The alternative (or an engineering trade off!) can be doing the opposite: Only care for on-axis sound, and while at it put most of the energy on the axis to reduce energy of reflections. Drawback: Works best with one or at most two listeners, plus speakers and listener are constrained in their relative positions. Bad for the living room, not an issue in a study.

The bundling is a matter of membrane diameter and frequency. Bigger diameter result in stronger beam forming, however lower frequencies have less beam forming. You can see the effect very well in the directivity pattern of this 8" wide band speaker: https://www.visaton.de/sites/default/files/dd_product/B%2020...

I've a FAST/WAW with a 4" wideband (250Hz XO). As personal monitor speakers these work great with an amazing stage and "resolution" (the illusion of being able to pinpoint the exact spatial location of a single instrument).

//woah: Thanks you two (you&GP) for triggering me on this (not /s)! While grabbing a coffee I spent a few minutes thinking about beam forming in audio applications; and came up with the line array. Not so novel, I know, but I'm happy to have gotten there on my own.