How can a subwoofer expand the soundstage?


I have recently added a Rel Storm III to my two channel system (Essence Sapphire amp, modded Essence Reference Super Gems, Arcam FMJ 23T CD, SOTA Sapphire TT, Benz Glider, Audible Illusions Preamp). I immediately noticed an improvement in imaging and depth of the sound stage at all frequencies. The REL manual specifically mentions these benefits. Can someone please explain how adding a driver that's designed to play at lower frequencies can have this kind of impact? I will NEVER take the REL out of my system.
rockyboy
Well said Horacio. Being passive of course REL must advise running the main speakers full range. I'd withdraw my previous post if I could, it's not relevant here.
Horacio,

Your observatons comport with my experience. I use KEF R104/2s with a Velodyne HGS-15. Crossover by the pre/pro is set at 80 Hz. The 104/2s sound fine full range by themselves, but I think they have a bit more transparency when relieved of LF duty by high passing. OTOH, when both the 104/2s and the sub cover the same mid-bass region transparency seems to suffer just a bit.

db
"I thought its because the subwoofer is omnidirectional in the lower region and thus adds to and expands the soundstage that the conventional speakers, whose sonic signature is directional, can't possibly convey."

Omni=directional speakers apply this same concept and resulting sonic effects to higher frequencies as well.
Dbphd,

Thanks for your feedback. This is valuable info for me, as I ponder over the value of adding an external crossover before the amp. Would appreciate your thoughts on this.

I run B&W 804s, which are said to have a frequency response down to 38Hz -3dB and while B&W doesn't publish distortion figures I believe they probably increase distortion quite a bit at the lower frequencies...maybe under 50 Hz?. I also have a REL Storm III, which as noted doesn't like being crossed over much higher than 50 Hz...therefore I wonder if getting an external crossover, like a Bryston 10B, to let the B&Ws reproduce only freuqencies above say 50Hz is worth it. Unfortunately I live in a place where buying used and giving it a try is not easy...Any thoughts?

Sorry I'm way off topic!