Passive Radiators vs Ports w/r/t speaker loading at low frequencies

[dfuller]

I think it's pretty well understood here that below the tuning frequency of a port, a driver is totally unloaded (which is part of why distortion goes through the roof at high levels). I haven't been able to find anything via Google about this, so here I am asking my question. Do passive radiators suffer the same problem as ports below the frequency they're tuned for?

 

[Pharos]

A drone blocks much HF junk whereas a port may allow its passage, and a drone has an inherently inferior transient response.
In both cases the driver becomes unloaded and its excursion rockets, and so much of the distortion will be common to both because it is working outside it designed Xmax, and the mass of the drone may result in the driver excursion being greater..

 

[jhaider]

Do passive radiators suffer the same problem as ports below the frequency they're tuned for?

Yes. Some argue they’re a little better, as maybe there’s some cabinet air spring. However, it’s not enough to matter practically.