I've just got round to changing the front speakers in our mk2.5 Sport so thought I'd write up a quick guide while I was at it.
The first step is to remove the door panel. First of all remove the three clips as shown below;
There are two at the rear edge of the door and one by the front tweeter. Carefully put your finger nails behind each side of the centre part and gently pull towards you - this releases the clip as shown.
Next step is to remove three cross head screws - one behind the door pull leaver and two sunk within the door pull. With these removed you now need to carefully remove teh trim plate around the door pull/lock
Now pull the bottom of the door card away from the door. Be quite firm doing this so you can release the hidden trim clips. Once they are all free lift the door card up from the door to release it. The last step is to release the wiring to the tweeter. If you look at it you will see a small piece of plastic that you need to depress with a screwdriver or something similar to release the wiring clips. You can see it in this picture where the clip has just been released.
You can now put the door card to one side ready for refitting later. The original speaker is a 5"x7" dual cone speaker mounted on a plastic housing. Just remove the four outer screws that screw the housing to the door and wiggle it a bit to remove it. The speaker cable is a similar arrangement to the tweeter and needs a screwdriver to release it.
The hole that remains is a good size and will easily take a 6" round speaker mounted to a collar. It will also accept a very deep speaker because the speaker recess is below the front quarter light and well clear of the winding window.
I used 6mm ply to make the collar, first tracing around the original mounting collar
After cutting it out I marked holes for the four screws and drilled them out before trial fitting it to the door. Once I was happy with it I marked out the centre of the circle I wanted for my speaker by drawing two straight lines joining opposite screw holes giving the centre where they cross. I then used a protractor to mark out the circle I needed to cut out. Once you're happy with your collar you can use it as a template for the other side. Here it is mounted in the door
I cut the existing wiring plug about an inch or so short so that I can rejoin it if I need to refit the original speakers, and put bullet connectors on the cars wiring to connect up to my new speakers as tehy had flying leads terminated with bullet connectors. As I was using KEF UNI-Q speakers I didn't need to worry about crossovers and separate tweeters. If you decide to use component speakers you'll need to remove the factory tweeters and wire in the crossover. The factory tweeter 'crossover' is just a crude capacitor mounted on the back of the tweeter (most cheap component speakers are like this - the midrange speaker takes the full range signal and the tweeter is protected by a simple capacitor)
The KEFs crossover is altogether more sophisticated!
I put a plastic bag over the back of the speaker to protect the crossover and back of the speaker from splashes, and then mounted the speaker to the collar
As I will not be using the factory tweeter I tucked the wiring for it neatly behind the protective plastic shield in the car door. All that remained was to put the door card back on which is a simple process of dropping it in from the top, pushing the bottom in to re-engage the retaining clips, replacing the door pull trim, replacing the three screws and the three push in clips.
If I'd had the inclination I would have bought some Dynamat (or equivalent) and lined the door behind the speaker with it, but I didn't have any lying around so I shall just see how the KEFs sound as they are - it'll be an easy enough job to go back and do it if I feel the need.
I'm sure lots of you have already done this, but hopefully this little guide will help anyone that hasn't done it yet and was contemplating upgrading their speakers.