Denis and I were trawling through a breaker's yard when we found an early S-Type with Premium Sound. So we decided to have a go at retro-fitting it to Denis' car.
In principle, it seemed a reasonably easy retro-fit but it didn't end up so. In hindsight, I should have consulted the wiring diagrams before we started buying the bits and pieces.
Having retro-fitted several Premium Sound installations to later cars, I assumed that there would be only one amplifier, the bass sub-woofer amp. Ha, but I was wrong. There was another one called the "Centre FIll" amplifier. I didn't find this out until I got home and checked the wiring diagrams. We were also missing the "Centre Fill" speakers as well. Those are the two speakers mounted low down on the dash roughly at knee level and, to be fair, they claimed the lion's share of the grief for this retro-fit.
We had the door speakers, head unit, rear parcel shelf sub-woofer unit with integral amp and we found that the wiring for the amp was in situ, tucked into a wiring loom. The door speakers use the same connectors and the plug for the Premium Sound head unit was found behind the centre console. It all plugged in and worked. The only problem at that stage was the fact that Denis' interior is black and the head unit we had was beige so it took some surgery on both head units to recover the black front panel and fit it to the Premium Sound head unit, replacing the DSP switch at the same time. Not difficult but a little bit fiddly getting it all back together with the cassette door lid correctly sprung.
For information, the Premium Sound head unit has the "Premium Sound" text across the upper edge of the head unit and also has a "DSP" (digital signal processing) button.
At this stage we were aware that there were no Centre Fill components but nonetheless, it all seemed to work, including the DSP.
Eventually, after much searching and asking of questions we found out that the Centre Fill amp was located way up in the dash cavity just to the right of the steering wheel.
Our concern now was the fitting of the Centre Fill speakers. Neither of us was confident of cutting the original dash to leave the oval holes and mounting points for the speakers. We were aware of a black Premium Sound car at a breaker's yard in Mansfield so decided to try replacing the whole dashboard rather than cutting out the speaker holes. A dashboard from an S-Type JUST fits in the back seat, albeit with a few worrying creaks and squeaks but no damage to my car in transporting the beast from Mansfield to Wolverhampton.
Let me tell you, changing out the dashboard is not a minor undertaking and if it wasn't for Denis' dogged persistence, then I think we would have been defeated. Eventually though, he got the dashboard fitted despite my well-meaning "assistance" and, subjectively at least, I thought the Centre Fill speakers made a big difference, even seeming to emphasize the sub-woofer "bassiness". The DSP function certainly makes a great deal of difference to the ambiance of the sound as well.
Was it worth the overall effort? I'm not at all sure I can give you an answer. It was a lot of work for poor old Denis, changing the dashboard over, and although it definitely sounds better to my ears, how much of that is placebo effect I don't know. However, in the final analysis I don't think it compares with the Premium Sound system fitted to the later vehicles and, even worse. It DOESN'T have the "Alpine" badges mounted in the door speaker grilles. In fact, I'm pretty sure that those badges are what makes the later version sound so much better
Anyway, if you're contemplating it you will need:-
Premium Sound enabled Head unit
Rear parcel shelf including speakers grilles with sub-woofer box and integral amplifier
All four door speakers
Two centre fill speakers
Centre fill amplifier.
All the wiring and connectors are in situ so no additional wiring needed.