should I need another battery?

I have a 2001 Jeep Grand Cherokee and I just installed the Sony XM-D1000P5 amp to 2 12" XS-L121P5's.  It hits really hard, I think I could somehow get it to hit harder and sound louder out side of the car just trying to figure that out.  Just trying to get some expert advice on where I would need another battery or not and also wether there is better sound with the speaker facing the rear of the vehicle or towards the front??

they definitly will be louder if the subs are facing the back of the vehicle, as far as an extra battery, i doubt you need that.  if you say its loud now, i wouldnt try to get too much out of them.  those subs are the sony 5sided subs right?  if they are, then they are pretty good, they sure suprised me compared to the subs sony made in the past!  but dont try to push them too hard, i dont trust the power ratings on them.  but if you want to turn them up, just listen for any distortion.  if it distorts, turn it back down.

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To get the max proformance in a jeep face them towards the back and make sure they're in the proper box.  I personally don't like, don't trust and wont buy Sony.  They have had issues in the past with low quality and the speakers cant usually handle the listed power.  Hold on to the reciept, you may need it.  The box will make all the difference. Allow plenty of air space and if your using a ported box, tune the box to 35Hz or below.  Air space is the key to hard hitting subs.  always allow as much air space as possible.  

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420 right on time

a 2nd battery wont do you any good unless you listen to your system with your engine off. The alternator runs your stereo, the battery is there for when the current draw is more than the alt can produce, and for starting the vehicle. Get a volt meter installed unless you already have one. If the voltage drops below 12.5 volts when the system is at normal listening volume, then you need a more powerful alt. but if it stays in the 14v range, your fine and dandy, but a capacitor may help for the peaks, it will help reduce the dimming of your lights when the stereo hits hard.

A cap is not a fix to insufficient power problems. It is a bandaid at best and can add to the problem instead of helping it. Caps are designed for voltage regulation, and are primarily used in SQ vehicles to even out the current flow.

If the alternator is to weak, then adding a cap only puts one more thing in line to use the alternator output, thus adding an increased strain on something that is insufficient in the first place. If you're having a dimming light problem then you should look into a HO alternator before adding a cap.

If you have a dimming problem then you can pretty much rest assured that your amp isn't getting enough power to run at it's full potential. Solution: get a HO alternator.

As far as the enclosure goes, I agree with everyone else. Face the subs towards the rear, and have them as close to the back of the rear seat as possible. Airspace is crucial for SPL.

And as far as Sony goes, I wouldn't put another piece of Sony equipment in my vehicle if you gave it to me (well, maybe just to destroy it ). I've dealt with their explode line before, and it was junk. The headunits shutdown/skip at excessive bass levels/frequencies, their subs have the same issues that Kicker does with non-rounded shapes (from what I've read), they overrate their power handeling capabilities for speakers/subs as well as their amps, and their internal speakers are junk IMO.

By no means am I trying to insult you because of your taste or what you were able to afford, but you wont find many users on this forum with many good things to say about Sony car audio products. The first thing that usually gets said when someone asks how to make a Sony system louder is find another manufacturer.

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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
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I have them facing towards the back and they hit hard!!!!  I have heard so much downing Sony, but I think the new P5 subs that I have are nice!!!  They sound a little distorted with really low bass, but I think I just need to tweek the amp a little, I have a subzero enclosed box with 1.4sq.  I have only had the system running for about a week now.  but thanks for the info!!!