Cardiod to extend LF? Your mind is playing tricks on you. Cardiod sub doesn’t give more out front, it reduced some in the back. My understanding is that you actually get less out front with cardiod, than would would woth them stacked forward-facing.
I've heard this before and my experience contradicts it.
This summer I had a little series where I used 4 double 18 subs a couple times (Bag End ELF), and 2 boxes once or twice. The use depends on the music, and a few times I didn't use any subs.
The first time the two boxes per side were stacked one above the other. The sound beyond about 75' was underwhelming.
The second time only seemed to need one box per side, set up standing up. It sounded fine at the stage, but throw was minimal, like 50'. Not a lot of sub signal source (from one bass guitar). Band repeatedly said from the stage how great it sounded, but I felt it was okay.
The third time, last show of the season, I set all 4 up, standing up (edit: 2 per side), with 3' box front to box front, and delayed the front ones by 3' on my BSS Omnidrive Compact (End Fire array, the Bag Ends don't seem to work very well with the arraying Luke describes). Processing was single channel from the Bag End stereo Integrator, don't remember the model number, then sent to the BSS then to the amps.
Each time, during setting up, the front boxes needed to be disconnected to avoid cable run where the band would be loading in. Listening to one box even on the stage, they didn't sound like they went down very deep and seemed tubby.
Plugging in the second box brought the bottom down, got rid of the perceived tubbiness, and made it really sound solid. I, too, felt that the cardioid extended the LF response. I felt the stack configuration also sounded tubby. All the x-over settings were the same for all the shows, as were the amps and their settings.
This listening during setup was all just playing background music.
Walking out into the crowd area, and during the show, the bass projected out to at least 150' and really, really sounded good. This was a community family concert in the park and not super loud levels, so YMMV.
The band this night said from the stage that they'd never heard outdoor sound so good (their words), and people came up to me all evening saying how good it sounded (not bragging). Mid/highs for all shows are 2 Meyer UPJ-1P per side. This was the 16th year I've done that series and it's always sounded pretty good, IMO, FWIW.
I've varied the subs over the years, mostly putting two Meyer USW-1P's on the ground in front of the stage, usually splayed in an outward pointing V (stage at top of V, and the V much flatter), but sometimes in End Fire. This was the first year using a Power Alley config and had no problems with it.
Now that I think about it, the first show this year I used the Bag Ends in the flattened V, and it was OK but nothing like the End Fire using 4.
This season ending configuration visually looked like there was hardly anything there, but it worked great and was real easy to set up, compared to lifting boxes down to and up from the ground, plus the hassle of kids climbing on the subs (it's a low key event). Although we try to keep them off.
If my mind is playing tricks on me, I'm happy to have that trick played repeatedly and look forward to the next time.
