When it comes to speaker parameters, power is the most mentioned by us. Although in the past few years, everyone has not talked about the peak power of PMPO, nor has it been seen that the power value of hundreds of kilowatts is often presented in the speakers, but can the current power of speakers and multimedia speakers be really credible? We can easily see that two speakers with the same power have completely different performances at medium or high volume, and sound distortion is even more frequent. 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 simple harmonic signal and is a complex signal with instantaneous changes.
If we look at this signal from its waveform, the original signal has many spikes, their energy is not large, but the peaks are very sharp and high. These peaks have a small contribution to loudness, but a significant impact on sound quality. If clipping occurs, the amplified sound sounds dry and hard. This has a certain relationship with the details in what we commonly refer to as objective listening. If during power amplification, we only pay attention to the transmission of energy (corresponding to loudness) and do not pay attention to the changes in the waveform during the transmission process (resulting in distortion), then we may hear a loud but unpleasant sound.
For an active speaker, the power amplifier is partially located inside the speaker, and its job is also to drive the speaker and bring sufficient output power to the speaker. However, the nominal wording of speaker power we see is not very standardized. Ordinary speaker manufacturers label the power of "speakers" as the "output power (RMS)" of the power amplifier (a part of the power amplification circuit of an active speaker), while RMS (root mean square) refers to the root mean square. Currently, in multimedia speaker labeling, most of them are labeled as root mean square power.
The root mean square power is different from the uniform power and rated power. The detailed algorithm is to take the mean square of the power values at each point in the sample and then square it. We will not delve into the calculation of the root mean square for now. What we need to discuss next is the relationship between the "root mean square" power and rated power, as well as speaker power.
As mentioned earlier, the signal amplified by a power amplifier is a complex signal. Based on the investigation results of various instruments and program signals from different genres 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 a large part of the program signal 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 that to ensure that the output signal does not exhibit clipping. This is why we choose a power amplifier with a 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 current low-end products, the maximum output power of power amplifiers should not be able to store power 10 times the root mean square power of the signal, and power storage is definitely different when designing. This is one of the reasons why we encounter distortion issues at different or higher volume levels during normal testing. On the other hand, when labeling the power of multimedia speakers, there is little clarification on whether this power is rated power, maximum output power, output RMS power, or even speaker power, which is a very chaotic parameter indicator.
Additionally, if we pay attention to the nameplates on some speakers, which also have a value related to power, what is the relationship between this value and the output of the power amplifier? In the Software design description, we can see the following statements: "In order to ensure the safety of the loudspeaker system to which the power amplifier is connected, the rated output power of the power amplifier is requested to be equivalent to the nominal power of the loudspeaker system to which it is connected", "In order to ensure sufficient power storage, the power amplifier with 1.2~2 times of the loudspeaker power is usually selected", etc. This formulation is incorrect in practice, as the power of a power amplifier is not the same concept as the power of a speaker.
The output power of a power amplifier generally refers to the sinusoidal output power under certain distortion limitations. We usually see that manufacturers indicate that the regular Total harmonic distortion is 0.1% after the power. When the output signal of the power amplifier on the rated load reaches this distortion, 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, which is often provided by manufacturers, is the powder noise power, which refers to the power that is fed within the rated frequency range of the speaker, with a regular simulated program signal, and operates continuously for 100 hours without generating thermal or mechanical damage. Obviously, these two powers were regulated and tested from completely different perspectives, and the two are incomparable. If the manufacturer can provide the sinusoidal power of the speaker (referring to the power fed back when using a sinusoidal signal as the test signal), then the two are comparable.
However, manufacturers generally do not provide this data. So, can there be a certain correspondence between the powder noise power and sinusoidal power of speakers? The answer is - no! The powder noise power and sine power of speakers are completely different for different configurations, materials, and specifications of speakers, and the latter is also related to frequency. Therefore, it is not advisable to compare the power of power amplifiers with the nominal power of speakers in the design of speakers and amplifiers to characterize their power storage.
Obviously, comparing the power of the speaker with the power of the amplifier in numbers is meaningless. From the previous text, everyone can also understand that the current topic of whether similar power is sufficient and whether power storage is sufficient can only be based on objective listening experience. It is meaningless to see the authenticity of the labels on the speaker. Due to different labeling methods and specifications, there is naturally no comparability.
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