These are great speakers. Don’t take my word for it though – read some reviews.
I removed the crossovers and I am bi-amping them. You can read about bi-amping here.
They were powered by two modified Charlize II class-t amps for many happy years. The amps had their own AMB Sigma11 regulator and 200VA transformer each. Each amp is fed from its own active 18dB/octave 3rd order LR crossover @2250Hz which uses Mundorf silver/oil and Relcap RTE capacitors, and are powered by Sigma22 regulators and 80VA transformers. I use Neotech speaker cable, available here.
Recently, I started using TPA3251 amps and a dbx234xl crossover for them. It’s a work in progress but sounds amazing and is extremely loud. To set this up, I recreated the crossover on the tweeter using Mundorf Supreme silver/oil caps and a Jantzen cross coil inductor. Values for this were 2.2uF, 0.36mH and 6.8uF, as the original. The tweeters are incredibly revealing so it was worth using premium parts. I removed the crossover on the woofers completely and dialed in the electronic crossover to match. The tweeter’s electronic crossover is at about 500Hz – enough to reduce IMD but not affect the tweeter’s frequency range. I’m so pleased with this sound I haven’t got round to setting up the tweeter with fewer components.
The original crossover was a third order on the tweeter – 2.2uF, 0.36mH and 6.8uF. It was attenuated by a 5W 11R resistor. The woofers were second order – 1.4mH laminate core and 24uF. All poly caps labelled Klipsch. Interestingly, the RB-51 have 1.5mH and 20uF with a 50R shunt on the driver, with 25R, 1uF, 0.52mH and 6uF on the tweeter.