Originally Posted by Pres2play
Can you explain exactly what we're seeing?
If you were to surround a loudspeaker with a sphere of tiny microphones, you could measure how loud the speaker was in every direction simultaneously, trying test tones at various frequencies: 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, etc.
The graph is that sphere, with volume level being shown as distance from centre. The further out the pink data points, the louder the speaker is in that direction; the outer edge of the sphere being the loudest the speaker can go.
As the frequency goes up (listed in the top box of the graphic), the speaker becomes more directional. The lower the frequency goes, the more omni-directional the speaker becomes. The increase in directionality isn't because the speaker gets louder in the front, but instead because it gets quieter in every other direction.
Notice that when you are on-axis to the speaker (front of the sphere in the graph), the volume doesn't go down as frequency rises. But if you are off-axis (above, below, behind, to the side), the speaker becomes quieter. In the low frequencies, it is like a lantern. At the higher frequencies, it is like a flashlight.
The reason I posted it was to show that even when a speaker is pointed away from a wall, there can still be enough
sound radiating from behind the speaker to cause a boundry cancellation.