JPS5972298A - Dynamic speaker - Google Patents

Abstract

PURPOSE:To utilize a cavity in a magnetic circuit effectively by charging at least one magnetic gap with magnetic liquid, and flowing air from at least one cavity in the magnetic circuit to the space between a diaphragm and the front surface of the magnetic circuit or reversely. CONSTITUTION:The magnetic gaps 8 and 9 are charged with magnetic liquid materials 10 and 11 in order to damp an oscillation system mechanically. Consequently, no air flows in the magnetic gaps, so the cavity in the magnetic circuit is not utilized. Namely, when the diaphragm 3 oscillates by driving force from voice coils 12 and 13, the air surrounding the diaphragm 3 and in the space 20 is compressed and expanded, and its pressure is propagated to the direction at right angles to the center axis of the speaker. For this purpose, bobbin holes 21 and 22 are provided. The pressure exerted by the air in the space 20 is propagated to the cavities 14 and 15 through the magnetic gaps 8 and 9. Then, the cavities 14 and 15 operate as an air-spring to contribute to release the pressure in the space 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrodynamic speaker, and particularly to an ivI electrodynamic speaker with improved frequency characteristics and high fidelity reproduction.

[Prior art]

Conventional electrodynamic speakers may have one magnetic gap or multiple concentric magnetic gaps, and the magnetic gap is either a literal air gap or filled with a magnetic fluid.

In the former case, it is necessary to apply electromagnetic braking by driving the speaker at a constant voltage, since conventional speakers generally have a relatively small mechanical resistance in order to brake the photographing string at the lowest frequency.

In this case, if the electroacoustic conversion efficiency is high, over-braking may occur, and in that case, bass may be insufficient. Additionally, as a result of the voice coil's inductance increasing the impedance towards higher frequencies, the drive current and drive force may decrease, resulting in a lack of high-pitched sounds. Also, since it is a constant voltage amplifier, the output voltage waveform is always kept constant regardless of the load.
When the magnetic flux accompanying the current flowing through the voice coil passes through the non-straight magnetic material, the drive current and drive force may be distorted due to a reaction. Furthermore, when a large input power is applied, the voice coil generates heat due to the energy consumed by the voice coil, and its resistance value increases, so that the sound pressure may no longer be proportional to the amplifier input.

The above-mentioned drawbacks can be improved by filling the magnetic gap with a magnetic fluid with an appropriate viscosity, mechanically damping the vibration system, and driving the speaker with a constant current, but simply doing so will not solve the problem. The diaphragm receives a reaction due to the resonance of the air in the space between the diaphragm and the front side of the magnetic circuit (on the diaphragm side), and even if the bobbin has a sufficiently large hole, the frequency response may not be as audible. This creates valleys and peaks that cannot be ignored. In order to widen the distance between the imaging plate and the front of the magnetic circuit so that it can be ignored, it must be made to be about the same diameter as the diaphragm, which would make the bobbin too long and the mass too large. Also, it is not practical because the driving force transmission characteristics at high frequencies deteriorate (・.

If the magnetic gap is filled with magnetic fluid (or not), the behavior of the space is that air enters and exits through the magnetic gap, and the cavity in the magnetic circuit joins as a simple cavity sandwiched between the diaphragm and the front of the magnetic circuit, and the space changes. It acts like expanding the volume of the air, and absorbs air resonance energy as a Helmholtz resonator due to the air in the magnetic gap excluding the bobbin and voice coil, and the compliance of the cavity in the magnetic circuit. In either case, the cavity within the magnetic circuit can be used advantageously.

[Purpose of the invention]

An object of the present invention is to provide an electrodynamic speaker in which a magnetic gap is filled with a magnetic fluid and a cavity in a magnetic circuit is effectively utilized.

[Summary of the invention]

The present invention provides for filling at least one magnetic gap with a magnetic fluid in an electrodynamic speaker having one magnetic gap or a plurality of concentric magnetic gaps, and leaving the remaining gaps unfilled or filling the magnetic gaps. One or more ventilation holes are provided near at least one of the magnetic gaps to connect the cavity of the magnetic circuit and the space sandwiched between the front surface of the magnetic circuit and the imaging plate.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

The figure shows an embodiment of the electrodynamic speaker of the present invention.
1 and 2 are bobbins, 3 is a diaphragm, 4 is an edge suspension, 5, 6.6', 6" and 7, 7' are yokes, 8
, 9 is a magnetic air gap, 12.13 is a voice coil, 14.1
5 is a gap in the magnetic circuit, 16 is a front surface of the magnetic circuit, 20 is a space between the diaphragm 6 and the front surface 16 of the magnetic circuit, 21.22 is a bobbin hole, and 25.26 is a magnet.

In order to mechanically damp the vibration system, magnetic fluids 10 and 11 of appropriate viscosity are filled in the magnetic gaps 8 and 9.

This prevents air from flowing through the magnetic gap, making it impossible to utilize the cavities 14, 15 in the magnetic circuit. In other words, when the driving force of the voice coil 12.13 is transmitted and the diaphragm filter picks up images, the space 2 between the diaphragm 6 and the magnetic circuit front surface 16 is
The air at position o is compressed and expands, and the pressure propagates in a direction perpendicular to the central axis of the speaker. At that time, bobbin 1,
The bobbin holes 21 and 22 are provided so that the propagation of pressure is not obstructed by the bobbin holes 21 and 22. The pressure received by the air in the other space 20 passes through the magnetic gaps 8 and 9 into the cavity 1 in the magnetic circuit.
This also applies to 4.15. The cavities 14 , 15 act as air splashes and serve to relieve the pressure in the space 20 .

Magnetic gap 8 and cavity 14. The magnetic cavity @9 and the cavity 15 each form a Helmholtz resonator.

At the consonant frequency of this resonator, the impedances shown by the air quality cover of the magnetic gap 8°9 and the compliance of the cavity 14.15 have opposite signs, resulting in a very low impedance due only to the air resistance within the gaps 8 and 9. . At frequencies higher than the resonance frequency, the impedance gradually approaches that of the air mass, and at lower frequencies it approaches the impedance of the cavity 14.15. If this effect cannot be utilized, unless the distance between the diaphragm 3 and the front surface 16 of the magnetic circuit is about the diameter of the imaging plate 3, peaks and troughs that affect the auditory sense will appear on the frequency characteristics.

Therefore, ventilation holes 17, 18, 18', 1 in place of the magnetic air gap are used.
9 is provided on the yokes 5, 6〃, 7' to connect the cavities and spaces on both sides of the magnetic gap filled with magnetic fluid.

The present invention does not treat multiple cavities independently; if there are two or more cavities in a magnetic circuit, they may be connected by providing a ventilation hole (not shown in the figure) between the cavities. The space 20 referred to in Figure 3 also includes the space inside the bobbins 1 and 2.

Since vibration &6 and the resonance of the air in the space 20 are the problem, a ventilation hole may be provided from the cavity inside the magnetic circuit to, for example, the rear surface of the magnetic circuit, but this alone is not effective.

As stated above, in this example, all the magnetic gaps were sealed with magnetic fluid, but since the purpose of optically filling the magnetic fluid is to achieve appropriate damping, the magnetic fluid was optically sealed in one magnetic gap, and Bamboo ventilation holes may also be provided. Alternatively, instead of providing a ventilation hole for that cavity, provide a ventilation hole that leads to the adjacent cavity, and ventilate from the magnetic cavity of the adjacent cavity. The resonant frequency between the mass and the cavity in the magnetic circuit can be determined by providing a non-magnetic cylinder or cylinder that extends the cavity on one or both sides of the cavity, or
Change the shape of the yoke to increase the volume of the cavity in the magnetic circuit.
Conversely, by filling the cavity and adjusting the volume of the cavity with paper, you can change the frequency characteristics of the speaker to some extent. Therefore, if there are multiple Helm and Holtz resonators, their resonant frequencies can be aligned or shifted.

However, they are not critically effective, and the larger the volume of the cavities in the magnetic circuit, the better the number. And if some cavities are kept sealed with magnetic fluid, the inner cavities are less affected.

〔Effect of the invention〕

As described above, according to the present invention, the resonance of the air in the space created between the diaphragm and the front surface of the magnetic circuit in an electrodynamic speaker is caused by a magnetic gap not filled with magnetic fluid or
The damping of the vibration system is achieved by the magnetic fluid, which is damped by the action of the vent provided next to the cavity filled with magnetic fluid and the cavity in the magnetic circuit, making it possible to obtain an electrodynamic speaker with a wide band and good frequency characteristics. can.

[Brief explanation of the drawing]

The figure is a sectional view showing an embodiment of an electrodynamic speaker according to the present invention. 1.2: Bobbin roller: Vibration plate 8.9: Magnetic air gap 12.13: Pois coil 14.15: Air gap in magnetic circuit Procedure amendment form C Method Mr. Commissioner of the Japan Patent Office "''"゛ 5 yen 33712
Indication of case 38 Patent application No. 181316 filed in 1982 Title of invention Electrodynamic speaker corrector 2, Dake (510) Hayashi Shikikai and 1 Manufactured by Hitachi
Representative R 3 [II Katsu Shigeyo
Subject of manager's amendment Contents of amendment to the full text of the specification Reprint of the specification (no change in content) 4;

Claims (1)

[Claims] An electrodynamic speaker that has one magnetic gap or a plurality of concentric magnetic gaps, wherein at least one of the one magnetic gap or the plurality of concentric magnetic gaps is filled with a magnetic fluid, and a magnetic circuit An electrodynamic speaker characterized in that air can flow from at least one cavity therein to a space between a diaphragm and a front surface of a circuit, or in the opposite direction.