| This article guide: The so-called electronic crossover technology, it should be said that it is not a new thing, has been widely used in high-end speaker equipment, but in the field of PC multimedia speakers that value the price, it is rare before, the reason is nothing more than realized The mechanism and cost are too high, and whether it can bring about the ideal sound quality improvement. |
However, recently there have been many multimedia speakers claiming to use electronic crossover technology. How should we treat these "electronic crossover" technologies: Is it a gimmick in the promotion or a real technological advancement?
The concept and meaning of frequency division is well known. The human ear's perception range of sound frequency is about 20Hz - 20KHz, and the frequency span is very large. However, due to the limitations of principle and technology, the current mainstream speaker cannot achieve perfection with one unit. Now all the bands that the human ear can hear, so there are tweeters and woofers for different frequencies.
At present, the frequency range of the woofer used in multimedia speakers is about 40Hz - 4KHz, and the frequency range of the tweeter is about 2KHz - 20KHz, that is, at least two or more units can cover all the frequencies that can be heard by the human ear, and The frequency converter is the bridge that connects the tweeter and the woofer to make it work synchronously.
On the other hand, due to the low power consumption of the tweeter, if the input of large power or let it work in the low frequency range, it is easy to cause damage or even burnt of the tweeter. Therefore, the frequency divider is also required to divide the frequency to make the tweeter work. In a safe frequency range.
Power Dividing: The frequency division method of the traditional PC multimedia speaker The so-called power frequency division refers to the power amplification of the sound signal first, and then the frequency division circuit composed of high-pass, low-pass, band-pass and other passive filters, the treble and The bass signals are separated and sent to the corresponding treble and woofer units. The power divider circuit is simple and can be implemented using standard LC circuits, namely inductor (L) and capacitor (C). As shown below:
The power divider has the advantages of relatively simple structure, low cost, and convenient production and manufacture. For PC multimedia speakers, it only needs one amplifier per channel, which can greatly reduce production and manufacturing costs, so it is widely used. At present, almost all active speakers use power dividers.
A disadvantage of the power divider is that the inductor coil tends to be bulky and has a DC resistance, which results in a large value of insertion loss and a reduction in the damping factor. ——The so-called damping coefficient reflects the control power of the amplifier to the speaker. The value is the speaker impedance / (power amplifier internal resistance + transmission impedance). In general, the internal resistance of the power amplifier is generally 0.1 ohm, and the internal resistance of most power dividers exceeds the internal resistance of the power amplifier even reaches 0.2 ohms or more, which means that the power divider reduces the damping coefficient by half or even more. many. - Therefore, the power divider has a large negative impact on control.
At present, almost all PC multimedia speakers are successfully assembled, and the thrust and control are very limited. The insertion loss of the power divider and the influence on the damping coefficient further deteriorate the set of defects in the thrust and control. Blurring the bass and losing the details it deserves. For example, we can obviously feel that some PC multimedia speakers have slow bass speed and unclear sound. In fact, this is the insertion loss of the power divider.
Principle of Electronic Frequency Division Electronic frequency division is sometimes referred to as active frequency division. The biggest difference between power and frequency is that the electronic frequency division is divided by the electronic frequency dividing circuit before the audio signal is sent to the power amplifier, and then the signals of different frequency bands after frequency division are respectively sent to the respective power amplifiers to drive. Speaker units in different frequency bands.
It can be seen that the advantage of electronic frequency division is that, firstly, because the power amplifier directly pushes the speaker, there is no insertion loss generated by the power divider and the influence on the damping coefficient, so the electronic frequency division can significantly improve the control power of the power amplifier and increase the full frequency band. The analytical power makes the speaker retractable, the sound is clear and powerful, and the speed is strong. Secondly, the accuracy of the electronic crossover is easy to control. The high-quality device can control the crossover point very accurately, so that the high and low woofer units work at the most appropriate level. In the frequency band, the performance of the speaker is exerted, and this is difficult to achieve with power division.
The disadvantage of electronic crossover is that the cost is higher, because each channel needs to be equipped with a corresponding power amplifier circuit, and the number of successful discharges needs to be multiplied.
Implementation Mechanism of Electronic Frequency Divide Let's take a closer look at how the current use of PC multimedia speakers achieves electronic crossover and how the signal after frequency division is amplified. The following is the electronic crossover amplifier of a certain 2.0 speaker. Generally speaking, due to the use of electronic crossover, for the 2.0 speaker, the number of amplifiers needs to be doubled, that is, the 4-channel power amplifier needs to be configured, and the cost is higher than the ordinary 2.0. Speaker.
Due to the different characteristics and needs of the treble and woofer, the speaker uses a 1875+7265 amplifier combination.
The treble channel uses a 1875 power amplifier chip. Because the multimedia sound source generally has "digital sound", the sense of hearing is rough, and the 1875 sound is full and round, the high frequency is soft and delicate, and it can neutralize the digital sound of the multimedia sound source, so it is very suitable for use in the high-pitched channel.
The bass channel uses ST's original TDA7265 chip. TDA7265 has a large power and strong thrust, and it has a good control power. With the electronic crossover, it can fully exert its strong control.
From the actual effect, the combination of 1875+7265 is still acceptable, and the advantages of the two chips are exerted, which not only ensures sufficient acousticity, but also naturally reveals musicality during playback.
Rational view of electronic crossover From the above introduction, it can be seen that the introduction of electronic crossover technology in PC multimedia speakers, in theory, should be able to improve the sound quality to a certain extent, give full play to the potential of the speaker.
However, after all, the speaker is a product that requires the human ear to subjectively feel. It is not enough to have a beautiful and good frequency curve. In many cases, it is not possible to achieve a good performance by adjusting the frequency curve and straightening, and the electronic crossover technology. The theoretical advantage requires the design and quality of other components as a guarantee. In many cases, the effect of the electronic crossover depends on whether the setting of the crossover point is reasonable or not, and it depends on the quality of the components. In the above examples, it is difficult to call the circuit and materials rigorous, of course. This is also a helpless choice to ensure that the speaker cost is within a certain range. But it also shows that the use of electronic crossover technology does not mean that a certain speaker will certainly have better sound quality than the power divider speaker.
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