Passive Radiator enclosures?

[mwoehr 1]

Could someone please explain how these work. I know of the advantages of sealed and ported over eachother but where do these fall in?

[johnecon2001 82]

Tunable sealed. Or, in their own category altogether.

[mwoehr 1]

Tunable sealed. Or, in their own category altogether.

Do they have more output than sealed? Do they run as big as sealed or in between sealed and ported?

[bobonit 5]

www.diysubwoofers.org has a great write up on them. Here is the direct link to the Passive Radiators page: http://www.diysubwoofers.org/prd/