hu eq

And I have another question, I have an Absolute audio amp that is a Class D 800W RMS and it says its stable at 1 ohm, everything i know about car audio ive learned over the past 2 months so i didnt know anything when i first bought this amp and the pair of 12s to got with it, I didnt know what DVC was so when I hooked it up myself I only used 1 VC, i had this running for a while and was getting a descent amount of bass, when I bout my components and my coax I started messing with my amp a lil, me and my bro were messing with it for a while and I got it to where I could feel the vibrations from about 10-15 feet away! but i dont feel that anymore, someone said that the best way to wire these subs was in parallel/parallel   my subs are 4ohm 12000w and i forgot who, but they said I couldnt bridge this amp, what is the 180 knob for? this amp also has a subsonic filter and a slave input, I dont know what these are for. How can i get the most out of my amp and subs? I want to feel that bass again.

I disagree, however, some good points were brought to light.  If you do any tweaking with the eq, do it before setting the gains.  A good rule to keep in mind is to only cut frequencies, not boost, which can give you early clipping, as Flakman suggested.  Also, setting gains properly will take care of some noise issues as stated by killer.  Do a search here if you're unsure how to go about this.

Just because your amp is 1 ohm stable does not mean it's the "best" way to do your setup.  "Best" can mean a lot of things.  It'll produce the most power at 1 ohm (and volume), but with that comes extra heat production as well as distortion.  If you're going for sound quality it's not the best, but if you just want it loud, that's the way to go.  The 180 switch will change the phase of the sound, sometimes helping it better blend with your interior speakers.  You can try it both ways and see which you like the best.  A subsonic filter can protect a woofer from trying to produce frequencies that are lower than it's intended to handle, and keep it from getting damaged.  This is very critical when using a ported box, as your sub can easily "bottom out" below the tuning frequency.  It's not as much an issue when using a sealed box, though.  The slave input would only be used if you're using two of the same amps together- "strapping".  If you're just using one amp, don't worry about it.  You can do a search on it if you're curious.

I agree with all of the above, in that it is a process...not a one-time thing.  The hardest thing that people have to do is to first set up a gain-setting procedure that includes test tones and knowledge of the steps involved.  This takes time and effort. 

Install the system, secure the wiring, check all the safety factors (wiring and fuses).  Play the test tones, set the deck output level with all controls at flat and no EQ boosting.  Then set the amplifier gain to match the deck output by doing the same listening tests using the test tones.  Now, gains are set but you haven't yet taken the extra steps to do the tweaking you might want to do.

Tweak over time, and take your time.  Listen to several of your favorite CDs, adjust position of front speakers for best sound.  Adjust sub bass by positioning the box differently or trying out the 180 switch to reverse sub phase.  All of these tweaks come first before using the tweaks built into the deck.

If you then want to tweak using the deck controls, do what geepherder said and slightly lower the controls instead of raising them.  At first it will sound like you are losing power, but that will not be the case in the end.  In the end, you will have the most power available and the highest signal-to-noise ratio.  After these extended tweaks, and you feel satisfied that you've EQ'd the system to  your liking, go through the gain-setting procedure again, taking as much great care in doing it correctly as you did the first time.  Once done, you will not have to make adjustments to your system or set the gains again unless you add to or remove some of it.

If you do tweak it some more with the deck controls at some later time, reset the gains.