The premise of listening to music is to restore through equipment. Since it is necessary to restore through equipment, sound technology needs to have meaning. If the application, matching and debugging of the sound is a homework, then the near-flat frequency response curve is the first lesson.
Through the placement of the speakers, we can get a good frequency response curve in different room environments, hear more information, and make correct and intuitive judgments on the sound of the speakers. Below I want to prove my point of view by testing the results of a pair of 3-inch full-range speakers at a distance of 2.8 meters.
Then a 3-inch speaker, on a metal stand with a height of 60 cm, will there be any changes in the position of the different positions?
Figure 1: The internal spacing of the two speakers is more than 2 meters. At this time, the approximate frequency response of the emperor is shown in the figure. 
The horn is in the straight forward direction. We will see that there are obvious bump changes above 1.8KHZ. Then the frequency of sag attenuates the original information of the music. We can't hear the information that is attenuated, or feel the information weakly. The 1.8K sound sounds like a high-pitched area in the ear.
Figure 2: Reduce the spacing between the two speakers to about 1.7 meters. The horn is still facing forward.
At this time, the frequency of the depression in most areas is substantially flat. In fact, the sense of hearing is also a lot of high-frequency information, and the lip-toothed sound is better. The natural performance of the gas-sounding instrument, the position of the instrument in the sound field distribution is accurate. The front and rear instruments are positioned symmetrically. The effect of reaching this picture is no problem for listening to most of the music. The steep abrupt attenuation at 8K is generally difficult to detect. If there is no comparison of the frequency and flat equipment, it can't be distinguished by the ear!
Figure 3: Carefully place the horn in a corner at a small angle. At this time, the horn and the emperor are at a small angle. When the speaker is tested, this should be considered as the axial response. It is also the straightest part of the factory anechoic chamber test. Frequency response . 
The off-axis response of small-caliber full-range is very difficult to see. If you play a small-diameter full-range straight position, it depends on the relationship between the listening distance and the center axis of the horn. If the horn can't move, then the position of the person can move? Ha ha. The tree is moved to death, and the people are moving! The advantage of this is that the steep attenuating pit is widened and the attenuation is reduced! The ears can't hear this subtle change!
Every enthusiast is pursuing perfection. If you don't see the map, you won't have an impact on your psychology, but you see it? I will feel very uncomfortable in my heart. Didn't hear it, didn't see it, nothing happened. But we saw it. Obviously, the mobile speaker is not acceptable, and the angle adjustment has been exhausted. Well, I tried to pad the horn and put it on the face. At this time... 
As a three-inch small speaker, this is done at a distance of 2.8 meters. I can feel at ease. The design of each speaker is different, and the position is not static. Three inches and four inches are different! I want to hear more and richer information than others. It is not just a matter of spending money on expensive amplifiers or expensive speakers. The quality of the equipment is of course important, and the sound of the equipment is subject to the environment, and the replay information is for people. As long as we master some methods, such as listening, measuring and other means of interaction, it is possible to adjust the balance of sound in different environments.
Before the end, I will answer another question: What is the relationship between the frequency response of the listening position and the expression of the sound field? It is natural that the frequency response is good, or is it that the frequency response is generally not too far? Or is there another factor?
In my opinion, there is no need to contact the frequency response and the sound field, but in the ordinary environment (most people's homes) there is indeed a necessary connection between them!
For a simple example, we push the horn to the corner of the wall. At this time, the low frequency will swell up around 63-250, and the low frequency reverberation time will become longer. The depth of the sound field tends to be flat. Low-frequency, low-thickness boxes push into the corners and there will be low frequencies, such as small three-inch speakers.
If the speaker is placed in the wall, it is another situation. At this time, the rear of the box is equal to the infinite area, which is to offset the reverberation reflection behind the box. The sound we hear is reduced by the speaker and system distortion, which is basically close. The status of the original work. At this time, you can think of the wall as an infinite baffle!
If the horn is pulled away from the front wall, the relationship between the horn and the front wall is the superposition of the horn direct sound and the room reflection sound. Therefore, the position of the horn determines the starting point of the overall reverberation characteristics of the room. It can be seen that the horn placement affects the acoustic changes and thus the frequency response .
The above is the theoretical rhetoric. The real environment we are in is mostly irregular. Then we have to rely on some means to find the balance, the straight frequency response is a prerequisite. The sound field is a virtual effect of room reverberation and direct sound superimposition, so the house is different and the sound field is different. Contrast measurements cannot be made.
There is no measuring device, using the method of ear contrast. It can be adjusted with the monitor headphone system, mainly to listen to the peak-to-valley characteristics of the instruments in the band. Adjusting the sound must have a reference to get twice the result with half the effort.
I especially reminded that the speaker frequency response can not represent the performance of the speaker sound, so the straight frequency response is the first priority of HIFI. If we are sitting in the emperor's position and the sound information is not comprehensive, how to talk about HIFI? Reflecting from the side, using the speaker position to obtain a balanced response is the most basic basis of HIFI audio!
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