I have a vfl 100.1 American Bass amp with 2 12 inch dual 4 ohm subs. I noticed that my mono amp has 2 positive and 2 negative inputs. Is there a reason it is like that or does it internally bridge it to 1ohm after hooking up both 12inch subs to each terminal? Thank you any help would be appreciated.

It's wired in parallel inside the amp so if you use both sets of terminals the amp will see half of what you have hooked up.

For example, if you parallel both of your subs (which will drop them to 2 ohms) and the use both + and - terminals (one for each sub) then the amp will see 1 ohm.

They are internally wired, just there for easy of wiring.

I hooked it up the way you guys said on a ported box with subs firing to back of trunk and sounds amazing. I can't wait to upgrade to 1000rms subwoofers in the future. Im running 600rms subwoofers now and it rocks.

Welcome

Glad you recieved good info from our awesome members!

Going with bigger subs at 1000 watts will make a big difference. the same size sub at 1000 watts wont gain you much.