What is your take on high efficient speakers vs. low efficient speakers?

@johnnycamp5   100% , just want to figure out , how  you know( My mains (104db) start to drop like a stone at around 80Hz. )

Because the speaker manufacturer displays frequency response graphs for each loudspeaker they sell.

i’ve also run sweeps myself, seeing the same response.

My experience this is not a particularly unique frequency response using high sensitivity loudspeakers. More common than not.

My friend is a DIY speakers builder. He also fixes drivers.

He had and measured dozens different 15' driver JBL, Tannoy, Altec,... He says the maximal sensitivity of 15' driver in vented box (of any size) at 100Hz is 94-95dB. Some 15' drivers like Altec have higher sensitivity around 200-300Hz but it drops to 95dB at 100Hz. 10'-12' have even smaller sensitivity at 100Hz.

Most driver manufacturers measure sensitivity while mounted in an anechoic chamber running 1000Hz. 
That’s why it’s important to look at the entire F.R.

High efficiency requires low power amp, while low efficiency requires high power amp. The majority stand mount speakers need 150wpc to sound its best.