We get this question a lot since a lot of cable manufacturers still offer Y-cables specifically for subwoofers.
This is a relic of the past where old subwoofer amps needed to have both inputs populated to get the full gain. This is not needed anymore.
With our modern sophisticated subwoofers, you only need to run a single mono RCA cable from your subwoofer output, or a stereo pair if you use the pre-outs on your stereo component.
You can still use your old Y-cables you just have to set the Input on the subwoofer to RCA 1 & RCA 2 / XLR 1 & XLR 2.
