[Home Theater Network HDAV.com.cn] Several pictures take you inside the speaker to understand how it works. The fly in the ointment is that the picture is all in English. Fortunately, as long as the process is known to be electric → magnetic → piston movement → eardrum feeling, you can also understand that it is inseparable. 　　
Look at the reason why the speaker sounds here.
To understand the principle of speaker sound, we first need to understand the way the sound is transmitted. The transmission of sound requires a medium (vacuum can not transmit sound); the sound depends on all gases, liquids, solids as a medium to spread out, these substances as a medium of transmission called medium.
Just like water waves, you throw a stone on the calm water, there is a wave on the water, and then spread to the shore for 4 weeks; so is the sound wave. The frequency of the sound wave is in the range of 20-20,000 Hz, which can be heard by the human ear; below or above this range, the human ear can't hear it.
Water waves and sound waves travel in the same way. Through the propagation of the medium, the human ear can hear the sound.
Sound waves can travel in gases, solids, liquids
Let's talk about how the speaker works. A horn is a device that converts an electrical signal into an acoustic signal. It consists of a coil, a magnet, a cone, and the like. A current of different magnitudes (alternating current) is outputted by the amplifier, and the coil is moved by the magnetic field by the coil. The coil is connected to the cone to drive the cone to vibrate, and then the vibration of the cone pushes the air to emit sound.
Speaker structure
The principle of horn sound
When the horn receives an electrical signal output by the source device, the current passes through the coil on the horn and generates a magnetic field response. The current through the coil is alternating current, and its positive and negative poles are constantly changing; the positive and negative poles meet each other, and the coil is attracted by the magnet on the horn to move backward (in the box); when the positive pole and the positive pole meet each other, they mutually repel each other. The coil moves outward (outside the box). This rhythm of convergence will produce sound waves and airflow, and it will make a sound, which is the same effect as the throat vibration we speak.
Frequency response curve SPL vs Freq
The frequency range that can be heard by the human ear is 20Hz-20KHz, (<20Hz is called infrasound, >20KHz is called ultrasound). The icon ordinate indicates the sound pressure level in dB. Icon abscissa - indicates frequency in Hz.
The left side of the icon is the woofer frequency response curve, the right side is the treble single, and the left and right speakers are included. From the frequency response curve, you can know several important parameters:
Characteristic sensitivity (SPL): The average sound pressure is obtained by taking the measured sound pressure at one meter distance with one watt of electric power and taking four points from the frequency response curve.
Effective frequency range (F0~20KHz): It can be SPL-10 dB, so that a straight line intersects the curve with two points. The effective frequency range between these two points. The effective frequency range of the above speaker is 45Hz-20KHz, the effective frequency range of the woofer is 40Hz-3KHz, and the effective frequency range of the treble monomer is 1800Hz-20KHz. The flatter the frequency response curve, the better the bandwidth and the wider the bandwidth.
Several important parameters can be known from the impedance curve:
Impedance value (Ohm):
The lowest point after the peak is shown is the impedance value corresponding to the ordinate.
Minimum resonance cycle number (F0):
Single horn (single peak)—The point at which the peak of the impedance curve corresponds to the abscissa is F0. Speaker speaker (double peak) - the point corresponding to the abscissa of the valley between the first peak and the second peak of the impedance curve is Fb, the first peak is the sound tube F0, and the second peak is the single unit F0. Speaker horn + treble monomer (three peaks) - the point where the abscissa corresponding to the valley between the peak and the peak of the impedance curve is Fb, and the third peak is the F0 of the treble unit.
1. DC impedance (Ohm):
The impedance is measured by a static speaker, so the result is the DC impedance, which is the impedance of the total length of the copper wire wound around the voice coil. The DC impedance is not affected by the frequency.
2. AC impedance (Ohm):
The AC impedance value obtained after the dynamic speaker, that is, after power-on. (Normally the tolerance for the voice coil is ±15%.)
3. Standard input power (W): It is the rated power of the speaker, which is the guaranteed value.
4, the maximum input power (W): refers to the maximum power of the speaker, only withstand 1 second peak voltage, non-guaranteed value.
5, output sound pressure, also known as sensitivity (dB):
Sensitivity is also called characteristic sensitivity. It is generally defined as the sound pressure generated by the speaker placed on the reference side of the anechoic chamber with a signal voltage equivalent to one watt of electric power at the rated impedance. In the case of decibel "(dB)", the characteristic sensitivity is expressed. The sensitivity of the speaker has a great relationship with the performance of the speaker vibration system and the magnitude of the magnetic induction in the air gap.
6, polarity:
A pulsed DC signal is applied to the input end of the speaker. If the vibration is pushed forward, the positive terminal of the horn is connected to the positive terminal of the horn, and vice versa. If the connection is reversed, the phase of the horn vibration will be incorrect.
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