Hello my audiophile friends, after a long time of struggle I replaced radio (other origional ones and also aftermarket ones) and all four speakers - but the sound is still far from good. So I was wondering, if there are diplexers (Frequenzweichen?) in the car, that divert between subwoofer and tweeters. Maybe these need to be changed as well. But I canīt find them anywhere without ripping apart the interior.
Can you point out, where these are to be found?

 

I think that in Germany or the EU in general, Premium audio was optional for the XJ12. So we need to know which you have. Premium has the Harman Kardon amplifier in the trunk, as well as the CD changer, plus a subwoofer on top of the rear deck.

Any diplexers, or crossovers (or frequenzweichens?) are built into the Harman Kardon audio amplifier in the trunk, including those for the subwoofer. If you don't have Premium audio, the speakers were wired up to the original head unit with nothing more than a capacitor at the tweeters to filter out low frequencies. No subwoofer in the non-premium system, only the 4 door speakers and tweeters.

If the sound is still bad it is probably because the tweeters are not working. The crossovers are usually not an issue.

So the premium system will have 4 tweeters: 2 in the front pillars and 2 on the rear doors above the window switches.

The non-premium system also has 4 tweeters: in the 4 corners of the cabin at the base of the front and rear glass.

I had to replace all 4 of the tweeters in my Premium system, they were all dead. Ironically, the tweeters of the non-premium system seem to be more durable. After I replaced them the sound was much better, with good clarity and detail.

Here is a link to a thread with more info: Is this a speaker?

 

Nah, although mine is said to be US spec, it has the standard sound system, there are tweeters (working) mounted in the dash.
- if there is one cable going to the radio, there should be something that splits between speaker in the door and the tweeters, correct?
- how can I access these dash tweeters and does anyone have a hint for replacing them? Todds picture looks, as if you can just pull them out.
- my system sounds, as if there are laptop speakers, zero subwoofing and everything else is terrible also. If volume turned up, the tweeters yell at you but there is no substance

I replaced all four door speakers by something more or less premium, although I forgot what it was...

 

I am not clear if you are now using an original Jaguar head unit, or some aftermarket unit? The wiring of an aftermarket might affect the sound.

Without an actual subwoofer like the premium system has, the low-end audio response is a little thin. But it should be better with your new door speakers. What is their size and response? Originals were small 5 1/4" speakers, but 6 1/2" speakers generally fit and usually have a better low-end.

The tweeters are easy to remove, just pry up the trim as in Todd's picture and the tweeter comes out with a quarter-turn. But you will probably want to leave them in if they are working.

 

After installing new speakers (something wiht the original size) I changed the original headunit to a other used one, then I fixed the capacitors on the old one, but sound didnīt improve. Then I tried two different aftermarket headunits, still no big improvements.
I thought there might be something between headunit and speakers, that corrupts the sound. Iīll unplug the tweeters now and test again.

 

Okay, here is the update:
I bought ANOTHER aftermarket radio (JVC KD-X561DBT) because I liked the idea of having a reverse camera. All my other cars do have that or at least the beeping thing that warns you before you hit something. The rare events when I drive the Jag, I tend do reverse until I hear something. Luckily no crashes yet... Anyway: this radio has a relatively big screen for a DIN1 radio and you can plug a camera in. Illuminations is blue - what sucks - but maybe I will try to solder green leds in one day. Other than that I like it so far. Feels solid for such a radio, bluetooth with an iPhone works well too.

It sounds like tweeters and subwoofers are completely our of balance. Tweeters already yell at you at a point, when you can hear nothing from the subwoofers. When you make the headunit to crank out all base, then it kind of works, but still no pleasure.
So I tried to unplug the tweeters for a test - but Iīm not able to open anything. How do you do that, with the windscreen in? My fingers can get no hold of anything from this panel. Tried with a small lever, but couldnīt get grip before the windscreen is in the way. Any ideas here?