QUAD ESL-63
Copyright 2020 © Troels Gravesen

QUAD samples 13817 and 13818. Probably from the mid 80'ies.
Read extensive review here: https://www.stereophile.com/floorloudspeakers/416/index.html

My neighbor inherited these speakers from his granddad together with a Thorens turntable with SME tonearm and some other good stuff - and I had them for loan a few days. This granddad had good taste and cherished his vinyls with the best of best in the 80'ies.

Anything that can be said about these speakers has been said. Listening to Diana Krall, Live in Paris, 45 rpm, is mind-blowing. If you can live without deep punchy bass and limited sound pressure you may never return to conventional dynamic speakers again. This doesn't mean the bass is bad. The bass is phenomenal in its coherence with midrange and treble. A truly remarkable speaker - and eventually I ended up buying a demo pair of 2812 for reference. And they do so well in our living room at the usual place for speakers and works wonder with my bridged EAR-861s.
The QUADs are like having the room embraced by gigantic - and very good - headphones.

 
QUAD ESL-63 driven by bridged EAR-861s. A very good match indeed.

Non-gated frequency response of 13817 in my workshop @ ½ meter distance at middle of panel (red) and +/- 10 cm vertical, green and orange.

Horizontal dispersion @ 0, 10, 20 and 30 deg. off-axis.
Having done some serious listening tests before the measurements, I wasn't surprised by this. Very good indeed.

Vertical dispersion @ 0, 5 and 10 deg. off-axis (red, green and orange).

Far-field response @ 1 meter, 2.8V merged with near-field response @ 300 Hz.
I do have a hard time confirming the claimed 86 dB sensitivity, maybe 83-84 dB is more like it.

I'm just showing this for the unusual profile of a near-field response.
Rather unusual we have 50-20,000 Hz in a near-field measurement. Never seen anything like it.

Oh.... this is what we would like all speakers' step response to look like. Very few do.
This speaker can do square waves!

I'd say this is quite a nice matched pair despite having some 35 years on their back and never serviced.

Impedance measured with a sampling frequency of 192 kHz, thus displays impedance up to 80 kHz.
I just wanted to see where it would go at very high frequency.

Impedance and electrical phase measured with 48 kHz sampling rate.

Some pictures of the electronics.
I wonder how much an up-grade of the blue electrolytic might do as it is by-passed by a very low 1.5 Ohm resistor.
 Well, easy and worth a try.

My wife thought they looked nice :-) Certainly smaller and more domesticated compared to my TL-2s.