Close to that long ago I used 3 way cone speakers driven by bi-amped 45 SETs.The crossovers were complicated by notch filters controlling resonant drops in impedance. It was not the simple matter of using more active filters between the 6SN7 drivers of the 45s to try to simplify the speakers by eliminating passive speaker crossovers to sound even as good as the complicated elaborate passive crossovers. I looked at ribbons and quasi-ribbons and preferred the quasi-ribbons to ribbons which often needed adjustment and replacement to fragile pleated aluminum. I imagined an all magnetic planar speaker system. I discovered Magnepan and they had a new 0.7 which is all quasi-ribbon and only two elements with simple first order crossovers and 4 Ohm impedance throughout the frequency range without need for any crossover circuits to make the frequency response consistent.
But you can't drive them with a 45 SET. By coincidence I discovered how simple it is to have a 45 drive an 833A and run the 833A at 1 kV on zero grid bias with a Hammond 1642SE output transformer. This was a perfect match for the power demanding Magnepans. I prefer it to cone speakers costing over $50,000 I have heard demonstrated.
But you can't drive them with a 45 SET. By coincidence I discovered how simple it is to have a 45 drive an 833A and run the 833A at 1 kV on zero grid bias with a Hammond 1642SE output transformer. This was a perfect match for the power demanding Magnepans. I prefer it to cone speakers costing over $50,000 I have heard demonstrated.
