Hi, I am just about to start my build in my explorer and I have a few questions.

I will be running Phoenix gold rsd 6.5 components in the front doors,

Soundstream pcs.6.5 3 ways in the back.

I have a kicker zx650.4

now the question is what is the difference between active/passive? and do I have

the option to do the better sounding one?

Also the subwoofer box I will be building I want to put the port inbetween the 2

subs but I don't know how to calculate it that way.

Any info would be greatly appreciated.

In a passive set up the crossover is set at a certain point. You can't adjust it (the crossover block). In an active set up you can "actively" adjust the crossover points in your system, whether it be at the headunit, amplifier, or an external processor. Going active will (usually) give you better sound IF SET UP PROPERLY.

Are you looking at doing a slot port, or aero?

slot port

Are you looking at doing a slot port, or aero?

what is the difference in ports?

aero ports are the circular tube openings,

slot port is a port going up and down on the box