Install front speaker in a Lotus Esprit (what else) looks easy, but can be a little difficult due to the angle on the windscreen. The standard speaker size for the Front Speaker is 4'' (10cm), after market replacement can be purchased for as little as £20, but I would advice spending at least £50. I purchased some 4'' 2-way Infinity Kappa 42.1i's for £65.
As seen below, these speaker look and sound great and the new grills will fit without any cutting. The speaker I installed in my 1988 N/A didn't fit well at all, and the new grills were to big, so I had to reuse the originals, cracking one in the process.
A flexible screw driver is a must for this job as the windscreen angle stops you from using any normal sized screw driver. You can use a screw driver with removeable ends, just use the end with a pair of pilars to create a 90 degree angle. Remove the 4 visible screws and remove the grill. Gently remove the speaker, making sure not to damage the leather around the speaker. Disconnect the speaker wires, making sure you have hold of the two wires.
Reconnect the speaker wires to the new speaker and gently replace the speaker. Reposition the speaker so you can use the original screws and holes. Careful re-screw the speaker back in. If your using the original grills, replace them first and screw them back in, if your using the after market grills (as I have) you'll properly rescrew the surround in and then place the grill over the top.
As you can see above, I couldn't manage to fit the last screw in on the drivers side, this is particularly difficult because of the binnical.
I strongly recommend removing your original speakers before purchasing new ones, and checking the surrounds on the speakers, a close match to the screw holes on the speakers will make the job 10 times easy. Getting a drill in to make new whole is a job I wouldn't fancy doing.
Changing the Rear Speakers is easy pre-V8. Just pull the seat forward, undo the 4 screws, remove speaker, unconnect wires. Replace with new speakers. I decide to rewire the rear while installing my iPod. The wire used was very poor quailty and I was re-routing the cables to the amp. I just cut the old speaker wire short as it would be a large job to try to remove it from the Esprit.
I re-routed the speaker wire under the carpet and up the door seal. Then along the trim under the rear window and down the opposite door seal and again under the carpet. To get the wire into the hole I drilled as small whole to feed the wire into the pod.
This is a little bit of a pain to do and you have to be careful when pulling back the carpet. I only did it because of the poor sound from the rear speakers and the fact that I was redoing the install anyway.