you most likely won't need a alt upgrade. do the big three upgrade first. here's the main thing unless replacing the radio or flattening out the factory EQ settings and bass roll off most of the improvements are wasted.
if you want to learn more about SQ/SQL diymobilaudio its a forum lots of knowledge and great guys.
leaving the tweeters in factory is wasted=bad sound stage
you are already building a-pillars for the mids add a tweeter next to them. aim them to center of the front seats.
why would you add tweeters to the mid box what is that even mean??
do the big three upgrade first.--do not attach a GRD wire before or on top of the voltage system. attach it to where the battery ground connects to the frame. if you can replace the battery ground to the frame with a big gauge wire without disturbing the factory sensor do it.
try a AGM battery after that. the biggest you can fit and mod into the factory location. it's a small battery...ford has a voltage control system now that regulates the amount of voltage the battery gets to help reduce fuel consumption.
then if you are still getting dimming lights Singer Alternator...he can set your voltage to what you want. above 14.4 will set off a battery light on your dash.
2018 fiesta SE hatchback
this is a SQ system am building for my daughter not a SPL. so i care about the quality of the sound not how loud it gets. but it will be plenty loud.
i just bought premade rings on amazon for the front and rear 6.5 they had the wire adapters so i dont have to cut wires.
the mids and tweeters are going on the dash in that useless window spot. ill have to run new wires to the t-harness.
the subwoofer is firing at the rear hatch passenger side-- sound wave gets a boost and develops a little more- small car needs all the help it can get.
the dsp and amps are going into a false floor in the cargo area.
the sound dampening is important helps stops the rattles and buzzes. the foam stops the back wave and improves the sound of the speaker as well as does some sound proofing from external road noise. use the wrong CLD and waste money and time. use none hydrophobic stuff inside doors mold and fungus and mildew happens. the deadening on facebook.
the doors have cld and hydrophobic melamine foam.
the rear cargo area is cld with some heat wave jute 1/2 because thats all that i could fit. i wanted more though.
the hatch itself has cld and 1" hydrophobic fiber mat.
ill do the big three upgrade doubt i need it.
ill use the dsp to flatten out the EQ and bass roll off. ill try to flatten out the EQ and bass roll off in forscan. am not changing the HU since it is just to expensive and am not keeping the car for more than 18 months.
i did not take the inner plastic card off. i worked through the speaker hole and the edges. took all the bolts off pried the side back a couple of inches carefully since if you break something its a waiting list to get replacements.
these are the type of mids,tweet pods am having made.
i did the cargo area last night and will finish the hatch tonight.
the sub box is being made by AudioArte on facebook. he uses baltic birch. this is the one i had made for my other daughters HRv. the daughter with the fiesta is getting the same style and size just a different color.
i am not on here often. just when i cant find info on the site above. on the other site am silvergor69 diymobileaudio i have a build log of what am doing to the fiesta on that site