Phase distortion in Bluetooth speakers directly affects the stereo effect and positioning accuracy of sound, and the layout design of the driver units is a core aspect of solving this problem. Phase distortion typically stems from the time difference between the arrival time of different frequencies of sound from driver units located at different positions. This difference causes phase cancellation or enhancement when sound waves overlap, thus distorting the original sound. By optimizing the physical arrangement of the driver units, this time difference can be significantly reduced, thereby mitigating the impact of phase distortion.
Common driver units in Bluetooth speakers include tweeters, midrange drivers, and woofers, each responsible for reproducing different frequency bands. In traditional designs, these units may be arranged vertically or horizontally, but this layout can easily lead to different path lengths for high-frequency and low-frequency sound waves to reach the listener's ear. For example, if the tweeter is located at the top of the speaker and the woofer at the bottom, the difference in distance between the listener and the two units will cause a phase difference. An improved approach is to use a coaxial or coplanar layout, aligning the center points of the tweeter and woofer, so that sound waves radiate from the same location as much as possible, thereby shortening the path difference. One way to achieve a coplanar layout is by using a two-way or three-way coaxial design, nesting the tweeter in the center of the woofer, or using a special bracket to place them on the same vertical plane. This design not only reduces phase difference but also improves the coherence of the sound field, making the transition between high and low frequencies more natural. Furthermore, some high-end Bluetooth speakers use a multi-unit array layout, precisely calculating the angle and distance of each unit to ensure time consistency of sound waves at the listener's position, further reducing phase distortion.
Besides the physical arrangement, the directivity design of the driver units is also crucial. Tweeters typically have strong directionality, while woofers have a wider radiation angle. If their directions are inconsistent, the propagation directions of high and low frequency sound waves may deviate from the listener's position, exacerbating phase problems. Therefore, modern Bluetooth speakers often optimize the diaphragm shape, magnetic circuit structure, and horn design of the units to make the directivity of high and low frequencies more consistent. For example, tweeters using waveguide technology can control the sound wave diffusion angle to match the radiation range of the woofer, thereby reducing phase differences. The design of the crossover also affects phase performance. Traditional crossovers distribute frequencies using components such as inductors and capacitors, but these components can introduce phase delays, causing inconsistent arrival times for different frequency bands. To address this issue, some Bluetooth speakers employ digital crossover technology, using a DSP chip to precisely process the audio signal, ensuring time synchronization between high and low frequency signals. Furthermore, the application of phase compensation circuits can effectively correct phase shifts generated during crossover, maintaining the original phase relationship when sound waves are superimposed.
The speaker enclosure structure also significantly affects phase distortion. If resonance or reflection exists within the enclosure, it can cause phase changes in sound waves during propagation. Therefore, Bluetooth speaker enclosures often use high-density materials or damping coatings to reduce internal resonance. Simultaneously, a well-designed internal structure, such as the arrangement of air vents and sound-absorbing material, can optimize the sound wave propagation path, avoiding phase problems caused by reflections or interference.
Ultimately, the phase performance of Bluetooth speakers needs to be verified through a combination of subjective listening and objective testing. Designers utilize acoustic measurement equipment to analyze the speaker's frequency response and phase curves, ensuring phase consistency across different frequency bands. Simultaneously, blind listening tests are conducted to evaluate the soundstage's stereo effect and positioning accuracy, further optimizing the driver unit layout and tuning. This comprehensive design approach allows modern Bluetooth speakers to deliver phase performance approaching that of professional audio equipment while maintaining a compact size.
