Ok, I just installed my 4 ga wire kit and my Kicker 450.2 amplifier. It is running in stereo right now to 2 RE12's. The problem is this, at a certain point the amplifier actually starts getting a little quieter even though the subs move more and more. It sounds like a fan in the back because the foam stuff on the metal ring has come loose a little. The new amplifier. Which is rated at 2.5X the power of my Alpine is in fact not as loud... Something is wrong there. The SQ is shitty too in the cabin. Maybe due to the major leakage of air? I can't find where all the air is coming from though. Any suggestions? I am taking it to shops tomorrow if I can't figure it out.
You should check the xover setting on the amp. Is your sub box ported or sealed? If it's ported and you have the xover close to the port's tuned frequency, it'll sound terrible. Also, if you play bass that's below the tuned frequency, the sub will move a lot without making much bass. There should be no air leak besides the ports. Anything else will just aid in creating distortion and bad SQ. Another thing to keep in mind is, if you have a weak ground, then after certain point, the bass will not get any louder cause the amp isn't getting the needed current.