Full Range Drivers and SET's, why is a classic combo?

A 300B uses a plate voltage of about 400. The 211 and similar transmitter tubes use 1200 volts. It is difficult to build an OPT primary that can handle 1200 volts, compared to 400. The same for the power supply components!

The SE 300B can do about 7 watts at 1+ per cent distortion. The 211 and similar transmitter tubes can do about 15 watts SE. That is about a 3 db difference in drive capability for a whole lot more cost and complexity!

A good single-driver speaker for low-watt SE amps is an Altec 755. I had a pair. Put it in a one-cubic foot box and it will work from 60 hz to 12k hz with fairly flat response and enough sensitivity! Add a subwoofer for the bottom two octaves.

I own three SE tube amps: a 2A3, a 45 and a 6BG6. The best speakers in my collection for them are the venerable. Klipsch Heresy Mk1's (99 db sensitivity).

Thanks for the detailed explanations.