How does a REL subwoofer add dimensionality and depth to a sound system?

I'm no expert but I do have two RELs and my 'selling' demo was listening to 'Fields of Gold' by Eva Cassidy with the sales guy gone and me turning it on and off. There is no bass on the track, per se, but with a good REL engaged the sense of the recording space was night and day. It's a demo you can recreate at home.

I think a good sub-bass system can offer that ability to play bass so deep as to give cues to a recording space is way cool. Just my guess though.

If you have multiple well placed subs, usually it takes your what is likely pretty uneven bass response from the mains and evens it out. Limiting woofer excursion on the mains can also significant reduce their distortion.

Why are REL’s so often given credit for providing the sound quality improvement to a system that all good subs provide, as if there are two classes of subs: REL’s, and all others? REL’s are not that unique, there ARE other subs that are great at reproducing music, Rythmik for one.

I’m tempted to also dispel the myth that a high-level input on a sub is superior to a line-level one. I’m very aware of the rationale given for doing so, but why on Earth would you want to add the distortion added to the signal by the output transformer(s) of a tube amp to the signal fed the sub amp? There is a reason OTL amps are known for their outstanding reproduction of bass.

Brian Ding offers two Rythmik plate amps which provide both high-level and live-level inputs (another myth is that REL is unique in proving high-level inputs on their subs), but prefers and recommends using line-level for best sound quality. His XLR amps forfeit the high-level input to make room for XLR connections.