For a sealed enclosure to get down to 30hz without EQ, the best option is the SBP woofers. They are similar to the TDS but have a dustcap and additional mass. An SBP12 will give an F3 of 39hz and F10 of 22Hz in about 3 cubic foot. The SBP15 will give very similar in about 5 cubic foot. Both can be used up to about 500hz with no issue. If you have DSP available, I would use the TD12S or TD15S instead. Same enclosure sizes. The modeled F3 points are a lot higher but this is just because of the extra high end efficiency. Using EQ to pull down the upper end retains the driver efficiency, reduces power requirements and keeps distortion lower.