Hi Wayne,
A couple of silly questions then...
If Qes is dependent on the amp you are connecting a driver to, then what assumptions are behind the driver's specs in this area?
And then when picking drivers for use with tube amps, we're generally looking for more efficient speakers, which tend to have stronger motors, which exacerbates the issue, or lighter mass which helps the issue... It still seems like there's an opportunity for a driver selection optimizer thingy to sort ot these engineering trade-offs.
Thx, Chris