Amazon.com: PRV AUDIO Low Pass Crossover 1DF180B Low-Pass Filter for Speaker and Subwoofer Crossover Point at 180 Hz with Unique Selectable Features : Electronics
Passive 120Hz Low Pass Subwoofer Filter
Dictionary of Electronic and Engineering Terms. Audio Speaker Crossover Circuit
72-130Hz AC 9-12V Subwoofer Low Pass Filter Subwoofer Electronic Crossover NE5532 Subwoofer Preamp Electronic Frequency Divider - AliExpress