All-in-one low-pass filtering and subwoofer optimization in a single power design. This compact module simplifies integration for 2.1 systems and minimizes routing complexity. Direct audio path through the filter, with high and low frequency responses set by capacitors. The tone shaping is determined by discrete capacitor values to achieve the desired spectral balance. Main function: a tuned passive mixer that adjusts the high and low frequency content of the input signal before it is sent to the amplifier board for amplification. Includes a 2.1 channel preamp board. Ready to pair with standard amplifier boards and subwoofers for quick assembly. Compact, integrated design suitable for DIY audio projects and 2.1 channel configurations. No specialized enclosure required beyond common chassis. Performance: provides predictable, repeatable control of spectral balance, enabling smooth integration of subwoofers with main speakers. Use scenarios - Home theater or hi fi setup: shape bass and treble in a 2.1 system for balanced, cohesive sound with minimal external EQ. - DIY amplifier or speaker project: embed in a custom chassis to manage high and low frequency content prior to amplification. - Small studio monitoring: configure sub crossover and high/low paths for clear, controlled listening in a compact environment.