FI118030B - A method for measuring the movement of a speaker element and a speaker with motion measurement - Google Patents

Description

118030; Γ

A method for measuring the movement of a speaker element and a speaker with motion measurement

The invention relates to a method for measuring the movement of a speaker element based on changes in capacitance, and to a speaker implemented on the basis thereof.

Typical dynamic speakers have various shortcomings that cause the speaker-5 to produce unwanted sound features such as harmonic distortion, frequency response unevenness, and reverberations. To remedy these problems, various methods have been employed to measure the actual sound produced by the speaker and to correct it as closely as desired. One way to measure the sound produced by the speaker is to measure the movement of the speaker-generated element 10 (most commonly a cone) and, based on the result obtained, to correct the control signal applied to the speaker accordingly.

Previous methods have attempted to implement motion feedback e.g. an accelerometer (U.S. Patents 4,573,189 and U.S. Pat. No. 4,727,584), a series resistor or similar methods based on measuring current through the speaker (e.g.

US Patent 5,542,001) or by means of a coil moving in a magnetic field (e.g. US Patents 4,550,430 and US 5,493,620). Methods more closely related to the present invention are pre-emptive. . ·. disclosed in U.S. Pat. Nos. 2,857,461 and 3,057,961, where the movements of the speaker cone are measured • * «• 4«: *, ·. capacitors parallel to the surface of the speaker cone. In addition, the sound produced by the speaker; · • ·. ** ·. can also be measured, for example, with a microphone (U.S. Pat. No. 3,009,991).

* * * * · * • · * • ·: * '20 In previous methods based on capacitance change, the problem is the non-linearity of the capacitance change with respect to the cone deflection and the reduction of the capacitance with large deflections, whereby the capacitor plate spacing increases: .

It is an object of the present invention to eliminate the problems encountered in the use of the capacitance change method by implementing a capacitor such that its capacitance; ] *** # dance is directly proportional to the taper deflection and also the capacitance value is # · * higher than in the previous methods. This is achieved by con-. ·. i.,: 118030 2 the charge surfaces of the denaturator are placed in the direction of movement and the value of the capacitor is changed either by changing the area between the plates or by moving the object between the plates. More specifically, the method of measuring the movement of the speaker element according to the invention is characterized by what is stated in the characterizing part of claim 51. /

A way to carry out the method of the invention will now be described with reference to the accompanying drawing, which is a sectional view of a conventional loudspeaker and the modifications required therefor. Other possible structural solutions for implementing the rigid system according to the invention are also listed below.

10 A conventional dynamic loudspeaker consists of a magnet 1, a front plate 2, a combined rear plate and a center piece 3, a cone and dust cup 4, an outer cone suspension 5, an inner suspension 6, and a magnetic field coil 7 moving in a magnetic field.

To this speaker is added a cylindrical measuring capacitor according to the invention at the center of the speaker. The outer peripheral 9 connected to a constant voltage of this capacitor, in the example case 1200V, is electrically isolated from the voice coil cylinder 8 by an insulator 10, * but is mechanically coupled to its movements. The voice coil cylinder 8 is an example • · · i · f ··. in the case of a 0V voltage, the inside of the capacitor is formed by a magnet · · · · 20 cylinder 11 mechanically fixed to the center of the magnet · · · · · 20 electrically insulated from both the magnet 3 and the constant voltage. The inner part 11 of the capacitor is connected to a measuring circuit 13 by an operational amplifier which, with suitable component values, produces a voltage proportional to the speed of motion of the cone 4. In the case of example. the value of the resistor is 1ΜΩ and the OpF of the capacitor and the operational amplifier • · · [·. 25 type TL071 Produced by input signal 14 and correction circuit 15. · · ·. control signal to the speaker. The implementation of this coil switch 15 is very dependent on both the speaker element used and the case, so it is not meaningful to illustrate it here ·· «" **. Also, a capacitor is formed between the voice coil cylinder 8 and the central body 11, the capacitance of which changes with the movements of the cone 4. Also this capacitance 3 '' 1 1 8030.

the change can be used for measurement purposes. However, in the case in point, this possibility has not been used. ;

Since, in the example method, the movement of the speaker cone changes the area between the plates of the measuring condenser directly proportional to the cone deflection, the value of the capacitance is also directly proportional to the cone deflection. In addition, the spacing between the measuring capacitor plates may be quite small (in the order of millimeters), so that the change in capacitance of the capacitor is large enough to provide a sufficiently reliable and undisturbed measurement.

Within the scope of the present invention, it is contemplated that the measuring capacitor will be well implemented in many different ways. For example, the shape of the charge surfaces of the capacitor need not be cylindrical, but may be implemented using, for example, a honeycomb or the like, which provides a higher capacitance per unit length of movement of the speaker. It is also possible to implement the capacitor so that the plates of the capacitor itself remain stationary, but the material interposed between them, which is connected to the curl motions, is moved. The material to be moved may be either a guide or an insulator. For the process according to the invention, it is preferred that the conc. the structure of the denaturator is such that the normal surfaces of the capacitor charges are · · · * perpendicular to the direction of motion of the oscillating body such that the change in capacitance is proportional to the cone deflection with the required accuracy. The capacitance of a measuring capacitor or its change can also be measured in many different ways. For example, a capacitor can be used as part of an electronic oscillation circuit, which is • · U, • *. ···. Also, the capacitance capacitance is affected or can be measured by the capacitance • «♦ · * impedance of the capacitor at alternating voltage or current. Also the above mentioned ways. the combination may come into play, for example, if you want to know • · ·; 1; 25, as well as the value of the cone deflection, for example for limiting movement misalignment * ·· \, and at the same time its movement speed or acceleration.

···· • · · · · * *

Although the examples covered a dynamic speaker, the same method could be used.

• · · can also be used for application in other types of loudspeakers, such as electrostatic speakers. Also, the measurement result can be used in a wide variety of ways. For example, measurement can be used to protect the speaker against excessive deviation values.

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Claims (6)

Device for generating sound by means of at least one vibrating object (4, 7, 8), 7 & l characterized in that the device has at least one capacitor (9,11) for measuring _ * movements of some noise-generating vibrating object ( 4, 7, 8) by means of the change of the capacitance, normals of the charge surfaces (9, 11) of the capacitors which lie substantially vertically relative to the direction of movement of the vibrating object (4, 7, 8) in the area where the change of the capacitance used for movements are measured. Device according to claim 1, characterized in that the device intended for generating sound is a dynamic speaker. Device according to claim 1 or 2 or bed, characterized in that one of the capacitor (11) of the capacitor is mechanically fixed to the body (1,2, 3) of the device for generating sound and the other of the charge surface (9). at the swirling object (4,7,8). · '. 'S Device according to claim 1 or 2 or bed, characterized in that the capacitance of the capacitor (9, Π) is changed according to movements of the vibrating object (4, 7, 8) between the charging surfaces with an object (9) which is moved in the relative state of the capacitor. the charge surface (11). Device according to any one or more of claims 1-4, characterized in that the measuring capacitor (9,11) is a cylinder capacitor. Device according to claim 5, characterized in that one cylinder (9) in the cylindrical measuring capacitor (9,11) has been mechanically coupled to movements of the vibrating object (4, 7, 8) and a second cylinder (11) at the body. (1,2, 3) of the device.