Joe X

So here is a suggestion, power: to sub rated, amp subsonic filter to 28Hz, minimum port clearance 4 1/4", figure is just an assembly guide:

As a first step disconnect signal at the mids and highs amp and see if this disconnected but powered amp still shows the noise.

Your power cables into the loc are of the same color and your speaker cables as well, that usually lead to disastrous results. Get some help from a professional installer.

7 cubes net not possible on those dimensions, I am sure you can go wider and taller in that vehicle, preliminary calculations shoe a maximum of 5 cubic feet net is possible for a double layer box and about 6 net for a single layer with double layer baffle is possible (heavy bracing).

Your figure is missing port dimensions of with and length so I cannot tell you if the design is correct, what is obvious is lack of necessary bracing, As for the wood, any stiff decent quality wood will do, MDF is relatively less expensive and that's why is used more.

"music was playing on the radio and WITHOUT RCA’s" If you mean that the amp was playing music without the RCAs connected then your car is possessed most definitely, you could start throwing some holy water around and see what happens, if the amp keeps playing like that then you are in big trouble.

Yes sorry I misread the specs BUT its the same you just wire coils in series, subs in parallel down to 2.66 ohm and you will get 1200W to the 3 subs. You won't get any less power than 1200w because it is a constant power amp, in normal amps you wire down to the lowest impedance to get the most power but not with this one, also will deliver 1200W regardless of the input voltage (12V, 14 V) unlike normal amps.

You got it exactly backwards, the HD1200/1 will give 1200W at 1.33 ohm bu the RD1500/1 will not give 1500W at 1.33, it will give less, I wouldn't recommend getting the RD1500/1 at all unless if you like how it looks or something like that, you won't get louder at all. As for the alternator the 220A one will suffice for either amp no problem as long as you don't play continuous sinewaves as you say, just music, that includes the car services and a mids and highs amp 400-500W RMS, just do use well installed quality power wiring for your amp or amps.

If your amp is rated above 1000W RMS you also need a HO alternator, batteries and wiring are good upgrades but what makes energy is the alternator. Feel free to check your subs but since you say the final impedance of 1.4 ohm has not changed likely you will find everything in order. A small upgrade you could do is getting a voltage gauge and connect it to your amp power terminals, with your car on and on the road your voltage should be about 14 volt and should not dip a lot when the bass hits, if you see 12V or less and 2+V dips then you electrical is dying and needs

Was away for a few days so a bit late, let me know if you still need the assistance.

For some reason Sundown did not provide an X10 design so here it is for you and for whoever needs it: Same style as Sundown's X12 design. Will fit most trunk cars.

Do you have any electrical upgrades? systems above 1000W of power need upgrades, a high power system without upgrades will start under performing (getting less loud among other symptoms) overtime and at some point that electrical system will fail.

In a van generally you benefit from a subs up / port back type of enclosure.

If listening to rap and such go for a 35Hz tuning or less, if you want fast bass avoid building a larger than recommended box, keep it average to slightly tight. Ideally modeling software can help you find a good balance for a specific sub.

I would recommend you to temporary place your tweeters in different locations and see what you like, bear in mind that tweeters installation angle is also important not just location.