Home theater soul - overweight subwoofer (subwoofer) Detailed

Replay bass is a very tricky thing, it gives the speaker designer and audio enthusiasts add a lot of trouble. But this is also a challenge, the potential return to fully prove that efforts to improve the bass playback is worth it (it turns out that starting from the subwoofer is the most obvious way to enhance the home theater effect).

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        The heart of the problem is that the speakers are not running in isolated environments, but many speaker designers and Hi-Fi audio enthusiasts tend to ignore this, designers are always with the actual environment isolated anechoic chamber to develop their product. Practice has proved that the sound quality of the speaker and the actual listening room has a very close relationship between the two, in the bass band this relationship is particularly close. As we all know, the frequency range of the human ear is about 20Hz from the lowest sound to 20000Hz the highest sound, the span of about 10 octaves, the piano center C sound is located in the lowest sound from the fourth octave central. Therefore, the bass zone itself is almost limited to the lowest octave (20Hz ~ 40Hz) and above the second octave (40 ~ 80Hz) range, although the simple bass in the real life is not too much But it plays a very important role in creating the realism and intensity of music.

        If you do not use subwoofer and completely rely on ordinary speakers to create a bass, this speaker is not only bulky, and very cumbersome. Subwoofer with a small size, placed in the room is not noticeable, the box with their own amplifiers and filters and thus no additional requirements on the system, and many other advantages. The system has a special reproduction of the bass subwoofer, other channels can use the smaller speakers, the entire system configuration and use are more flexible and convenient. Generally speaking, to create a bass need to use a larger speaker, but as long as a pair of ordinary small speakers placed on the wall, enough to make the playback sound dive to the bass range. Part of the reason is placed on the wall to help improve the bass 50Hz ~ 100Hz, another part of the reason is the shape and size of the room caused by the "standing wave resonance" provides a "room gain effect." Most of the commercially available subwoofer's common problem is that the low-end roll-off frequency can not dive below 50Hz, and its frequency response can not match the other speakers of the ordinary channel, and their partial frequency response often constitutes a harmful overlap phenomenon.


Impact of standing waves:

        Each room, whether it is a concert hall or an ordinary family living room, there are standing wave phenomenon, it is caused by bass replay the main source of the problem. The standing wave frequency is closely related to the size of the room. In the large chamber of the interior space, the standing wave frequency occurs in the lowest sink bass and infrasound areas, lower than the lowest frequency of the bass instrument, and thus does not adversely affect the bass playback. But in the ordinary family of small living room, because the size and space of the room are very small, the frequency of the standing wave will be higher and into the music bass area, and the latter overlap, so that the sound quality worse. The standing wave, while providing "room gain", also makes the frequency response of the bass area very uneven, that is, it will increase the response of some of these frequencies to offset some other frequency response. In addition, different rooms have different standing wave patterns, and it is with the room in the wall materials, furniture furnishings, listening position and speaker placement and many other factors, it is difficult to accurately predict it.


Create a bass in the room:

        As we all know, to make the sound of the loudspeaker, it is necessary to use the vibration of the cone to move the air molecules, in the air to stimulate the frequency and vibration frequency of the same sound wave. As the frequency of the bass is very low, the bass loudspeaker cone is also very slow, so to produce a strong bass in the room, it is necessary to make the cone in the unit time to move a lot of air molecules. For this purpose, subwoofer usually uses a large diaphragm, a small stroke of the cone or a small diaphragm, a large stroke of the cone. The latter of the basin diameter is small, is conducive to reducing the size of the entire bass speaker, and has the power and loudness advantages, has become the mainstream of modern subwoofer.

        However, the subwoofer installed in a large speaker, although you can reproduce the film in some of the shocking sound and landslides and other special sound effects, but listening to music, the playback of a large number of high Intensity bass will be very unpleasant. In addition, the results of research and practice have proved that the subwoofer loudness than the system of other speakers and not much practical significance. These are the reasons why the size of the modern subwoofer is smaller.



Subwoofer (subwoofer) position and connection:

        The inherent variability and unpredictability of the standing waves in the house make it possible for people to tolerate them. Although some computer software provides some interesting ways to control standing waves, but can not completely solve the standing wave problem. Fortunately, the wavelength of the bass is much larger than the size of ordinary rooms, bass actually no direction. With this feature, the average user simply use a separate subwoofer, you can get almost unlimited freedom to test the best place in the interior of the bass speaker. Although it is not as important as the main speaker, but different positions still have different sound effects. The following describes the three subwoofer positioning methods, they have their own advantages and disadvantages, the reader can be selected according to the experimental results.

        Place the subwoofer at the corner. This way helps to avoid the indoor acoustic reflection, so that the sound playback is more clear and clear. But at this time the room model to obtain a stronger incentive, will make the bass response becomes not flat enough. Since the subwoofer in the entire system is the farthest from the listening position, the bass will hear a slight delay than the voice 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 subwoofer and the main speaker and the distance between the listening position is equal, so the sound from the three speakers is almost at the same time to reach the ears of the listener, there will be no time difference. The disadvantage of this arrangement is that the amount of reflected sound in the room increases, and these delayed reflections reduce the sharpness of the reproduced sound.

        Place the subwoofer in a location near the listening area. This method is worth a try, for some difficult to get the best sound effect of the room even more so, because it will reduce the degree of indoor mode to minimize the minimum, but also greatly shorten the direct sound of the transfer path and bass to reach the ear Of the time, but also makes the indoor reflection sound becomes more vague.

        Another less scientific way is to first place the subwoofer in the usual listening seat and let it play music, and then slowly move around and listen to music at the same time, until you find the bass sound quality So good. The point is placed in the best position of subwoofer, and finally it can be placed in the place.

        In addition to two high-level (speaker-level) output terminals with left and right main channel speakers, the modern home theater AV amplifier also features a low-level (line-level) output terminal, an active subwoofer It has an input terminal corresponding thereto. In order to make the system play music and film programs have the best sound effects, in addition to the subwoofer two sets of speaker level input terminals are connected to the AV amplifier corresponding output terminals, but also the two line level The terminals are also connected together, as shown in Fig. The advantage of this connection is that the system can effectively enhance the bass when playing two different channels of two-channel stereo music and 5.1-channel movies.

        Some controversy about bass:

        At present, people on the role and effect of the bass there are still some controversy. One of the more easy to understand is that "subwoofer can enhance the bass of the sound system." However, many people think: "increase the extra bass can also improve the midrange, and even high-frequency band characteristics and sound quality," " Subwoofer can improve the depth of the stereo sound field "," increase the bass extension can disrupt the original role of the main speaker, if deliberately choose the relative level of bass and treble, but also make them in the middle of the middle of the band offset each other " ... and so on, these views are quite difficult to understand. Although these views are difficult to present a scientific explanation, but there are many "evidence" in the widely circulated. Some psychoacoustic phenomena are often difficult to understand, and history shows that in the development of high-fidelity technology, some subjective views are often more authoritative and influential than theoretical assumptions. In view of this, many aspects of the audio field still need people to carry out more in-depth exploration.