How many subs?

@m-db

The Rel subs have to be on the floor - another disadvantage.  I tried platforms and it really sounded much worse.

Subs that can be decoupled from the floor, with proper bass extension, and ability to knock some lowest frequencies out of the mix when playing particularly annoying bass heavy music, looks like a good solution.

The sound track to Blade Runner - CD (probably all formats) has some excellent bass moments.  It would be great to hear that with fully capable subs.

I like that there is a preset - 6 - that is too much.

You always need a preset that risks causing an earthquake.

Iam using three 2 pioneer sub modified by a guy who sold Teajay the pioneer modified. I heard them at his house pre pandemic with the ps 12. One sub Iam using  denon. I used three because of my room configuration.Atmasphere is right audiokinesis does has swarm set up, that I considered but I decided to do 3.

@jayctoy any number of subs is good - I just got the 3 sub system going with some outrageous hardware. It sounds fantastic.  Not the lowest bass - I don't want that (yet).

Delays with a Drive Rack. Low pass filter for the right subs with a CR1 - nothing spared.

I need some tweaks to get it right.  When you hear a Tyrannosaurus Rex on S/510s - you will run.

Everyone will be pleased that the experimentation with delays for subs 2 and 3 is done and it is a fail.  It takes a few sessions and many tweaks of levels to hear what is happening.  To get the sound so subs 2 and 3 don't noticeably interfere with the main speakers is a very low level.  I turn off output 1 on my amp and listen to only output 2 which feeds the 2 delayed subs.  Really not a lot happening.  Not worth it.

@bilateral  Just a thought.

Saturday January 11, I filled in on Bass at a benefit held in a medium sized hall. After the sound check I noticed the front of house equipment rack included a 1U spaced component called DBX Drive Rack (something). 

The tech had left after the check. He was still working after I left that evening so I was unable to question. 

I think it might be a more recent Auto EQ system for both stage and / or front of house EQ. Just how this would function using REL's preferred speaker/high level connection without also affecting the mains? 

Front of house or FOA sound is a whole other world of audio. You might want to get clarification as to what the intended use of this DBX Drive Rack model is designed to control. Don't give up on your low frequency reinforcement.