It appears I misread or misunderstood a little of what you were asking initially as we did not provide dual sealed box specs for the Dcon. The box plans are on the tech center fine, there is no law that says as the number of drivers incrementally increases, the initial suggested box design should increase in a linear fashion matching the driver increase. As said a few times above, going ported with a pair would be, in most cases, a better choice then going with a trio sealed. With a driver like the Dcon, there is no worry in terms of clean sound when going ported (as long as the enclosure/amp settings are done correctly). Not saying to not go sealed, not at all, but if you take a look a the specs of the Dcon it will really tell you about the driver design. Meaning, if you break it down, the Dcon will play great in both sealed or ported, (many people go by the EBP {efficiency bandwidth product} to gauge ported or sealed, and in the Dcon's case it will be comfortable in most any enclosure), but upon further review, you will see that it really sets it self apart from the competition in smaller ported enclosures. But for sure, you can run a trio of Dcon's sealed, that will still be an excellent option. There is not much on the internet based market in terms of higher performance, low-mid power sub woofers. There are plenty of entry level low-mid power sub woofers out there, especially in the mainstream market, but few are manufactured and designed with in the same standards and specifications as the high end models. As in the Dcon is built here in the USA, by the exact same people that build the monster Xcon.