The stock oem sub in
our TJ center console got all blowed up recently too.
In researching the options, this is some of the information I've compiled:
The most important thing in replacing any speaker is making sure the ohms and the wattage are correct for your system. With wattage you want to look at the RMS watts not the peak. Peak is sort of like the gas mileage on the sticker of a new car (the bloated number you never actually get), the RMS is like the real life gas mileage you get on a consistent, daily basis. You want to make sure the amp’s RMS output is equal to or less than the subwoofers RMS handling. Obviously if the amp is putting out more watts than the subwoofer is rated to handle it’s only a matter of time before you blow the subwoofer.
The ohms can be a little more confusing but the important thing is that the amp and the sub run at the same number of ohms. Ohms are a measure of impedance or resistance. This site explains it pretty well if you want to try to understand it
http://www.hifisoundconnection.com/Shop/Control/fp/SFV/30046/view_page/Subwoofer_Wiring_Ohms_Law
All this being said, the manufacturers of the stock subwoofer have done their best to make it impossible to replace just the subwoofer. First of all finding specs on the amp and subwoofer is next to impossible. Some of the other jeep forums say that the speaker is a 2ohm 6 ½ inch dual voice coil subwoofer that is wired for a 1ohm load from the amp. I wasn’t able to confirm any of this officially and most the car audio install techs I spoke with said it was extremely unlikely that a small stock amp would be a rated at 1ohm (1ohm amps tend to be very high-end, large, and rare).
I ended up ordering a replacement subwoofer that was recommended on another jeep forum before really doing the research.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-270 All the reviews were positive and several said it sounded better than the stock sub. After installing it myself I would have to completely disagree. It sounds better than a blown sub but it doesn’t even come close to the stock one. It basically sounds like just another speaker. If you don’t care that much about the low end, this route sounds better than no subwoofer, but not by much. I think the problem is that the subwoofer is a 4ohm and the amp is working at 2ohms. Just a theory but it definitely sounds like the replacement subwoofer is hugely underpowered which fits if I understand the laws of ohms correctly.
So the options seem to be: find a replacement subwoofer that is compatible with the stock amp or replace both to be assured they are compatible. You might be able to have the amp tested by a car audio place to know for sure how many ohms it runs at. My best guess would be that it is a 2ohm amp since the experts don’t think it could be a 1ohm and it leaves my 4ohm sub underpowered. The only 2ohm 6 ½ subwoofer I found under $100 was this Kicker
http://www.ecrater.com/product.php?pid=6764979. It’s a little deeper than the stock one so you will have to shave some of the plastic out of the center console to make it fit. Since I already bought and installed the cheap 4ohm subwoofer I am going with replacing the amp as well. When I bought the speaker it said it was 150 RMS/300 peak at 4ohms so I went with this Kenwood amp
http://www.millionbuy.com/kenkac6104drb.html . The RMS output on the amp is a little higher (200) so I need to confirm that’s ok before I recommend this particular set up. I was told by one tech this would be ok I would just have to watch the volume but I want to verify that with a few more experts. Worst case though I blow a $13 speaker and upgrade to the kicker 4ohm.
I'll post up my final results and some pics once I have the new amp installed.