Heya thanks everyone for the posts here - I too needed to replace the front speakers in my 2000 Blazer LT 4x4, when I got to them it looked like the glue holding the paper cone had just crumbled away over the past 10 years, but now I've got them both replaced and my sound is 100x better!
I might just change out the tweeters and maybe rear speakers next.
Here's a quick step-by-step how it was done just in case someone wants the procedure... I'd say it only took about 10 mins per door, half hour or less to do the whole thing, but your mileage may vary
Front Door Speaker replacement for 2000 Chevy Blazer LT 4x4:
Step 1: Remove the phillips screw from behind the inside door handle.
Step 2: Pry the plastic surrounding piece loose so that it comes away from the upholstery. Then pull the door handle (as if opening the door) and remove the plastic piece- just turn it and work the "hole" around the door handle as it comes off.
Step 3: Look just under the arm rest, see those 2 bolts on either side? Remove those next with a metric 7mm driver.
Step 4: Remove the round black plastic rivet by popping it out gently with a standard screwdriver.
Step 5: Pop up the switch panel, by pulling up near the front of it, it is wedged in the back and sort of clips in the front, it's easy to loosen. Just let it dangle there for now.
Step 6: Now we're going to remove the door panel, it is fastened by little tree-like clips, you can use a puller tool or carefully coax them with a large standard screwdriver, being careful not to scratch your finish. First, pull away the top one from the triangular corner of the panel. If you like, slide it out of the holder by pushing it out. This will keep it from popping back in while you are working the other ones. Next, pop out the ones along the bottom. Then, pop out the ones along the side.
Step 7: Now, holding the door panel, lift up at about a 45 degree angle toward the window; as you continue lifting, the panel should come right off the metal lip of the window and pull away. Push the switches through the hole in the door panel, the whole thing will fit through it if you twist it a bit, now the panel is free. If you're looking for a place to put it, the back of your blazer is a great spot. Open the hatchback and put it there
Step 8: Now look at the speaker. It's held on with 4 Torx 10 (T-10) bolts. Remove those and the speaker is free from its housing. The speaker is wired on with a GM style clip, which you can re-use, or discard. I chose the later. I'd take the old speaker somewhere and get one a similar size. The housing will accommodate larger magnets but that's up to you. if you need to remove the blue enclosure, it is riveted on. If you don't have a riveting tool then you can use self-threading metal screws. However, my speaker fit in the existing enclosure without having to touch it, I just screwed it in exactly how the old one was before.
Step 9: if you have a GM style replacement speaker, just unclip the old one, clip in the new one, and you're done. If you want to solder it, cut and strip the wires and then solder in your new speaker. If your replacement speaker is threaded, just cut and strip the wires, feed them through the thread bolt and screw them down.
Note: For my Canada model Blazer, the driver (left) side has yellow and brown wires, the passenger (right) side has dark and light blue wires. Look at this thread for a complete map-out of the wiring:
Stereo Wiring and Install Parts
Step 10: With your new speakers wired, put them into the enclosure and before you put the door panel back on, test and make sure they are connected/working properly. Be sure to put the torx screws back in to hold the thing in
Putting the panel back on is just the reverse of taking it off. As you put the window seal back on, just line up the rubber part along the edge and work it on from one side to the other, it should be fairly easy but if not, angle it a bit and try again.
Use some English to push the tree things back into their holes, screw the 7mm bolts in, screw the phillips screw behind the door panel, close the doors and crank up the tunes hehe..
PS: Found this blazerforum from a Google search.