Now thats what you call a sales trap , go back to the shop and bring those drivers back
It also depends on how you wire the drivers in your LS , what your X over looks like etc as to how efficient a transducer will be in the end
Wiki.
Loudspeaker efficiency is defined as
the sound power output divided by the electrical power input. Most loudspeakers are inefficient transducers; only about 1% of the electrical energy sent by an amplifier to a typical home loudspeaker is converted to acoustic energy.
Looking at those numbers i reckon audiophilia as an industry will get shut down by the green brigade by 2030 -2035.
No more howling V12 s and no more sound at home