2014 Ford Focus ST/Sundown SA-8 v.2 D2 Custom Enclosure Advice

[thethriller]

Hello all. I'm hoping for some box guru advice to see if this is even possible...

I'm hoping to attempt to put an SA-8 in my new Focus ST utilizing the space under the hatch floor cover over the full size spare tire. First off I'm going to just put this planning picture out there so you can see what I'm working with:

I hope the general idea is represented here, obviously the spare tire is located in the void of my SolidWorks representation. The drawing takes the place of the foam inserts that are under the carpetted piece of cardboard that is the "floor" of the cargo area in the hatch. If I built the blue parts out of 3/4" MDF surrounding the entire green area SolidWorks tells me the net internal volume is 1811 cubic inches (or 1.048 cubic feet). Obviously I realize this won't house the SA-8 due to its depth, I will have the sub sticking up higher and a new custom floor cover replacing the factory cardboard POS.

What I'm wondering here is if there's any realm of possibility where I could port this enclosure to around the .75ft^3 @ 35Hz that is recommended for the sub? Could the entire right side of the enclosure be turned into a viable port at ~4"x4" square or less if necessary?

Amp plans:

I'll be replacing the factory door speakers/components with 6.5" component sets (Infinity PrimusPR6500cs most likely as I've seen them fit). My plan is to use the HiFonics BR5000.5 which should produce around 1000W RMS x1 @ 1Ohm to the sub. (I'm still open to amp suggestions at this point, but I'll likely stick to a 5Ch amp for ease of installation.

[thethriller]

After much thought and deliberation I think I have come up with a box design. Please feel free to comment with any concerns or suggestions for my design.

Test fitting cardboard dummy:

The actual size of the "box":

40" Long x 28½" Wide x 5¾" Deep. Using the left ~half as the box and adding a 4¼" tall 9" x 9" square chamber in the front left area I come up with a gross airspace of 0.79ft^3. After woofer displacement and some minor corners and reinforcement it nets ~0.7ft^3.

Now please let me know if there's any flaw in the results from Torres Box Calc:

Too much port area? Wouldn't be hard to make the port smaller and thus shorter... Any heads up would be great. I plan to give it ~750 Watts or so with a Soundqubed Q1-750 (Or maybe bigger) Or alternatively going with an RF P1000X5 which should put out what, 650+ RMS?

[Triticum Agricolam]

So where is the sub going to go within that outline?

[thethriller]

In the top left corner of the cardboard cutout, in a raised 9" x 9" square (slightly down from the "top" or back from the "front of the car" to allow for the rear seats to fold up (roughly 65° angle there.) As soon as I finish the actual cut dimensions in solidworks I can give a better representation, but it'll be facing upward. It'll look like a bigass SA-8 in a 9" x 9" x ~4" high box after covering the whole compartment to look close to stock.

[thethriller]

Work is being a pain in the ass lately, so this is just a glimpse into the plan...

[mrazandrewm]

I would ditch the the hatch floor cover and make your box as tall as you want. Then when you are done, create a false floor to cover up the spare tire.

[thethriller]

That is literally what I'm doing. To get the air space and to accommodate port length I've gone ¼-½" higher than the factory "floor." If you're talking about the raised area for the sub itself, I'm not going to raise the entire factory "floor" 3+ inches to accommodate just the sub. If I wanted to just use the whole back of the car for a sub box, I'd keep my two Alpine Type-R 12's and MRX-M110. What I'm aiming for here is a minimal amount of stock space used, while utilizing the useless space beneath which is just air and foam; all while retaining the factory full-size spare.

Let's be real here, ideally I'd ditch the spare, glass the whole airspace underneath and put a couple 10 or 12's in that space on a few K watts. Back to reality though I've made literally one payment on this car and as such I'm going completely unmodified and replaceable. My goal is to get smiles based on average Joe hearing one 8" woofer, then seeing one 8" woofer, then seeing not the entire trunk used to do so. (BTW, "Average Joe" IMO is the guy that has a pair of 10/12's and a 3000W Sony taking up his whole trunk/back-seat/etc)

[Joe X]

The single sa 8 is great for what it is but is not going to really overtake any half decent couple of 12s well setup, giving up bass for groceries space..

[Rev. Wrath]

If you did the whole right side as a port, what would that be firing into?

[thethriller]

It'll be vented upward at the end.