JPS6174497A - Speaker device - Google Patents

Abstract

PURPOSE:To detect and control radiated sound pressure from a speaker box to the external correctly by forming a back room on the back of a microphone and connecting the back room with outside air. CONSTITUTION:The back room 12 is arranged on the back of the microphone 4 to prevent the microphone 4 from the direct application of sound pressure in the speaker box to its back. A hole 10 is formed on a holding unit 5 of the microphone 4 to uniform the inner pressure of the back room 12 with the outside pressure. Even if sealing of an output signal extracting part 11 of the microphone 4 is not complete and the pressure in the box 1 is made to flow into the back room 12 through the gap of the signal extracting part 11, the pressure is discharged to the outside through the hole 10 and the pressure to be applied to the back of the microphone is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a speaker device for high-fidelity reproduction.
It is something to do.

Conventional configuration and its problems Conventionally, there has been a method for lowering the low frequency reproduction limit of a speaker system, which is known as a monophonic feed panoch (MFB).
Among them, the sound played by the speaker is detected by a microphone,
There is an acoustic feedback method in which the output of this microphone is fed back to a speaker via an amplifier. Below, such a conventional acoustic feedback type speaker device will be explained.

Figure 1 is a configuration diagram of a conventional MFB system, in which a microphone 4 is installed on a panfer plate 2 to detect the sound radiated from a speaker 3, and its output is fed back to the inverting input terminal of an amplifier 80 to apply negative feedback to the speaker 3. ing.

Note that there is a single speaker box, 5 is a holder, 6 is a speaker drive cord, 7 is a microphone output signal cord, and 9 is an input device.

In general, microphones are designed to maintain a balance with the atmospheric pressure by providing a vent hole in a part of the microphone case to prevent the diaphragm from shifting in one direction due to the difference in pressure between the front and back surfaces of the membrane when the atmospheric pressure changes. I have to. Even in the case of omnidirectional microphones, ventilation holes must be made.

Therefore, when attaching the microphone 4 to the speaker box 1 as shown in FIG. Therefore, although only the sound pressure from the surface of the microphone 40 should be detected, the sound pressure from the back surface of the microphone 4 is also detected.

In this case, since the sound pressure on the surface of the microphone 4 and the back pressure are in opposite phases, negative feedback due to the sound pressure on the surface of the microphone 4 cannot be applied, resulting in positive feedback, and if a predetermined condition is exceeded, oscillation occurs. There was a problem in reaching .

Purpose of the Invention The present invention solves this problem by preventing the back sound pressure inside the speaker cabinet from being applied to the back of the microphone, and correctly detecting and controlling the sound pressure radiated to the outside from the speaker box. The purpose is to

Structure of the Invention The present invention is a speaker device that applies MFB using a microphone, in which a back chamber is provided behind the microphone, and this back chamber is communicated with the outside air. In this way, unnecessary back pressure is not applied to the microphone, and as a result, accurate MFB can be applied based only on the sound pressure from the speaker.

DESCRIPTION OF THE EMBODIMENT FIG. 2 shows an embodiment of the present invention, which differs from FIG. 1 in that a back chamber 12 and a hole 10 are provided behind the microphone. Reference numeral 5 denotes a holder for holding the microphone 4, which is generally used to reduce mechanical transmission of shocks applied to the speaker box 1 to the microphone 4.
It is desirable to use a cushioning material such as rubber.

In this way, in the embodiment shown in FIG. 2, the rear chamber 12 is provided behind the microphone 4, so that the sound pressure inside the speaker box 1 is prevented from being directly applied to the rear surface of the microphone 4. Further, a hole 1 is provided in the holder 5 of the microphone 4.
0 is provided so that the internal pressure of the back chamber 12 and the external pressure are the same. With this configuration, the output signal extraction portion 11 of the microphone 4 is not completely sealed, and the pressure inside the speaker box 1 passes through the gap between the output signal extraction portion of the microphone 4 and leaks into the rear chamber 1 of the microphone 4.
Even if air flows into the microphone 2, the outside air escapes through the hole 10, so that the pressure applied to the back surface of the microphone 4 can be significantly reduced compared to the conventional one.

FIGS. 3 and 4 are diagrams showing the effect. The broken line a in FIG. 3 indicates the microphone 4 when the hole 10 is closed and sealed.
The solid line represents the output signal characteristics actually measured with the hole 10 open, the horizontal axis represents the frequency, and the vertical axis represents the output voltage of the microphone 4. Also, the solid line C in Figure 4
The sound pressure inside the speaker box 1 was measured by inserting the microphone 4 into the speaker box 1 with the hole 1Q sealed. , This data shows that when hole 10 is sealed, speaker box 1
Internal sound pressure (actual C in Figure 4) flows into the rear chamber 12 from the output signal extraction portion 11 of the microphone 4, and the bass portion rises in proportion to the influence on the rear surface of the microphone 4,
Compared to the output signal of the microphone 4 when the hole 10 is open (actual b in Figure 3), the output signal when the hole 10 is sealed (the third
The dashed line &) in the diagram indicates that the bass is rising. Also, when negative feedback is actually applied to speaker 3, hole 10
It was confirmed that when it was sealed, it oscillated at a low frequency. This is because the sound pressure inside the speaker box 1 is in reverse phase with the sound pressure outside the speaker box 1, so the phase-inverted output signal of the microphone 4 is further inverted at low frequencies, resulting in positive feedback.

In particular, when applying motional feedback to the speaker to increase the low-frequency playback level, it is advantageous to seal the speaker bonox 1, so do not apply motional feedback to the bass with a sealed speaker box 1. A signal with a level higher than the state is from speaker 3.
In addition to this, the internal pressure of the speaker box 1 becomes extremely high. Also, if you want to increase the bass level with a monophonic feeder, the speaker box 1 should be small.

Before feedback is applied, the minimum resonance frequency determined by the speaker diaphragm diameter and the internal volume of the box is high, so the pressure inside the speaker box 1 is as low as the internal volume.
Even higher. Furthermore, even if the output signal extraction portion 11 of the micropon 4 is sufficiently sealed, it is extremely difficult to completely seal it, and it requires a large number of man-hours to mass produce and inspect each product one by one. It is practically impossible to ensure complete sealing.

In this respect, according to this embodiment, the above-mentioned problems can be solved at once by simply providing the rear chamber 12 and the opening 10, and the airtightness of the take-out portion 11 can be simplified. .

FIG. 5 shows a second embodiment of the invention. This has a cylindrical boss 13 integrally protruding from the baffle plate 2 of the speaker box 1, and at the tip of the boss 13 there is a hesode amplifier 15 for converting the output impedance of the microphone 4 or a variable volume 16 for making the output level of the microphone 4 variable. The rear chamber 12 is constructed by fixing the printed circuit board 14 with the components attached thereto with screws, and the rear chamber 12 is also used as a room for storing the head amplifier 16 and the like. In this case as well, the seal between the printed circuit board 14 and the boss 13 cannot be maintained sufficiently with just the packing or bond, but since the hole 1o is provided in the rear chamber 12, the inside of the rear chamber 12 and the outside air are the same. This can significantly reduce the compressed pressure inside the speaker box 1 that is applied to the back of the microphone 4, which eliminates the possibility of the control system oscillating due to uncertain sealing as in the past. Does not occur.

Effects As described above, according to the present invention, there is no need to perform sufficient sealing processing at the output signal extraction part of the microphone, and a speaker using a sound pressure detection method using a microphone can be controlled reliably and stably. This makes it possible to increase the reliability of knowing the oscillation in low frequencies.

In addition, since the highly distorted signal inside the speaker is not detected from the back of the microphone, it can be detected as a sensor with less distortion.As a result, a high-performance speaker can be configured, and the reverse The margin for oscillation increases by the signal whose phase signal is reduced, and the control amount (feedback amount of the speaker's sound pressure) is increased accordingly, making it possible to construct a speaker with higher performance.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional speaker device, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is the output sound pressure characteristic of the detection microphone, and Fig. 4 is the sound pressure inside the speaker box. The characteristic diagram, FIG. 5, is a sectional view of a microphone mounting portion in a second embodiment of the present invention. 1...Speaker box, 2 Yamaba'7 full board,
3...Speaker, 4...Microphone, 5...Holder, 6...Speaker drive code, 7...Microphone output signal code ,
8...Amplifier 19...Input terminal, 10
...hole, 11 ... cord drawer part,
12... Back chamber, 13... Boss, 14...
Old...Pu IJ 7 board, 15...Head amplifier, 16...Semi-fixed volume. Name of agent: Patent attorney Souo Nakao and 1 other person
Figure 2

Claims (2)

[Claims] (1) A speaker and a microphone are provided in the speaker box, and the sound pressure of the speaker is detected by the microphone,
The output of this microphone is configured to be returned to the speaker via an amplifier, and a rear chamber is formed behind the microphone by a holder of the microphone and a wall surrounding the rear of the microphone, and the rear chamber is connected to the outside air. A speaker device characterized by communicating with. (2) A cylindrical boss is integrally protruded from the back of the baffle plate of the speaker box, and a printed circuit board is attached to the tip of the boss so as to cover the entire boss, and a microphone is placed inside the boss. 2. The speaker device according to claim 1, wherein a rear chamber is configured with a microphone holder, and a head amplifier of the microphone is configured on the printed circuit board.