Due to space constraints and the unique installation method, wall-hanging soundboxes require crossover designs that balance high and low frequency performance within a limited enclosure. They must avoid muddy bass while ensuring clear treble, and also accommodate the acoustic effects of wall mounting. The core function of a crossover is to divide the audio signal into different frequency bands and send them separately to the tweeter and woofer. The compact structure of wall-hanging soundboxes demands that crossover design focus more on component selection and circuit optimization.
For low-frequency processing, wall-hanging soundboxes often use small-diameter woofers to save space. However, the limited diaphragm area of small drivers can restrict low-frequency extension and dynamic range. The crossover needs to precisely cut off low-frequency signals using a low-pass filter to prevent high-frequency interference with the woofer, while simultaneously using attenuation resistors to balance the sensitivity differences between the tweeter and woofer. For example, if the woofer has higher sensitivity, the crossover will reduce its input signal strength through a resistor to prevent low frequencies from masking high-frequency details. Furthermore, some designs incorporate impedance compensation networks to flatten the speaker's impedance curve, facilitating amplifier driving and reducing low-frequency distortion caused by impedance fluctuations.
In terms of high-frequency performance, the tweeter in a wall-hanging soundbox is typically located at the top or edge of the enclosure to minimize the impact of wall reflections on the sound field. The high-pass filter of the crossover needs to rigorously filter low-frequency signals to prevent bass energy from entering the tweeter and causing distortion or damage. Simultaneously, to improve high-frequency extension, the crossover may employ a second- or third-order filter design, resulting in smoother high-frequency attenuation and avoiding a harsh sound. Some high-end wall-hanging soundboxes also incorporate time-calibration circuitry in the crossover, adjusting the phase difference between high and low-frequency signals to address sound image shift caused by differences in driver position, ensuring that high and low frequencies arrive synchronously at the listening position and improving sound field positioning accuracy.
The choice of crossover point is crucial for balancing high and low frequencies. Due to the relatively small size of the wall-hanging soundbox enclosure, the low-frequency resonant frequency is relatively high. Therefore, the crossover point is typically set between 2kHz and 3kHz. This avoids distortion in the bass driver due to excessively high frequencies and prevents the tweeter from being overloaded due to excessively low frequencies. If the crossover point is too low, the woofer needs to cover a wider midrange, potentially leading to a muddy midrange; if it's too high, the tweeter may sound thin due to insufficient power. Therefore, designers need to repeatedly adjust the frequency response based on the driver characteristics to find the optimal balance.
Component selection directly affects crossover performance. Due to space constraints in wall-mounted soundboxes, crossovers must use miniaturized components, such as surface-mount inductors and film capacitors, while ensuring precise component parameters. The Q value (quality factor) of the inductor coil needs to be moderate; too high a Q value will cause low-frequency peaks, while too low a Q value will result in excessively rapid low-frequency decay. The loss tangent (DF) of the capacitor needs to be as low as possible to reduce high-frequency signal loss. Furthermore, the crossover layout needs to be compact to avoid electromagnetic interference between components, which could affect signal purity.
In actual tuning, both subjective evaluation and objective testing are indispensable. Designers optimize crossover parameters using data such as frequency response curves and distortion, while also adjusting details through listening tests. For example, if the low frequencies are perceived as excessive, it may be necessary to lower the crossover point or increase the attenuation resistor of the woofer; if the high frequencies are harsh, the slope of the high-pass filter needs to be optimized or a tweeter with smoother high-frequency characteristics needs to be replaced. Some wall-hanging soundboxes also offer crossover adjustment functions, allowing users to fine-tune the high and low frequency gains according to the room's acoustic characteristics to achieve personalized sound effects.
The crossover design of a wall-hanging soundbox must balance space constraints and acoustic performance. Through precise crossover point selection, component optimization, and subjective tuning, a balance and harmony of high and low frequencies must be achieved within the limited enclosure. This process not only tests the designer's technical skills but also requires a deep understanding of acoustic principles and user needs. The final sound effect should be clear and natural, yet layered, meeting the listening needs in different scenarios.
