Yes, "transducers" was the term I was looking for!
As a matter of fact, running through the photos at sites I was given, I think the lower end items of AURA's "bass shaker"s are exactly what I've used in the past.
Thank you all for the references.
Frank, thanks for the note on PD-ot. I can't believe I've been missing out on it all of these months. On my way to subscribe now.
-- David Shimamoto