Low-Pass Choke Coil (400-1326) Features Faxback Doc. # 14185 Your Realistic Low-Pass Choke Coil helps your audio system's woofer or subwoofer work more efficiently to produce a cleaner sound. It does this by electronically channeling low frequencies (below about 150 to 300 Hz) to the woofer and filtering high frequencies. You can also connect two coils in series to lower the cutoff frequency of the woofer or subwoofer. (ALL-03/15/95)