Bgavin - Is there any freeware software or algorythms for manual calculation you can recommend for determining driver excursion over frequency for a paticular inptu power? WinISD does not do this. This calculation seems to be of fundamental important when designing a sub-woofer system. I saw the plot of the magnum 18LF on your website and it apparently can have an 800watt 30hz signal put through it and remain within xmax (if I read the graph correctly). That seems quite incredible, and totally 'bowel shaking' if you run a synth through it. So, I'd like to compare excusion data between Magnum 15LF and Kappa Pro LF. If the avatar B15 box is tuned lower then it should be high performance right down to 30 hz (at least with the magnum, if its anything like the 18) - with group delay pushes out of the way. Its fun just testing configurations on winISD, and realizing how totally lacking deep fundamentals many bass cabs and home hi-fi generally are. Even with the trend for 5 string/detuned bass guitars, it the clanky sound of detuned/low string harmonics which appeals to listeners (myself included) rather than the actual presence of the fundamental - which should be there but isn;t conveyed well on low end hi-fi. All this work for 10hz down from 40.... whats that, 5 notes? Having said that, my bass guitar doesn;t put out too much 30hz when detuned by filtering out a lowB note on the computer with a low pass. Nonetheless, it is there, and a better bass would generate more I presume.