The directivity of best column speakers
decreases with the decrease of frequency. That is to say, the directivity at low frequencies is very poor. Therefore, the vertical directivity of the sound column should be improved, even if the directivity at high frequency is weakened, while the directivity at low frequency is increased.
Usually, the sound column can be divided into high and low frequency bands, followed by a frequency division network, so that the long sound column can produce low frequency sound, while the short sound column can produce high frequency sound to improve its frequency response. Or some important venues commonly used methods, in the frequency band above 1KHz with a high-frequency loudspeaker separated to sound, to improve high-frequency directivity and high-frequency band timbre. Based on the principle of acoustic filter, a layer of sound-absorbing material (such as ultra-fine glass wool) with gradually varying thickness is coated on the best column speakers
The sound-absorbing effect of the material is better when the thickness of the material is larger than that of the medium and high frequencies. The sound column is thicker at both ends of the sound column and thinner in the middle. The effective length of the sound column is related to the frequency, and becomes shorter with the increase of the frequency. Improve the frequency response of the sound column. Change the shape of the sound column into concave or convex curves to disperse the high frequency main sound beam. The smaller the radius of curvature of the shape is, the larger the angle of dispersion is. Usually, the radius of curvature R = 2L is chosen. This method of changing the shape of the sound column is the simplest and more widely used.