oops, those speakers aren't coaxials, so yy1 is right, low freq. is 40hz. these speakers aren't designed really to run with a subwoofer, thats why the frequency response is so wide. i would still start around 80hz and probably work up the scale to find the best response.
if the bass is too loud just turn down the amp a number or so until it blends nicely. hope this helps.