There is a lot of arguments going on at the forum re the influence of back EMF.
Just to give some perspective to beginners, here is a simulation, using as a load a real speaker model (also posted in the forum):
U1 is a high gain voltage stage (gain = 10K, BW = 30MHz) like the input section of an amp, U2 is an unity voltage/high current gain stage, like a triple EF output.
Zo is the open loop output impedance of U2.
The components to the right of Zo model the speaker, to which a 10V peak (possibly a very high value) back EMF is apllied at 110 Hz, where the speaker is reactive.
First, the circuit, with U2 input connected to ground - this is a no feedback situation.
Just to give some perspective to beginners, here is a simulation, using as a load a real speaker model (also posted in the forum):
U1 is a high gain voltage stage (gain = 10K, BW = 30MHz) like the input section of an amp, U2 is an unity voltage/high current gain stage, like a triple EF output.
Zo is the open loop output impedance of U2.
The components to the right of Zo model the speaker, to which a 10V peak (possibly a very high value) back EMF is apllied at 110 Hz, where the speaker is reactive.
First, the circuit, with U2 input connected to ground - this is a no feedback situation.