I cannot answer your question scientifically. But in my system the
directivity of my subwoofer/transformation to omnidirectional was noticed
when I reset my crossover from 80 to 50 Hz. I would imagine your listening 
area would have something to do with this also. But with me, the answer was 
someplace in between 50 and 80. I suspect closer to 50 than 80.
        Prior to this, (at 80 Hz) the location of the sub could be discerned 
only on the longer passages and parts of movie soundtracks with heavy bass. 
The momentary low bass notes/effects were less noticable coming from a 
specific direction.
        At 50 Hz, I really believe I could put the sub in my kitchen and 
other than volume level, not get the directional cues and not tell it wasn't 
in the same room with the remainder of the system.
        I have read figures of 100 Hz being the cut off, but it wasn't so 
with my area and system. But I have the "Listening Area From Hell" to deal 
with so I wouldn't take any of it to the bank.
Cheers, John
grump@phnx.uswest.net
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