Your second spud arrived I see, I am reminded of the words spoken by Monty Burns excellent.
At a time when you feel like pushing black boxes around for fun, there are a couple things you might want to try in addition to sitting on them.
Given ones room has a strong impact on the results, it is often the case where setting up one way in one rooms works best while in another room, a different setup works best.
In other words, there are things in room acoustics where if you have the luxury to experiment, you may find that the best path to the best possible results.
You mention you have the ability to measure response, this is good.
While I am not familiar with the product it appears you have this?http://www.hometheaterhifi.com/volum...05-part-1.html
The write up for the controller has some things to consider;
It mentions there is a subsonic high pass filter, confirm it is set to 15Hz.
Make sure there is not a high pass or subsonic filter in your amplifier and what ever is driving it. Often commercial amplifiers have a high pass protection filter, it should be mentioned if present in the manual.
Note the eq provided on page 3.
It is mentioned that you shouldn't try to lift the dips, this is correct in more than one way. A dip is likely to be caused by a reflection, a delayed signal that arrives and cancels the original. That kind of problem can't be fixed, the more energy you apply, the stronger the reflection is, with pink noise and a simple RTA, it can appear that your helping but your not, your increasing the Q of it, not filling it in. . \\
EQ is a correction linked in magnitude AND phase, unlike things you can fix with EQ, you can improve the amplitude sometimes but you screw up the phase if you try to fix these kinds of problems.
The bottom line is, your normally much better off cutting a bump than lifting a depression. On page 3, the unmodified in room response and eq is shown.
To make the speaker they show flat to 15Hz, given the eq available, it would all have to be cuts.
If there were a slider at 15Hz, then that could be lifted instead as it is the box roll off and not a reflection / cancellation. Fwiw, this would be too much to fix with eq too.
You would need to make up for the reduction in output over most of its band by increasing the gain post eq say in the amplifier drive or gain.
Anyway (staring outside at the snow falling again), like I said when you feel like some exertion, try these;
Try placing the outlet for each spud in the outer corners with the box moved into the wall / wall corner. This produces an acoustic mirror for the box by being up against the corner and raises the efficiency and lowers the low corner.
Try placing the subwoofers standing up together with the outlets at the bottom together.
This replaces the mirror image the room wall provided above with an actual source.
Also, this pair has some forward directivity over a point source due to it's physical shape at /near the exit, in effect being a 180 degree horn.
Now what may not be clear is unlike a vented box or other direct radiator system, with horns you have a factor one can fiddle with. In the Tapped horn as with a conventional horn, the path length is partly what governs the low corner frequency.
Placing the spuds near a boundary or second unit does increase the length and lower the corner f .
If you want to try tuning the system lower, there is another configuration you can try.
Place the cabinets either together in the center or separately in each corner BUT place the outlet facing into the back wall / corner and move the cabinets about 8 inches away from the back wall.
In this configuration, one is extending the path length as well. Normally one see's some loss of sensitivity above the low corner compared to the conventional mounting but that is in trade for a much lower corner F.
Given the sensitivity of a pair of spuds compared to normal subs, its worth a try especially since you have a way to measure and compare the results.
It's too bad with room acoustics you can't just say do this and it works the best, I mean you can to a degree but I can't tell you what will work best in your room / house.
Since your playing with LF, Try the fireworks recording on our website, it has no high pass or compression and if I remember correctly, it was as strong at 10Hz as it was at 50Hz.
Approach the level carefully as this will tax the headroom in every part of your system and won't sound loud at all.
Sit back and pretend your sitting in the dark, near the woods in my backyard and to make it a lot nicer, pretend there are no mosquitoes.
Merry Christmas, Happy Holidays, wishing good sound to all.