All this tools are very nice but achilles' heel of frequency calculation is the compliance value. Some manufactures are publishing C values @100 Hz which is useless. Look at this thread, there is a nice calculator which can be used at 100 Hz.
http://www.vinylengine.com/phpBB2/viewtopic.php?t=36347&start=0
http://www.vinylengine.com/phpBB2/viewtopic.php?t=36347&start=0