Looks like 15 is okay, but an order of 16 will crash. (For accurate frequency analysis i need more than 15)
The reason is the use of alloca in FFT::performRealOnlyForwardTransform, which seems to be limited to 8 MB on MacOS X (not sure what the windows boundary is)
FIX:
There should be an fallback to use an conventional malloc . (I checked this. Seems it works flawlessly. )