Power is actually a basic parameter to measure the performance of a multimedia speaker, but it has become a meaningless parameter in the description of many products because of the intentional avoidance of manufacturers.

The marked power of multimedia speakers mainly includes the following contents:

1, Rated Output Power (RMS):RMS power can be said to be the only truly meaningful power labeling method. Refers to the maximum power that the power amplifier circuit can continuously output within the rated distortion range. Also known as "effective". When discussing the power amplifier circuit in the previous section, we usually refer to the rated output power.

2. Music output power (MPO): refers to the instantaneous maximum output power of the power amplifier circuit under the condition that the distortion does not exceed the specified range.

3. Peak music output power (PMPO): refers to the instantaneous maximum output power of the power amplifier without considering distortion.

In fact, the latter two forces are meaningless, because their so-called "moments" are often a few milliseconds that are simply inaudible. However, many manufacturers are still willing to use these two kinds of labels, especially PMPO power, out of the hope of increasing product power. Most speakers on the market, such as hundreds of watts, are like this, and some even mark their own power as 2000 watts!

This is really a joke! The real 2000-watt amplifier and speakers are enough for everyone in your community to hear your music, and even the real 300-watt speakers are enough to make the whole building restless. Can a small desktop speaker do it? No wonder PMPO power supply is nicknamed "JS power supply" by enthusiasts.

According to the general practice, the ratio of PMPO power to RMS power is generally 5-8: 1, that is to say, a speaker with a nominal power of 300W is actually just an ordinary speaker with an output power of about 30W!

Real famous brand manufacturers will not use PMPO power supply. If the product is really excellent, why use this disguise? Therefore, seeing PMPO's logo at least shows that manufacturers have insufficient confidence in this product.

Besides the power amplifier, the power parameters in the multimedia speaker also include the maximum bearing power of the speaker and the maximum output power of the power supply. The smallest of these three parameters is the maximum output power of the speaker, and there is also a certain collocation relationship among these three parameters. For example, the root mean square power must be less than the maximum bearing power of the speaker, otherwise the speaker will be burnt out, and the maximum output power of the power supply must be at least 150% of the root mean square power. The extra 50% is the so-called "power reserve", otherwise the sound will be distorted when the volume is loud or dynamic (this problem exists in a large number of speakers on the market).

Second, the frequency range and frequency response

These are two basic parameters to identify the speaker's voice reproduction ability. The former refers to the range between the lowest effective playback frequency and the highest effective playback frequency of the speaker, in hertz (Hz); The latter refers to the phenomenon that the sound pressure generated by the loudspeaker increases or decreases with the frequency change and the phase changes with the frequency when the loudspeaker system is connected with a constant voltage audio signal. This relationship between sound pressure and phase and frequency is called frequency response, and the unit is decibel (dB).

Generally speaking, there are many frequency ranges marked on multimedia speakers. The larger the scope, the better the effect. But the problem is that many products are not labeled as "the frequency range of speakers", but as "the frequency range of power amplifier circuits". As a result, values covering the human hearing range, such as 20Hz-20KHz, appeared.

The principle of ordinary (trumpet) sound

In * * * vibration mixed sound, sound principle, using vibrator vibration sound+paper eardrum speaker sound, we often use audio people know that ordinary audio is not enough except professional audio, generally good bass volume is not small, mainly because the sound of using speakers is greatly affected by the size of the sound generating unit, so many multimedia audio directly use subwoofers and external speakers. Fully expand the volume range of its sound generating unit, but this will greatly limit the shape of the sound, which is why the sound we see in the market is generally square, angular and the bass effect is not very good.

Acoustic interpretation

Auditory psychology

A tree fell in the forest and made a loud noise, but there was no one in the virgin forest, so no one heard it. Is this a sound? The sound is definitely coming, because when the trunk and branches touch the ground, they will all produce some sounds, but no one will hear them, but the sounds are different for humans or other animals, so this is what acoustics calls psychology.

Principles and history of acoustics

The principle of acoustics I'm talking about here is mainly to let a Andhadhun know all aspects of acoustics, not to do acoustic research or master's or doctoral thesis on acoustics, so the acoustic theory I'm talking about in this book can actually be used by people who operate acoustics on the spot.

In 19 15, an American named E. S.Pridham put a telephone monitor at that time on a speaker that could play recordings. When the sound could be heard by a group of people celebrating Christmas in San Francisco, electroacoustic was born. After the end of World War I, at the inauguration ceremony of President Harding in the United States, Bell Company of the United States connected the receiver of mobile phone to the speaker of the record player at that time, which could transmit the sound to a large group of people watching the inauguration ceremony of the president. Therefore, many professional sound research and sound reinforcement projects have been developed. Sound researchers not only strive to improve sound equipment, but also do various experiments on different sounds to understand human responses to hearing. However, the most advanced audio researchers understand that acoustics should be studied as a whole, and they should understand every link of audio equipment, and

Audio equipment probably includes power amplifier, peripheral equipment (including voltage limiter, effector, equalizer, exciter, etc. ), speakers (speakers, speakers), mixers, audio sources (such as microphones, musical instruments, VCD, DVD) display devices, etc. Among them, the speaker is a sound output device, a speaker, a subwoofer, etc. A speaker includes high, low and medium.

Main characteristics of digital audio

1, high signal-to-noise ratio

The recording form of digital audio is binary coding, and only need to judge "0" or "1" when playing back. Therefore, the noise of the recording medium has little influence on the signal-to-noise ratio of the reproduced signal. The recording form of analog audio is a continuous audio signal, which will be affected by noise such as tape during recording and playback. If it is superimposed on the audio signal, the sound quality will become worse. Although noise reduction measures have been taken for analog audio, they cannot be eliminated fundamentally.

2. Low distortion.

In the process of analog audio recording and playback, the nonlinearity of magnetic head will introduce distortion. Therefore, measures such as AC bias magnetic recording must be taken, but the distortion still exists. In digital audio, the magnetic head only works in magnetic saturation or non-magnetic state, which means 1 or 0, and there is no linear requirement for the magnetic head.

3, good repeatability

The sound quality of digital audio equipment will not deteriorate after repeated copying and playing. Every time the traditional analog cassette tape is re-recorded, the noise recorded by the tape will increase, which will reduce the signal-to-noise ratio by about 3 dB. The sub-band is not as good as the master tape and the solar tape is not as good as the sub-band, and the sound quality will deteriorate one after another.

4, the sloshing rate is small.

Because sometimes the instability of the base correction circuit, the rotating system and the driving system will not cause chattering in the digital audio playback system, there is no need for a precise mechanical system as in analog recording.

5, strong adaptability

Digital audio records binary codes, and all kinds of processing can be carried out as numerical operations. It can be operated only by software without changing hardware, which is convenient for microcomputer control, so it has strong adaptability.

6, easy to integrate

Because of digitalization, it is convenient to adopt VLSI, the whole machine is convenient to debug, with stable performance and high reliability, which is convenient for mass production and can reduce the cost.