The most fun speakers I owned were a pair of G. R. Research OB7's. I did many experiments with them to test the orthodoxies extolled in audio magazines and books on how to create the ultimate stereo system. I tried bi-amplification with the tweeters on their own 245 SET amps and the midrange (2 5" cones open baffle) and the low frequency (4 5" cones sealed box). Then I read about the Wavac 833-A stereo and I made a pair of 833-A SET monoblocks which I connected to the low frequency speakers. Separating the tweeters from the midrange by powering them with separate 245 SET amplifiers sounded better than running both the tweeters and the midrange on the same amplifier. Active crossovers made of resistor and capacitor networks inserted between the mu-follower 6SN7 drivers sounded good and they are supposed to sound better than passive speaker crossovers. But the passive crossovers sounded better. Finally, I tried running the speakers on only 833-A's to all three speaker elements and this sounded better than anything I had tried before. I learned that not everything which is supposed to be the best way to run amplifiers and speakers applies universally to every system and I should not be surprised because speakers costing over $50,000 use passive crossovers.
Eventually I upgraded to Magnepan 0.7's the biggest Magnepans I can fit in my small house of 500 square feet floor space including the bedroom, the shower room, and an open kitchen because I was put off by the complications of cone speakers, their need to have elaborate notch filters in addition to high and low pass filters for crossovers, and boxes which require so much bracing, lined with sound deadener layers inside. I auditioned the Magnepans and they sounded more like live performances in the opera house where I go than any $50,000 speakers I had heard. But you can't drive them with thw 300B, let alone the 245 SET because they are insensitive. That is the price for circumventing the excessive variations and complications caused by back EMF of cone speakers influenced by the surrounds and even the cone material and the cabinets, all with resonances and wild variations in output with respect to frequency. When I got them home they sounded even better with the 833-A's driving them.
GR Research has impressive speaker kits which rival 4 figure factory made speakers and they are well suited for low power SET amplifiers if you don't want to use tubes which take 100 Watts just to heat the cathodes.
