When it comes to speaker parameters, power is the most mentioned by us. It is even easy to see that two speakers of the same power have completely different performances at medium or higher volume, and sound distortion occurs from time to time. Is this set of data related to power output again "digital" game"?
The main function of the power amplifier in the speaker is to amplify the signal and provide enough power for the load (speaker). The impact of the power amplifier on the sound quality mainly depends on whether the input signal can be amplified and transmitted without distortion, so as to provide enough power to the load. The signal amplified and transmitted by the power amplifier is different from the simple harmonic signal, and is a complex signal that changes instantaneously.
If we look at the signal from the waveform, the original signal has many spikes, and their energy is not large, but the peaks are very sharp and very high. These spikes contribute little to loudness, but have a great impact on sound quality. If clipping occurs, the amplified sound sounds dry and stiff. This has a certain relationship with the details in the subjective listening that we usually say. If during power amplification, only pay attention to the energy transmission (the corresponding amount is loudness), and not pay attention to the change of the waveform during the transmission process (causing distortion), then we may hear the sound very loud but not good.
For active speakers, the power amplifier part is built inside the speakers, and the work it has to do is also to drive the speakers and bring enough output power to the speakers. And what we have seen about the nominal writing of speaker power is not very standard. Generally speaking, the power of speaker manufacturers labeled "speaker" refers to the "output power (RMS)" of the power amplifier (the power amplifier circuit part of active speakers) , RMS (root mean square) refers to the root mean square, currently in the multimedia speaker label, most of the root mean square power.
Root mean square power is different from average power and rated power. The specific algorithm is to take the average of the square of the power value of each point of the sample and then extract the square. How to calculate the specific root mean square will not go into details for now. What we need to discuss next is the relationship between "root mean square" power and rated power and speaker power .
As mentioned earlier, the signal amplified by the power amplifier is a complex signal. According to the survey results of a variety of musical instruments and program signals of different dramas in acoustic engineering, the maximum root mean square power of most program signals (that is, the peak of the program signal— The ratio of the peak power on the load) to the average root mean square power (that is, the average power of the program signal on the load) is 3 to 10, up to 12.7.
If the rated power of the power amplifier corresponds to the average root-mean-square power of the program signal, the maximum output power of the power amplifier should be 3-10 times to ensure that the output signal does not appear to be clipped. This is the reason why we choose the power of the power amplifier to be much larger than the average root mean square power of the amplified program signal. This is what we usually call the power reserve.
Judging from the current low-end products, the maximum output power of the power amplifier should be less than 10 times the power reserve of the signal root mean square power. The power reserve is definitely different when designing. This is one of the reasons why we will encounter distortion problems at different or higher volumes during our usual tests. On the other hand, when labeling the power of multimedia speakers, it is rarely stated whether the power is rated power, maximum output power, output RMS power or even speaker power. This is a very confusing parameter index.
In addition, if we pay attention to the nameplate on some speakers, there is also a power-related value on it. What is the relationship between this value and the output of the power amplifier? In the design document, we can see the following statement: "In order to ensure the safety of the speaker system connected to the power amplifier, the rated output power of the power amplifier is required to be equivalent to the nominal power of the connected speaker system", "In order to ensure sufficient The power reserve is usually 1.2~2 times the power of the loudspeaker. This formulation is actually incorrect. The power of the power amplifier is not the same concept as the power of the speaker.
The output power of the power amplifier generally refers to the sinusoidal output power under certain distortion constraints. The manufacturers we usually see indicate that the required total harmonic distortion is 0.1% after the power. The output voltage when the output signal on the rated load of the power amplifier reaches this distortion is called the maximum output voltage. This voltage is used to calculate the power amplifier. The output power is the nominal output power of the power amplifier, which can also be understood as the maximum output power of the power amplifier.
The nominal power of the speaker is often provided by the manufacturer as the pink noise power, which refers to the power that is fed to the specified analog program signal within the rated frequency range of the speaker and works continuously for 100 hours without heat and mechanical damage. Obviously, these two powers are regulated and tested from completely different angles, and the two are incomparable. If the manufacturer can provide the sine power of the speaker (referring to the power fed when a sine signal is used as the test signal), the two are comparable.
However, manufacturers generally do not provide this data. So, for speakers, is there a certain corresponding relationship between the pink noise power of the speaker and the sinusoidal power? The answer is-no! The pink noise power and sinusoidal power of the speaker are completely different for speakers of different structures, materials and specifications, and the latter is also related to the frequency. Therefore, it is not advisable to compare the power of the power amplifier with the nominal power of the speaker to characterize its power reserve in the design of speakers and power amplifiers.
Obviously, it doesn't make any sense to compare the numbers of speaker power and amplifier power. From the above, everyone can also understand that the current topics we are talking about whether the power is sufficient and whether the power reserve is sufficient can basically only be based on the subjective listening experience. It is really meaningless to look at the labels on the speakers, because Everyone's labeling methods are not standardized, and the standards are different, so naturally there is no comparability.