Hey, JohnK.
Checking things out again, the source of the vibration is probably the rather thin walls leading to speaker vibration, but then again they vibrate because of the sub. The carpet pile is actually thin, and you can easily feel the spikes striking concrete when the speakers are placed.
I'm wondering if the effect is a result of so-called "sub-wall interactions", and might decrease with a forward-firing sub with non-floor firing ports.
In addition, does room vibration cause damage to loudspeakers?
