One Thing Audio
Quad
ESL 63, Reviews, Keylines (Hifi-Review January
1990 )
This article first appeared in Hifi-Review January 1990 and was written by Noel Keywood (Provided by Christian Steingruber, February 2002).
Keylines
Noel Keywood gives his personal views on the world of hi- fi.
Quad's ESL63 loudspeakers are the cause of my growing mania. Every time I peruse through their extensive theory and contemplate what can be done to improve them, answers drift in off the wind. These loudspeakers represent flawed perfection. Conceptually, they are stunningly pure. They are the only massless, more-or-less distortionless, point source spherical radiator currently available in the world, as far as I am aware. The theory behind their operation is obscure but astonishingly clever. The problem is one of removing the flaws.
Let me explain the treble beaming I talk about in the Arcici stand review and what can be done about it. The heart of the 63s is a moulded plastic panel assembly on whose outer face, front and rear, is a conductive copper film. Unfortunately, this film is exposed and carries around ten thousand volts (10kV) from a source impedance, the step-up transformer, low enough to provide enough current to kill you. To prevent users or their pet budgies being fried, Quad use an aluminium mesh grill as protection, over which they stretch a fabric cover. The grill has to have very small vents so a child cannot poke a metal knitting needle or suchlike through. The mesh used has louvres angled downwards and it is these that beam treble down toward the floor. Long have I wanted to rid the Quads of these items, since obviously they were affecting their sound, to a degree I could only determine by getting the hatchet out.
So I did it. Off came the sock first, then the aluminium panels. They are held in place simply by their own tension and some fabric tape. It was obvious that the aluminium panels can be turned around so the Quads beam upward. This i~ one simple way of getting them to sound brighter when floor standing at least. I can't suggest you do this yourself, but a Quad dealer may well be able to and I see no safety objections. Quad told me they fit the louvre angled down so you can't see daylight through the speaker, since some people might think they were empty and they'd been done!
People without enquiring children or daft pets could well have a wide mesh fitted. I recall seeing plastic meshes for garden use that could be ideal, having enough mechanical strength, being pliant enough to bend and being dead-sounding (non-resonant) too. Again, I can only suggest you get an experienced person to perform this modification. Ideally, the mesh should be just fine enough to prevent a finger going through by accident, then the sock can be left off. Otherwise, it might be safer put back on.
What I haven't mentioned is that a very thin mylar film (a thin industrial version of Clingfilm) completely covers the electrodes to keep dust and hairs out. This must not be removed or broken, since dust will cause arcing and breakdown inside the speaker. If this occurs a rebuild by Quad will be necessary, which is expensive.
Temporarily, I am using the 63s without grills or sock and the transformation is stunning. Apart from removing all the dullness and beaming, it has made the loudspeakers incredibly sweet sounding, got rid of some fine overhangs and colorations - probably caused by the aluminium - and provided even more finely differentiated low-level detail. The latter property of the Quads, which was always one of their great strengths, is now absolutely stunning. Their low-level delicacy is profound. I noticed that, generally, classical music benefited more than Rock. Violins have a smoother and more natural tone, a slight wiriness having being removed. Instruments in restrained passages sound beautifully pure and extremely delicate. These speakers now have such a light touch with fine details that I am quite stunned by their presentation. The Quads have always been radically better than coned loudspeakers in this respect, but it is difficult to imagine without having heard it just how much better they can be. Or, put another way around, it is difficult to understand just how much fine low-level information is completely erased by conventional loudspeakers, due to mass, stiction and other losses.
I was surprised when Quad agreed that the ESL63s do sound better naked. They normally politely pooh pooh any suggestion that a Quad product can be improved. But they did stress that an operation like this was not a practical proposition, being extremely dangerous. I tiptoe past mine with caution, half expecting a lightning bolt to streak out and hit me. Some sort of wide protective mesh will go back on, because the likelihood of getting a terminal belt is just too great. I used to build valve amps and well know what one receives 85 retribution for a careless moment: and they deliver only six hundred volts at most. Ten thousand volts sounds like no fun at all to me!
Positioning is another thorny problem with the ESL63s, even though Quad claim they are not position sensitive (this is a some-what theoretical claim). Quads radiate sound from front and rear out of phase, i.e. when the diaphragm moves forward to compress air at the front, it is rarifying it at rear (and vice-versa). Where these positive and negative pressure waves meet at the side of the speaker, they cancel. Consequently, to either side is a dead area, allowing the speaker to be moved up close to side walls. This is the basis for their claim for ease of placement. However, it is the rear radiation that is a problem: I am learning how to cope with it as I move the speakers around the house.
To obtain the startling images only Quads can set up, the rear radiation must not reflect forwards too soon or in too much quantity. Keep them away from rear walls by at least three or four feet if possible, or ensure there is something behind to soak up as much sound as possible. In my lounge I rely on heavy, full height curtains to do this (I further suggest the use of interlining). One could use large panels (try 6ft x 4ft) with acoustic foam or flooring felt, covered by an attractive cloth covering of your own choice. Don't put any solid panels directly behind the Quads, even it they do carry sound damping. Put them against the wall.
Also, I noticed that when new, heavy furniture was moved into my lounge the room stopped booming. Settees and suchlike do a marvellous job of breaking up sound waves and absorbing them with all loudspeakers. With the Quads though, if you place any substantial piece of furniture beside them in the dead area - preferably in between - it will act as an absorbing baffle, improving~ bass and stereo imaging. So Quads love furniture!
This became very apparent when I moved the speakers to a sparsely furnished, reverberant work room to strip them down. Or the Arcici stands, whilst their basic sound was superb, imaging was confused by early reflections off a rear wall and bass was weak. A temporary cure proved fascinating. I got the ten cardboard boxes from the loudspeakers from last month's test and piled them up randomly behind (but away from) and between the speakers. This was so effective in breaking up the rear radiation, absorbing high frequencies and increasing apparent baffle area that stereo imaging, was brought back to normal and, quite magically it seemed, the Quads developed bass! What you have to remember is that the 63 do actually produce bass, but you don't hear it because of cancellation. Overcome the cancellation effects with anything like books, soft furnishing - perhaps bean bags or whatever - and bingo, you improve the bass.
Finally, a tip on widening the useful listening window. To avoid the narrow, ideal "sweet-spot" problem, toe the 63s in heavily so the right one points directly at the leftmost listening position and the left one the right listening position Sitting full right or left, the most distant loudspeaker will then beam straight at you, maximising its contribution. The nearest will be slightly muted, reducing its contribution, resulting in a good subjective balance and a complete soundstage.
Hifi-Review January 1990
