[Mondial]

There is some evidence that the radiators are effective in reducing low frequency resonances in the cabinet. 

Rather than actual passive radiators, they are more like damping elements, which are tuned to the resonance of the enclosure. They have a lossy material mechanically coupled to the back of the cones, which absorbs the sound energy at the resonant frequency.

Here is a link to the actual Philco patent, which goes into a lot of detail regarding their operation. There is also a graph of the bass freq response, with and without them installed.

https://docs.google.com/viewer?url=paten...059929.pdf