JPS6216067Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an MFB speaker device. MFB
The speaker device detects vibrations of a vibrating body of a speaker using a vibration detection means, and feeds back a voltage corresponding to the vibration to an amplifier for driving the speaker to control vibration characteristics of the speaker. As the vibration detection means, there are various methods such as a method of detecting the vibration speed and vibration amplitude of the vibrating body of the speaker.

A known method for detecting the latter vibration amplitude is to detect changes in capacitance between a movable electrode and a fixed electrode that vibrate together with the vibrating body. However, since the fixed electrode is provided separately from the speaker components (vibrating body such as a voice coil, yoke, etc.), the structure is complicated and has the disadvantage of being impractical.

The present invention improves on these conventional drawbacks, and will be explained below with reference to the drawings.

This will be explained in FIG. Bass speaker 1
In a composite speaker in which a treble speaker 4 is attached to the top of a center pole 2 which constitutes a magnetic circuit through an insulating member 3, the cylindrical surface of a pot-shaped yoke 5 which constitutes a magnetic circuit of the treble speaker 3 is fixed to a fixed electrode. The upper end of the metal foil voice coil bobbin 6 of the bass speaker 1 is extended to form a facing surface between it and the yoke 5, and this extended portion 6a
is a movable electrode, and the change in capacitance between the movable electrode and the fixed electrode is extracted as the MFB detection output.

The change in capacitance between the movable electrode and the fixed electrode is caused by a change in the opposing area between the movable electrode and the fixed electrode, that is, a change in the vibration amplitude of the metal foil voice coil bobbin 6 of the bass speaker 1. Compatible.

The change in the capacitance, that is, the change in the vibration amplitude of the metal foil voice coil bobbin 6 of the bass speaker 1, can be controlled by, for example, a known capacitance-to-voltage conversion circuit as shown in FIG. It is converted into a voltage proportional to the change in amplitude.

In FIG. 2, reference numeral 7 denotes vibration detection means formed by a fixed electrode (yoke 5) and a movable electrode (extension portion 6a of metal foil voice coil bobbin 6);
is a known capacitance-voltage conversion circuit. This capacitance. The voltage conversion circuit 8 is constituted by a source hollow circuit using a field effect transistor 9. A vibration detecting means 7 is connected between the gate of the field effect transistor 9 and the ground, and a high DC voltage is applied between the fixed electrode and the movable electrode. The electrical impedance between the fixed electrode and the movable electrode changes according to a change in capacitance (several pF to several + pF), and the source voltage of the field effect transistor 9 changes in proportion to the change.

As described above, in the present invention, the metal foil voice coil bobbin 6 of the bass speaker 1 is extended to serve as a movable electrode, and the yoke 5 of the treble speaker 4 is used as a fixed electrode. Since it is skillfully used as a movable electrode and a fixed electrode, there is no need to separately provide a movable electrode and a fixed electrode as in the conventional case, and the structure has a practical advantage of being extremely simple.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of the main part of the MFB speaker device of the present invention, and FIG. 2 is a diagram showing the configuration of the capacitance-voltage conversion circuit. 1 is the bass speaker, 2 is the center pole,
3 is an insulating member, 4 is a treble speaker, 5 is a yoke, 6 is a voice coil bobbin, and 6a is an extension part.

Claims (1)

[Scope of utility model registration request] This is a composite speaker device in which a treble speaker 4 is attached to the top of a center pole 2 constituting a magnetic circuit of a bass speaker 1 via an insulating member 3, and the vibration of the bass speaker 1 is detected by a vibration detection means. In the MFB speaker device, a voltage corresponding to the vibration is fed back to an amplifier for driving the bass speaker 1 to control the vibration characteristics of the bass speaker 1. The yoke 5 constituting the circuit is used as a fixed electrode, the upper end of the metal foil voice coil bobbin 6 of the bass speaker 1 is extended, and the extension 6a is used as a movable electrode, so that the vibration amplitude of the bass speaker 1 is controlled by the movable electrode. An MFB speaker comprising vibration detection means that detects a change in capacitance between an electrode and a fixed electrode, and capacitance-voltage conversion means that converts the change in capacitance into a change in voltage. Device.