The sound column is a combination of multiple speakers and connected in phase. The direction characteristic of the sound column is similar to that of a single speaker in the horizontal direction, but it is greatly improved in the vertical direction. It propagates in a wave pattern in the horizontal direction, but has a strong directivity characteristic in the vertical direction, forming a "plate"-like three-dimensional radiation effect.
Install the sound column near the stage entrance and point this "sound plate" toward the audience. The sound beam radiates to the back row of the auditorium with strong sound energy, while the front row is mutually affected by the phase difference caused by the different vertical distances of the speakers. Attenuation may be lower than the sound pressure of a single speaker here, which makes the direct sound distribution of the sound field tend to be even. The horizontal direction of the sound column should not be "bunched", and there should be a large horizontal radiation angle, so that the sound field can be more uniform in the left and right directions.
The column speaker usually refers to the combination of 4 to 10 paper cone speakers arranged in a straight line. The feature is that when transmitting sound in the horizontal direction, the radiation angle of the speaker is the same as the radiation angle of a speaker, while when transmitting the sound in the vertical direction, the radiation angle of the speaker increases with the combination of speakers, especially when high-frequency sound , The sound beam can be transmitted in a certain direction.
The effect of column-type speakers to control the sound vertically is quite effective. In an environment where the reverberation situation is more serious, the column speaker can effectively concentrate the sound to the listener, reducing the occurrence of rebound after being transmitted to the wall.
The characteristic of the sound column is that it has a strong directivity in the vertical direction. The longer the sound column, the narrower the sound beam, the more concentrated the energy, and the stronger the directivity. When the length of the sound column is fixed, the higher the frequency, the narrower the sound beam and the stronger the directivity.
The sound column can be formed into a variety of specifications according to different structures. The smaller the area of the "sound plate", the stronger the bunching effect, the sharper the directivity, and the sensitivity on the axis is much higher than that of a single speaker. The sound axis efficiency of the sound column on the main shaft is higher than that of a single speaker. Generally speaking, the more speakers that make up the sound column, the higher the sensitivity on the main axis and the farther the sound radiation distance.
Reasonable control of the suspension height and depression angle of the sound column can make the sound field more uniform and clear. Since the total rated power of the sound column is several times that of a single speaker, and at the same time, due to the focusing effect in the direction of the sound axis, the sensitivity is doubled, which is more effective for long-distance sound reinforcement.
The low-frequency radiation efficiency of the sound column is greatly improved compared with a single speaker, thereby increasing the low-frequency response and enriching the tone. Using the directional characteristics of the sound column, placing the microphone outside the main sound beam (that is, the lightest sound in the up and down directions at both ends of the sound column), at the position where the sound pressure is the weakest, can improve the howling phenomenon and increase the sound transmission gain. In places where the reverberation time is long, the use of the sound column can greatly improve the clarity of the sound.
The directivity of the sound column weakens as the frequency decreases. That is, the directivity at low frequencies is very poor. Therefore, the vertical directivity of the sound column should be improved, that is, the directivity at high frequencies is weakened, and the directivity at low frequencies is increased.
Usually the sound column can be divided into high and low frequency bands, connected to a crossover network, so that the long sound column emits low frequency sound, and the short sound column emits high frequency sound to improve its frequency response. Or use some methods commonly used in important venues to separate the sound with a high-frequency horn speaker in the frequency band above 1KHz to improve high-frequency directivity and high-frequency sound.
Using the principle of acoustic filter, a layer of sound-absorbing material (such as ultra-fine glass wool) with a gradually changing thickness is covered on the sound column panel, which can absorb mid- and high-frequency sound, and the greater the thickness, the better the sound-absorbing effect. The sound column is thickened at both ends and thinner in the middle. The effective length of the sound column formed in this way is related to the frequency, and it becomes shorter as the frequency increases, thereby improving the frequency response of the sound column.
Change the shape of the sound column to a concave or convex shape to disperse the high-frequency main sound beam. The smaller the curvature radius of the shape, the larger the spreading angle. Usually the radius of curvature R=2L, which changes the geometry of the sound column. The shape method is the simplest and uses more.
But unfortunately, the bass frequencies do not go straight forward like the treble frequencies, and they spread more widely. In a space with a more severe reverberation environment, the wide spread angle of the bass frequency may cause mutual interference of sounds and poor sound clarity. When the microphone and the speaker are placed in the same room, feedback feedback may also occur.
In addition to the vertical directivity of the sound column, there are some defects that need to be improved by the above-mentioned method, and the horizontal directivity also exists.
These problems can be solved with the help of a tone controller or equalizer. Lowering the volume of the bass frequency helps the speech sound to be clear, but it has a negative effect on the reproduction of the music.
The installation angle of each speaker on a single speaker can also be based on the principle of sound wave diffraction, and the speaker hole on the sound column box panel can be opened into a rectangular slit to improve the horizontal direction of the high frequency band.
As mentioned above, the sound column as an important speaker device is still widely used in many occasions.