"John Stewart" wrote

...
In your example the DF for the group is 50. However, for each
speaker the source
impedance would be the amp Ro of 0.5 ohms plus the entire series
complex impedance's of
the other nine speakers in the group. That is a condition I would
prefer to avoid.
...

Seems to me this is the crucial point, John. Could be seen as
another example of current sources in series.

cheers, Ian