- Crossover filter: easy to install; enhances practicality and user-friendliness of your speaker with a clear 3-way audio divider. - Woofer: simple, reasonable design; easy to install and convenient to disassemble; compatible with soundshelf crossover filter woofer. - Bass height divider: suitable for stereo systems and various speakers; supports bass three-way DIY or sound quality upgrade; 3-way frequency divider. - DIY upgrade tool for speaker crossover: printed circuit board design with precise cut-outs and lines for welding; very suitable for DIY projects and for adding tweeter components. Use scenarios - Upgrade a home bookshelf or floorstanding stereo to a 3-way crossover for clearer mid and high frequencies and deeper bass response. - Build a custom DIY speaker system (bookshelf, mini monitor, or cabinet) that uses a 3-way crossover and dedicated woofer for improved sound separation. - refurbish vintage or damaged speakers by replacing the original crossover with this PCB-based kit to improve reliability and sound quality while enabling easier maintenance.