I finally fitted a stereo into my STi. For those who are not experienced at doing such things I thought I would pass on a few things I learned.
Firstly, I asked around on this forum about how to start. I was informed that 6.5 inch speakers would fit into the front and 5.25 in the rear. This turned out to be true (sort of). In the front there is not much clearance to the bottom of the lowered window so a spacer is required for any decent speaker. No problem there. I made a pair using particle board after making a template from cardboard. There is reasonable clearance forward to the plastic door cover. The rear was more tricky beacuse there is lots of space behind in the door cavity, but very little forward. The Kenwood speakers I bought had central tweaters mounted on arms into the middle. I had to use every trick in the book, and some that are not, to get the plastic door panel on again. This involved trimming back the plastic honycomb reinforcement that runs on the speaker grill. Doing this the plastic fasteners engauge, just.

I was kindly pointed at http://users.sisna.com/ignatius/subaru/mods/index.html for photos of how to get the door off in this first place. These are accurate but leave a couple of tricky points out.
Firstly it says, remove the door handle bezel. This is not trivial. The bezel is designed to be fitted in 5 seconds but not to be removed. After removing all four I learned a trick, but I still broke the first one I tried despite taking care. You need a metal round ended poker, I used the blunt end of a metal scapel handle (blade removed). Work this in from the top between the bezel and the door panel. Push down and the top part of the bezel should release. Put you fingers behind this to stop it popping straight back in. Then work the poker from below trying the same trick. It should release again and you can place more fingers behind. With this much released you can wiggle the bezel out from the round end that is still attached. It takes practice.

Secondly, you have to release the electrical fitting from the window switches. I looked at this for a while before I worked out what to press. In fiddling I accidently released the door switch mechanism and had to **** around putting springs and ball bearings back in place. Best avoided. I will attempt to draw one side of a typical connector.

|..............|
|-----------|
|.....|--|....|
|.....|--|....|
|..............|
|_________|

There are black plastic 'ears' at the top. Ignore these. Half way down one side there is a white square release. I found that if you press a small flat bladded screw driver in BELOW this and then twist up the connector falls out easily. This is good because it only requires one hand. The other is needed to support the weight of the door panel on the rear doors.

Otherwise, things went well. I cut off the Subaru speaker connector that is filled with nasty white grease and put on spade fittings. I don't think I have cross-wired and polarities.

The CD player was professionally installed since it was free and they assume the risk of snapping the dash panel. Because I am a lazy sod I bought one of the new goast CD player. These look like a black hole when off and next to the map slot effectivley disappear. This way I do not need to remove the CD player front every time I park in town.

I hope these rambling notes help a few people.

 

They were Kenwood Excelon. 6.5 inch in the front, 5.25 in the rear. It might be worth looking for a different model for the rear to save yourself trouble. I bought mine because they were reasonable speakers and they were virtually giving them away on Ebay.
Some time I might add a subwoofer in the back but frankly I am not sure I want the hassel of running wires all the way through the car. A CD changer would also be nice, but again I might spend the money elsewhere (new brake pads, winter tyres, serviceing etc.)

 

Anyone know the official +/- color codes at the speakers?
I assumed the + on the fronts were the ones with the capacitors on the tweeters... The rear + is?

 

Oh great, I'm planning to do this in a week or two and now you got me scared!

Any reason why you decided to cut the speaker wires instead of just installing a wire harness adapter?

What did you do with the connections to the tweeters? Does it matter if you don't hook them up to something?

Thanks for the heads up on the problems with those Kenwoods in the rear because I was thinking about getting them.

 

To be honest I cut the wires to save me having to dig out the nasy, sticky grease they pack the fitting with. I could not see my ever connecting OEM subaru speakers and even if I did the spade terminals I put on would fit. Additionally, I figure the fewer joins the better, but who knows.

I am afraid I forget the exact wire colour combination in each door. The advice on the web link seemed correct. The + terminal wire was generally redish. More tricky is making sure you know which terminal on the speaker is which because most seem to have an electrolitic DC blocking capacitor. If your amp puts out any DC bias and you wire the speakers up backwards, about 10 minutes after you run the system the caps will pack-up (sometimes violently).

Re the CD head. Maybe it will get pinched, maybe not. I cannot live my life worrying about every little thing. I happen to live in a US town with some of the lowest crime rates in the western world. When I park elsewhere I am taking a bigger risk. Either way I am a) too lazy to remove and hide front panels b)too forgetful c) thoose bloody flickering modern head displays on most other units pi** me off at night.