Bass traps - foam cushiony items from Amazon ok?

The vri-bass resonators are interesting, but expensive and they offer no measurements, or pictures to see what they look like in a room.
Compare to the GIK soffit traps, which are about $250 each and are also effective around 50 Hz.

Hey,
I think there is a minimum critical mass for room acoustic treatments. Maybe start with 6 to 8 2'x4' panels and start there.