Will a subwoofer add depth and clarity to my system, or just bass?

Yes what you describe makes perfect sense. Every room has lots of modes, or places where certain frequencies reinforce and make for a lot louder sound. The exact location of these modes changes depending on frequency. But if you play a steady tone and move around you will find lots of places where the tone is much louder (a mode) and much less loud. Depending on the frequency these may be very close together. So in other words its certainly possible for you to feel vibration from a mode on your ankles that doesn't sound like it up where your ears are. Play the same bit with your head down where your ankles were and see.

None of this matter much with bass because we don't get our sense of direction from bass, we get it from much higher frequencies. So like the other night, Jennifer Warnes Bird on a Wire, there's these really awesome drum whacks which even though its mostly very low bass you absolutely here them as being very precisely placed in 3D at several different locations. Each whack sounds individual, each drum stays put in each location. My Swarm is two amps stereo but I tried it one amp mono with the same degree of imaging.

Its like we have two almost completely different hearing pathways or systems, one for low frequencies another more precise for higher.

Dear @millercarbon : Thank's. Yes we can't detect the low bass sources but in the system seems to me comes always from the in between speakers space and even that the subwoofers are not " looking/facing " to my seat position but at 90°. 

Your J.Warnes experiences are similar to what my system performs in several recordings, one of them is the Telarc 1812 LP where the cannon shots comes from different direction and the shots does not recorded with the same caliber cannon but different ones. One of those cannon shots goes down to 6-8hz that was the lowest frequency ever cutted in a LP.

When people like you, me and many others are accustom to satellite/subs room/system we just can't come back to the " past ", the experience is unique for a home audio system.

The " feelings/emotions " that MUSIC wake up on each one audiophile goes to the sky shinning as ever before. I know I can't live I can't listen it with out that quality level performance.

Like in your system my subs never " tells " you " I'm here ", only when the recording ask for it. Even in normal recordings we can't imagine those subs are swich onn.

Only through subs we can be sure that digital alternative outperforms analog one and the most important issue: why outperforms it.

CD's from the 80's outperforms today audiophiles same recordings as: Gladiator, Glory, 300 ( all these Original Soundtracks. ) and many many others.

There are LP recordings that we really can't enjoy it in all its magnificence  but only through a room/system with subwoofers. Example is the Wilson label recording Center Stage but there are hundred of LP recordings where thousands of music lovers need " discovery " as if was their very first time listen to.

Regards and enjoy the MUSIC not distortions,
R.

Btw, my subs are a head/front the main speakers maybe 1m. a head facing 90° respect the main speaker at the other channel the posoition is the same and both subs are facing/radiating each to other with around 3.5m-4.0m. in between.

Each sub has at one side the main speaker and at the other side  the side of a sofa and behind one sub is a wall with Sonex ( that I used not for the subs but for the main's. ) and behind the other is a furniture with hundred of LP's.

Both subwoofers are " seated " over three Van Slike footers/isolators along with inverted Tip Toes ( position ) over these Van Slike isolators. Both subs have a dead-weight ( on top ) of 30kgs.

In the floor of the living room where the system is there is a  thick  ( like 2"  ) Chinese rug ( 100% wool. ) and atop of this rug and in the middle of the living room another 1" Paquistan rug ( wool/silk. ).

To achieve the today quality subs performance I never use it other than my live MUSIC experiences, ears and test/trial and error. Several months of hard work because the Velodyne's are heavy and I tested all over the room till where are finally seated.

R.

millercarbon,

     I own that Leonard Cohen/Jennifer Warnes Famous Blue Raincoat cd. The Bird on a Wire track does have some very good 3d imaging with those drums/bongos.  You said " each whack sounds individual, each drum stays put in each location. My Swarm is two amps stereo but I tried it one amp mono with the same degree of imaging".
     I think it's very interesting and telling that you heard the drums at the same positions within the 3d sound stage illusion whether you ran the bass in 'stereo bass' or 'mono bass'.  My Debra dba system is all 'mono bass' using a single mono amp to drive all 4 subs and I perceive the drum whacks the same way on my system as you described on your system.  
     My experience is that combining a very good mono 4-sub bass dba system with a very good pair of stereo speakers for the mids and treble results in a very natural, very realistic, palpable full range sound stage that I perceive as stereo and lif-like from top to bottom.  
     This supports the theory, which I believe we both agree with, that the higher frequency harmonics of those bass drum whacks reproduced by our l+r main speakers provides the necessary spatial clues to determine exactly where the individual bass drums are located within the 3d sound stage image.  Our ears receive the bass sound waves from the subs of the fundamental tone of the drum being struck first followed very quickly by our ears receiving the upper bass/lower midrange sound waves from the mains of the harmonics.  Then our brains process these inputs, associates the fundamental tone/note with its fundamentals and is able to determine precisely where the drums are located within the 3d sound stage it also created with the assistance of the combination of the 2 unique channels of stereophonic sound. 
     Voila, psycho acoustics in action.

Tim

Which yeah Tim sounds about right to me. But however it happens and whatever the explanation the fact is those drums are completely physically anchored in their locations. They never move around the stage even as they change a bit in tone and volume, each whack uniquely its own. There isn’t even a reverberation or anything coming from anywhere but where those drums are.

What with the recent tweaks (ECT, Blue Quantum Fuse, PHT, all kinds of HFTs) and now the dba, this sounds so good I went looking to the recording for some sort of reason. Well I haven’t found the drum story yet but what I found is maybe even better:

“The album was mixed to half-inch analog tape, at the very end of the project to give it warmth. So despite the fact that the first CD’s were issued with a ‘DDD’ marking, it was actually ‘DAD.’ In a blindfold test in Amigo Studio B, Frank Wolf, Jennifer, Henry Lewy, and myself, all chose half-inch analog tape over every digital mix format available that we could test—the Sony 1610, Sony 1630, and a Mitsubishi X-80 2-track digital recorder that used ¼-inch tape.”

Which answers the one question that has been gnawing away for so long, "How the hell did they make such a fabulous recording all digital?" Now we know: they didn’t! The Universe is in balance after all!

https://www.mixonline.com/recording/classic-tracks-first-we-take-manhattan-jennifer-warnes-366484