1: Power
Power can be said to be the most meaningful and meaningless parameter. It is most meaningful because it directly determines the maximum effective output sound pressure level (commonly understood as the maximum volume) and low-frequency quality of the speaker. And it is the most meaningless because there are more than a dozen kinds of power parameters. At present, many manufacturers on the market have abused the concept of "peak power" extremely, making the originally very reusable parameters meaningless. .
The power parameters related to active speakers mainly include the following:
(1) Power amplifier part: The output power of the power amplifier is the one that has the most changes (or is greasy) among various parameters. The output power measured by the same power amplifier is different due to different test methods. The common ones are the following.
â— Rated output power: refers to the maximum power that the power amplifier can continuously output within the rated total harmonic distortion range, which can also be called effective value power or root mean square (RMS) power.
â— Peak power (P max): Because the maximum value of the positive-swept AC voltage is 1.414 times the effective value. Therefore, the peak power (P max) is twice the root mean square power (P rms).
â— Music output power (MPO): refers to the instantaneous maximum output power of the power amplifier to the music signal under the condition that the output distortion does not exceed the specified value, referred to as MPO.
â— Peak music output power (PMPO): refers to the instantaneous maximum power that the power amplifier can output without considering the distortion. The peak music output power is generally 5-8 times the root mean square (RMS) power.
For users, the only thing that really makes sense among the above output powers is the rated output power. Only at this power, the power amplifier can continuously output music signals without (low) distortion. This is the real power. Generally not big. Due to the direct correlation between output power and cost, many low- and mid-range speakers are calculated in (RMS), and their output power is pitifully small, and they lack the temptation to ignorant customers, so many manufacturers evade the rated output power. Among these types of power, the most boring is the peak music output (PMPO) power. Its test conditions are to relax the distortion limit and extremely short moments (usually in milliseconds). In fact, who can tolerate sound without distortion, and what kind of music lasts only a few milliseconds? Therefore, for practical use, this kind of power is meaningless, but it is abused by profiteers. It is no wonder that some people call it JS (profiteer) power.
Most active speakers currently use power amplifier integrated circuits. Therefore, if you want to know the maximum output power of the active speaker (referring to the power amplifier part, not including the power supply), you only need to find out the model of the power amplifier integrated circuit used. The parameters of some commonly used power amplifier integrated circuits are listed below for reference:
model | Power (w) / distortion / impedance (Ω) | Power / distortion / impedance | Manufacturer | Recommendation (5 stars) |
TDA1521 / 2616 | 12 x 2/1% / 8 | 15 x 2/10% / 8 | Philips | ★★★ |
TDA2030A | 12 / 0.5% / 8 | 18 / 0.5% / 4 | ST | ★★ |
TDA7269 | 10 x 2/10% / 8 | ST | ★★★ | |
TDA7370 | 6.5 x 4/10% / 4 | ST | ★ | |
TDA7294 | 70 / 0.5% / 8 | 100/10% / 8 | ★★★★ | |
LM1875 | 20 / 0.015% / 8 | 25/1% / 8 | NS | ★★★★ |
LM1876 | 20 x 2 / 0.1% / 8 | NS | ★★★ | |
LM3886 | 50 / 0.1% / 8 | 68 / 0.1% / 4 NS | ★★★★ |
Note: ST's original TDA2030A is a very good power amplifier IC, but most manufacturers use their compatible models, and the sound quality and reliability are not as good as the original products, so only two stars are given in the recommendation.
(2): Speaker rated withstand power: No matter how high the power of the amplifier is, the speaker can't bear it is also a white. This is also an important factor restricting the actual output power of active speakers.
(3): Power supply effective output power: usually refers to the rated output power of the power transformer, which is a very important parameter. Because most power amplifier integrated circuits work in Class A and B states, the output power of the power amplifier generally does not exceed 70% of the power output power.
For an active speaker system, its output power is determined by the smallest of the above powers (typical bottleneck effect). If no more information can be found, the effective output power can also be estimated based on the price of the speaker. According to experience, the effective output power of low-end (less than 500 yuan) active speakers generally does not exceed one-tenth of its selling price (units are watts, not counted as slaughter), and high-end (more than 500 yuan) active speakers The effective output power generally does not exceed 15 to 20 times of its selling price. This empirical value is relatively accurate in most cases, because the loss-making traders will not do it. For general multimedia applications, it is basically sufficient to have 5-10 watts of power speakers per channel. If you have high requirements for sound quality, it is recommended to buy active speakers with more than 20 watts per channel.
2: S / N ratio:
The signal-to-noise ratio refers to the ratio of the maximum undistorted output voltage of the power amplifier to the residual noise voltage. The unit is decibel. It is a parameter that reflects the noise level of the active speaker, and it is also an important sign that reflects the design and manufacturing level of the active speaker manufacturer. Speakers with low noise may not sound good, but speakers with high noise must not be good. The signal-to-noise ratio must be at least 75 decibels or more to have a good playback effect. You can unplug the signal cable and turn the volume to the maximum when purchasing. If you can't hear the noise outside 20 cm, you can pass the level.
3: Frequency range:
The frequency range of the sound that can be directly heard by the human ear is about 20-20000Hz. With today's speaker technology, it is no problem to reach a high frequency of 20,000Hz, but it is very difficult to extend the low frequency end to 20Hz without distortion. Most The frequency range of low- and mid-range active speakers is about 100-16000Hz, and the frequency range of high-end active speakers is up to 50-20000Hz. Active speakers with a general frequency range of 80-16000Hz can be qualified for ordinary multimedia applications. If you have higher requirements for sound quality or for movie appreciation, it is recommended to purchase a lower limit of low frequency that can be extended to 40-50Hz, and high frequencies can be extended straight Active speakers up to 20000Hz. The parameters of the frequency range can be found in the product's publicity materials, but the indicators of some manufacturers are seriously untrue. Some speakers with only one or two hundred yuan dare to mark the frequency range to 20-20000Hz, but in fact they can be straight and not Loudspeakers that replay this frequency range with distortion can't find a few pairs in the world, so don't take it seriously. Readers can bring some records that are rich in high and low frequencies and familiar with them when they buy, and they can also use test CDs or test software with standard frequency signals such as "Davids Audio Sweep Generator" or "Audio100 Audio" Tester "audio tester software for testing.
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