Amazon.com: 8-Inch Low-Profile Amplified Subwoofer System - 600 Watt Compact Enclosed Active Underseat Car Audio Subwoofer with Built in Amp, Powered Car Subwoofer w/Low & High Level Inputs - Pyle PLBX8A :
Subwoofers With High-Level Inputs (Reviews)
Why are there two inputs on my subwoofer? - EarthquakeSound.eu
Subwoofer with speaker level input but no speaker level output : r/audio