Subwoofers - Front Firing or Down Firing - Which Sounds Best?

Well I tried my "mini swarm" today. I brought my 12" Polk sub (HT sub) into my music room, hooked it up and (sound of air coming out of balloon) my B&W sub wouldn't turn on. I was doing some electrical work this week (throwing breakers) and thought I blew a fuse. I opened up the B&W and found a wire looking like it was not connected (to the driver) but inspected the fuse anyway (a LOT easier said than done). Anyway, got everything working and Tool's "46 & 2" never sounded so good. Gobs of bass! Will need to optimize things (ordering another Polk) but looks very promising. Don't have room for the "holy grail" of four subs but think the matching Polk's should keep me happy for awhile. Party on Garth! 

I think you will probably find every sub added brings improvement. My initial plan when building my DBA was to sell my Talon Roc to offset the cost of the four DBA. So when the subs went in the Talon went out of the room. The four were amazing! But then just being curious I decided to try with 5. The Roc went back in. Wasn't expecting too much. The literature after all says going from 4 to 5 should only be a very small improvement. What I heard though, or more accurately what I felt, was not small at all! Most amazing of all was the definite feeling that the bass I was getting with 5 was so much lower than anything I ever felt was coming out of the Talon at any point ever.

I think what happens is any one sub on its own, it does go very low but because of room resonances does so at a much reduced level. Then we get a double-whammy because of the way human hearing works, Fletcher-Munson equal loudness counters rise a lot at low frequencies. In other words really low bass has to be quite loud in order to be heard at all. We simply aren't that sensitive to it. But then the instant it crosses that threshold where we do hear it, wow! Impressive!

So more subs increases the lowest frequencies to where we can really hear them. 

Aside from a Geoff K DIY cement open baffle one needs a with a proper amp and XO = $$$$- $$$$$

My 2 SVS 12' subs (Ultra and Plus) suck primarily because the volume control comes on at full blast when barely opened from zero. Impossible to blend, making the built in XO adjustments moot. I thought to remove the cabinet and do open baffle DIY, but...

In the meantime, Emerald Physics has several open baffle speakers with double 15" carbon fiber woofers. I am awaiting arrival of 2.8s before doing anything with the SVSs

@geoffkait 

Thank you for sharing your experience of 4' concrete cylinders.