To get the best results out of an SET, unless its fairly high powered, the speaker should really not be less than about 97 db. Otherwise the amp will be making a lot of distortion, meaning that it will not sound as transparent and will also take on a harsher quality.
Typically efficiencies 10x higher than stated in prior posts (101 db to 109 db) are preferred- with these higher efficiencies the distortion of many SETs becomes unmeasurable.
This is why horn systems like Altec, JBL, Klipsch, Electro Voice and others have held their value so well. But in general, you want either a horn system or a high efficiency single-driver full range speaker like a Lowther, PHY or similar.
Now if you are in a small room the lessor efficiencies may work. As in many cases, YMMV.
Typically efficiencies 10x higher than stated in prior posts (101 db to 109 db) are preferred- with these higher efficiencies the distortion of many SETs becomes unmeasurable.
This is why horn systems like Altec, JBL, Klipsch, Electro Voice and others have held their value so well. But in general, you want either a horn system or a high efficiency single-driver full range speaker like a Lowther, PHY or similar.
Now if you are in a small room the lessor efficiencies may work. As in many cases, YMMV.