The Significance of Speaker Impedance – Avantgarde’s Change from 8 to 18 Ohms

[DonH50]

Sensitivity is defined in my grad acoustics text as SPL output for given input, e.g. dB/W/m or dB/Vrms/m. Efficiency is acoustic power output for (electrical) power input and is not usually provided in a consumer data sheet. 100 W from a power amplifier is quite a bit, and in fact 1 acoustic watt is very loud (my prof said it would "blow your ears off!") The efficiency of even high-sensitivity speakers is very low.

 

[MPS]

In practice we can consider sensitivity value being the SPL that occurs at 2.83V/1m. This is because amplifiers are voltage sources so they will output same voltage level at the same gain regardless of the load. This voltage (2.83V) is practical because it also equals 1 W output power when the load is 8 ohms. That means that for 8 ohms speaker it doesn't matter if the SPL value is given as dB/2.83V/1m or dB/1W/1m but as soon as load (the speaker) is something else these values will differ. The point of all of this is that one should pay attention both to the sensitivity and impedance.
I don't think it's necessary here to go more to the details as there are several sources available. Such as:
https://geoffthegreygeek.com/understanding-speaker-sensitivity/