Depends: non-directional as you hear it or when the low frequency wavelength becomes long enough to bend around objects?
The frequency that you perceive to be non-directional depends on the distance between your ears. This happens when the distance between your ears is less than 1/2 the wavelength - so take twice the distance between your ears (in feet) and multiply by the speed of sound (1080 fps) and that's the frequency where you start to lose directionality of the source (about 1000 to 1500 Hz for most people).
Where the frequency starts to bend is about 300 Hz.
All of the above is independent of the source. Where the source comes into play is based on the size of the driver. So the point of non-d depends on a specific ratio of woofer size to wavelength (for most drivers anywhere from 80 to 125 Hz).
The frequency that you perceive to be non-directional depends on the distance between your ears. This happens when the distance between your ears is less than 1/2 the wavelength - so take twice the distance between your ears (in feet) and multiply by the speed of sound (1080 fps) and that's the frequency where you start to lose directionality of the source (about 1000 to 1500 Hz for most people).
Where the frequency starts to bend is about 300 Hz.
All of the above is independent of the source. Where the source comes into play is based on the size of the driver. So the point of non-d depends on a specific ratio of woofer size to wavelength (for most drivers anywhere from 80 to 125 Hz).