How do I calculate the input sensitivity for my application?

Input sensitivity is dependent on the desired output power, the impedance of the speaker and the gain of the amplifier. Naturally the desired output power cannot be higher than the rated maximum of the amplifier. In the example the input sensitivity for a 400W output in 4 Ohm is calculated. The gain and maximum output power is given in the datasheet. The speaker load is dependent on the user application.