To add a bit more. The Shiva was one of the drivers that was well suited for downfiring, without any sag in the surround, unlike some others. Adire Audio was founded by Dan Wiggins who was a true gentleman, esp to the DIY community, and when the business of making drivers when bust I think( i dont know for sure) the Shiva part of the business went to Kevin Haskins who now markets them. I have dealt with Kevin and found him to be always courteous and very helpful.
Another subwoofer driver mfr was Nick McKinney of Lambda who made outstanding drivers but also went bust.John Janowitz of AE Speakers took over his designs and now offers the Lambda range of premium subwoofer drivers, one of which I have in a dual passive radiator alignment.