At the heart of the problem is that speakers are not operated in isolated environments, but many speaker designers and Hi-Fi audio enthusiasts tend to ignore this. Designers always develop their anechoic chambers from the actual environment. product.
Practice has proved that the sound quality of the speaker has a very close interaction with the actual listening room, especially in the bass band. As we all know, the frequency range of human ear listening is about from the lowest sound of 20Hz to the highest sound of 20000Hz, the span is about 10 octaves, and the central C sound of the piano is located at the fourth octave from the lowest sound. central. Therefore, the bass zone itself is almost confined to the lowest octave (20Hz~40Hz) and the second octave (40~80Hz) above it, although the pure bass does not hear too much in real life. But it plays an important role in creating the realism and strength of music.
If you don't use a subwoofer and rely on ordinary speakers to create a bass, the speakers are not only bulky but also very bulky. The subwoofer has many advantages, such as its small size, its unobtrusive appearance in the room, its own amplifier and filter in the box, and no additional requirements on the system. The system has a subwoofer that reproduces the bass, and the other channels can use smaller speakers. The entire system is more flexible and convenient to configure and use.
In general, creating a bass requires a larger speaker, but simply placing a pair of small, ordinary speakers on the wall is enough to make the replayed sound dive into the mid-bass range. Part of the reason is that it is placed on the wall to help boost the bass from 50Hz to 100Hz. The other reason is that the "standing wave resonance" caused by the shape and size of the room provides a "room gain effect." The common problem with most commercially available subwoofers is that the low-end roll-off frequency can't dive below 50Hz, the frequency response can't match the normal speakers of other channels, and their partial frequency response often constitutes harmful overlap. phenomenon.
Standing wave effect
Each room, whether it is a concert hall or the living room of an ordinary family, has a standing wave phenomenon, which is the main source of the problem of bass playback. The standing wave frequency is closely related to the size of the room. In a concert hall with a large indoor space, the standing wave frequency occurs in the lowest subwoofer and infrasound zone, which is lower than the lowest frequency of the bass instrument, and thus does not adversely affect the bass reproduction.
However, in the small living room of an ordinary family, since the size and space of the room are small, the standing wave frequency generated is high and enters the low range of the music, and overlaps with the latter, which deteriorates the sound quality. Standing waves provide "room gain" while also making the frequency response of the low range very uneven, ie it will increase the response of some of these frequencies to offset the response of some other frequencies. In addition, different rooms have different standing wave modes, and it is related to many factors such as wall materials, furniture furnishings, listening position and speaker placement in the room, and it is difficult to accurately predict it. Welcome to China Home Theater Network
Create bass in the room
As we all know, in order for the speaker to make a sound, it is necessary to use the vibration of the cone to move the air molecules, and in the air, the sound waves having the same frequency as the vibration of the cone are excited. Due to the low frequency of the bass, the vibrating speed of the woofer cone is also very slow. Therefore, to generate a strong bass in the room, the cone must move a large amount of air molecules per unit time. To this end, subwoofers typically use large diaphragms, small-stroke cones or small diaphragms, and large-stroke cones. The latter's small diameter of the cone is conducive to reducing the volume of the entire subwoofer, and has the advantages of high power and loudness, and has become the mainstream of modern subwoofers.
However, the subwoofer is housed in a large speaker, although it can reproduce some special sound effects such as some shocking explosions and landslides in the movie, but when playing music, the playback is high. The intensity of the bass will be very unpleasant. In addition, research and practice results have proven that making the subwoofer louder than other speakers in the system does not make much sense. These are the reasons why modern subwoofers are made smaller.
Subwoofer placement and connection
The inherent variability and unpredictability of indoor standing waves make it impossible for people to tolerate them. Although some computer software provides some interesting methods of controlling standing waves, it does not completely solve the standing wave problem. Fortunately, the wavelength of the bass is much larger than the size of an ordinary room, and the bass is actually not directional. With this feature, the average user can use almost a single subwoofer to get almost unlimited freedom to experiment with the best placement of the subwoofer indoors.
Although its placement is not as important as the main speakers, the different placements still have different acoustics. The following describes the positioning methods of the three subwoofers, each of which has its own advantages and disadvantages, the reader can choose according to the experimental results.
Place the subwoofer in the corner. This way helps to avoid the acoustic reflections in the room, making the reproduced sound clearer and more vivid. However, at this time, the indoor mode is more excited, which makes the bass response not flat enough. Since the subwoofer in the entire system is farthest from the listening position, the bass heard will be slightly delayed than the sound of the main speaker. When placed, the subwoofer should be at least 10cm away from the wall.
Place the subwoofer on the same line as the main speaker. At this point, the distance between the subwoofer and the main speaker and the listening position is equal, so the direct sound from the three speakers reaches the listener's ear almost simultaneously, and there is no time difference. The disadvantage of this type of placement is the increased amount of reflected sound in the room, and these delayed reflected sounds reduce the clarity of the reproduced sound.
Place the subwoofer in a position close to the listening area. This method is worth a try, especially for some rooms that are difficult to get the best sound, because it minimizes the incentive of the indoor mode, and also greatly shortens the direct transfer path and bass to the listener's ear. The time, but at the same time also makes the indoor reflection sound more blurred.
Another unscientific placement method is to place the subwoofer on the usual listening seat and let it play music, then move slowly around it and listen to the music carefully until you find the bass sound quality. A little better. This is the best place to place the subwoofer, and finally place it there.
In addition to the two high-level (speaker level) output terminals that connect the left and right main channel speakers, the modern home theater AV amplifier also has a low level (line level) output terminal, active subwoofer. Then there is an input terminal corresponding thereto. In order to make the system have the best sound effect when playing music and movie programs, in addition to connecting the two sets of speaker level input terminals of the subwoofer to the corresponding output terminals of the AV amplifier, the line level of both should be The terminals are also connected correspondingly as shown in FIG. The advantage of this connection is that the bass is effectively enhanced when the system plays two different programs, two-channel stereo music and 5.1-channel movies.
Some controversy about bass
At present, there are some controversies about the role and effect of bass. One of the easier-to-understand points is that “subwoofers can enhance the bass of the sound system.†However, many people think: “Adding extra bass can improve the characteristics and sound quality of the midrange and even the high audio segmentâ€, “Use Subwoofers can improve the depth of the stereo sound field." "Increased bass expansion can disrupt the original function of the main speakers. If you deliberately select the relative levels of the bass and treble, you can also cancel them on both sides of the middle audio section." ...and so on, these views are quite difficult to understand.
Although it is difficult to make scientific explanations for these views, there are many "evidences" that are widely circulated. Some psychoacoustic phenomena are often difficult to understand, and history shows that in the development of high fidelity technology, some subjective methods are often more authoritative and influential than theoretical assumptions. From this point of view, many problems in the field of audio still have to be further explored.
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