When it comes to the parameters of speakers, power is the most commonly mentioned. Although in recent years, people have not exaggerated the peak power of PMPO and have not seen power values of hundreds or even kilowatts displayed in speakers, can the power of multimedia speakers be truly reliable at present? We can easily see that two speakers with the same power have completely different performances at medium or high volumes, and the distortion of sound occurs from time to time. Is this set of data related to power output a "digital game"?
The main function of a power amplifier in a speaker is to amplify signals and provide sufficient power to the load (speaker). The impact of power amplifiers on sound quality mainly depends on whether the input signal can be amplified and transmitted without distortion, providing sufficient power to the load. The signal amplified and transmitted by a power amplifier is different from a harmonic signal and is a complex signal with instantaneous changes.
If we look at this signal from the waveform, the original signal has many peaks with low energy, but the peaks are very sharp and high. These peaks contribute little to loudness, but have a significant impact on sound quality. If there is a wave clipping, the amplified sound will make people feel dry and hard. This is related to the details in objective listening that we usually refer to. If we only pay attention to the transmission of energy (corresponding to loudness) during power amplification, and do not pay attention to the changes in waveform during transmission (resulting in distortion), then we may hear a loud sound but not pleasant.
For active speakers, the amplifier is located inside the speaker and its job is to drive the speaker and provide sufficient output power to the speaker. However, the nominal writing of speaker power that we see is not very standardized. Ordinary speaker manufacturers label the power of the "speaker" as the "output power (RMS)" of the power amplifier (the power amplification circuit of the active speaker), where RMS (root mean square) refers to the root mean square power. Currently, in the labeling of multimedia speakers, it is mostly the root mean square power.
Root mean square power is different from uniform power and rated power. The detailed algorithm is to take the mean square of the power value of each point in the sample and then square it. We will not delve into how to calculate the root mean square for now. What we need to discuss next is the relationship between the "root mean square" power, rated power, and speaker power.
As mentioned earlier, the signal amplified by a power amplifier is a complex signal. According to the investigation results of various instruments and different types of program signals in acoustic engineering, the ratio of the maximum root mean square power (i.e. the peak to peak power of the program signal on the load) to the uniform root mean square power (i.e. the uniform power of the program signal on the load) of most program signals is 3-10, with a maximum of 12.7.
If the rated power of the power amplifier corresponds to the uniform root mean square power of the program signal, then the maximum output power of the power amplifier should be 3-10 times to ensure that the output signal does not exhibit clipping. That's why we choose power amplifiers with much higher power than the uniform root mean square power of the amplified program signal, which is also commonly referred to as power storage.
From the perspective of current low-end products, the maximum output power of power amplifiers should not be able to achieve a power storage of 10 times the root mean square power of the signal. Therefore, power storage is definitely different when designing. This is one of the reasons why we encounter distortion problems at different or higher volumes during regular testing. On the other hand, multimedia speakers rarely specify the rated power, maximum output power, output RMS power, and even speaker power when labeling power, which is a very chaotic parameter indicator.
Additionally, if we pay attention to the nameplates on some speakers, there is also a power related value on them. What is the relationship between this value and the output of the power amplifier? In the design document, we can see the following statements: "In order to ensure the safety of the speaker system connected to the power amplifier, it is requested that the rated output power of the power amplifier be equivalent to the nominal power of the speaker system connected." "To ensure sufficient power storage, a power amplifier with 1.2 to 2 times the speaker power is usually selected. This statement is incorrect in practice, as the power of a power amplifier and the power of a speaker are not the same concept.
The output power of a power amplifier generally refers to the sine output power under certain distortion constraints. The manufacturers we usually see indicate a total harmonic distortion of 0.1% after the power output. When the output signal of the power amplifier reaches this distortion at the rated load, the output voltage is called the maximum output voltage. Using this voltage to calculate the output power of the power amplifier 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, often provided by manufacturers, is the pink noise power, which refers to the power that can be fed with a regular simulated program signal within the rated frequency range of the speaker, and can work continuously for 100 hours without generating heat or mechanical damage. Obviously, these two powers were formulated and tested from completely different perspectives, and they are incomparable. If the manufacturer can provide the sine power of the speaker (referring to the power fed when using a sine signal as the test signal), then the two are comparable.
However, manufacturers generally do not provide this data. So, for speakers, can there be a certain correspondence between the pink noise power and sine power of the speaker? The answer is - no! The powder noise power and sine power of a speaker are completely different for speakers of different structures, materials, and specifications, and the latter is also related to frequency. Therefore, it is not advisable to compare the power of the power amplifier with the nominal power of the speaker in the design of speakers and amplifiers to characterize their power storage.
Obviously, comparing the speaker power to the amplifier power has no meaning. As you can also understand from the previous text, the topics we are discussing about whether similar power can be sufficient and whether power storage can be sufficient can only be based on objective listening experience. It is meaningless to see the authenticity of the labeling on the speaker because everyone's labeling methods are not standardized and the norms are different, so there is naturally no comparability.
