Help me diagnose tweeter problem w/ factory H/K stereo, please

[adamnitti]

Neither of my door tweeters are working. I assumed they were blown, so I went and picked up some replacements; identical BMW H/K tweeters from another M3... Switched them out, and still no sound from my tweeters.

What is going on? All wires seem to be connected on my amp. Door panels appear to never have been removed before. Any ideas or suggestions how to test, etc?