What are the designs and classifications of subwoofer speakers?

                What are the designs and classifications of subwoofer speakers?

Subwoofer is also called subwoofer, which plays a very important role in creating a shocking momentum effect. It is divided into two categories: active and passive. Active subwoofer refers to a subwoofer that includes a power amplifier. In addition to power amplification, the circuit part also has units such as audio frequency filtering (filtering audio frequency components above the bass), phase adjustment, and volume adjustment; passive subwoofers are the same as general subwoofers. The speaker is the same, consisting of a unit and a passive power divider. Today, Huayun Xiaobian will introduce the design and classification of subwoofer speakers.

1. Closed subwoofer

This kind of speaker box is completely closed, which is the same as the general so-called closed box structure. It is characterized by simple structure, good transient response, deep and clear sense of hearing. The disadvantage is that compared with other types of speakers with the same volume, the low-frequency dive cut-off frequency is higher. If you want to obtain a lower low-frequency dive frequency, you usually need a larger cabinet volume and use a speaker with a larger diameter. unit. In addition, the efficiency and sensitivity of the speakers are lower than other types of speakers. In terms of cabinet volume design, when the resonance frequency Fs of the speaker unit is lower than 50Hz, the cabinet volume should preferably be greater than 1.4 liters. When Fs is greater than 50Hz, the volume of the box should preferably be greater than 2 liters. When making and adjusting the closed box, it is usually necessary to fill a large amount of sound-absorbing cotton in the box. The material is mainly glass fiber and long-fiber wool, so as to improve the flexibility of the speaker and achieve the effect of equivalently increasing the volume of the box. In theory Up to 40%, in practice, it can be calculated by equivalently increasing the volume by 15%-24%, which is equivalent to reducing the volume of the box. Filling sound-absorbing cotton can also improve the efficiency of the speaker. The correct filling amount can increase the efficiency of the speaker by up to 15%. The amount of sound-absorbing cotton usually needs to be determined by repeated auditions to ensure that the sound is not muddy (the amount is too small). Dullness (too much volume) is the principle, and the same is true for other types of speakers. Closed-box subwoofers have stricter requirements on the unit than other types of speakers. It is hoped that Fs should be lower than 40Hz, Qts should be 0.3-0.6, and Fs/Qts≤50. In addition, the unit diameter is preferably greater than 20cm, and it is a long-stroke design.

2. Bass reflex subwoofer

There are usually one or more bass reflex holes on the box of this subwoofer. The front wave of the woofer can pass out of the box through the bass reflex hole and mix with the positive wave of the woofer, thereby increasing the volume of the low frequency. The advantage of this kind of speaker is that it has low distortion and can withstand relatively large power. It can be lower than the lower cut-off frequency of the closed cabinet, but the transient response is slightly worse.

3. Passive subwoofer

That is to say, passive subwoofer. There is no special drive amplifier in this subwoofer, and it has no driving ability. It must be driven by an external power amplifier. The group signal output terminal transmits the divided music signal to the main box. Since the power amplifier has to drive the main box and the subwoofer, the load increases, so the driving force will be dispersed. There are relatively few such subwoofers at present.

4. Active subwoofer

Also known as an active subwoofer, this type of subwoofer has a built-in amplifier, so it can get low-level music signals from the subwoofer output of the AV amplifier. Moreover, most active subwoofers also have additional high-level input and output terminals, that is, use speaker cables to connect. It is impossible to connect the subwoofer with a speaker cable in a home theater, because whether it is an AV amplifier or a pre-decoder subwoofer signal output is output through the low-level RCA terminal or CLR terminal, not from the 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.

5. Band-pass subwoofer

The box of the band-pass subwoofer includes two independent boxes, one is hidden inside, the box is airtight, and the bass unit is installed inside, and the diaphragm faces the other box outside, which cannot be seen from the outside. The other box room communicates with the outside through the bass reflex hole. 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. Handling power is optimal. The instant response is only a little worse than that of a closed subwoofer. However, the high cost of such a subwoofer is relatively rare.

6. Transmission line subwoofer

This kind of subwoofer has 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 lower cut-off 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. Transmitted subwoofers are more expensive designs and are therefore rare.