Jadis JA30 - Quad ESL63 .. 4,8 or 16ohms?

That's right Sbrown .. also my friend is getting tremendous bass response at 16 ohms taps but if you take a look at the Quad ESL63 impedance graphic ..

http://img147.imageshack.us/img147/2903/quadfig1py5.jpg

... you are gaining from 0 hertz to 600/700 hertz but you are losing from here to the 15.000 hertz and above
While theoretically with the 4 ohms tap you should gain between 600/700 hertz to the whole rest band expecially in mids and highs area .. the most important to our ears .. and where we have the most important part of musical message.

My Defy 7 sounded better on 4 ohm taps and it makes sense when one factors in that ESL's require the most power in the highs (the speaker acts like a big capacitor as a load). FWIW, I doubt if they have enough power regardless of what tap you use.

4est, you are discussinging the Quad ESL63 with the same ideas that are usually applied to electrostatics such as SoundLab and Martin Logan, but the ESL 63 is a different case. SoundLab and MartinLogan have impedances that can be as low as 1 ohm, but the ESL63 never goes lower than 4 ohm, being 5 ohm at 10kHz. Unless you listen to a lot of heavy rock and electronic music the power of music at frequencies above 5 kHz is much lower than average power - I have measured it with a spectrometer. Some versions of Shostakovich symphonies or some challenging test disks have peaks that are exceptionally rich in high frequencies, but most of the music some one typically listens in ELS63 is not a problem. Remember Peter Walker designed the ESL63 for the Quad 405 that was also current limited.
May be you prefer the 4 ohm tap because with this tap the damping factor of the amplifier is more adequate for your taste and listening environment.
I did some research and plenty of measurements on electrostatics because I own an amplifier that sounds lovely with electrostatics but it is current limited - the Dartzeel.
If someone has interest in the original HifiNews 1981 measurements I will be pleased to email them.

why not just try for yourself and hear the difference

4 ohms will have a tighter but somewhat dryer sound

Because it's useful , if not necessary , to listen and compare your experiences .. Philijolet