Imagine a perfect audio speaker creating a planar square wave - driven into a parabolic reflector.
The fundamental wavelength is around twice as wide than the parabolic reflectors diameter.
I've read that parabolic reflectors can only really concentrate wavelengths a multiple less than the radius of the reflector, with the gain relative to frequency.
However a square wave comprises a number of frequencies (harmonics of the fundamental).
If I am driving a speaker with the square wave as described, approximately what kind of waveform would be picked up at the focus microphone?