The first figures tells the minimum amplifier power needed to drive the speaker properly.
The efficiency of all of these products originally provided high sound pressure levels from the limited amplifier power available at the time.
Such sensitivity requires less amplifier power to achieve the same loudness.
By way of loose analogy, amplifier power may be compared to horsepower in cars.
Some also believe that they have a greater level of perceived loudness for a given amount of amplifier power.
Of course, the receiver must provide enough amplifier power for all those speakers.
For every 3 decibel sensitivity difference between the two speakers, you will have to double the amplifier power of the lower speaker.
This uses more amplifier power and may drive the speaker cones into non-linearity.
In addition, the theater has 20,000 watts of amplifier power and over 50 speakers.
Much more amplifier power is required to reproduce low-frequency sound, especially at high volume.