The Subwoofer for Cinema Members

                                       The Subwoofer for Cinema Members

As a part of the home theater system, the subwoofer is responsible for reproducing the low-frequency sound effects in the movie sound effects, and is used to make up for the lack of low-frequency volume of the main speaker, or the low-frequency and extremely low-frequency areas that cannot be reached. If it is distinguished by whether it has a built-in amplifier, it can be divided into two types: active subwoofer and passive subwoofer. According to the box design, it can be roughly divided into bass reflex design, bandpass design, transmission line design and so on. If it is distinguished by the direction of the sound, it can be divided into sounding toward the front, sounding toward the back, sounding toward the ground, sounding toward the top, and sounding toward the left and right sides. If it is distinguished by a single action mode, there is a push-pull type composed of two speakers. The same-phase sounding type composed of two or three, the same-phase sounding type composed of a single passive radiator. Among them, the most ideal subwoofer is designed with a set of bass equalization circuit in addition to the built-in amplifier, which can moderately attenuate the indoor medium and low frequency standing waves to a certain extent, so that the low frequency band below 100HZ or 80HZ can reach a relatively low frequency. Flat frequency response curve.

Closed Subwoofer

The cabinet itself is airtight without any holes or gaps communicating with the outside world. The woofer can be placed facing the front, rear, left, right, up and down. This kind of box is the easiest to manufacture, and it is easy to meet the quality requirements. It responds quickly in an instant, can withstand large power, and the volume of the box can also be made relatively small.

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Bass Reflex Subwoofer

The box itself has one or more bass reflex holes, so that the front wave of the woofer in the box can be transmitted out of the box through the bass reflex hole, and mixed with the positive wave of the woofer, thereby increasing the volume of the low frequency. The distortion is relatively low, and the power amplifier is relatively large. Compared with closed cabinets, the lowest cut-off frequency of the bass reflex type can be lower. But the instant response is not as good as the closed box.

Band-pass subwoofer

The bandpass box design usually includes two independent box chambers, one is hidden inside, and the other communicates with the outside through the bass reflex hole. The chamber hidden inside is airtight. The woofer is installed in this airtight room, and the diaphragm faces another box room outside. The woofer cannot be seen from the outside of the cabinet. When the woofer starts to move, the air that drives the outer box chamber passes through the bass reflex hole to form a sound wave filter, which produces a four-order filter effect on a certain frequency band. The power to withstand is the highest among different box designs. The instant response is only inferior to the closed design. This design cost is relatively rare.

Transfer line type subwoofer

There must be a closed pipe that gradually decreases from large to small. The large end is connected to the back of the woofer to receive the back wave of the unit, and the small end is the outlet. The length of the pipe must be at least a quarter of the wavelength of the lowest cutoff frequency, and the inner wall of the pipe needs to be equipped with appropriate sound-absorbing materials. The function of the pipe is to use the back wave of the woofer to extend the low-frequency cutoff frequency down to achieve a lower frequency response. Low frequencies can be extended even lower. The cabinet manufacturing cost of the transmission type subwoofer is also the most expensive, so the gun of this design is even rarer.

Passive subwoofer is passive subwoofer

In the early days, there was no dedicated driver amplifier in the subwoofer, only a passive crossover network responsible for frequency division. This kind of subwoofer was called passive subwoofer or passive subwoofer. It has no driving ability, and must be driven by an external power amplifier. The music signal is obtained from the output terminal of the power amplifier, and it also has a set of signal output terminals to transmit the divided music signal to the main box. Since both the main box and the cannon are driven by the same power amplifier, the driving force will be dispersed as the load of the power amplifier increases. This kind of gun is very rare now, and it is thankless.

The active subwoofer is the active subwoofer

With the formulation of the home theater surround multi-channel system, the subwoofer must have a built-in amplifier. Therefore, low-level music signals can be obtained from the subwoofer output of the AV amplifier. In addition, the general active subwoofer will also have another high-level input and output terminal, that is, use the speaker cable to connect. It is impossible to connect the cannon with a speaker cable in a home theater, because whether it is an AV power amplifier or a pre-decoder subwoofer signal output is output through a low-level RCA terminal or CLR terminal, not from a speaker cable terminal. In the case of two-channel cannon, the music signal can be transmitted to the cannon through the second output of the front stage or the rear stage.

What kind of amplification method is used by the built-in amplifier of the subwoofer

The vast majority of active subwoofer built-in amplifiers use Class D amplification, because this method is very efficient, does not generate heat, and the output power can easily reach hundreds of watts or even kilowatts, and the cost is low. Furthermore, the frequency bandwidth of the woofer is about 20HZ-150Hz, and the class D amplifier has high distortion, which is not conducive to the disadvantages of mid-frequency and high-frequency bands, but it is not a big problem in the use of subwoofers. There are also a few high-end subwoofers that insist on using the AB method. The area of the heat sink on the back of this type of subwoofer is bound to be quite large.