A Pause for Explanation
A little more detail about the radiation pattern is justified, I think. We are all used to looking at frequency response graphs and saying, ah yes, there is the little bulge that does this, that, or the other. But with the Quads there is something in addition. This has to do not with “on-axis” response but with power response, the total radiation into the room. Box speakers are omni in the bass and then shift over as frequency rises to forward radiation primarily and even higher up become somewhat “beamy” in the treble.
But the Quads are not like this. They are dipoles all the way down and up into the higher frequencies, too. The radiation pattern does not change until around 5kHz, above which it narrows. So in effect there is a lot less power in the room from say, 300Hz on down than with a box speaker—the box will have become omni, the dipole Quads remaining dipole.
Now this matter is not standardized. One could make an argument that speakers ought not to change pattern with rising frequency. But there is no way around the fact that the difference in directivity will make a difference in sound. Even corrected to be measured flat at the listening position, the Quads sound superb. But they sound different from box speakers because the energy in the room is different. Better or worse…your call. But different for sure.
Almost everyone likes a crisp conclusion. But the Quad ESL63 and its variants have been from the start a speaker family that has gone its own way. They have low distortion, among the lowest; they have almost unparalleled coherence and unity of voice; they have an exceptionally uniform radiation pattern and a very low level of resonant coloration. They are also phase-linear, which I did not mention in much detail earlier, but which is known to have subtle but definitely audible positive effects, on transients in particular (try some woodblocks). In these categories they have always been in the very top echelon and they still are. “Alone at the top” is a phrase that one is tempted to use, though it would be a slight exaggeration since others are in the same realm, though not many. No amount of money will buy a speaker that does definitively better the things that the Quads do well.
But at the same time, nowadays one can find box speakers at much lower prices that will go deeper, play louder, and be flatter in room, and which handle certain types of hard transients better. The Quads are thus something of a paradox, even more than when they first appeared (when fewer box speakers did really well).
The Quad exists in a realm of theoretical design that makes most speakers seem a bit catch-as-catch-can. And anyone who is seriously interested in speaker design needs to listen carefully to this speaker and think hard about what it does and how it does it, just to understand what is possible in certain directions.
Speaker choice is a personal matter, and perhaps especially so with the Quads because of their distinctive sound and balance. But no one’s experience of audio is complete without a careful audition of this great classic of audio design.
SPECS & PRICING
Type: Floorstanding electrostatic panel loudspeaker, 3-degree fixed tilt
Frequency response: 37Hz to 21kHz -6dB
Distortion (100dB at 1m): Above 1kHz 0.15%, above 100Hz 0.5%, above 50Hz 1.0%
Max. power: 200 watts
Impedance: 8 ohms nominal
Dimensions: 25" x 42" x 15"
Weight: 77 lbs.
MOFI DISTRIBUTION (U.S. DISTRIBUTOR)