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
I can only expand on what has been said. The lowest note on a double bass is 42HZ and most speakers are rated to that frequency, however, a good subwoofer can put power (pressurize your room) in the bottom octave, This both gives dynamic life to the bass instruments, and it can reproduce the resonant frequencies of large halls. Your brain interprets these low sounds everyday in your environment and when they are missing from a recording it sounds less lifelike.
It also works when you run the main speakers full range as I do [and as REL recommends]. The English call the frequencies below the range of most instruments "Infra-bass" and that is what the REL is intended to reproduce. I start rolling my subs off at 23Hz but they still make a difference even on music you would not expect.
Is it possible that the higher frequencies travel through the air more easily when the way is cleared by the low frequency waves? In other words they "draft" behind the low waves with less resistance.
Depotec - I like the way you think!

The sub gives "dynamic life" (as Stanwal puts it) to all frequencies. Kind of weird; but I like it.

Thanks to all who commented. Have a great day and keep enjoying the music!
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. So, together, you get both directional and omni-directional cues which gives a larger soundstage beyond the mere boundary of the listening room and somewhat takes you to the recording venue instead. Unless you have already a gargantuan full ranger, most speakers can use the help of a good sub or two in this department.

Regards,

Kenobi