JPS58222700A - Flat loudspeaker - Google Patents

Abstract

PURPOSE:To extend the operating range up to the vicinity of an fh, by providing a diaphragm section where the 1st resonance frequency of the section is constituted so as to be coincident with the fh as for the speaker, at the center of a flat diaphragm main body. CONSTITUTION:A hone-comb core 1 in axis of symmetry constituted of aluminum foil, 20mum thick is cut off for the center in the shape of a circle. Surface members 2-3 made of aluminum foil of 40mum thick are pasted together with the honey-comb coil 1 with an epoxy resine adhesives to form a ring-shaped diaphragm. A voice coil 5 wound on the outer circumference of a voice coil bobbin 4 resonating with the 1st resonance frequency of the diaphragm is coupled with a magnetic circuit of the speaker. The diaphragm section 6 forming a carbon fiber reinforced polyethylene sheet into a dome is bonded to an inner circumference of the ring-shaped diaphragm. The resonance frequency of the diaphragm section of the dome shape is 3kHz.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention uses a sand char structure in which surface materials are bonded to both sides of a core material as a planar diaphragm, and is arranged inside a cylinder at the first resonance frequency of this planar diaphragm. This invention relates to a flat speaker configured to be driven by a voice coil.

Conventional configuration and its problems It is ideal for the diaphragm of a speaker to vibrate as a piston over the frequency band used, but if the diaphragm deforms during vibration or split vibration occurs, the sound pressure frequency characteristic and distortion rate will be 1 phase. Characteristics, etc. deteriorate, which impedes high-fidelity reproduction. In order to solve these problems, a planar diaphragm using a honeycomb sandwich structure or the like has been adopted in recent years. In addition, in many planar speakers, a voice coil is glued to the inside of the cylinder at the diaphragm's primary resonance frequency, and when driven, the primary resonance frequency is canceled out, and the fh of the speaker is adjusted to the diaphragm's secondary resonance frequency. It can be raised to the vicinity. A so-called node drive method is used.

FIG. 1 shows a cross section of a conventionally used flat diaphragm assembled into a speaker. In this case, the circular nodal circle a
The open end of the coupling cone 18 is glued to the part,
The other end is connected to a magnetic circuit via a voice coil. In FIG. 1, 11 is a yoke having a center ball 12, 13 is an annular magnet disposed on the yoke 11, and 14 is an upper plate disposed on the yoke 13. Center pole 1 above
The outer peripheral portion of the frame 16 is connected to the frame 16 by the edge member 17.
is supported by The flat diaphragm 16 has an opening 1] of a coupling call 18 connected to the circular nodal circle a, and a voice coil 20 wound around a voice coil pobbin 19 provided at the other end of the magnetic circuit. It is supported by a damper 21 so as to make piston movement within the magnetic gap.

By the way, according to the node drive method described above, the Jh of the speaker
This produces a pronounced sound pressure peak. Even if the piston vibrates to a high frequency range, this resonance peak makes system design difficult, and in the end, the level has to be lowered from a fairly low frequency to suppress the effect of the peak, narrowing the usable band.

Conventionally, the persimmon method has been studied in order to suppress this sound pressure peak.

One of them is to try to absorb unnecessary vibrations by using materials with high mechanical loss as constituent materials, but the effect is small, and conversely, it is difficult to reduce the sound pressure peak without reducing fh. However, this was the biggest problem for this type of flat speaker.Objective of the InventionThe present invention solves these conventional drawbacks.
There is no decrease in fh, the sound pressure peak is significantly reduced, and fh
The object of the present invention is to provide a planar speaker that can expand the usable band to the vicinity of .

Structure of the Invention The flat speaker of the present invention has a material or structure similar to that of the flat diaphragm body in the center of the flat diaphragm body. With this configuration, the center part also resonates at fh of the speaker, but since the center part vibrates in the opposite phase to the outer circumferential part, they cancel each other out, and the sound pressure peak is apparently suppressed, making it more flat. This provides high-frequency characteristics.

Description of examples Examples of the flat speaker of the present invention will be described below.

. FIG. 2 shows an embodiment of the present invention. In FIG. 2, 1 is an axisymmetric honeycomb core made of aluminum foil with a thickness of 20 μm, and 02 and 3 have a circular cutout in the center. Surface material made of 40μm thick aluminum foil,
It is bonded to the honeycomb core 1 using an epoxy adhesive to form a ring-shaped diaphragm. 4, a raw voice coil 6 is coupled to a speaker magnetic circuit (not shown) at the first resonance frequency of this diaphragm. Reference numeral 6 denotes a diaphragm portion made of a carbon fiber-reinforced polyethylene sheet formed into a dome shape, and is adhered to the inner peripheral portion of the ring-shaped diaphragm. This hard-reinforced polyethylene sheet is made by mixing 80 parts (weight, etc.) of polyethylene with a fiber length of 6 mm and a fiber diameter of 1 μm and 16 parts of carbon fiber.
It is made by thermoforming a paper made into paper, and has the characteristics of light weight and high rigidity.

Measurement of a 25 m diameter speaker using the diaphragm of this example (
i m/1 w ) L shown in Figure 3. In FIG. 3, A shows the characteristics when using the diaphragm according to this embodiment, and B shows the characteristics when using the diaphragm having a homogeneous honeycomb core up to the center. At this time, fh of curve B is 3.0 KHz, which coincides with the resonant frequency of the central dome. Therefore, the sound pressure peaks are suppressed by canceling each other out by resonance.

In addition, because the central part is lighter, the weight of the vibration system is reduced, and as a result, the reproduced sound pressure is improved by approximately o, ydB.
This also contributes to increased efficiency.

Fig. 4 shows another embodiment of the present invention. In Fig. 4, 1 is a stone side made of a ring-shaped honeycomb core, and surface materials 2 and 3 are bonded together with an epoxy adhesive to form a diaphragm. . At this time, the inner peripheral part of the surface material 2 is integrated with the outer peripheral part, and the back surface is filled with a urethane resin foam 7 to form the diaphragm part 6. With the above configuration, the surface is completely flat and has the same effect as the above embodiment.

FIG. 6 shows still another embodiment of the present invention. In FIG. 5, instead of using the diaphragm section made of carbon fiber-reinforced polyethylene sheet in the center, This material is roughened and formed into a dome shape and is bonded to a core material 1 made of a ring-shaped honeycomb core. If the shape of the dome as the diaphragm portion 6 is made such that its resonant frequency is the same as fh of the speaker, the same effect as in the above embodiment can be obtained.

FIG. 6 shows still another embodiment of the present invention. In FIG. 6, reference numeral 8 denotes a core material made of a honeycomb core in which the thickness of the outer circumferential part and the thickness of the inner circumferential part are changed, and the surface material 2.3 At the same time, the surface material 9 is bonded. In this case as well, the resonant frequency of the thin portion and lh of the speaker are made to match, and the same effect as in the above embodiment can be obtained.

Although aluminum honeycomb was used as the core materials 1 and 8 in the above four embodiments, the same effect can be obtained even if foamed resin is used.

In addition, the same effect can be obtained with a diaphragm in which the core material is a skeleton member obtained by bending a rectangular plate into a zigzag shape, and bonding material is bonded to both sides. According to the present invention, the first
The planar diaphragm is configured to be driven by a voice coil disposed inside the cylinder at a secondary resonance frequency, and the center portion of the planar diaphragm is configured such that the primary resonance frequency matches the high-frequency resonance frequency of the speaker. Since the diaphragm section is constructed with a diaphragm section having a rigidity such that suppressed, and a more even frequency characteristic can be obtained. This has the advantage that the usable band can be expanded to the vicinity of fh.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional flat speaker, Figure 2 is a central sectional view of a diaphragm portion showing an embodiment of the flat speaker of the present invention, and Figure 3 shows the sound pressure frequency characteristics of the same speaker and the conventional speaker. Comparative views, FIGS. 4, 6, and 6 are central sectional views of diaphragm portions showing other embodiments of the flat speaker of the present invention. 1.8... Heart material, 2, 3.9... Mark/Surface material,
4...Bobbin, 5...Voice coil,
6. River... Vibration plate part. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 Figure 2 Figure 5

Claims (1)

[Claims] The planar diaphragm is configured to be driven by a voice coil disposed inside the cylinder at the first resonant frequency of the planar diaphragm, and the central part of the planar diaphragm is set at the first resonant frequency of the speaker. A flat speaker consisting of a diaphragm section with a rigidity that matches the high resonance frequency.