I'd recommend speakers with a nominal impedance of 8 ohms or above, and without any wild swings into the low impedances.
For amps of 8 watts or more(like 300B), I recommend you select speakers with 93db/watt or higher sensitivity.
For amps of 3.5w - 5w(like 2A3) I recommend speakers of at least 96db/watt.
For amps of 2w(like a 45) I recommend speakers of at least 99db/watt.
Drivers like Lowther, Fostex, AER, REPS, Diatone, Coral, and similar single-driver speakers work well with SET amps, and are often used. Front horn, back horn, or TQWP setups are common.
Some commercial speakers that a commonly mated with SET amps are Cain & Cain Abbey, Beauhorn, Lammhorn 1.8, Lowther(various models), Oris horns, Avant Garde horns, Klipsch horns, etc.
For amps of 8 watts or more(like 300B), I recommend you select speakers with 93db/watt or higher sensitivity.
For amps of 3.5w - 5w(like 2A3) I recommend speakers of at least 96db/watt.
For amps of 2w(like a 45) I recommend speakers of at least 99db/watt.
Drivers like Lowther, Fostex, AER, REPS, Diatone, Coral, and similar single-driver speakers work well with SET amps, and are often used. Front horn, back horn, or TQWP setups are common.
Some commercial speakers that a commonly mated with SET amps are Cain & Cain Abbey, Beauhorn, Lammhorn 1.8, Lowther(various models), Oris horns, Avant Garde horns, Klipsch horns, etc.