoustic impedance convergence between the transducer of the loudspeaker and the horn depends on a successive increase in the distance separating the two walls of the horn located in the input area. Inside the horn, one wall 25 is fixed, and the other wall 27 is made of a diaphragm 20, part of which is movable.

In the first part of the input region 23 the displacement of the diaphragm encloses a small volume of air and changes the pressure substantially as a result of the narrow wall spacing. - direction final output area 26
In this case, the displacement of the diaphragm encloses a large volume of air, and as a result of the sufficiently large distance between the diaphragm and the wall, which are arranged opposite each other, the change in pressure is small.

Moreover, at a considerable distance from the input region 23, the cumulative impedance of the volumes preceding it remains greater than the impedance of the volumes following it. Furthermore, the volumes and pressures vary in opposite directions between the manual power region 23 and the power region 26 of the horn, respectively. This phenomenon effectively constitutes a favorable convergence of acoustic impedance.

FIG. 3 shows a second embodiment of the speaker according to the present invention which incorporates the concept of rotational symmetry. This embodiment is based on the horn-equipped speaker structure shown in FIG.
Obtained by rotating 360° around 9.

All speaker components share this axis of symmetry. The electro-acoustic transducer comprises a moving coil 1 actuating a diaphragm 30 held in place by a flexible suspension such as 37 and 38; according to this embodiment the diaphragm is It is a component of the input region of a hollow horn 32 having a conical wall. The operation is identical to that of the loudspeaker shown in FIG. 2, which generates acoustic energy that is emitted along the axis of symmetry 39 primarily in the direction shown in FIG. The energy emitting surface also forms two lobes 40 and 41.

FIG. 4 shows a modification of the speaker embodiment shown in FIG. In this embodiment, an energy emitting surface is provided with one lobe 50 that ensures a pronounced directivity in the direction of the axis of symmetry 39. This result is achieved by reducing the angle formed between the conical diaphragm 30 and its axis of symmetry.

It will be clear from the embodiments of the device described above that many other variations and modifications of the device of the invention are possible and will readily occur to those skilled in the art, and therefore The scope is not limited to the disclosed embodiments, but includes all such embodiments that may fall within the scope of the claims appended hereto.

[Brief explanation of the drawing]

FIG. 1 shows a horn-equipped loudspeaker known in the prior art; FIG. 2 shows a first embodiment of the loudspeaker according to the invention; FIG. 3 shows a second embodiment of the loudspeaker according to the invention; and FIG. 3 shows a modification of the second embodiment of the horn-equipped loudspeaker according to the invention; 1... Electric coil, 2.3... Input terminal. 4... Magnetic means, 21... Spring means. 22...Hollow horn, 23...Manpower area. 24...Output area, 25.27...Horn side wall. 29...Axis of symmetry. Cleaning of the drawings @ (No changes to the contents/4'L Zhuzi Mutual 9If ig, 1 Procedural amendments published December 6, 1989 Patent Application No. 196439, 1999 2, Name of the invention Sound reproduction device And how to generate high fidelity 3゜Amendment Person related to the case Address Name Lucas.

Claims (10)

[Claims] 1. an electro-acoustic transducer for converting an electrical signal into an acoustic signal; a coil having an input terminal for supplying the electrical signal; at least one movable diaphragm for emitting the acoustic signal; and a hollow horn having walls arranged such that the distance therebetween gradually increases, the horn having a small input area and a large output area; is formed as a portion of one of the walls of the horn in the input area. 2. 2. The sound reproduction device of claim 1, wherein the wall of the horn and the diaphragm are formed by a plane of revolution about a common axis of symmetry. 3. 3. The sound of claim 2, wherein the movable diaphragm is displaced by actuation of the electric coil; the coil is displaced within a magnetic circuit; and the diaphragm, the coil, and the magnetic circuit have the same axis of symmetry. playback device. 4. 2. The sound reproduction device according to claim 1, wherein the distance between the walls of the horn follows a linear function. 5. 2. The sound reproducing device according to claim 1, wherein the distance between the walls of the horn follows an exponential function. 6. a horn having mutually opposing side walls separated by an increasing distance; an electric coil having an input terminal for receiving an electric signal corresponding to the sound to be reproduced; and generating a magnetic field around said electric coil. and a movable diaphragm coupled to said coil and arranged to move in accordance with said electrical signal, said diaphragm being formed as part of one of said side walls. playback device. 7. 7. A sound reproduction device as claimed in claim 6, wherein said diaphragm is suspended by spring means along said side wall to allow said diaphragm to move freely in response to said electrical signal. 8. 7. The sound reproduction device according to claim 6, wherein said side wall is formed by a plane of revolution about a common axis of symmetry. 9. 7. The sound reproducing device according to claim 6, wherein said diaphragm and said magnetic means have the same axis of symmetry as a side wall facing said diaphragm. 10. mutually opposing side walls separated by an increasing spacing; an electrical coil having an input terminal for receiving an electrical signal corresponding to the sound to be reproduced, said coil being surrounded by a magnetic field and having an input terminal for receiving an electrical signal corresponding to the sound to be reproduced; a method of generating high fidelity sound from a sound reproduction device having: the electric coil coupled to a diaphragm arranged to move; A method of generating high fidelity sound from a sound reproduction device comprising: