Gain level on a REL sub

I had this same issue with my Carbon Special. I could not get the high level connection working with the Ayre amplifier I was using. It turned out the problem was that I had the ground cable connected to one of the Ayre’s chassis screws (the foolproof way to connect high-level to a balanced amp according to REL). When I finally tried floating the ground cable (ie connected to nothing), the problem went away and now the sub kicks like a mule on steroids. 
 

Perhaps oddly, I didn’t have that problem with my Yamaha 2100 integrated when connecting the REL’s black lead to the Yamaha’s phono ground. It’s also a fully balanced amp, so not sure what the difference was. 

Another thing, you want that high-level cable cut as short as possible once you finalize your sub placement. It makes a difference. 

Lots of information on REL web site. I also think it’s maybe the wiring?

@helomech +1 This plus type of wire used makes a qualitative difference. I'm using 6' L of Duelund tin plated copper litz wire at present, have some VHAudio Airlock OCC solid core copper to try next, always use the authentic Neutrik connectors at sub end, bare wire at amp end thus far.

I have a single REL T2 (8" driver+ 10" radiator). 10'x15' room. I can barely turn on the gain knob or the bass is overwhelming. The notes about the phase switch and placement seem best. You can also play with the crossover point to put it higher so the REL plays more of the audible bass frequency-even though that is not the REL method. The notes about needing two seem less relevant to your issue. Good luck!