BOSS Audio Systems CUBE8 8 Inch Car Audio Subwoofer and Amplifier Package – Powered, Built-in Amplifier, Passive Radiator, Remote Subwoofer Control, For Truck, Boxes and Enclosures - Walmart.com
AMPIRE universal RCA level control for amplifier or active subwoofer | RCA Controller | Car Audio Electronics
AudioControl 2-Channel Active Line Output Converter with AccuBASS and Subwoofer Control Black LC2i PRO - Best Buy
Nobsound Auto Car Amplifier Audio Subwoofer Bass Control Knob Sub Gain Equalizer Regulator Frequency Controller RCA Line Level Adjust : Amazon.in: Electronics
AMPIRE spare parts - level controller for ACTIVE8-PRO subwoofer | Active Subwoofers | Ampire | Product Archive
Amazon.com: XMSJSIY Bass Control Knob Remote Amplifier Replacement Bass Controller Car Audio Adjustable with 6 Pin Extension Cable for Subwoofer-3.8M/12.6FT Cable : Electronics
Subwoofer Controller | Anistardi's Blog
Pyle Active Down Firing Subwoofer - 10 Inches, Ported Design with High-to-Low Input Level Controller, Invisible Down-Firing Speaker, Color Black, Built-in Convenience - PSUB10A - Walmart.com