Like you have your vehicle resonance, but you cut the trunk air out of the cabin air, then your resonance is going to act differently. Your car is like a leaky sealed box, in a way. Like I say, you're gonna have more wattage pressurizing less air when you do that.
You could still try to make an extendable face for the front. These subs just typically want a larger box, and that's also based on what we talked about for so long, sound-wise. But you can modify this box smaller by however much you want to work on it.
The first time I did a box like this, it was actually for a competitor, and we broke the record for the whole class for that year the first day we metered it. Zero testing, like we installed the box that week then went down there and I'm pretty sure Mike Smiley was there, it was in Smyrna, because he metered my truck too. That box was tuned at 35 hz with 2 DC XL 10's on a 3800 CT Sounds amp IIRC with 2 crap 50 ah batteries and a RX-8 factory alt and we did a 147.1 @ 35 or so hz firing forward. That RX-8 cabin is super small. That 35 hz would play down to the high 20's with authority and play very high, being tuned to 35 hz and being stiffer DC 10's.
Then you have boxes like this where you're peaking at 30 hz, which is super low. It may have to do with your type of car, cars are built a little differently than they use to be, I think the unibodies are stronger now, resonate differently. Some walls and trunk walls and things like blowthroughs, where you have a fully forward firing sub system that's a wall or half wall, I've seen more of those types of systems peak very close to tuning, more so than just a "loose" ported box.
Cancellation can be a big problem when you're pressuring two different air spaces.
So, if you have something like a ported box and a rear deck blowthrough, right? If you fire the subs into the trunk, and the port out through the rear deck, you have a much larger risk of cancellation, because the subs are pressurizing the trunk, then the trunk pressurizes the cabin, where the port directly goes into the cabin. That causes cancellation, because the sub pressure is switching phases somewhat in the trunk, before the wave meets in the cabin with the rear wave coming out of the port.
When you put a ported box in your trunk rear firing, putting it in the trunk almost acts like a series 6th order. The trunk is it's own enclosure IF the trunk has a huge constriction of surface area when the air tries to flow into the main cabin area. That shrinking down of surface area that makes the air in the trunk have to compress before it's able to escape into the cabin, that acts like a ported box, where the delay of the wave bouncing around in the trunk is shifting the phase of the wave, before it tries to get back into the cabin. This happens. NEVER have your subs and port pressurize separate air spaces; they always need to pressurize the same airspace, the same vehicle plane, however you see that. Putting the subs and port in two different airspaces, where one is in the cabin and one is in the trunk, that is like putting a box in between the front and rear wave, which makes the wave phases cancel out, depends. Different notes move differently inside of the car.
So, like I say, with your box not being sealed off and firing forward, you could very well be cancelling your cabin bass out somewhat with your trunk pressure. Those subs have super long coils, strong motors, and like big boxes. They shouldn't roll off that quickly. If they aren't bottoming out or completely unloading when they roll off on the high end, I suspect it's some cancellation, or it's some weird cabin resonance you have. That box should play higher than that, IMO, significantly higher. I expect it to, eventually.
If I took that exact box you have and put it in my Explorer I had, firing rear, that box would play easily up to 60 hz, probably higher, and probably play down into the teens, since those subs are what they are. Those subs are monsters.
I'm just saying don't settle for mediocre sound. I feel like there's a ton more to be had out of this whole setup. You literally have like a perfect setup man. You can't get much better, if at all, than what you have right now. Anything that's said to be much better is more personal choice. Give it time and have some patience, I think you can get this thing to really open up.
