It is with no small measure of pride that I am reviewing the latest incarnation of the phenomenal Quad ESL63. Y'see, I had a teensy-weensy, but possibly pivotal role in its development. If that taints me with a conflict of interest, so be it. But I'm telling you upfront. As there was no exchange of funds, I sleep clear of conscience.

Some time ago, Quad's Dave Patching asked me in detail about the astounding performance Alastair Robertson-Aikman extracted from his almost-unrecognisable ESL63s. I've lost count of the number visits I've made to the SME Music Room, a journey I undertake willingly because it is an education every time. Think of it the way you would constant returns to the concert hall of your choice. Dave was wondering, too, if I could arrange an introduction, so he and a Quad engineer might examine AR-A's handiwork.

Additional Resources
• Read a Quad II Reissue Preamp Review from Ken Kessler
• Read a review of Quad 989 Loudspeakers from HomeTheaterReview.com
• Learn more about Quad's 33 Preamp and Quad 303 Amp. 

So, in a way, I played matchmaker. Alastair was, as ever, a genial host, utterly forthcoming in his description of his handiwork. But he reiterated what every Quad/SME fan knows: the reason his '63s sound so incredible isn't simply the extensive modifications he devised. There's the small matter of the most robust, solid and generously-dimensioned listening room you could hope to find. And there's the other small matter of a pair of pristine Krell Reference Monoblocks, the genuine Class-A 200-watter that many still believe to be the finest solid-state amp ever produced.

Dave was taken aback by the many hundreds of kilos added to AR-A's '63s by virtue of the machine steel blocks on top. I'm sure he was mentally calculating what the shipping costs would be if Quad were to emulate even a small part of the SME treatment, incorporating only bits of it. Regardless of the impossibility of releasing even a limited run of cloned 'SME Quads', Dave left with one important realisation: he knew that the ESL-988 and ESL-989 were capable of more.

Armed with ideas, the Quad design team got to work. They applied the tweaks to both models. The smaller uses four panels, the larger six, increasing the speaker's height and bass output. Other than that, they're virtually identical and sound different only at the (far) frequency extremes.

For readers unfamiliar with the Quads, they are full-range electrostatics. Instead of cones, they employ a very thin MYLAR membrane, one-tenth the thickness of a human hair, treated with a special conductive coating. Stretched between two electrode plates, both plates have a high positive charge (+5000v), but there is a slight difference between the charge on each electrode. This difference causes the negatively-charged membrane to be more attracted to one than the other, resulting in movement of the diaphragm.

Mounted on an open frame, the diaphragm is free of any cabinet coloration. Because the diaphragm behaves as a full range driver, there is no need for a crossover. As Quad states, 'There are no discontinuities in the frequency response curve, so you get the full music spectrum, as it was recorded.'

Where the ESL63, the 988/989 and now the ESL-2805/ESL-2905 differ from rival ESLs is in a neat approach that Peter Walker spent 18 years perfecting. Working from the premise, recognised by acousticians, that an ideal loudspeaker should be a point source from which sounds waves ripple like a pebble in a lake, he set out to emulate such behaviour.

He created a panel using a series of concentric anodes, instead of just two plates, allowing Quads to produce a spherical sound pressure pattern. A series of electrode rings are fed with delay lines, so each ring responds to the change in current a split second after the previous ring. This produces movement in the diaphragm identical to the 'ripple in the pond'. This is principle behind every Quad ESL since the '63.

Quad continued to refine the '63, the first major deviation being the addition of two extra panels to create the near-double height '989. As exhibited by the specifications of the ESL-2805 vs the ESL-2905 - the eventual replacements, respectively, for the less expensive, still current 988/989- the differences are few but notable:

Impedance variation: 4-15 ohms (2805), 4-20 ohms (ESL-2905)
Frequency Response (useable): 33Hz-23kHz (2805), 28Hz-21kHz (ESL-2905)

That's it. Everything else is the same bar weight and dimensions: 34.8kg vs 41.6kg and 1040x695x385mm (HWD) for the smaller speaker and 1430x695x385mm (HWD) for the taller, plus up to 55mm for the spikes. So, footprints are the same, but the height does make them more visually imposing. And, in black, they are rather monolithic. Take note of those specifications, though, as I will return to the differences.

Given that Quad could neither provide every customer with an SME-like room, nor justify shipping speakers weighing 200 or 300 or more kilos, all that could be emulated were improvements to rigidity. Most visible is a full-height strut running from the top of the speaker to the back of the base plate, shaped so as not to interfere with the rearward firing sound. The strut features tensioners so you can tighten the hold, and there's a choice of substantial spikes or floor-friendly feet. Quad also supplies a pair of hefty, 8kg metal slab to fit under the plinth, as much for EU rules (no kidding - you have to ensure that a brat can't tip over your speaker) as for adding mass for sonic purposes.

But nothing beyond the diaphragm itself has been left alone. As has been cited to the point of entering urban mythology, build quality, by virtue of moving production to China, has gone up. Price, of course, has gone down, and I'm sorry for all of those who still manufacture in the West, but it's a fact of modern life, like hell at airports and reality TV.

From the bottom up, the base, which houses the electronics, is made of steel, with piano-lacquered trim. It features a sloped rear connection panel, with mains input and speaker terminals, with a neat, see-through dustcover. Attached to this are two extruded aluminium vertical rails, which hold the speaker assembly. The drivers are locked in place by a solid-steel top-brace, also capped with trim finished in black lacquer; the sides retain their natural metal colour for contrast. Protecting the elements are black grilles, and the look is finished with the Quad logo at the bass, illuminated a soft white. This can be dimmed or switched off if so desired, but I prefer knowing they're connected to the mains and ready to rock.

Set-up is straightforward, provided you have someone to help with their bulk. I did it on my own, but it's a minor struggle. From cold, the Quads need mains charging for at least an hour, some would say a day. Burn-in period is harder to discuss because I don't know how many hours the review pair had before reaching me. What I can say is that after three days left on, with a CD in repeat mode, they appear to have reached optimum burn-in. Warm-up is not an issue, because I leave them powered at all times.

Positioning was the trickiest part. Although relatively immune to proximity to the sidewalls, and well-known to need at least 2ft behind them, the ESL-2905s are incredibly sensitive to toe-in. Quad specifies 5-20 degrees, with a minimum of 2.5m between them measured at the inner edges. The latter seemed a bit draconian; I used them with only 1.6m between the inner edges and it satisfied Dave Patching.

Amplification? They like power, end of story, and they can take a bit of a hammering before the protection circuitry kicks in. I managed it only once, when playing Bad Company's 'Can't Get Enough' for my son. One side went silent. I lowered the volume control, and seconds later, the speaker was on again. While a 909 will drive the ESL-2905s, Quad purists might want to buy a pair of the forthcoming 909 monoblocks, which will have in excess of 200W each. Whatever else I might suggest, the McIntosh 2102 was a blissful match. Then again, ESLs and valves always seem to get along like Kate'n'Pete.

Bad analogy: Charles and Camilla.

Anyway, it took all of three seconds to realise that my life was about to change. Word had already reached me that my colleague Tom Gillett, at Stereophile in the USA, had gone nuts about the ESL-2805, while AudioReview in Italy almost ran out of superlatives. Paul Seydor of The Absolute Sound, as righteous a Quad devotee as exists anywhere, was waxing glorious, as was Robert Greene. Little details had emerged. 'Half the distortion of the ESL-989' and 'bass that makes you wonder where the subwoofer is hidden' and 'you won't believe how loud they'll go', ad nauseum.

C'mon. I knew they weren't gonna suck from the outset because, after all, weren't they just '989s in extreme-sport clothing? Uh, no. Whatever are the undisclosed modifications, the '2905 is a lot more than an armoured '989. It's a '989 on steroids. But from a health food store.

Anyone who 'knows' what Quads sound like will be disarmed from the very moment the bass kicks in, so be warned. It is best to approach these first with something light, something acoustic, because you will be so disconcerted by the lower registers as to need a period of readjustment. Read my lips: the Quad ESL-2905 delivers real bass, as no full-range ESL I've ever heard has done before. And that includes some with four times the radiating area. I'm not just talking about boom-boom quantity. I'm referring to extension and control.

There's a tautness, a rightness to the '2905's bass that made think 'WATT Puppy' again and again. Not quite the same levels of slam, but certainly similar quality and realism. Nothing will ever plaster over the schism that divides dynamic speakers from panel-types, so the '2905 and speakers like the Wilsons are not mutually exclusive, any more than the tubes vs transistors gap will be breached. But two theoretically-perfect speakers of differing topology have to sound the same, or one is not perfect. And in the lower registers, the '2905 emulates the power of a dynamic speaker's bass with a proficiency you do not expect of a panel smaller than a barn door.

Once you can get past the notion of deep bass from a Quad - sort of like the shock of hearing something intelligent from a guest on Big Brother - you also have to deal with the fact that they'll go as loud as you will probably ever need. But this, and the bass, raise a question I can't yet answer: what you give up when moving to the smaller, £4500 ESL-2805. Hence my noting the specs, above.

Y'see, I am never letting go of the new Quads. But they're a tight fit in my room. Dave Patching himself uses the smaller model in (no kidding) a converted barn, while my American colleagues have both enthused about the smaller speaker. I am hoping that I won't miss the extra 5Hz down below. But that's a practical concern of mine - nothing do to with the speaker overall.

After realigning my prejudices, after finally accepting that Quad had achieved what was deemed impossible short of going to the lengths of AR-A, I sat back to hear what are simply the most translucent, open, spacious sounds ever to caress my ears. Somehow, the speaker has quieter silences, suggestive of greater dynamic range and the concomitant lower noise floor. Even with vinyl, and the low-level whoosh of groove tracing, you'd be hard-pressed not to think that you were listening to a CD. Sounds hovered against the proverbial black velvet background. You heard the recording and nothing else.

Quad got everything right with one proviso. But it's a proviso that harks back to no less an authority than Peter Walker. It was Peter who posited that every recording has a perfect playback level, when everything snaps into place. The '2905 enforces this notion with a handy mechanism: if the playback level is too low, the music appears to be coming from a space below your line of sight, and it occupies a smaller stage. Turn up the level to the correct amount, and it rises up, while filling the left-to-right plane. Go too loud, and it grows a touch edgy.

This is not a criticism, and it has nothing to do with power handling or distortion. It has to do with 'rightness'. No more, no less. You will find yourself treating the music the way you would an image being focussed by a camera with manual lens. And you will know when it's spot-on.