OK guys, just before I went to get the van TermLab'ed I asked around what would be a good number below 30Hz, a bad number, what should I expect. No one knew what to expect. Then I got 148.2dB@ 25Hz and everyone said it was weak, terrible, pathetic. A few months later, after I let everyone forget, I asked what it would take to get a 150 @ 25Hz. I was told it was impossible without tearing the vehicle apart by some, others posted up videos of vans with 20-40 15"-18" subs, 20 plus amps, 20 or more batteries, doing well over 150dB @ 25Hz.... then I was told my score was good... yadda yadda. I fully know I am doing apples in the van and oranges in the HT, I am just summing up my previous experience of pre-test, testing, post-testing.
So anyway, what can I and what should I expect for what I have? I know full well I went cheap cheap cheap and milked everything for what it's worth. My goals were to build the largest enclosures possible using standard 4'x8' sheets without having to butt ends up or anything like that. As much airspace as possible for the lowest responce possible... very peaky as low as I can get, without going too low and things simply not working. Tuning lower than 13Hz started to have too much of a dip after the peak. 13Hz had the largest subsonic peak and just started to have a little dip above tuning. Tuning a little higher had no dip, just a peak, but was too high for my tastes.
Weaknesses that I'm sure will be an issue:
Power supply. My old wiring is atrocious, I easily made ONE EP4000 clipp on ONE IB3 wired to 4 ohms... not enough power supply to a single amp, let alone two.
Entry way. I have a dining room connected to a living room, the living room is the HT, with a 60"x90" entry way between the two. The 2nd tower, right tower, is right at it. When I only had the one IB3 in the Aztek box, tower two location was a lot quieter than tower one.
Ceiling. My ceiling litterally bounces up to 2" during serious sine waves. My ceiling fan has already ripped itself out of the ceiling from this. It is secure now, but bounces a couple of inches with the ceiling.
The 2nd bedroom door. I tried tightening the door knob, stuffing rags underneith the door, shutting rags in the door, and finally just caulked it. I uncaulked the door and leave it open 2-4" so that it doesnt rattle.
Outside wall, left of listening room. Flexes a good 1/2" during heavy sinewaves. Plenty of loss.
Rear window between the towers. That was my loudest most anoying rattle all along, I fixed it a couple of weeks ago: Caulked all the way around the window panes. Now I hear the entire frames rattle...more like knock... inside the frame/track/guide. Probably a small issue compared to entire walls and ceilings.
Enclosure flex. These things are not tanks, everyone knows it. Sure I'd love to have made a # sign on every single wall of both enclosures, but I just couldn't. Flex WAS atrocious, now it's tollerable. They flex a little, but nothing outragious.
Platform. I can't think of anything off hand, but I just have a feeling the 8'x8' suspended bed does something. Laying on it, it certainly helps you notice the ULF effects. The entire thing wobbles during ULF and it's the majority of the ULF experience.
Co-location vs spread. There's certainly large peak spots and large dips. Standing directly between the towers vs standing right in front of one or the other changes everything, stepping back or forward, left or right, different fequencies... we all know different wavelengths will combine here, cancel out here, and somewhere inbetween here, change the frequecy, change the effect. Standing at the top of the bleechers, loading between the ceiling and the front wall opposite the towers, very loud. Sit down and its a lot quieter. Move forward (away from wall) toward listening position (center of room/platform) a lot quieter.
I know none of this is news, just trying to outline everything ahead of time