So that means output inpedence on an output coupoled amp is in the basement?
Sort of Lee, I know what you are driving at. The act of putting a transformer to couple the amp output to the load preserves the impedance that the speaker wants to see very faithfully but that secondary of the transformer is basically running open loop, without feedback control.
Let me give you an example that may compare.
The big power transformer on the Phase Linear has a secondary that is only loosely coupled to the AC Grid input. The AC grid input could be said to have a very large damping factor, that is you have to do something really major to it to change its frequency or output voltage by very much. The Grid is very stiff.
However on the secondary of that PL power transformer, you can short a bridge rectifier for example, it blows the 10A input fuse but has not really affected what happened on your line voltage (primary side) very much.
Probably a lousy example but one that has some relevance.