Learn Me: Basic Car Audio System

So I brought this home tonight:

Agreed over some beverages this past weekend to buy the sub and amp off a friend of mine, who found them in the garage when he bought his house last year, without knowing a damn thing about them. My XJ came equipped from the factory with the super deluxe 2 speaker sterio, which is proving woefully inadequate for listening to much else than am talk radio, so some audio upgrades need to happen sooner rather than later. Not looking for anything crazy loud, just want it to sound good bumping some tunes at moderate volume, mostly metal and rock. I think what I have is a JBL DA4002 2 channel amp rated at 40w rms per and an Infinity 1230w 12" subwoofer. I also have a Kenwood head unit already installed, which was salvaged from my former e36 when it was totalled. I would like to upgrade the existing front door speakers and add an amp for them as well.

So, bearing in mind that the extent of my prior experience in car audio is installing a couple of head units and replacing the blown door speakers in my old Volvo, I've got some questions as to what to do with this stuff:

First off, did I buy a pile of Walmart garbage or is this crap halfway decent? Anything I should/can test? I honestly don't even know whether it works right now.

Is this amp adequate to run the sub or am I better off using it to run the door speakers? Power seems a bit low to me, but I have very little frame of reference.

How does one "bridge" an amp? I feel like this is perhaps a stupid question...

What do you all recommend for good, cheap door speakers? Certainly open for buying used on eBay but have no clue what to look for.

Thanks as always, GRM!

I would test the amp before installing in the vehicle. The way I do it is just jump it to a battery with a couple wires and give it some tunes from your phone or mp3 player using a headphone-to-rca adapter cable which I have a few of kicking around, like this: http://www.amazon.com/gp/product/B00004Z5CP?keywords=headphone%20to%20rca&qid=1445438869&ref_=sr_1_1&sr=8-1

The amp will probably run the sub just fine for moderate-volume listening. In fact, i'm not sure why you would want an amp for the front speakers if not intending to make a LOT of noise. In my experience the only time an amp really benefits your front speakers at 'normal' volumes is better low-midrange production.

The instructions for bridging the amp are usually labeled right on the speaker output area of the amp. You're just hooking 1 wire from each speaker channel output to your speaker load.

Yep pos from one channel to the neg of the other channel. Should work just fine for that single 12. Biggest amp I've ever had was something like 400w and it was pushing a pair of 10w6's. Loud enough and produced enough pressure I couldn't keep the hatch on my Camaro sealed. My dad swore he could hear the bass thumping from about 3 miles away. Granted that was almost 20 years ago.

I typically find rear speakers to be a waste. muddle the soundstage. in your application, being a jeep, I don't know if thy are beneficial or not.

what I find is a great budget setup is a 10/12 in a sealed boc, being fed around 100 watts RMS. this seems to be what you have already.

I also use a quality aftermarket head unit. I prefer JVC or alpine, but kenwood makes some good stuff. so you've got that covered.

next, I install good door speakers. my ears prefer the low end infinity reference series with the +1 woofer and 2 ohm load. they work noce, sound great, and are inexpensive. I also tend to upgrade the factory speaker wires on most things, as the bigger wires tend to distort less and sound better to my ears. no hard data to support this, but just what it sounds like to me. I run ~14ga speaker wire.

run 8 gauge minimum power and ground to that amp. small amps hit harder and run cooler with bigger than necessary feeding. don't know why, just do in my experience.

this is all just my limited experience with cheap/low end/used components. the ONE system I spent the "good" money on, I have been less than happy with.

my current darling is an old eclipse three channel amp driving two 6.5 infinity reference 2 way speakers in the kicks, with a 10 inch elemental designs sub in a too small sealed box. head is a 70 dollar JVC. amp fed by 4 gauge power ground directly to the battery, and speakers fed by 12 gauge speaker wire. the best sounding system, and cheapest, I have ever done.

also, don't underestimate the importance of sound deadedning and insulation in the quest for good stereo. a well deadedned/insulated car with absolute crap components sounds better than a penalty box with the top shelf E36 M3.

Vigo wrote: I would test the amp before installing in the vehicle. The way I do it is just jump it to a battery with a couple wires and give it some tunes from your phone or mp3 player using a headphone-to-rca adapter cable which I have a few of kicking around, like this: http://www.amazon.com/gp/product/B00004Z5CP?keywords=headphone%20to%20rca&qid=1445438869&ref_=sr_1_1&sr=8-1

Ok I have a question after reading this. Can I just have an amp hooked to speakers and connect my phone as a car radio without using a head unit? On my old mustang it still has the original head unit in the dash. I don't plan to use it, but I want to leave it in there. I don't really use cds anymore, and I would be perfectly fine without over the air radio. If this works I think it would be a great solution for me.

In reply to gearheadmb:

I've done it. I wasn't happy with the results.

I have used the cheap two channel lepai motorcycle amps powering 6x9 rear speakers with a cord between iPod and amp and been happy.

I didn't know this existed prior to searching;

http://www.amazon.com/BOSS-MC900B-Weather-500-Watt-Amplifier/dp/B00IBI518Y/ref=sr_1_2?s=car&ie=UTF8&qid=1445450868&sr=1-2&keywords=bluetooth+amp

Car audio amp with an integrated Bluetooth receiver. I'm not suggested a Boss product per se, just a link, and maybe there's better. Or maybe this is awesome. But for folks that are pulling the "I just want to use my phone" card this might be a really useful way to go. I know I get tired of monkeying with cables to connect and disconnect for this kind of thing.