Need some help deciding on what to do for sub box for two twelves

[Joshdashef]

So I just recently got into car audio, and first went with a single rf 12 in a prefab box... later upgrading to a dual prefab box. I haven't experienced crazy bass but to me they hit pretty good even though I'm running them both at about rf's rated 750 watts (birth sheet rated 860 watts.) My current setup is with the QBomb(power) dual 12 box and two p3d4-12s wired to 2ohm each then wired in parallel internally by the R750-1D into 1ohm load. The vehicle I'm using is a 08 Honda civic ex, with all stock electrical right now. 

I have two questions. 

1. Is it worth it upgrading the box into a custom ported one? or even a custom sealed one?

2. If so, how would I go about making my own design or bouncing them off this forum? I tried to use WinISD but I'm not sure if what I'm doing is correct, and I don't understand how to calculate the BL or Z (picture below). All the manufacturer lists is the

Magnet Weight (oz):

96 oz. (2.73 kg.) but doesn't give amperage? "The formula is mass in grams divided by the current in amperes" Does this mean the amps drawn by the subs rms rating?

 

 

I'm not too sure where to go from here but any help or advice would be appreciated 

-Josh

[MotorCityFats13]

when I first got into car audio in the mid 90's I always built boxes around what the sub manual suggested and even to this day I use that info to start my base box design, I would say any ported box to an extent would perform better than a sealed box but personal tastes are tastes and I have never liked sealed sub setups .... with my current setup I emailed rusty flowers and asked him the largest size he would recommend on my sub "DC audio level 3 12" and planned power and built around that since space was not a concern and I could always tweek the size in other ways... ie larger ports or filler blocks, unless you are competing its not an exact science and its not too hard to get a favorable outcome ..... my personal formula is 33hz tune and I stick to the larger side of the maximum recommended box volume and I try to use that awesome port area tool made by  Triticum Agricolam for reference when designing my port area 

 

[94caddy]

*Not an expert, so believe nothing I write, but I entered this speaker in the newer version of WinISD and it fills in the blank of unknown specification. I will share my file of the driver parameters and this screenshot.

Playing games, I made some charts but with your current ported box 4.5 cubic ft and tuned to 40hz, its already very loud and seeming tuned as high as you'd want to go. When signal of 750 watts, current box shows overexcursion the speaker at 28hz using the 13.9mm figure from your speaker's owners manual (in conflict with the item description Xmax figure at 15.9mm. So a chat to RF might clear what the true figure is.)

Charts don't make the proposed sealed box look good at any angle. If you take your current box and just seal off the port, you'd be suffering same over-excursion issue but with reduced output across the whole field. 

One experiment, that not take too much work, would be to lower box tuning. Reduce the port size adding material inside, along full length of the port, or add extension outside, at the same size of the existing port.

It will let you be louder at lower range and avoid speaker damage when playing low. But this will come at a cost to the output at higher frequency. 

aaa Rockford Fosgate P3D4-12.wdr