Oblgny, efficiency is not necessarily the same as sensitivity, and 2.87 Volts is not necessarily the same as 1 Watt.
The 3.5’s depending on vintage were rated as 88-89 dB @ 2.87 V. in to 8 Ohms. That does not account for for the 4 Ohm nominal/minimum impedance rating (though not dropping below 5 Ohms in independent testing ). Suffice to say one could round down to a 85-86 dB sensitivity into actual load.
The same holds true for the 3.7’s, only more so as the impedance drops even further. If you consider the actual impedance load the more relevant sensitivity drops accordingly.
This is why the power levels into lower impedances need to increase as much as they do.