Ghxamp 300w 600w Subwoofer Speaker Crossover Audio 1 Way Filter Frequency Divider Super Woofer For 12 Inch 15 Inch Speakers 1pcs - Speaker Accessories - AliExpress
Subwoofer Crossover Speaker Bass Filter 200w Rms Cabinet Accessories Parts For Home Theater Professional Audio 18pa - Speaker Accessories - AliExpress
Woofer crossover & offset
How to Set Crossover Frequency for Speakers - Audiosolace