JPS5975800A - Movable magnet type speaker - Google Patents

Abstract

PURPOSE:To obtain a small-sized speaker having the large amount of air release and an infrasonic frequency range by attaching the magnet part of a speaker driving part to the back surface of a plane diaphragm, and projecting a voice coil on the internal surface of the back plate of a speaker cabinet facing oppositely to the magnet part. CONSTITUTION:This speaker system consists of the plane diaphragm 2 having a permanent magnet on an internal surface, the cabinet 4 having the voice coil 3 projected to the position facing oppositely to the permanent magnet 1, and an edge 5 which coupling movably the end surface of the plane diaphragm 2 and the opening part of the front surface of the cabinet 4. A diaphragm which has superior strength and rigidity is used suitably as the plane diaphragm 2, but the weight of the diaphragm is incremented by the weight of the permanent magnet to not always limit diaphragm with lightweight structure. The permanent magnet 1 is formed in a disk shape, magnetized from the center of the outer circumferences, and attached at the position corresponding to the oscillation knod of the plane diaphragm 2. The oscillation knod is the knod of split oscillation depending upon the shape, size, and rigidity of the diaphragm. The voice coil 3 is formed by winding a bobbin 6 with an insulating wire having thickness several times as thick as that used for a conventional movable coil type speaker.

Description

[Detailed Description of the Invention] The present invention provides an ultra-low-temperature system in which the magnet section of the speaker drive section is attached to the back surface of the flat diaphragm, and the voice coil is protruded from the inner surface of the back panel of the speaker cabinet facing the magnet section. This invention relates to a highly efficient movable macnet type speaker that enables uniform reproduction across the range.

In a so-called direct radiation speaker that emits sound waves directly into space from a diaphragm, the lower frequency range that can be reproduced with uniform intensity is the bass resonance frequency J7f of the vibration system. Kimimaru.

If you want to produce good bass, this bass resonance frequency f. It is necessary to set it as low as possible. Speakers currently on the market that reproduce ultra-low frequencies, the so-called super woofers, raise the bass resonance frequency r by unilaterally softening the support system of a large-diameter movable coil beaker.

Most of them were made by using a movable speaker to indirectly drive a drone cone with a large inertial mass. These playback devices reproduce bass sounds at a bass resonance frequency f. Since it also relies on the following elastic control range, it is essentially impossible to obtain reproduced sound with good damping in the ultra-low range. In this way, none of the current speakers can comfortably reproduce the ultra-low frequency range of 20 to 60 tlz, and as digital audio systems that can uniformly reproduce 20 to 20 to 11 z are commercialized, There was a desire to develop a speaker that could handle this.

On the other hand, in current analog audio systems based on voltage transmission, there is no electroacoustic transducer superior to electrodynamic speakers in terms of availability of main parts, durability, efficiency, ease of maintenance, etc.

For the same reason, it is thought that it is best to construct an electrodynamic speaker using a moving coil or a moving Macnet in the technical audio system.

As mentioned earlier, the bass reproduction limit of an electrodynamic speaker is the bass resonance frequency r. I can do it. This is the bass resonance frequency f. This is because the radiated sound pressure decreases rapidly at frequencies below f, and in reality, it is the bass resonance frequency f. The playback limit is slightly below . Bass resonance frequency f. is the stiffness of the diaphragm support part and the image mass m. It is generally known that it is proportional to the square root of the ratio of , and this can be expressed as an equation.

Each constant of the speaker is the value when installed in an infinity buckle, so for example, when installed in a closed cabinet,
The bass resonance frequency is f. To do this, the volume of the cabinet and two can be found as follows. The bass resonance frequency f at that time is as follows. In this equation, Se is the equivalent stiffness of the cone and S is the effective diameter of the cone. The equivalent stiffness of the speaker is 5eit, the volume of Vi is different, and the speaker is N.
If we take a longer distance, we can assume that the air inside the cage gives elasticity to the cone and has the same effect as if the support material had become hard, so it is 1.4X107 a' 5e-(dyneA- rrL)
It is given by ++・(4). and the bass resonance frequency f.

The following is the volume of a closed cavity with good radiation characteristics.

V = 3.5 ~, 7 X105 a'/f
(i'm. [cm]
- It is said that approximately i51 is required.

In order to lower the bass resonance frequency fo, as can be seen from equation (1), the image mass m is equal. Kaj Nobrians 1/S.

Compliance 1/S has no choice but to increase.

Since it is proportional to the volume of the container, it cannot be made too large for household use. Therefore, f.

To lower the image mass m. There is no choice but to make it bigger.

, but the equal image mass m. If the value is increased, the vibration and mass of the system will increase, reducing efficiency, and it will become extremely difficult to hold the voice coil between the magnetic poles and ensure sufficient amplitude.

This invention was made in view of the above points, and its focus is on equal image mass m in order to improve low frequency characteristics. To provide a speaker capable of driving a large diaphragm with sufficient amplitude.

The present invention will be described below with reference to embodiments shown in the drawings.

This movable Macnet type speaker has 1 permanent magnet on the inside.
A cabinet 4 has a flat diaphragm 2 attached thereto, a voice coil 3 protruding from a position facing the attached permanent magnet 1, and an opening on the front surface of the cabinet 4 between the end face of the flat diaphragm 2 and the front side of the cabinet 4. It consists of movably connected edges 5.

As the planar diaphragm 2, a diaphragm with excellent strength and rigidity, such as a diaphragm with a honeycomb sandwich structure, is suitable, but in this invention, the weight of the diaphragm is increased by the weight of the permanent magnet. However, the present invention is not necessarily limited to a diaphragm having a lightweight structure.

For example, the permanent magnet 1 is made of haliuno ferrite (Hao・
6■-C203) or strontium ferrite 03) is molded into a disk shape, magnetized from the center toward the outer periphery, and attached to the back side of the planar diaphragm 2 at the part corresponding to the vibration node. . What is a vibrational node?

This is the node of divided vibration determined by the shape and rigidity of the diaphragm. It is known that in such split vibration, if the driving point is symmetrical with respect to the center of the diaphragm, the nodes passing through the center will automatically disappear.

Also, if a node does not pass through the center of the diaphragm, it is not possible to eliminate the divided vibration normally, but if the node is driven at a position symmetrical to the center of the vibration moat, the divided vibration can be eliminated. Therefore, the frequency and vibration mode of the divided vibration of the plane diaphragm 2 are analyzed, the frequency band in which piston vibration is required is set, and the vibration node t of the vibration mode that appears in that band is attached and driven by the permanent magnet 1. can prevent split vibrations in the frequency band. A voice coil 3 protrudingly provided on the inner surface of the cabinet 4 at a position facing the permanent magnet l attached to the back surface of the flat diaphragm 2 is mounted on a winding frame 6 made of, for example, aluminum and is attached to a conventional moving coil type speaker. It is made by winding insulated wire that is several times thicker than that used for.

The edge 5 movably connecting the end face of the flat diaphragm 2 and the front opening of the cabinet 4 is preferably capable of linearly following the amplitude of the flat diaphragm 2.

In this embodiment, since the amplitude of the flat diaphragm 2 can be made much larger than that of the conventional one, the distance d between the end face of the flat diaphragm 2 and the inner surface of the opening on the front surface of the cabinet 4 is approximately d. A pantograph-type edge 5 with a rectangular cross section that can linearly respond to reciprocating motion is illustrated. This pantograph type edge 5 is made of cloth whose surface is coach-inked with a synthetic resin material or the like, and the distance d between the end face of the flat diaphragm 2 and the inner surface of the front opening of the cabinet 4 is 1ψ.
It is formed into a rectangular cross-sectional shape with the length of one side as one side, and the connecting points on each side are movable. This is connected to a part of the front opening of No. 4. With this configuration, when the plane diaphragm 2 reciprocates linearly, the coupling point a on the plane diaphragm 2 side follows this and moves linearly,
During this time, the connection point b' that is not connected to the plane diaphragm 2 or the key V' hitch 4 is connected to the edge 5 with a' as the center.
It reciprocates in an arc whose radius is one side a' b or a'b'. In this case, the amplitude of the plane diaphragm 2 is at most 2d
However, the effective amplitude that can be followed linearly is expected to be at least about the distance d. For this reason, voice coil 3
It is necessary to keep the tip of the permanent magnet 1 and the tip of the permanent magnet 1 at least 2d apart from the unattended position.

As described above, the present invention can produce the following effects. First, by attaching permanent magnets to the vibration nodes of the vibrating surface behind the plane diaphragm to both reinforce the diaphragm and prevent split vibration, it is possible to cause the diaphragm to vibrate over a wide range of pistons. Second, by increasing the weight of the diaphragm and increasing the equivalent mass m6, the low-frequency resonance frequency can be lowered, so that the acoustic characteristics up to ultra-low frequencies can be improved. Third, unlike conventional moving coil speakers, the voice coil does not need to be held in a narrow cap between the yoke and the pole, so thick insulated wire can be wound and fixed around the winding frame, and the voice coil It can withstand continuous electrical input several times more than conventional ones.

Finally, fourthly, by adopting a winding frame with good thermal conductivity to improve the heat dissipation effect, it is also possible to increase the input power.

That is, according to the present invention, it is possible to easily provide a small-sized, large-displacement ultra-low-frequency speaker.

[Brief explanation of drawings]

The figure is a sectional view showing the structure of a movable macnet type speaker according to the present invention. In the figure, 1 is a permanent magnet, 2 is a plane diaphragm, 3 is a whistle coil, 4 is a cabinet, 5 is an edge, and 6 is a winding frame.

Claims (1)

[Claims] A voice coil wound and fixed around a winding frame is protruded from the inner surface of a speaker cabinet equipped with a flat diaphragm on the front, and a permanent magnet is placed at a position facing the voice coil on the inner surface of the thousand-sided diaphragm. A movable macnet type speaker, further comprising: a planar diaphragm reciprocably attached to the front surface of the cabinet with the voice coil tip and the permanent magnet tip facing each other with a gap between them. .