What sensitivity actually tells you
Sensitivity describes how much sound pressure a loudspeaker produces for a defined electrical input at a defined distance. It is useful because it helps estimate how much amplifier power is needed to reach a target level, but it does not describe sound quality.
A higher-sensitivity speaker needs less voltage for the same nominal SPL. In a cinema, that can translate into more headroom before the amplifier or loudspeaker reaches its limits.
Why impedance changes the amplifier conversation
Impedance is the electrical load presented to the amplifier, and it varies with frequency. A “4 ohm” speaker may dip lower than the nominal number. That is why amplifier current capability, ventilation and channel count matter in a large multichannel system.
Distance consumes headroom
Published sensitivity is normally referenced at one metre. Seats in a cinema may be three, five or ten metres away, and room behaviour complicates the simple free-field calculation. The farthest important seat is often the better design reference.
Cinema peaks are the reason for headroom
Average listening level can be comfortable while transient peaks are many decibels higher. Designing only around average power is one of the easiest ways to create a system that sounds compressed when the soundtrack becomes demanding.
How we size amplification
Start with target SPL at the seat, listening distance, loudspeaker sensitivity, impedance and the number of channels sharing the amplifier platform. Then leave sensible electrical and thermal headroom.