I have the Alpine Premium Stereo in my 2002 XJR.
Both A pillar tweeters started cutting in and out on the way home the other day. Today with the stereo schematic in hand I tried to diagnose the problem, but I did not have my Torx head screw driver set so I could not remove the amp. After A while I blasted the stereo and they came back on temporarily and then died again. Since they work on and off it leads me to believe that it is not the amp in the boot but maybe a connection some where. But since both tweeters have the same problem it only seems feasible that it is the amp.
I found used amps on Ebay for around $150 and new for $750 at Gaudin Jag Parts.
Any suggestions to verify if it is the amp are appreciated.

 

I found that I blew the tweeters. Searching on line and at the dealer the front tweeters are no longer available. The rear tweeters are available, so I suspect since the fronts have their own amp and are no longer available that blowing them is a common problem (when you play your stereo to loud).
After a lot of searching I found ones that will fit in the original location. Below is what I did in, every other option would require modifications that would not look original.

This is the original from tweeter that came with the premium sound system (Alpine)


This is the replacement that I could modify to fit, these are available at Parts Express
BOSS TW18 Micro-Dome Tweeter | 265-396


This is what the tweeter looks like out of the package


In order for it to fit in the pillar I had to remove the tweeter from the shell by splitting it in two at the seam using a screw driver


This is what it looks like out of the shell


The tweeter has delicate wire and parts inside as I broke the capacitor for the crossover. I fixed this by dabs of super glue on the wires, capacitor and circuit board.


The tweeter fit well but I had to put to dabs of super glue to hold it in place in the pillar. The tweeter sounds brighter that the original but is not harsh. I think the reason is the replacement is a piezoelectric and the original was dynamic type with a magnet for the motor.

It was not difficult to remove the A piller trim. Remove the handles above the doors and use a upholstery tool (fork) to remove the trim. which is held in by a plastic screw that the threads are held in by friction.