Bigger is better, lower is better. That means bigger cone size and lower resonant frequency. These speakers need to reach down below 20hz with authority unlike in car audio. If your speaker's Fs is around 30-35, by the time your 15hz depth charge explosion comes, your speaker will be about as torn to shreds as the submarine in the movie. For that reason, you typically need big drivers with high compliances and moving masses as Fs is an inverse relationship of the product of the compliance and the moving mass. If you want, you can add mass to the rear of the cone which has been done before but I would generally just recommend that you use a larger sub with a decently high Cms and Mms, or just a low Fs. In this case, Qts is critical to look out for. Unlike in car audio, if your Qts is .8, don't even THINK about putting that into a ported box. That thing will flop around like a dying fish. Instead, you will need to follow the >.7 = sealed and