When should I use the LFE/.1 input on my REL?

You should use the LFE/.1 input any time a REL subwoofer is being used in a Surround Sound system. The Subwoofer/LFE/.1 output from the processor or receiver should be connected to the .1/LFE INPUT and appropriate volume adjustments made using the .1/LFE level control. Make sure you set your speakers to "Large" or "Full Range" to receive the full benefits of the High Level connection coupled with the LFE/.1 connection.