american bass xfl 15

i have two american bass xfl 15 and i am useing a vfl150.1 amp. i made a box that is 9.2ft3 before displacement. it is installed in a toyota highlander. the box sound like it is tuned to high pitch and would like it to be lower, the port is 84.56 square oping by 18" deep. it is not a slot port but a square port facing the hatch and the subs fire up, is my box to big for these subs as it sounds like it would hit good for spl but i'm not looking for that. i want it to hit low. i aslo have a kinetik hc2400 and all 0g wire even the big three in 0g. any help would be appreciated... thanks

for got to put the box dims, it is 38wx18hx28d...

also for got to say subs fire up and the port to the rear with a square port.....

To begin with your box for those speakers is WAY to large and that is why your speakers do not sound good. I looked up the thiele-small parameters (specs) for those exact speakers and the recommended box size for one speaker is 2.75 cubic feet. Taking your dimensions of 38X18X28 it equates to having a 5.54 cubic foot box for one speaker, that is entirely too large.
You can build one box with two chambers, but each chamber needs to be 2.75 cubic feet, that is 4750 square inches, or an approx internal box dimension of 17X17X16.5. You will also need a port 3 inches in diameter and 5 inches long and that will be for both chambers.
With that size speaker, use nothing less than 3/4" MDF wood. Use plenty of glue, wood braces and screws. Also use poly-fill for each chamber. Lightly fill each chamber, do not pack it in there.
I can pretty much guarantee 99.9% with this box size you will have an awesome sounding system, as long as you have the proper size amp with the gain and variable crossover frequency set within reason.
Also, I would have the subs fire down to protect them, also buy speaker grills to protect them. Bass frequency is non-directional, it does not matter if the subs point down.
I would like to know how this turns out for you. Good luck and have fun.

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jpeterman15