1STec 7m Professional Grade Extra Long Audio Lead with 2 x 6.3mm Jack to 2 x RCA Male Phono Plugs for Stereo or Mono Signal Extension Active Subwoofer ...
Loops 3.5mm Stereo Jack Male to RCA/PHONO Female/Socket Adapter/Converter – Headphone, AUX, Amp/Amplifier, Subwoofer, Speaker, TV, Audio: Amazon.co.uk: Electronics & Photo
The Stereo-to-Mono Summing Cable That No One Makes | Late Reflections – the Silent Sky Studios Blog
Subwoofer cable (mono) | AV-Connection
My factory head unit only has a mono output. Can I just send a mono signal into my LC2i? - AudioControl
How does my subwoofer run with one rca cable?... : r/subwoofer
Can we use an RCA cable for a subwoofer? - Quora
Wireworld Stream Subwoofer Cable Mono to Stereo RCA to 2RCA 6 Meter | PERFECT HI-FI
AmazonBasics RCA Audio - Y Splitter Cable For Mono To 2 Channel Audio (Unboxing Review)
RCA Stereo to Mono Adapter, 2 Pack RCA Male to Dual RCA Female Y Splitter Cable Adapter, 8 Inches Gold Plated Connectors Audio Cable Extension Cord RFAdapter for Subwoofer Splitter : Amazon.ca: Electronics
Combining 3.5mm stereo subwoofer out (from the amp) into combined both channels mono RCA via adapter | Headphone Reviews and Discussion - Head-Fi.org
Connecting Mono Speaker-level Output to Stereo Speaker-level input on Active Subwoofer | AVS Forum
Simple Way to Convert Stereo to Mono : 5 Steps (with Pictures) - Instructables