Amazon.com: Mediabridge™ Ultra Series RCA Y-Adapter (8 Feet) - 1-Male to 2-Male for Digital Audio or Subwoofer - Dual Shielded with RCA to RCA Gold-Plated Connectors - Black - (Part# CYA-1M2M-8B) :
ATAUDIO HIFI RCA to 2 RCA Subwoofer cable High Quality One Sub-2 Splitter Y RCA Cable - AliExpress
Monster 12 ft. L Subwoofer Cable RCA - Ace Hardware
Difference Between Subwoofer & RCA Cable - The Tech Edvocate
SKW BG01 / BG-01 RCA Audio Cable Male to Male Subwoofer Digital Coaxial 6N OCC — HiFiGo