Simple speaker crossover 1st order filter design
It's a cheap crossover. You're right about the corner frequency, even if the speaker's impedance is not resistive, but not about the role of the tweeter: it's meant to play only the high frequencies, and nobody says they have to stop at 20 kHz. But the amplifier, in general, limits the total bandwidth.
As for the power, the &quot;cross-over&quot; leaves the high frequencies that have a much smaller energy than their low frequencies counterparts, so the handled power is lower for the tweeter than it is for the &quot;woofer&quot; (I'm slightly generous with the terms). Since the &quot;woofer&quot; gets all the frequencies and the tweeter only some, then it's the &quot;woofer&quot; that determines the total power, and in this case it's 6.3 W.