I've had them back in the 80': one of the best speakers I can remember (with the due consideration about their limits!). Their impedance is quite high in the mid (more than 500 ohms if I remember correctly) and drop only at around 20 Khz. All the solid state amps I've tried failed miserably (no power at all!) and when I was going to buy a pair of Counterpoint SA4, something happened and I was forced to sell the Stax. Still missing the sound (or lack of it!). OTL is the way to go as suggested above.
Stax stax ESL-F81 - please help
I am trying to figure out what amps would drive F81 best. I have a Class A 20W custom made ECC88/MOSFET Amp that works great with high sensitivity speakers but fails badly with Stax, McCormack DNA-1 Deluxe that drives Stax fine but is not as fluid as Aleph 3, Pass Aleph 3 works fine but clips at higher SPL and Symphonic Line RG11 that works nicely but does not bring anything special to the table. These are very demanding speakers.
Frequency Characteristics: 40Hz ~ 20KHz (-10dB)
Impedance: 4Ω or full band
Sound pressure level: 73dB (equivalent 8Ω 1W/1m)
Maximum input instantaneous: 300W (equivalent 8Ω)
With impedance all over the place from 2 to 32 depending on the frequency. Any suggestion for under 2K tube or sand amp?
Frequency Characteristics: 40Hz ~ 20KHz (-10dB)
Impedance: 4Ω or full band
Sound pressure level: 73dB (equivalent 8Ω 1W/1m)
Maximum input instantaneous: 300W (equivalent 8Ω)
With impedance all over the place from 2 to 32 depending on the frequency. Any suggestion for under 2K tube or sand amp?