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You mention the first cancellation -
Don't stop there! They repeat at EVERY multiple thereafter.
And the spatial polar lobing is real as well.
And the additional delay from the other sources simply exacerbate that! (e.g. another spaced null repeated at integer based intervals and concomitant polar lobing!). And yes, the reflections off the boundaries (for all frequencies greater than 1/4 wavelength) will serve as yet additional virtual sources that will combine and create more CF and PL.
Superposition is fundamental, there is no case where this is avoided. And only the Bessel array allows for the combination in such a manner to occur where the original polar and frequency response is maintained.
We use this very feature (superposition and gain of spaced drivers) as the foundation for designing 'directional' cardioid subs!
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