Hi all,

I about to convert my 97 XK8 Coupe (with HK premium sound) to an aftermarket ISO stereo and I was after any advice from those who have already done so. As I cannot decide weather to buy the kit to run the ISO stereo through the existing amp or just wire the new stereo directly into car's speakers with an aftermarket amp for the subwoofer.

The first option is quicker and easier as I do not need to locate the speaker wiring to connect to.
The second option is cheaper (I already have an amp I can use) and might sound better.

So I guess it comes down to how hard it is to locate the speaker wiring and how much better a modern stereo would sound directly wired to the speakers then through the existing amp, can anyone advise??

Thanks,

 

One thing, doesn't the factory amp have active high pass filters built in to it? If I remember correctly your going to have to set up some kind of crossover for at least the dash speakers. Not sure if the door rear speakers are full fidelity or not.

Note: the super tweeter in the door sail has a capacitor in series as a high pass filter. As I recall it is -3db at 6k hz.

Just didn't want you to miss this if you go with a new amp.

John

 

Yes your right; with a 'modern' stereo you can you set the a high pass filter on speaker outputs so the the mid woofer are protected, I would just have to check if the dash tweeters need another higher filter. I guess my thought process is the money saved on the wiring kit for the OEM amp would allow to by some new speakers!

 

OK here is what I did,

Fitted an ISO stereo using an ISO wiring kit for 'non-premium sound' with steering wheel control - so the speaker connector does connect to anything.
Removed the rear amp and CD player
Fitted an aftermarket amp (in the same position) and connected it direct to new stereo via RCA leads
Fitted new sub in rear shelf, I brought a 10" sub as the original 8" sub has an adapter ring around it but the opening in the shelf is not quite a 10" so I ended up folding back the metal part of shelf and cutting back fabric/board part (about 5mm). Also part of original sub cover needed cutting on the underside to fit over the new sub. It all fits and looks good but this might be more luck then judgement
The sub is then wired direct to the new amp
Then I connected the speaker wiring on new ISO connector direct to car's speaker wiring - I connected all the front speakers to ISO front speaker wiring (behind the stereo - the cables run up the side of the center console and the tweeters and dash speakers on on the same wiring), and the rear speakers to the ISO rear speaker wiring at the connector block under the armrest (yes the original rear speaker wiring goes from the amp to the armreast then back to the speakers!)
I also installed a switch on the aerial power, and a DAB aerial on the rear window

Results
Well the sound is far better then the original, I was unsure how good the sub would be as it is not in a proper acoustic closure but no there is lots of clear bass, and the standard front and rear speakers seem to be holding up well. I set the HPF on the new stereo to 160Hz (front and rear) so they not handling the low bass. Of course the main advantages are I now have USB, bloothtooth etc.. plus control of the sub level and crossover.
Did the dash speakers survive? No, they seemed OK when testing on the driveway but as soon as I was driving and had to turn the volume up higher they stared distorting so I just disconnected them. I don't think this matters to much for music (I turned the treble up to balance the sub) I think they are more useful for talk radio etc... But I'm going to look at replacing them or adding another set of/upgrade the tweeters.

So is it worth keeping the premium sound amplifier?
I think not. I'm generally happy keeping the car all original but I think the stereo is something that is a useful update (especially for long drives) that does not change the car too much, plus speakers can deteriorate over time and the premium sound amplifier limits what can be updated.