I saw on another blog that each speaker has their own amp, so each speaker works independently from each other. I have a 2005 that the left rear speaker works part time, but the right rear speaker does not work at all, but yet the front speakers are fine. I have not taken the time to take mine apart to validate, just thought I would pass along what I had read from someone else.
6.5" front and rear door speakers
6/9
I believe they are 6 - 1/2" speakers.
If both front speakers are not working, then either the fade control is set to rear speakers only, or the front speaker plug has fallen out - very unlikely. Check the fade control, first. Or, I suppose a particularly loud blast of music could blow both speakers at once . . .
6 1/2 front and rear
Same as the front (6.5 inch) although the speaker basket does not have the tweeters in it for the rears. www.trailvoy.com All the answers for your Trailblazer!
The speaker size for a 2004 Chevy Trailblazer is 6 1/2 inches. This includes the front, door, and rear speakers.
if it is a non bose factory system your truck takes 6 1/2 inch speakers in bot thte front and rear doors
No
you cant change the front shocks on the trailblazer without a spring compressor because on a trailblazer they all have struts and they have to be compressed down
It is fairly simple after you undo a few hidden screws. We have complete instructions at out enthusiasts forum at www.trailvoy.com
According to http://www.installdr.com/Harnesses/GM-Wiring.pdf the connector for the rear speakers is separate from the front speakers. If the connector for the rear speakers is loose or disconnected, the rear speakers would not work while the front ones will. The amp in the head unit (dashboard radio) powers the front door speakers. The rear door speakers and roof (pillar) speakers in the rear are powered by a second amp under the drivers seat. Either this amp is bad or is not hooked up.