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This is the top view of my enclosure for two 10" T110D4's, where the subwoofers are facing upwards near the opening of the trunk in my E36 325i, and the ports are facing towards the cabin where I have a midsized opening in my rear seats (was made as a ski hole, in this case it will be used for the port blowing into the front cabin. Also, if you can tell there is a divider in the middle, which seperates this enclosure into two seperate chambers (better for SQ + protects both subs from going out if one goes out)
My question is, is the port opening on the inside of the enclosure too close to the subwoofers? I would ideally like to move the subwoofers up towards the cabin (left of diagram) much further away from the opening of the port inside the box but I am unable to because the ceiling in my trunk is too close to the top portion of the box in that if my subs hit max excursion they could ultimately bottom out and hit the ceiling of my trunk and damage the drivers.. And I cant reshape the box, as I cannot build the box an inch bigger on any sides, and I cant build it smaller because it'll be too short of the 1.5 cu. ft. NET I need for each chamber (right now, it is tight enough and I was only able to work it up to 1.4 cu. ft per chamber, but without bracing)
Last question, and a very big one at it.. should I redesign this enclosure to make use of 1.25" instead of 1.50", so that I can have extra left over cu. ft. to do some bracing, and to increase the width of the divider from 0.50" to 1.25", and increase each chamber's space to a full 1.5 cu. ft. as called by the recommendations from the manufacturer?
Sorry, the last link did not work, so here is another try at it.
The port structure walls can be made of 1/2" MDF as well as the center divider in your configuration. Together, they form a strong center in that design. That would free up some space so that you could position one or two braces in the center of each chamber; the braces don't have to be massive, they just have to connect side-to-side and top-to-bottom and could be as small as a dowel rod. Using 1.5" MDF for the walls as you are, this bracing is not entirely crucial.
I suggest you should reverse the flow direction of the ports so that they begin on the opposite side as the woofer and exit toward the rear of the trunk. Allow the complete sound of the subs/enclosure to access the cabin through the ski hole which will occur naturally as the subs pressurize the airspace. The port intake on the inside of the box should be as far from the driver as possible, and the sound that enters the cabin should be an equal blend from drivers and ports. This may also give you the possibility of positioning the drivers as side-firing instead of up-firing. It would be ideal if both the driver and port fired toward the rear of the trunk. You should check the woofers for up/down firing suitability using a sag calculator as well.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
subs and port facing the same direction is always ideal. That way the wave exiting the port is in phase with the sub and little cancellation will occur. Once you start changing the directions the phase is thrown all out of whack which effects the sound.