Does speaker placement affect frequency response testing?

The premise of enjoying good music is to restore the music through the equipment. Since it needs to be restored through the equipment, audio technology is very important. If the application, debugging, and matching of audio is a lesson, then a nearly flat frequency response curve is the first lesson to get started. We can obtain a good frequency response curve in different room environments by positioning the speakers, so that we can hear more abundant information to make a correct and intuitive judgment on the sound of the speakers. Next, I would like to prove my point through the test results of a pair of 3-inch full-range speakers at a distance of about 2.8 meters.

So what changes will occur when a 3-inch speaker is placed in different positions on a 60-centimeter-high metal stand?

Figure 1: The internal distance between the two speakers is more than 2 meters. The approximate frequency response at the emperor's seat is shown in the figure.

The speaker is facing forward, and we can see obvious changes in the frequency above 1.8KHZ. The sinking frequency attenuates the original music information, and we can't hear the attenuated information, or we can only feel it faintly. The sound of 1.8K is already considered a high-pitched area in the ear.

Figure 2: The distance between the two speakers is reduced to about 1.7 meters. The speakers are still facing forward.

At this time, the concave frequencies in most areas are basically flattened. In fact, the listening experience also adds a lot of high-frequency information, and the labiodental sounds are better. The wind instruments are natural, and the positions of instruments and vocals in the sound field distribution are accurate. The positioning ratio of the front and rear instruments is symmetrical. Achieving the effect of this picture is no problem for listening to most music. The deep and steep attenuation at 8K is generally difficult to detect. If there is no equipment with a flat frequency response for comparison, it is impossible to distinguish by ear!

Figure 3: Carefully bend the speaker inward at a slight angle. This way, the speaker and the emperor seat form a small angle. When testing the speaker, this should be considered an axial response, and it is also the flattest frequency response in the factory anechoic chamber test.

The off-axis response of a small-caliber full-range speaker is ugly. If you use a straight position for a small-caliber full-range speaker, it depends on the relationship between the listening distance and the speaker's central axis. If the speaker cannot be moved, then the position of the person can be moved, right? Haha. A tree that is moved will die, but a person who is moved will live! The advantage of doing this is that the steep attenuation pit becomes wider and the attenuation becomes smaller! The ears cannot hear this subtle change!

Every audiophile is pursuing perfection. If you don’t see the picture, the pitfall of 8K will not affect your psychology, but what if you see it? You will feel very uncomfortable. I didn’t hear it, I didn’t see it, nothing happened. But we saw it. Obviously, moving the speaker is not an option, and the angle adjustment has been exhausted. So, I tried to raise the speaker and make it tilted upward. At this time... ..

As a small three-inch speaker, it can do this at a distance of about 2.8 meters. I can rest assured. The design of each speaker is different, and the placement is not fixed. Three inches to four inches is different! If you want to hear more and richer information than others, you can't just spend money to buy expensive amplifiers and expensive speakers. The quality of the equipment is certainly important, but the sound of the equipment is affected by the environment after all, and the information reproduced is for people. As long as we master some methods, we can adjust the balanced sound in different environments by interactively applying means such as listening and actual measurement.

Before I finish, I want to answer one more question: What is the relationship between the frequency response and the sound field expression at the listening position? Is it that if the frequency response is good, the sound field will naturally be good, or is it that the frequency response will not be too different after the sound field is adjusted? Or is there another factor?

In my opinion, frequency response and sound stage are not necessarily related, but in ordinary environments (most people's homes) there is indeed a necessary connection between them!

For example, if we push the speaker to the corner, the low frequency of 63-250 will swell up, and the low frequency reverberation time will be longer. The depth of the sound field tends to be flat. A box with weak low frequency will have low frequency when pushed to the corner, such as a small three-inch speaker.

If the speaker is embedded in the wall, it will be another case. In this case, the area behind the cabinet is infinite, which cancels out the reverberation reflection behind the cabinet. The sound we hear minus the speaker and system distortion is basically close to the original state. In this case, the wall can be regarded as an infinite baffle!

If the speaker is moved away from the front wall, the relationship between the speaker and the front wall is the superposition of the speaker's direct sound and the room's reflected sound. Therefore, the speaker's position determines the starting point of the room's overall reverberation characteristics. It can be seen that the speaker's position affects the acoustic changes and thus affects the frequency response changes.

The above is a theoretical statement. The real environment we live in is mostly irregular. So we have to rely on some means to find the balance. Flat frequency response is a prerequisite. The sound field is a virtual effect of the superposition of room reverberation and direct sound, so different houses have different sound fields. It is impossible to make comparative measurements.

If there is no measuring equipment, the comparison method is to use ears. You can use the monitoring headphone system to make adjustments, mainly by listening to the peak and valley characteristics of the instruments in the frequency band. You must have a reference object to adjust the sound to get twice the result with half the effort.

Special reminder: The frequency response of the speaker cannot represent the performance of the speaker's tone. A flat frequency response is the first priority of HIFI. If we can't even hear the sound information fully when sitting in the emperor's seat, how can we talk about HIFI? From the side, it reflects that using the speaker position to obtain a balanced response is the most basic foundation of HIFI audio!