Connecting Subwoofer’s to Willsenton R8

You can use the Neutrik Speakon 3-lead cable that is delivered with most REL subs (or buy one separately) yellow and red to the positive speaker terminals on both channels and the black to either channel negative. I have a modded-upgraded R8 and use a Rel T7i (one sub). Works very well.

Thanks for info. Can I use 2 subs with that hookup ?

OP, for pair of subs, use the supplied high level Neutrik Speakon 3-lead cable as below,

Twist red and yellow wires together of LEFT REL sub and connect them to the L channel positive binding post. And connect black wire of left REL sub to the L channel negative binding post. Repeat these steps for your RIGHT REL sub / right channel.

In some instances, twisting red and yellow wires together may result in exceptionally high gain (output) from the RELs. If this is the case, please remove either the red or yellow wire from the twisted pair and use electrical tape to mask the loose wire. This will reduce output by half and restore a natural dynamic.

Can the same wires be used at the speaker binding posts instead of at pre/amp ?This would reduce cable length needed. 

Yes.