Subwoofer cable question

I would buy another sub as 2 subs are easier to integrate into your room. Otherwise, +1 imhififan has the best answer. In my opinion all subs I've tried sound better when driving through the low-level inputs.

Also a lot of subs that have L and R channel inputs, if you look at the circuit diagram they are summed inside. L and R are there for convience.

NO! If your main speakers are small monitors and started roll off at higher than 80Hz , if you connect only one channel to the subwoofer, you will loss some information from the other channel even the recording below 80Hz is mono!

A lot of bassist use stereo basses. Bridge or rear for tight,clean tone. Neck or front for depth. We also use stereo chorus effects, sound processers blending triple sub octives and octive up effects, stereo delay and on and on. They are not recorded in mono! Listen to Chris Squires bass on 'Yours Is No Discrace' sweeping left to right. This isn't your daddy's bass.Maybe your  set up or room is smearing the bass, but stereo bass exists. Sorry for the rant.

I don’t have the sub yet so I didn’t know about the included high level cable. So this cable connects to speaker taps on the amp and the other end to sub? Then normal speaker cables go from high level out on sub to main speakers?

Richard Edmund Lord (REL) originally designed his powered "Sub Bass System" to accommodate systems that lacked any preamplifier outputs and using tiny speakers with limited low frequency output. Hence the high or speaker level connectivity to the amplifiers speaker outputs.

There are many other subwoofer brands that offer high level connectivity as an option yet suggest using the more direct to the source low level (RCA / XLR) connection of the preamp outs as do professional and commercial installations.

I would never recommend one unless the only option was no sub at all. Do some more homework.

 I agree that sub freq are not locatable so it would seem that one output  might work.  But if there are two identical "low" signals in the outputs or as suggested, they are kept different for stereo,  wouldn't it still be true that half of the voltage output (spl) is missing if only one rca is used?  Hence a stereo to mono or Y adapter might be advised?  To those who say that you'll lose stereo info I have to think that the total effect is there this way anyway but as mono.  Which if below about 80 is how we'd perceive it anyway.  If you hear differences from L to R its prob above 80 in your mains.