JPH1051878A - Speaker system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a 2-way coaxial speaker system whose frequency characteristic is flat from medium and low sound frequency regions to a high sound frequency region. SOLUTION: Primary coils 24, 25 receiving a current in response to an input voice signal are provided in the vicinity of an air gap GP of a magnetic circuit. A secondary coil 26 consisting of a short coil in which a current in response to the current supplied to the primary coils is induced and to which a woofer diaphragm 29 is mounted is provided in the air gap GP. A secondary coil 27 consisting of a short coil in which a current in response to the current supplied to the primary coils is induced and to which a tweeter diaphragm 28 is mounted is provided in the air gap GP. The primary coils 24, 25 are driven by a digital signal to induce a secondary current respectively in the secondary coils 26, 27, from which not only a high frequency sound but also a low frequency sound is radiated through the configuration of electromagnetic coupling type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker device for converting an electric signal into a sound output.

[0002]

2. Description of the Related Art An all-band loudspeaker device combining a dynamic type and an electromagnetic coupling type is known. This loudspeaker device uses a low-tone voice coil as a primary coil, a low-frequency voice coil as a primary coil, and a low-frequency voice coil as a primary coil.
This is a so-called two-way coaxial structure in which high frequencies are radiated as electromagnetic coupling by the secondary coil.

In the electromagnetic coupling type, a secondary current is induced in a secondary coil by a signal current flowing through a primary coil, and an interaction with a magnetic flux generated in a gap in a magnetic circuit causes the secondary coil to respond to the secondary current. A driving force is generated, and the diaphragm to which the secondary coil is fixed vibrates.

In this electromagnetically coupled speaker, since the primary coil through which the signal current flows is fixed to a plate made of a magnetic material such as iron, there is an advantage that heat dissipation is excellent and a large input can be endured. However, if the length of the air gap in the magnetic circuit is increased, the sensitivity of the loudspeaker is reduced, so that the number of turns of the primary coil and the secondary coil cannot be increased.

Therefore, the inductance of the primary coil and the secondary coil cannot be increased, and the electromagnetic coupling force that induces the secondary current in the secondary coil by the signal current flowing through the primary coil is several kHz to 1 kHz. It becomes smaller in the following low frequency range, and it is impossible to reproduce up to 20 Hz necessary for reproducing sound. Therefore, the electromagnetically coupled speaker is mainly used as a speaker for reproducing high-pitched sounds.

FIG. 15 shows the structure of a conventional two-way coaxial speaker device of this kind.

The magnetic circuit of this speaker device comprises a donut-shaped magnet 1 and a first magnet made of a magnetic material such as iron.
And the second magnetic yokes 2 and 3 and the air gap GP. The first magnetic yoke 2 includes a cylindrical center pole portion 2a and a disk-shaped flange portion 2b orthogonal to the center pole portion 2a. Second
The magnetic yoke 3 is referred to as a plate, and has a donut shape having an inner diameter larger than an outer diameter of the center pole portion 2a by an air gap GP described later.

Then, the center pole portion 2a is inserted into the inner hollow portion of the magnet 1 and the inner hollow portion of the second magnetic yoke (hereinafter, referred to as a plate) 3.
The magnet 1 is sandwiched and attached between the front surface of the flange portion 2 b of the first magnetic yoke 2 and the plate 3. The contact portion between the front surface of the flange portion 2b and the surface of the plate 3 and the magnet 1 is bonded.

In this case, a magnet guide 2c composed of a stepped portion concentric with the center pole portion 2a is formed on the front surface of the flange portion 2b of the first magnetic yoke 2, and the magnet 1 is formed by the magnet guide 2c. The position of the edge portion of the inner circumferential circle is regulated, so that the inner circumferential surface position of the magnet 1 and the outer circumferential surface position of the center pole portion 2a are
It is made to be a concentric position.

Further, a predetermined jig is used so that a gap GP having a predetermined length is formed between the outer peripheral surface of the center pole portion 2a and the inner peripheral surface of the plate 3. The position is regulated, and the magnet 1, the magnetic yoke 2,
The plate 3 is joined.

Thus, a closed-loop magnetic circuit of the magnet 1 → the plate 3 → the gap GP → the center pole 2a → the flange 2b → the magnet 1 is formed. The speaker frame 7 is attached to the front surface of the plate 3.

As shown in FIG. 16, the low-frequency voice coil, which is a low-frequency coil unit, is configured by winding a coil 5 around a voice coil bobbin 4 made of a non-conductive material. Then, the bass voice coil is arranged such that the coil 5 is located in the gap GP between the plate 3 and the center pole portion 2a as shown in FIG. The voice coil bobbin 4 is attached to a speaker frame 7 via a buffer member (hereinafter referred to as a damper) 6.

A cone paper 8 as a diaphragm is attached to the voice coil bobbin 4 by bonding. The cone paper 8 is attached and fixed to the speaker frame 7 by a gasket 9 at the edge 8e.

The winding start end and the winding end of the coil 5 of the low-pitched voice coil are located at the voice coil bobbin 4, as shown in FIG.
b is connected by soldering. The tinsel wires 10a and 10b are connected to an input terminal 11 mounted on the speaker frame 7 by soldering.

The treble coil unit constitutes a secondary coil having a low-frequency voice coil as a primary coil. The secondary coil is a short coil, and generally includes a bobbin wound with a coil. However, in this example, FIG.
As shown in FIG. 2, a non-magnetic material having conductivity, for example, aluminum is formed in a cylindrical shape to form a one-turn short coil 12. That is, the coil bobbin is omitted, and the coil unit for high sound is constituted only by the short coil 12. A dome-shaped diaphragm 13 is integrally connected to the short coil 12, as shown in FIG.

Then, this short coil 12 as a coil unit for high sound is inserted into a gap between the voice coil bobbin 4 and the outer peripheral surface of the center pole portion 2a. Then, the cap 14 is attached so as to cover the bass voice coil portion.

In the speaker device having such a configuration,
When an analog audio signal is supplied from the input terminal 11 through the power amplifier, the coil 5 of the low-pitched coil unit
Then, a current corresponding to the audio signal flows, and the voice coil bobbin 4 is moved to its center axis by the action of magnetic flux between the center pole portion 2a and the plate 3 (Fleming's left-hand rule) in the air gap of the magnetic circuit. Vibrates according to the electric current in the direction along. In other words, the bass voice coil vibrates according to the driving principle of the dynamic speaker, whereby the cone paper 8 vibrates and radiates middle and low sounds.

The coil 5 of the bass coil unit
, A secondary current corresponding to the audio signal current is induced in the short coil 12, and the induced current causes the short coil 12,
The diaphragm 13 vibrates and emits a high sound. That is, when the coil 5 of the bass voice coil is used as a primary coil and a current flows through the short coil 12 as a secondary coil, a high-pitched sound is emitted as an electromagnetic coupling type.

[0019]

The loudspeaker device having the structure shown in FIG. 15 can realize a two-way coaxial loudspeaker which improves characteristics in a high frequency range as a loudspeaker by combining a dynamic type and an electromagnetic coupling type. You can,
There is a problem that an output sound pressure level of a high sound cannot be sufficiently obtained as compared with a middle and low sound range, and a frequency characteristic cannot be flattened to a high sound range.

In view of the above, it is an object of the present invention to realize a two-way coaxial speaker device having a flat frequency characteristic over a range from a middle to low range to a high range.

[0021]

To solve the above-mentioned problems, a speaker device according to the present invention is provided near a gap in a magnetic circuit, and is provided with a primary coil to which a current corresponding to an input audio signal is supplied; A first coil unit that is arranged in the gap and that forms a first secondary coil including a short coil that induces a current corresponding to a current flowing through the primary coil; and a first coil unit that is arranged in the gap. A second coil unit in which a second secondary coil formed of a short coil in which a current corresponding to a current flowing in the primary coil is formed; and a low-frequency vibration attached to the first coil unit. A high-frequency diaphragm attached to the second coil unit.

Then, by driving the primary coil with a digital signal, a current of a total sum of currents according to the weight of each bit of the digital signal is induced in the first and second secondary coils. Due to the interaction between the induced current and the magnetic flux in the air gap of the magnetic circuit, the low-frequency diaphragm and the high-frequency diaphragm vibrate according to Fleming's left-hand rule, respectively, and have characteristics over the entire frequency band. A flat speaker device is realized.

The sampling frequency for digitizing the audio signal is a high frequency such as 44.1 kHz or 48 kHz, which is twice or more higher than 20 kHz which is the upper limit of the audible frequency. Therefore, even a low-frequency component such as several kHz to 1 kHz or less of the audio signal before being digitized is converted to a digital audio signal of 20 kHz.
The frequency becomes higher than z.

In the electromagnetically coupled speaker, even if the length of the air gap of the magnetic circuit is reduced and the number of turns of the primary coil and the secondary coil is reduced so as not to lower the speaker sensitivity, the primary coil If the frequency of the signal current flowing through
At a high frequency exceeding 0 kHz, the electromagnetic coupling force does not decrease, and sound can be reproduced.

In the loudspeaker device of the present invention configured as described above, since the primary coil is driven by the digital audio signal, the low-frequency component of the audio signal before digitization is also one. The signal current flowing through the next coil has a high frequency exceeding 20 kHz. Therefore, reproduction up to low frequencies can be performed by the electromagnetically coupled speaker.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a speaker device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a speaker device according to an embodiment of the present invention. The loudspeaker device according to this embodiment is mechanically configured not only for high sounds but also for middle and low sounds by an electromagnetic coupling type.

In this case, when an analog audio signal is supplied to the drive coil (primary coil) in the electromagnetically coupled speaker structure, the primary coil and the secondary coil are not inductively coupled in the middle and low frequencies of the audio. Although the bass is not radiated, in this embodiment, the drive coil is supplied with a digital audio signal having a bit rate equal to or higher than the audible frequency, preferably equal to or higher than twice the highest audible frequency. An electromagnetically coupled speaker device capable of emitting low-pitched sound is realized.

As shown in FIG. 1, the speaker device of this embodiment has a first yoke 21 having a columnar center pole portion 21a and a disk-shaped flange portion 21b, and a donut forming a second yoke. Plate 22, a donut-shaped magnet 23 disposed between the flange portion 21 b of the first yoke 21 and the plate 22,
A magnetic circuit is formed by the gap GP between the magnetic pole and the center pole portion 21a.

Then, a drive coil as a primary coil is disposed on one or both of the outer peripheral surface of the center pole portion 21a and the inner peripheral surface of the plate 22 opposed to each other with the gap GP therebetween. In this embodiment, primary coils 24 and 25 are arranged on both the outer peripheral surface of the center pole portion 21a and the inner peripheral surface of the plate 22.

In the case of this example, the primary coils 24 and 25 are composed of a number of coil groups corresponding to the number of bits of the input digital signal. For example, in the case of a 2 'complement code in which the input digital signal is 16 bits / 1 sample and the most significant bit MSB is a sign bit (positive / negative bit), basically, the number of bits for the primary coil is Correspondingly, 15 coils are provided, of which,
For example, a group of seven coils corresponding to 7 bits excluding the MSB of the upper 8 bits is a primary coil 24, and a group of 8 coils corresponding to the lower 8 bits is a primary coil. Attached as 25.

Each of the 15 coils has a number of turns corresponding to the weight of each corresponding bit. If the digital audio signal is linearly quantized, 1
The number of turns of the five coils changes in a geometric series corresponding to each bit from the least significant bit LSB to the most significant bit MSB. For example, if the coil corresponding to LSB is 4 turns, the coil corresponding to 2SB is 8 turns, the coil corresponding to 3SB is 16 turns, and 4 turns.
The coil corresponding to the SB has an increased number of turns, such as 32 turns.

Examples of the primary coils 24 and 25 are shown in FIGS.

That is, as shown in FIG. 2, the primary coil 24 provided on the center pole portion 21a is composed of seven coils LA to LG having different numbers of turns, respectively. Leading and trailing lead pairs 37a-37g are derived. These lead wire pairs 37a to 37g extend through the through holes 34 provided in the flange portion 21b of the first magnetic yoke 21 to the rear side of the flange portion 21b. Each of these lead wire pairs 37a to 37g is
b, seven input terminals 38a to 38g provided on the back side
, Respectively.

In this case, in order to radiate heat from the lead wire pairs 37a to 37g, the lead wire pairs 37a to 37g are adhered to the outer surface of the center pole portion 21a and are directed in the direction of the flange portion 21b of the first magnetic yoke 21. Is derived.

As shown in FIG. 3, the primary coil 25 attached to the inner peripheral surface of the plate 22 is composed of eight coils 25i to 24p having different numbers of turns.
From each of the coils LI to LP, a pair of lead wires 37i to 37p at the start and end of the winding is derived. These lead wire pairs 37i to 37p pass between the plate 22 and the magnet 23 and are connected to input terminals 38i to 38p attached to the outer peripheral surface of the plate 22.

Also in this case, the lead wire pairs 37i to 37p are led out to the outer peripheral surface side of the plate 22 by contacting the plate 22 and the magnet 23.
The heat radiation from 7i to 37p is performed well.

In this embodiment, a low-frequency secondary coil 26 and a high-frequency secondary coil 27 electromagnetically coupled to the primary coils 24 and 25 are inserted into the gap GP. In the case of this example, the coil unit constituting the secondary coil 26 for low-frequency sound is composed of only the short coil 26C. Similarly, the coil unit that constitutes the secondary coil 27 for treble comprises only the short coil 27C. In this case, each of the short coils 26C and 27C is a non-magnetic material, and is formed of a conductive material, for example, aluminum, in a cylindrical shape to form a one-turn short coil.

That is, the short coil 26C for bass sound
Is constituted by an aluminum plate ring as shown in FIG. The short coil 27C for treble is also formed of an aluminum ring as shown in FIG. In this example, the coil bobbin is omitted, and the low-frequency secondary coil unit and the high-frequency secondary coil unit are constituted only by the short coils 26C and 27C.

Then, the short coil 26C for bass sound
Is attached to the speaker frame 31 via the damper 30. In addition, this short coil 26C for bass
, A cone paper 29 as an example of a diaphragm for middle and low frequency is attached. The cone paper 29 is attached to the speaker frame 31 by the gasket 32 via the edge 29e.

As shown in FIG. 5, a diaphragm 28 is attached to the short coil 27C for high sound.
The diaphragm 28 is provided integrally with the short coil 27C by being formed integrally with the short coil 27C or by bonding or joining a member separate from the short coil 27C.

The treble short coil 27C is attached to a support rubber plate 33 adhered to the top of the center pole 21a, and is configured to be movable in the axial direction of the center pole 21a.

A coil bobbin is made of a non-magnetic material such as paper or a non-conductive material, and a coil of one or several turns is wound around the coil bobbin, and both ends of the coil are short-circuited. Next coil 26,
27 may be respectively formed to form secondary coil units, or a ring made of a non-magnetic and conductive material may be fitted into a bobbin to form a secondary coil unit. , Of course.

A method of assembling the speaker device of this example will be described below.

The primary coil 24 shown in FIG. 2 and FIG.
25 is adhered to the outer peripheral surface above the center pole portion 21 a and the inner peripheral surface of the plate 22.

Next, a pair of lead wires 37a to 37
g and 37i to 37p are pulled out to the back side of the yoke 21 and the lower side of the plate 22, and the input terminals 38a to 38p are pulled out.
8g and 38i to 38p are soldered, and the lead wires are fixed to the yokes 21 and 22 with an adhesive. The fixing of the two primary coils 24 and 25 is performed before the assembly of the magnetic circuit.

Next, an adhesive is applied to the front surface of the flange portion 21b of the yoke 21, and the magnet 23 is placed thereon. The inner diameter of the magnet 23 and the outer diameter of the magnet guide 35 formed as a step between the front surface of the flange portion 21 are formed. And the center pole portion 21a and the magnet 23
So that their centers almost coincide with each other.

Next, an adhesive is applied to the upper surface of the magnet 23 and the plate 22 is placed. Then, a jig called a gap guide is inserted so that the inner diameter of the plate 22 and the outer diameter of the center pole portion 21a are concentric.

The speaker frame 31 is attached to the plate 22 in advance by caulking or the like. Alternatively, after the magnetic circuit is completed, the speaker frame 31 may be attached to the plate 22 by means such as screws.

After the adhesive between the plate 22 and the magnet 23 has dried, the gap guide is connected to the center pole portion 21.
Pull out from a. This completes the main body of the speaker.

Next, a short coil 26C constituting the secondary coil 26 for bass and a jig called a coil spacer are prepared, and the coil spacer is inserted into the inner diameter of the short coil 26C for bass. Is adjusted to be at a predetermined position in the gap GP of the magnetic circuit, and the bass short coil 26C is inserted.
The coil spacer is inserted into the center pole part 21a.

In this state, the outer peripheral portion of the damper 30 is adhered to the speaker frame 31, and the inner peripheral portion of the damper 30 is adhered to the outer diameter of the short sound coil 26C. Then, the outer peripheral portion of the cone paper 29 with the edge 29e is bonded to the outer peripheral portion of the speaker frame 31 via the gasket 32. Further, the inner peripheral portion of the cone paper 29 is bonded to the outer diameter portion of the short coil 26C for low sound. After the adhesive is dried, the coil spacer is pulled out from the center pole portion 21a.

Next, a supporting rubber plate 33 is bonded to a predetermined position inside a part in which the high frequency diaphragm 28 and the high frequency short coil 27C are integrated. Then, a coil spacer is provided inside the short coil for high sound 27C and the inside of the short coil for low sound 26C, and an adhesive is applied to the top of the center pole portion 21a. The coil with a coil spacer on the side is adjusted so that the high-frequency short coil 27C is located at a predetermined position in the gap GP, and the low-frequency short coil 26C is adjusted.
Place inside C and dry the adhesive.

After the adhesive is dried, the coil spacer is removed, and the cap 36 is bonded to the top of the cone paper 29 or the tip of the short coil 26C for low sound. Cap 3
Since the high sound is radiated from the diaphragm 28, 6 is made of a material having good air permeability, and is made of, for example, a thin cloth. After the adhesive is dried, the magnet 23 is magnetized, and the speaker device is completed.

The input terminals 38a to 38 of this speaker device
If signal input corresponding to each bit of the digital signal is added to g and 38i to 38p, current is induced in the short coils 26C and 27C as secondary coils according to the current flowing through the primary coils 24 and 25, Due to the interaction with the magnetic flux in the gap GP, Fleming's left-hand rule
The next coils 26 and 27 vibrate up and down. In this case, the changing period of the digital signal is the sampling frequency of 44.1 kHz or 48 kHz, and the inductive coupling force between the low-frequency secondary coil 26 and the primary coils 24 and 25 is:
The bass can be reproduced without lowering. In this case, the low-middle sound and the high sound are both of the electromagnetic coupling type, and the speaker device having a flat frequency characteristic from the low sound to the high sound can be realized.

Next, FIG. 6 shows an example of a sound reproducing system using the speaker device according to the present invention. The example of FIG. 6 is a case where audio is reproduced by a digital audio signal from a digital audio output device.

The digital audio output device 210 is a CD player, a DAT (Digital Audio Tape Recorder), or the like.
Stereo audio signals consisting of left and right channel audio signals digitized into 16 bits at a sampling frequency of z or 48 kHz are output as serial data alternately for each sample of left and right audio data.

The 16-bit digital audio signal of the serial data from the digital audio output device 210 is supplied to the serial / parallel converter 220, which separates the digital audio signals of the left and right channels from each other. Are converted into parallel data, and the 16-bit left and right digital audio signals as the parallel data are supplied to the left and right channel speaker devices 100L and 100R.

Although not shown, the serial / parallel converter 220 obtains a clock at a bit rate, and the clock at the bit rate is supplied to the decoder 70.

In this example, the loudspeaker devices 100L and 100R have a decoder 70 and a loudspeaker drive circuit 4 respectively.
0 and a speaker unit 110. The speaker device described with reference to FIGS. 1 to 5 is used as the speaker unit 110.

In the case of this example, the speaker device 10
In 0L and 100R, the decoder 70 generates a control signal, which will be described later, from the 16-bit left and right digital audio signals converted into parallel data from the serial / parallel converter 220 in the decoder 70. The primary coil 2 of the speaker unit 110 is supplied to the
4, 25 are driven.

When the primary coils 24 and 25 are composed of a plurality of coils, if the 16-bit digital audio signal is a 2 'complement code as shown in FIG. 7, its MSB (most significant bit) As a sign bit, as described above, and as shown in FIGS. 7 and 8, the primary coils 24 and 25 are divided into fifteen coils 1A to 1A.
1G, 1O to 1P. Then, the coil LA is set to L
For example, two turns are made in correspondence with SB (least significant bit). Hereinafter, coils LB, LC, LD, LE, LF, L
G, LI, LJ, LK, LL, LM, LN, LO, LP
To 15SB, 14SB, 13SB, 12SB, 11S
B, 10SB, 9SB, 8SB, 7SB, 6SB, 5S
B, 4SB, 3SB, and 2SB corresponding to 4
The number of turns is twice as many as the number of turns of the coil corresponding to the next lower bit, such as turn, 8 turns, 16 turns, and so on.

When the analog audio signal is non-linearly quantized and converted into a digital audio signal, the number of turns of the plurality of coils constituting the primary coils 24 and 25 is as follows:
As described above, it does not change in geometric series, but changes in accordance with the nonlinear characteristic of the nonlinear quantization.

FIG. 9 shows an example of a portion of the decoder 70 and the speaker drive circuit 40 shown in FIG. 6, and the speaker drive circuit 40 has fifteen coils LA to LG and LI to LP of the primary coils 24 and 25. , There are 15 coil drive circuits 40A to 40G and 40I to 40P.

The respective coil drive circuits 40A
40G, 40I to 40P are each composed of a constant current source 41 and four FETs 51 to 54 as switching elements.
And the corresponding coil are bridge-connected,
When the FETs 51 and 53 are turned on and the FETs 52 and 54 are turned off, the current Ia of the constant current source 41 corresponds to 1
When the FETs 51 and 53 are turned off and the FETs 52 and 54 are turned on and the FETs 52 and 54 are turned on, the current Ia from the constant current source 41 flows in the corresponding primary coil in the minus direction.

Coil drive circuits 40A-40G, 40I-
The currents of the 40P constant current sources 41 are all set to the same current value as indicated by the current Ia. When all the FETs 51 to 54 are turned on or off in the same coil drive circuit, no current flows through the corresponding coil.

The decoder 70 has fifteen control signals corresponding to the fifteen coils LA to LG and LI to LP of the primary coils 24 and 25, ie, corresponding to 15 bits excluding the MSB of the digital audio signal. Generation circuits 70A to 70G, 7
0I to 70P, and the respective control signal generation circuits 70
From A to 70G and 70I to 70P, the MSB of the digital audio signal converted into parallel data from the serial / parallel converter 220 and the respective control signal generation circuits 70A
To 70G, 70I to 70P (LS)
B to 2SB), four control signals G1 to G4 as described later are obtained, and the control signals G1 to G4
Is supplied to the gates of the FETs 51 to 54 of the corresponding coil drive circuit of the speaker drive circuit 40.

When the MSB of the input digital audio signal is 0 and the corresponding lower bit is 1, the four control signals G1 to G4 are at the levels at which the FETs 51 and 53 are turned on, and the control signal G2 , G4 are FETs 52, 5
4 is turned off, and the corresponding primary coil
The current Ia flows in the plus direction. On the other hand, when the MSB of the digital audio signal is 1 and the corresponding lower bit is 0, the control signals G1 and G3 are at a level for turning off the FETs 51 and 53, and the control signals G2 and G4 are at a level for turning on the FETs 52 and 54. The current Ia flows through the corresponding primary coil in the opposite negative direction.

When the MSB of the digital audio signal is 0,
When the corresponding lower bit is also 0 or when the MSB is 1
When the corresponding lower bit is also 1, the control signal G1
G4 becomes a level for turning off the FETs 51 to 54,
No current flows through the primary coil.

It should be noted that the control signals G1 to G4 correspond to the FETs 51 to
By turning on all 54, it is also possible to prevent current from flowing through the primary coil. In that case, a current always flows through the circuit, and a stable operation can be performed.

The driving force F of the vibration system of the electromagnetically coupled speaker is
The product of the secondary current i induced in the secondary coil, the density B of the magnetic flux generated in the air gap of the magnetic circuit, and the length L of the secondary coil in the air gap of the magnetic circuit is represented by F = BLi. , The magnetic flux density B and the length L are constant, so that the driving force F of the vibration system is proportional to the secondary current i induced in the secondary coil. The secondary current i induced in the secondary coil is proportional to the product of the signal current flowing through the primary coil and the number of turns of the primary coil.

In the example described above, the primary coil 2
The number of turns of each of the coils LA to LG and LI to LP of Nos. 4 and 25 is set to be the number of turns in proportion to the weight of each bit excluding the MSB of the input digital audio signal. When Ia flows, the short coils 26C, 27C constituting the secondary coils 26, 27
Has a direction corresponding to the value of the MSB of the digital audio signal,
A secondary current having a current value proportional to the weight of the bit corresponding to the primary coil is induced.

Therefore, the cone paper 29 as the diaphragm to which the short coil 26 as the secondary coil is fixed and the diaphragm 28 to which the short coil 27 as the secondary coil is fixed are provided with the MSB value of the input digital audio signal. Vibrates in the direction according to the amount proportional to the weight of the bit corresponding to the primary coil.
The sound is reproduced faithfully according to the input digital sound signal.

In this case, the input digital audio signal is 4
It is digitized at a sampling frequency of 4.1 kHz or 48 kHz, and the coils LA to LG and LI to LP of the primary coils 24 and 25 are driven by digital signals of the same sampling frequency, so that they are digitized. The low-frequency component of the previous audio signal also has a high frequency exceeding 20 kHz as a signal current flowing through each of the coils LA to LG and LI to LP of the primary coils 24 and 25. Therefore,
The speaker unit 110, which is an electromagnetically coupled speaker, enables reproduction to the low frequency range, and the first and second secondary coils 26, 27 enable the speaker device of this example having a two-way coaxial speaker structure to produce low to high frequencies. Can realize a speaker device having a flat frequency characteristic.

As in the case of a general speaker, the vibration system of the speaker unit 110 does not easily respond to high frequencies.
High frequency components exceeding kHz are hardly reproduced. Accordingly, each of the coils LA to LG and LI to LP of the primary coils 24 and 25 is set to 44.1 kHz or 48 k.
Even when driven by a digital signal having a sampling frequency of Hz, the sampling frequency component is hardly reproduced. Even if the sound is reproduced with a very small sound pressure, the sound exceeding 20 kHz can hardly be heard by the human ear, so that there is no trouble even when listening to music.

Further, it is easy to form a mechanical filter having a stop band of 20 kHz or more intentionally and incorporate it into the speaker unit 110.

Further, it is possible to realize a speaker device that reproduces sound directly by a digital sound signal without using a D / A converter and a power amplifier, that has a small distortion and a large maximum output.

The coil driving circuits 40A to 40G, 4
The switching elements of 0I to 40P are not limited to FETs, and other elements that operate at high speed can be used.

In the above example, the number of turns of each of the coils LA to LG and LI to LP constituting the primary coils 24 and 25 is
In this case, the difference in the weight of each bit of the input digital audio signal is reproduced by setting the number of turns in proportion to the weight of each bit excluding the MSB of the input digital audio signal. Each of the coils LA to LG, LI to LP Are the same, and the corresponding coil drive circuits 40A to 40A
By changing the current values of the constant current sources G, 40I to 40P, the difference in the weight of each bit of the input digital audio signal can be reproduced.

FIG. 10 shows an example of this case, in which fifteen coils LA to LG, L constituting the primary coils 24 and 25 are shown.
I to LP have the same number of turns, for example, 50 turns, and coil driving circuits 40A to 40G and 40I to 40P corresponding to coils LA to LG and LI to LP.
Currents Ia of the constant current sources 4LA to 41G and 41I to 41P
To Ig, Ii to Ip are changed as described later. The rest is the same as the example of FIG.

As described above, the speaker unit 110
Is proportional to the secondary current i induced in the secondary coil, and the secondary current i is the difference between the signal current flowing through the primary coil and the number of turns (impedance) of the primary coil. It is proportional to the product.

Therefore, in this example, although omitted in FIG. 10, the current of the constant current source of the coil drive circuit corresponding to the coil LB corresponding to 15SB of the digital audio signal as shown in FIGS. Ib is set to twice the current Ia of the constant current source 41A of the coil drive circuit 40A corresponding to the coil LA corresponding to the LSB of the digital audio signal. That is, Ib = 2 · Ia.

Hereinafter, 14SB, 13 of the digital audio signal will be described.
Coil LC, LD, L corresponding to SB, 12SB, ...
The current I of the constant current source of the coil drive circuit corresponding to E,.
, c, Id, Ie,... are currents Ib, Ic, Id,.
Doubled.

Therefore, as in the example of FIG. 9, in speaker unit 110, diaphragms 29 and 28 have a bit corresponding to the primary coil through which a signal current flows in a direction corresponding to the value of the MSB of the digital audio signal. Vibrates by an amount proportional to the weight, and the sound is reproduced faithfully to the input digital sound signal.

Further, when the difference in the weight of each bit of the digital audio signal is reproduced by changing the current value of the constant current source in this manner, one drive coil can be used as the primary coil. . The primary coil in this case is attached to either the center pole portion 21a or the plate 22.

FIG. 11 shows an example in that case. However,
In this example, the input digital audio signal, that is, 1 as the parallel data from the serial / parallel converter 220
This is a case where a 6-bit digital audio signal is a natural binary code.

In this example, the primary coil 111 is composed of one coil, and currents Ia, Ib,.
, 61P are connected via switch circuits 62A, 62B,..., 62P, respectively, and the switch circuits 62A, 62B,. It is switched by the data of the corresponding bit of the signal.

That is, when a certain bit of the input digital audio signal is 1, the corresponding switch circuit is turned on, and the current of the corresponding constant current source flows through the primary coil 111. The current Ib of the constant current source 61B is twice the current Ia of the constant current source 61A. Hereinafter, the current of the constant current source corresponding to each bit of the digital audio signal corresponds to the next lower bit. It is twice the current of the constant current source.

Therefore, in this example, in the speaker unit 110, the diaphragms 28 and 29 vibrate in one direction by an amount proportional to the weight of each bit of the input digital audio signal, and the audio is faithfully reproduced by the input digital audio signal. Is played.

Note that the number of primary coils 111 is not one,
It is also possible to provide two or more coils having the same number of turns, divide the current corresponding to each bit of the 16 bits into a corresponding number of groups, and flow the current of each group to one coil. . For example, a primary coil is constituted by one coil provided on the center pole portion 21a and one coil provided on the plate 22, and the digital signal is divided into upper 8 bits and lower 8 bits. ,
It is possible to adopt a configuration in which a group of currents corresponding to each of the two currents flows through the two coils.

Note that even when the input digital audio signal is a 2 'complement code, the coil drive circuits 40A to 40P as shown in FIG. 10 can be switched by the data of the corresponding bit of the digital audio signal. By doing so, the primary coil 111 can be reduced to one.

Further, the difference in the weight of each bit of the digital audio signal can be reproduced by a combination of the difference in the number of turns of the plurality of primary coils and the difference in the current value of the plurality of constant current sources.

FIG. 12 shows an example in that case. However,
In this example, the input digital audio signal, that is, 1 as the parallel data from the serial / parallel converter 220
This is a case where a 6-bit digital audio signal is a natural binary code.

In this example, the primary coil is composed of four coils 111S, 111T, 111 having a turn ratio as described later.
U, 111V, and each coil 111S,
Driving blocks S, T, U, and V are provided for 111T, 111U, and 111V, and the driving blocks S, T, U, and V include currents Ia, Ib, and Ib, respectively.
The constant current sources Ic and Id are respectively connected to the corresponding coils 111S, 111T, 111U or 111V via switch circuits.

That is, in the drive block S, the constant current sources 61A, 61B, 61C, 61D are connected to the corresponding coils 111S via the switch circuits 62A, 62B, 62C, 62D, respectively. The current sources 61E, 61F, 61G, and 61H are respectively connected via switch circuits 62E, 62F, 62G, and 62H.
In the drive block U, the constant current sources 61I, 61J, 61K, and 61L are connected to the corresponding coil 111U via switch circuits 62I, 62J, 62K, and 62L, respectively. Then, the constant current sources 61M, 61N, 61O, 61P
Are the switch circuits 62M, 62N, 62O, 6
The switch circuits 62A, 62B,... 62N, 62 are connected to the corresponding coil 111V via the 2P.
O and 62P are switched by the data of the corresponding bit of the input digital audio signal.

The coils 111S, 111T, 111U, 1
Turns ratio of 11V is from 1: 16: 16 ^2: is 16 ^3. The constant current source 61A, 61B, 61C, the current Ia of 61D, Ib, Ic, Id ratio is 1: 2: ² 2: is 2 ^3. That, Ib = 2 · Ia, Ic = 2 2 · Ia, are Id = 2 ³ · Ia.

As described above, the speaker unit 110
Is proportional to the secondary current i induced in the secondary coil, and the secondary current i is the square of the signal current flowing through the primary coil and the number of turns of the primary coil. It is proportional to the product.

Therefore, in this example, when a certain bit of the digital audio signal becomes 1, the corresponding one of the switch circuits 62A, 62B... 62P is turned on, and the primary coils 111S, 111T, 111U or 1
When the current Ia, Ib, Ic or Id flows through 11 V, the ratio of the secondary current induced in the secondary coil matches the ratio of the weight of each bit of the digital audio signal.

Therefore, as in the example of FIG. 11, in the speaker unit 110, the diaphragms 28 and 29 are shifted in one direction by an amount proportional to the weight of each bit of the digital audio signal, and are converted into the input digital audio signal. Sound is reproduced faithfully.

In this example, the minimum number of turns 1
The primary coil 111S and the primary coil 24 having the maximum number of turns,
The ratio of the number of turns between 25 V and 1:16 ³ = 1: 2 ¹²
And the ratio of the current value between the minimum current value Ia and the maximum current value Id is:
It can be significantly reduced to 1: 2 ³ .

Although not shown, the primary coil is composed of four coils having a turn ratio of 1: 2: 4: 8, and each of the coils is connected via a switch circuit. , The ratio of the current values is 1:16:16 ² : 16
³ , four constant current sources are connected, and the combination of the four constant current sources having the minimum current value and each coil is made to correspond to the LSB, 2SB, 3SB, and 4SB of the input digital audio signal, respectively. The combinations of the four constant current sources having the second smallest values and the coils correspond to the input digital audio signals of 5SB, 6SB, 7SB, and 8SB, respectively, and the four constant current sources having the second largest current values And the combination of each coil with 9SB, 10
The combinations of the four constant current sources having the maximum current values and the respective coils corresponding to SB, 11SB, and 12SB are used as the digital audio signals of 13SB, 14SB, 15SB, and M, respectively.
In this case, the ratio of the number of turns between the primary coil having the minimum number of turns and the primary coil having the maximum number of turns may be significantly reduced, such as 1: 8. it is possible to, the minimum ratio of the current value between the current value and the maximum current value of 1: 16 can be significantly reduced that so called ^3.

In this way, it is possible to reproduce low to high tones with flat frequency characteristics, and to reproduce audio directly from a digital audio signal without using a D / A converter or power amplifier. Thus, a speaker device having a large maximum output can be realized.

FIG. 13 shows another example of the speaker device of the present invention. In this example, an analog audio signal Ao from an analog audio output device 510 such as a cassette player or an FM tuner is supplied to a chopper circuit 520, and the analog audio signal Ao shown in FIG.
As shown by c, the chopping is performed at a frequency higher than the audio frequency, that is, at a frequency fc exceeding 20 kHz which is the upper limit of the audio frequency.

Here, the chopping frequency fc is
It is desirable that the frequency be about twice as high as 20 kHz, for example, 40 kHz. In addition, the time width of the chopping period is sufficiently shorter than the chopping cycle Tc.

Then, the chopped analog audio signal Ac from the chopper circuit 520 is amplified by the power amplifier 530, and
0 is supplied to the primary coil 111. In this case, the speaker unit 110 has one primary coil 111. As a result of the supply of the audio signal current to the primary coil 111, a secondary current is induced in the two secondary coils for bass and treble, and the bass and treble diaphragms vibrate respectively.

As described above, the speaker unit 110, which is an electromagnetically coupled speaker, has an electromagnetic coupling force that induces a secondary current i in the secondary coil by a signal current flowing through the primary coil 111, from several kHz to 1 kHz or less. Becomes smaller in the low frequency range.

However, according to the example shown in FIG. 13, since the analog audio signal is intermittently transmitted at a frequency fc higher than the audible frequency and supplied to the primary coil 111 of the speaker unit 110, the low-frequency component of the analog audio signal is also reduced. The signal current flowing through the primary coil 111 has a high frequency exceeding 20 kHz. Therefore, reproduction up to low frequencies can be performed by the speaker unit 110 which is an electromagnetically coupled speaker.

[0108]

As described above, according to the present invention, the low-frequency diaphragm and the high-frequency diaphragm are each realized by an electromagnetic coupling type, and one of the electromagnetically coupled speakers is provided.
By driving the next coil with a digital audio signal,
Alternatively, an analog audio signal supplied to a primary coil of an electromagnetically coupled speaker is intermittently transmitted at a frequency higher than an audible frequency, thereby realizing a speaker device having a good frequency characteristic from a low frequency range to a high frequency range and having good characteristics. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a structure of a speaker device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a primary coil used in the speaker device of FIG. 1;

FIG. 3 is a diagram illustrating an example of a primary coil used in the speaker device of FIG. 1;

FIG. 4 is a diagram illustrating an example of a secondary coil for bass used in the speaker device of FIG. 1;

FIG. 5 is a diagram illustrating an example of a secondary coil for treble used in the speaker device of FIG. 1;

FIG. 6 is a diagram showing an example of a sound reproduction system using an example of a speaker device according to the present invention.

FIG. 7 is a diagram for explaining an input digital signal.

FIG. 8 is a diagram for explaining the driving principle of the speaker device according to the present invention.

FIG. 9 is a circuit diagram showing a specific example of the partial circuit of FIG. 6;

FIG. 10 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 11 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 12 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 13 is a diagram showing an example of a sound reproduction system using another example of the speaker device according to the present invention.

FIG. 14 is a diagram for explaining the example of FIG. 13;

FIG. 15 is a sectional view of a structure of a conventional speaker device.

FIG. 16 is a diagram showing an example of a bass voice coil of the conventional speaker device of FIG.

17 is a diagram illustrating an example of a high-frequency short coil (secondary coil) of the conventional speaker device of FIG.

[Explanation of symbols]

21: first magnetic yoke, 21a: center pole portion,
21b: Flange part, 22: Second magnetic yoke (plate), 23: Magnet, 24, 25: Drive coil (1
26 ... Short coil as secondary coil for bass, 27 ... Short coil as secondary coil for treble, 28 ... Vibration plate for treble, 29 ... Cone paper as an example of diaphragm for bass , 30 damper, 31 speaker frame, 32 gasket, 33 support plate, 34 through hole, 35 magnet guide, 36 cap, 37
a to 37g and 37i to 37p: Lead wire pair, 38a
To 38g and 38i to 38p ... input terminals

Claims (4)

[Claims] A primary coil provided near a gap in the magnetic circuit and supplied with a current corresponding to an input audio signal; and a primary coil disposed in the gap and corresponding to a current flowing through the primary coil. A first coil unit in which a first secondary coil including a short coil in which a current is induced is formed; and a short disposed in the gap and inducing a current corresponding to a current flowing in the primary coil. A second coil unit on which a second secondary coil formed of a coil is formed; a low-frequency diaphragm attached to the first coil unit; a high-frequency diaphragm attached to the second coil unit; A speaker device comprising: A center pole portion formed of a columnar magnetic yoke member, an outer peripheral side surface of the center pole portion, and a plate portion formed of a magnetic yoke member having an inner peripheral side surface facing through the gap; The primary coil is provided in one or both of the center pole portion and the plate portion near the gap, and the magnetic circuit includes a center pole portion, the plate portion, the gap, The second secondary coil is configured to include a primary coil, and the second secondary coil is concentric with the first secondary coil in a gap between the first secondary coil and the center pole portion. The speaker device according to claim 1, wherein the speaker device is provided. 3. The speaker device according to claim 1, wherein a signal that changes at a rate higher than an audible frequency is supplied to the primary coil. 4. The primary coil includes one or a plurality of coils, and the primary coil is driven by a digital signal in which one sample of an audio signal is represented by a plurality of bits, and the primary coil is driven by the digital signal. 2. The speaker device according to claim 1, wherein a sum of currents according to the weight of each bit of the digital signal is induced in the first and second secondary coils. 3.