Directivity control for TV speaker boxes is a core technology for enhancing the home theater and multimedia audio experience. Essentially, it involves precisely manipulating the sound wave propagation path through a waveguide structure, concentrating sound energy in a specific direction while minimizing dispersion in other directions. This design not only enhances sound clarity in the target area but also reduces ambient noise interference. Optimizing the waveguide structure is particularly crucial for sound purity and localization in open-plan living rooms or complex acoustic environments.
The core function of the waveguide structure is to control the interference and diffraction of sound waves. Traditional TV speaker boxes often radiate sound waves in a spherical pattern, resulting in slow sound attenuation outside the listening area and prone to echo and reverberation. Waveguide structures, however, use specifically designed channel shapes, such as curved, tapered, or arrayed, to guide sound waves in a predetermined direction. For example, tapered waveguides utilize the principle of acoustic impedance matching to efficiently transmit sound energy in the target direction while minimizing lateral leakage. Arrayed waveguides, through the coordinated operation of multiple small-aperture drivers, form a more directional sound beam, concentrating sound energy within the listening area.
Controlling directivity in the high-frequency range is particularly important for TV speaker boxes, as high-frequency sound waves have shorter wavelengths and stronger directivity. However, the edges of the diaphragms of traditional speakers are prone to diffraction, resulting in an uneven sound field. Waveguide structures optimize the acoustic surface surrounding the diaphragm, such as by adopting a smoothly transitioning curved surface design, to eliminate phase shifts at the diaphragm edges, thereby reducing diffraction effects. For example, directivity-controlled waveguide technology, by designing a continuous acoustic surface around the high-frequency driver, maintains phase coherence during sound radiation, ensuring a smooth frequency response curve both on-axis and off-axis, avoiding frequency response fluctuations caused by diffraction, and enhancing the depth and detail of the sound.
Directivity control in the mid-frequency range requires a balance between efficiency and coverage. Waveguide structures in this frequency range often employ a composite design, such as integrating the mid-frequency diaphragm with the waveguide driver. Active control of the sound radiation direction is achieved through optimized diaphragm profiles. Some high-end TV speaker boxes utilize a directivity-controlled waveguide design around the midrange driver. This design utilizes the waveguide's curved surface to direct sound waves forward, while also controlling the radiation angle by adjusting the waveguide's opening size. This design ensures sound coverage in the midrange while preventing sideways sound waves from interfering with the higher frequencies, enhancing the clarity of dialogue and vocals.
Controlling directivity in the low-frequency range presents a greater challenge due to the longer wavelengths and weaker directivity of low-frequency sound waves. In this case, the waveguide structure must be integrated with the cabinet design to achieve indirect control. For example, the synergistic effect of the bass reflex port and waveguide can restrict the radiation direction of low-frequency sound waves to a specific area. Some TV speaker boxes employ a dual bass reflex port design, utilizing the waveguide structure to direct airflow, radiating low-frequency energy more focused forward and reducing low-frequency muddiness caused by reflections from the rear wall. Furthermore, the waveguide structure optimizes the acoustic path within the cabinet, reducing the impact of low-frequency standing waves and enhancing sound purity and depth.
Waveguide structure also plays a crucial role in multi-channel integration in TV speaker boxes. In a surround sound system, the directivity of each channel's speakers must be closely matched to avoid distortion in sound image positioning. By unifying the radiation characteristics across frequency bands, the waveguide structure aligns the frequency response curves of the main and surround speakers both on-axis and off-axis, ensuring a natural transition between the sound fields. For example, some TV speaker boxes utilize constant directivity horn waveguides, achieving a constant horizontal radiation angle of 100 degrees in the high-frequency range. This ensures a more precise surround sound dispersion and enhances immersion.
In practical applications, waveguide structure optimization also needs to consider the installation environment and usage scenario. For example, in an open-plan living room, a TV speaker box needs to use a waveguide structure to control the rearward dispersion of sound waves to avoid interference in adjacent rooms. In a small theater, however, the waveguide structure needs to enhance the sound field's envelopment, ensuring a consistent sound quality experience for listeners both on-axis and off-axis. Through the collaborative design of waveguide structure and room acoustics, the directivity control of the TV speaker box can be extended from the technical level to the user experience level, truly realizing the personalized listening needs of "sound follows people".
