So I connected my REL to the high level outputs on my Marantz integrated receiver and it did work well initially, but there were two issues:
The output from the Marantz began a few seconds before the M700s had powered-up. This meant I heard bass audio only for a few seconds before my main speakers output any sound.
The configuration worked well initially (aside from point 1 above) but then it developed a hum from the sub, loudest when the system was powered-off. The hum was present with both high-level (Neutrik) or low-level (0.1 LFE) connections.
I have therefore elected to connect the Neutrik directly to the M700s as detailed earlier in this thread. I am only using this connector now and have left the LFE cable disconnected.
My question is regarding where to connect the ground (black) wire to the M700. The post above states to the chassis. Others have stated this can be done by loosening a screw, then re-tightening over the wire. Would an alternative be to use the more accessible silver part on the balanced input? Does this connect to ground? See attached photo.
Finally, is it strictly necessary to use the ground wire at all? While connecting the REL to the M700s, when I had only the red and yellow cables connected, the sub seemed to run fine, and with no hum.
Thanks in advance for any help!