My XJ6L didn't come with premium sound. I have replaced the deck, tweeters and four 6.5" speakers with Alpine. I have been premeditating this upgrade and saw an Alpine amp in a thrift store yesterday. I got this beaut for $45. It's old school and will do the trick to push the 6x9" woofer I found here which will arrive tomorrow.
LS69W Magnadyne Car Audio Speaker 6" x 9" | High Power Subwoofer


I am hoping I can make this fit the existing spot in the vehicle. It says it is 3" deep. That should fit.

I also put flashing tape down on the metal. This controls temperature changes, reduces NVH (noise vibration harshness) and is still cheap and light. It's not Dynamat dense yet it does make a difference and is worth the time when you have the car take apart already.




The sub is wired up and the project has a lot brown can do for it tomorrow!

6x9 subwoofer install coming soon. Stay tuned

 

Will be interesting, esp if anyone is upgrading the stock amplifier, etc. since I think the OEM 6x9 "sub" is a dual voice coil unit. So this could give folks some options.

I wonder how the specs of this unit compare to stock:

FEATURES:
- Polypropylene coated paper cone - Kapton voice coil - 18 oz. magnet weight - 90 watts maximum power handling - 4 ohm impedance - 65Hz-3kHz frequency response - 89dB sensitivity - 59Hz resonant frequency - 3" mounting depth
Will be very curious to hear how the mounting depth works out at 3".

 

UPDATE:

The woofer is in. It required light massaging and some spacers. It sounds perfect. Exactly the amount of bass I was going for. While cutting out the opening on the back deck piece I severely slashed my finger with a fresh box knife blade...


Magnadyne 6x9 sub woofer. Perfect amount of complementary bass for the price of $32 shipped.




Nylon spacers from home depot

 

Will the package shelf and factory grill now install with no issues or modification?

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I don't have a factory grill like XJR/Premium sound. That is the last step. Cut out and put cover on it. No vibrations either. The woofer really fills in the gap in the sound system nicely.