Finally Learned: Subs serve much larger role than adding more low bass

I've had two subs for about twenty years.  Relieving the main speaker othe main speakers of the bottom octaves has several bebefits.  Less excursion of the woofer, lowering distortion.  It also takes load off main speaker amp.  And of course better bass.  On a side note, I recently put springs under the subs.  This added detail, more body to the bass.  I also have much less booming bass in other areas of the house.  

Human hearing is designed to gather far more information from the environment than we are at present able to measure. It is no problem at all to know whether you are in a closet, car, living room or concert hall even with your eyes closed by hearing alone. 

Consequently, the more closely we recreate the sonic signature of the recording venue the more realistically it feels like we are there.   

This is the first thing that hits you with a DBA. I mean, unless you crank it up to where you notice the extra bass. That is too much. With levels properly set you will never know there are any subs at all. People have to be reminded about mine even though they are all around the room obvious as hell. They just don't seem to be doing anything.

But the effect is noticed even on recordings that seem to have no low bass. The speakers and room disappears, the sound stage expands, and there is a sense of envelopment. 

I went through this first when adding multiple subs. Then again to a lesser extent when putting the subs on springs. Then again to a much greater extent when putting the subs on Pods. Each time the bass did improve a bit but this was only noticeable with music with obvious bass. The improvement however goes far beyond this, extending well up into the midrange and also with the really wonderful feeling of envelopment, of being in the sound stage instead of merely looking at it.

I am thinking of getting the Audiokinesis Swarm.

But I can only place them behind my main speakers facing the back wall.

Maybe 2 is enough. I have a friend that does the Swarm with only 2.

I could do all 4 but they would have to be lined up behind the speakers.

Maybe 2 on each side.

Or it the Swarm only effective scattered around the room?

Good reading on topic:

For Optimum Sound, How Many Subs, and Where Do You Put 'Em? | News & Views | Ohm Speakers | Custom Audiophile Speakers for Music & Home Theater

To my ears the most difficult aspect of bass reproduction is keeping up the same efficiency for the bass as for the midrange. When efficiency is kept high, then bass is effortless and flows with the rest of the music.