The production of subwoofer
Subwoofer speakers, commonly known as subwoofers, have a very important role in creating a stunning momentum effect. Most brands sell home theater products in the form of a package consisting of an AV amplifier plus five speakers and a subwoofer. The subwoofer is already an indispensable configuration. In fact, the design specification, superb production, and excellent effect of the subwoofer. Its effect in home theater system audio playback is quite fascinating. It's a pity that the superior price of subwoofer on the market makes it difficult for most people to accept. The effect of affordable people is difficult to accept, and things in the world are often not satisfactory. However, hands-on audio-visual enthusiasts are "self-employed and have plenty of food and clothing." Based on this, this article intends to make a brief introduction to the design principles of subwoofers for interested audio reference.
Generally speaking, in terms of the composition of the subwoofer, the bass is also divided into two categories of active and passive. The so-called active subwoofer refers to a subwoofer that includes a power amplifier, in which the circuit part is in addition to power amplification. Usually also has audio frequency filtering (filtering out audio frequency components above the bass) and phase adjustment. Volume adjustment and other units; passive subwoofers are no different from ordinary speakers, composed of units and passive power dividers, where the divider is a low-pass filter. Make the replay frequency range only subwoofer audio. The following is the introduction of subwoofer-large unit speaker, power amplification separately.
1. Design Principles and Classification of Subwoofer Boxes The design principles of subwoofers can be roughly divided into three categories, namely closed speakers, inverted speakers and band-pass filter speakers
1. Closed speaker
As the name implies, this speaker box is completely enclosed, the same as the general so-called closed box structure, see Figure 1
The characteristics of the enclosed speaker are simple structure and good transient response. The sense of hearing is deep and clear. The disadvantage is that in the same volume, compared with other types of speakers, the low-frequency dive cutoff frequency is higher than other speakers, so if you want to get a lower low-frequency dive frequency, usually a larger cabinet volume And select the loudspeaker unit with larger caliber, and the efficiency or sensitivity of the speaker is lower than other types of speakers.
In terms of volume design of the cabinet, there is an engineering design data for reference. When the resonance frequency Fs of the horn unit is lower than 50 Hz, the volume of the cabinet is preferably larger than 1.4 litres. When Fs is greater than 50 Hz, the volume of the cabinet should preferably be greater than 2 litres.
When the closed box is produced and adjusted, it is usually necessary to fill the box with a large amount of sound-absorbing cotton. The material is mainly glass fiber and long-fiber wool, which can improve the flexibility of the speaker and can also effectively increase the volume of the box. Theory Up to 40%, practically, it can be calculated by equivalently increasing the volume by 15% -24%, which is equivalent to reducing the volume of the cabinet. In addition, the filling of 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 trial listening to determine the amount of filling. Less), dull (too much) is the principle, the same is true for other types of speakers.
For closed-box subwoofers, the requirements for the unit are stricter than other types of speakers. Among them, it is desirable that Fs be less than 40Hz, Qts should be 0.3-0.6, and Fs / Qts ≤50. In addition, the unit diameter is preferably greater than 20cm, and belongs to the long-stroke design.
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