ESL57 vs ESL63

The 57's and 63's still hold their place as the very nearly best speakers ever! Peter Walker's marvels! I have two pairs of 57's. This gives me the option of stacking them for improved image height. Regarding power requirements, both the 57 and 63 work best with 25 to 50 watt amps. This rules out flea- watt SET's. A Dynaco ST70 is an excellent choice for either. Since both have quite extreme impedance curves (30 ohms to 1 ohm) a partnering amp should have a low output impedance (<1 ohm) for best response. Both are voltage-limited because of arcing (20 volts/50 watts for the 57's, 30 volts/90 watts for the 63's). Because of these limits there is no need for high-power amps (risk of damage to the Mylar diaphragms). 

I have a variety of tube and SS amps to use with my 57's: Dynaco ST70, Heath W5's, Golden Tube SE40, Futterman H3 and H3aa's, Quad 303, 50's, 405, GAS Son and Grandson, BEL 1001 ...

I bought my first pair of 57's back in 1981 and kept them in use until 2000. After my move down south in 2015 I purchased two pairs - the prices were right! One pair from Rhode Island, one from England. Yes, the 57 ESL is a speaker that one develops a romantic attraction for!

I can't help but feel that most of the mythology around the Quads originated from the high regard held by his contemporaries for the great man himself, Peter J Walker.

Box/cone loudspeaker manufacturers must have been alarmed upon the arrival of this new technology, but as we have seen, electrostatics were not the future road forwards but merely a sideline.

It's also interesting that although Walker himself believed the 63s to be superior it was the ESL that passed into Hi-Fi legend.

I have the 57s but have spent some significant time with the 63s as well. Overall I prefer the 57s, but I use a set of stands to raise them up a bit to improve the image height. While I use a woofer array and active crossover to biamp in my system, the 57s on their own do bass much better than I expected. They aren't going to go much below 40 Hz but what is there is pleasing. I play a wide variety of music with them including rock.

Mine have the clamp boards installed which means I can use just about any amp with greater than 20 watts power and not have to worry about arcing the speakers. It's a worthwhile upgrade if you purchase a pair without them. I either use Atma-Sphere M60s or a Music Reference RM-10 on the 57s. Both amps work quite well with the speakers.