Simple Way to Convert Stereo to Mono : 5 Steps (with Pictures) - Instructables
Inakustik Star Mono Sub (3 m, Mid range, Cinch) - buy at digitec
KabelDirekt – 1 m – Cinch-Subwoofer-Kabel, 1 Cinch auf 1 Cinch, Audio/Digital/Video: Amazon.de: Elektronik & Foto
DuKabel Subwoofer Kabel Cinch auf Cinch Digitales Koaxial Kabel mit 6N OFC Mono Cinch Kabel für Zuhause Theater, HDTV, Subwoofer, AV Receiver, Hi-Fi Systems - HiFi Series 1.2M: Amazon.de: Elektronik & Foto
Acoustique Quality W 1/10 - kabel pro subwoofer - 10,0 m (mono) | AQ AUDIO
in-akustik Star II Subwoofer Cable Mono Cinch - 2x Cinch 12 M for sale online | eBay
2x Infinity 10" High-Performance 1800W Peak Power Car Audio Subwoofers (Bulk Packaging) Bundle Combo with JBL Compact Class D Car Audio Mono Subwoofer Amplifier, Complete Amp Wiring Kit - Road Entertainment