| This article is a guide: The so-called electronic crossover technology should be said that it is not new. It has long been widely used in high-end speaker equipment, but it is relatively rare in the field of PC multimedia speakers that value the price more. The mechanism and cost are too high, and whether it can bring about the ideal sound quality improvement considerations. |
However, many multimedia speakers claiming to use electronic crossover technology have appeared on the market recently, so how should these "electronic crossover" technologies be viewed: is it a gimmick in publicity or a real technological advancement?
The concept and significance of frequency division are well known. The human ear's perception of sound frequency ranges from about 20Hz to 20KHz, and the frequency span is very large. However, due to the limitations of principles and technologies, the current mainstream speakers cannot achieve a perfect weight All the frequency bands that can be heard by the human ear, so there are tweeters and woofers for different frequencies.
Currently, 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. The frequency converter is a bridge that connects the tweeter unit and the bass unit to synchronize and coordinate their work.
On the other hand, because the tweeter's withstand power is small, if you input a large power or let it work in the low frequency band, it is easy to damage or even burn the tweeter, so you also need to divide the frequency to make the tweeter work In a safe frequency range.
Power frequency division: The traditional frequency division method of PC multimedia speakers is called power frequency division, which means that the sound signal is first amplified by power, and then the high frequency, low pass, band pass and other passive filters are used to divide the high frequency and The bass signals are separated and sent to the corresponding treble and bass units respectively. The power divider circuit is simple, and can be realized by using a standard LC circuit, that is, an inductor (L) and a capacitor (C). As shown below:
The power divider has the advantages of relatively simple structure, low cost, and convenient production and manufacturing. For PC multimedia speakers, only one power amplifier per channel is required, which can greatly reduce production and manufacturing costs, so it is widely used. Currently, almost most active speakers use power dividers.
The disadvantage of the power divider is that the inductance coil is often bulky and has a DC resistance, which results in a large insertion loss and reduces the damping coefficient. ——The so-called damping coefficient reflects the control power of the power amplifier on the speaker, and its 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 frequency dividers exceeds the internal resistance of the power amplifier and even reaches more than 0.2 ohm. many. -Therefore, the power divider has a great negative impact on the control force.
At present, almost the vast majority of PC multimedia speakers use integrated power amplifier, thrust and control force are very limited, and the insertion loss of the power divider and the impact on the damping coefficient further aggravate the defects of integrated power on thrust and control force Make the bass turbid and lose the details it deserves. For example, we can often feel that the bass of some PC multimedia speakers is slow and the sound is not clear. In fact, this is the insertion loss of the power divider.
Principle of electronic crossover Electronic crossover is sometimes called active crossover. The biggest difference between it and power frequency division is that electronic frequency division is to divide the frequency through the electronic frequency division circuit before the audio signal is sent to the power amplifier, and then send the signals of different frequency bands after the frequency division 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 drives the speaker, there is no insertion loss and impact on the damping coefficient generated by the power frequency divider. Therefore, 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 freely retractable, the sound is clear and powerful, and the sense of speed is strong; secondly, the accuracy of the electronic frequency division is easy to control. The use of high-quality devices can control the frequency division point very accurately, so that the high and low sound units work in the most appropriate In the frequency band, the performance of the speaker is exerted, and this is difficult to achieve by power division.
The disadvantage of electronic frequency division is mainly the higher cost, because each channel needs to be equipped with a corresponding power amplifier circuit, and the number of successful amplifiers needs to be doubled.
The realization mechanism of electronic frequency division Now let's take a specific look at how to use PC multimedia speakers to achieve electronic frequency division and how to amplify the signal after frequency division. The following is an electronic crossover amplifier for a 2.0 speaker. Generally speaking, due to the use of electronic crossover, the number of amplifiers for a 2.0 speaker needs to be doubled, that is, a 4-way amplifier needs to be configured, and its cost is higher than the ordinary 2.0 Speaker.
Due to the different characteristics and needs of the treble and woofer units, this speaker uses a 1875 + 7265 power amplifier combination.
The tweeter channel uses a 1875 power amplifier chip. Multimedia sound sources generally have "digital sound", which makes the sense of hearing rough, while the sound of 1875 is full and round, and the high frequency is soft and delicate. It can neutralize the rough digital sound of multimedia sources, so it is very suitable for use in the treble channel.
The bass channel adopts ST's original TDA7265 chip. TDA7265 has higher power and strong thrust, and it has a good control force itself. With the electronic frequency division, it can fully exert its strong control characteristics.
From the practical point of view, the combination of 1875 + 7265 is acceptable, and the advantages of the two chips are exerted, which not only guarantees sufficient acoustics, but also naturally reveals the musicality during playback.
Rationally view the electronic crossover. As can be seen from the above introduction, the introduction of electronic crossover technology in PC multimedia speakers should theoretically be able to improve the sound quality to a certain extent and 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. Its beautiful frequency curve is not enough to look good. It is not enough. In many cases, it is not possible to obtain good performance by leveling and straightening the frequency curve. Electronic crossover technology The theoretical advantage requires the design and quality of other components as a guarantee. In many cases, the effect of electronic crossover depends on whether the setting of the crossover point is reasonable, and it also depends on the quality of the components. For the components in the above example, it is difficult to be rigorous in terms of circuits and materials. , This is also a helpless choice to ensure that the speaker cost is within a certain range. But it also shows that just using electronic crossover technology does not mean that a certain speaker will necessarily have better sound quality than the power crossover speaker.
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