I'm assuming you mean tweeTer as opposed to tweeKer.
First, are you certain that the high frequencies haven't been suppressed on that particular channel? I don't know the exact capabilities of the 1909 or if you have the ability to EQ each particular channel. I would first check things out by swapping the speaker that's not playing high frequencies with a speaker from a different channel that is.
If the problem follows the speaker, then the tweeter is likely blown on the speaker. If the problem stays with the channel the speaker is connected to, then it's a problem with the receiver. And, my guess would be some sort of EQ setting since I don't think just the high frequencies would not work on a particular channel. Either it will work or it doesn't.
Listen to the woofer very closely with your ear only an inch or so away. Then move your ear up to the tweeter location. If nothing is coming out its either the tweeter or crossover. Its more likely the tweeter.
At this point I would call energy to see if they still have the tweeter and crossover in stock. If they do and they are not under warranty anymore I would take the woofer and tweeter out just unscrew the woofer for easier access, but disconnect the tweeter. Unhook the speaker cable before you do any of that and touch the ends to the positive and negative on the tweeter with the volume turned down just low enough that you can hear it. If there is no sound coming from your tweeter there is your problem and you need a replacement. If it does play then you need a new crossover or have that one fixed. Will probably be cheaper for a new one.
Do all of this after some listening tests from different material to make sure it wasn't just what you were listening to.
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