Quad ESL-63 Introduction


Quad ESL-63Quad ESL-63Quad

These are my Quad ESL-63 speakers.  These are the main front stereo pair in my current 5.1 home theatre system and have held that position for over 21 years since 1983!  There is no competition from anything that could possibly replace them!  ESL stands for Electro Static Loudspeaker and 63 stands for 1963 (when I was 1) when Quad first started the design.  People have either never heard of them or have always wanted to see & hear them and they are surrounded by more mystery and misinformation than any other Hi-Fi component on earth.  Either way, once seen & heard, everybody has something to say about them and I have had the pleasure of listening to them for all those years and hopefully many more to come!  I bought them new from University Audio in Cambridge England just before Christmas 1983 at a cost of 1100 GBP and they were serial numbers 11089 & 11090.  I had a small vibration problem with the original pair from the shop which I now believe to have been the dust covers.  I was listening to a digital remastered CD of Pink Floyd's "Dark Side of the Moon" (this is in 1983, think about that!).  At the beginning where there is only the sound of the heart beat, I could hear a kind of fuzzy rattle.  This was solved by Quad personally delivering a brand new pair tested at the factory that day direct to my house in Cottenham, near Cambridge, just a short distance form Huntingdon where they are made. These are serial numbers 13009 & 13010 delivered January 5th 1984 by Richard Ramsay from Quad, so some 1000 pairs newer than the originals.  Richard and I sat there and listened to the CD on the new speakers with my Sony CDP-101 CD player and Technics SE-A5 amp.  Remember at that time, only a handful of people in the world had even seen a CD player let alone listened to a Pink Floyd CD on electrostatic speakers!  We just sat there in total awe of what we were listening to.  The only thing I have done to them was in 1994 when I replaced the grill socks with a black version that Susan made and sprayed the base & top in black satin to update their appearance a bit.  Originally, they were teak with brown socks as shown above.  They have only gone out of production in recent years and are now replaced by the Quad ESL-988.  The last few that came into the U.S.A. were sold for around $6000 a pair!  I could actually sell them after more than 21 years of use for more than I paid for them new!  However, don't even bother asking - I will never ever sell them!  The only issue I could possibly describe as a problem is their cost and this is of course why they are not more widely known and used although there are plenty of more expensive speakers around.  While suited to classical music because of their superb mid range and treble but modest bass, I can tell you that they are just as good for pop and rock music where vocals sound like never before especially when used in a system with a subwoofer.  Because of this, some people actually think that Quad ESL-63's can be somehow damaged by listening to loud rock music.  This is total poppycock and I have been rocking my ESL's hard for years with no problems whatsoever!

What makes ESL-63 speakers special

Quad ESL-63 side view

Quad ESL-63 side viewThey have no moving coil or electromagnetic drive units!

They have no cabinet!

On a sunny day, you can see right through them!

There is no built in amplifier, but they have to be plugged in!

They have the profile of a bar of chocolate!

They are a 1-Way speaker system!

The diaphragm is 1/10 the thickness of a human hair!

I consider them to be the best speakers in the world!


How ESL-63 speakers work

ESL-63 with the sock off!Clearly, the ESL works in a totally different way to a conventional loudspeaker.  While most speakers work with multiple moving coil hard coned type drive units, the ESL uses a very thin flexible maylar (polyester film) membrane diaphragm that is one-tenth the thickness of a human hair! The diaphragm has a special conductive coating and is stretched between two electrode plates.  Relative to ground (Earth for the English), both electrode plates have a high positive charge of about +5000 volts, but there is a slight difference in the charge on each electrode.  This difference causes the negatively charged membrane to be more attracted to one than another, thus causing the movement of the diaphragm.  As the diaphragm is mounted on an open frame, it is free of any coloration from a cabinet because there is no cabinet, and because the diaphragm acts as a full range driver there is also no need for a crossover!  This means that it is a dipole speaker where the sound emanates from both sides at the same time but with inverted phase.  It can move more delicately than the smallest tweeter and is larger than the largest woofer to give reasonable bass, all from just 1 driver that is virtually weightless!  There are absolutely no discontinuities in the frequency response curve, so you get the full musical spectrum from the single diaphragm, just as it was recorded.  Because the speaker is a dipole with no cabinet, the bass is not quite as good as a speaker with a box of the same size,  but that makes no difference in a 5.1 system these days as you always have to have a large subwoofer anyway.  Quad sometimes refer to this design as FRED meaning Full Range Electrostatic Dipole.  By using a series of 7 concentric annular ring, anode electrodes, rather than just two plates, the Quads are able to produce a spherical sound pressure pattern on the diaphragm that gives the effect of producing a ripple like a pebble dropping into a pond.  The signal is fed to the series of electrode rings via delay lines, so each ring responds to the change in charge a split second after the previous ring creating movement in the diaphragm identical to the ripple in the pond.  So the diaphragm is not just moving forward and back in one solid piece, but is reproducing the fluid movement of air that would occur at a distance of about 1 foot behind the plain of the diaphragm from a point source of no dimension.  All in all, because of this unique design that has no solid resonance in the diaphragm or any cabinet, the sound reproduced it totally uncolored and very transparent with incredible stereo imaging.  There is nothing else on earth that sounds like them because quite simply, they sound like nothing at all!

Inside bsae of ESL-63Inside the base of the ESL are all the electronics that charge up the electrode plates and the delay lines that feed the signal to the anode rings.  There are 7 rings on each side so 6 delay lines are needed for each side so that the signal can be applied at the 7 points in time needed.  These are the 6 orange things on each side at the top of the picture.  The first ring gets the signal as soon as it comes in so there is no delay line needed for that.  The two large transformers are for stepping up the 120 or 240 volt AC input up to the 5000 volts DC needed for the electrode plates on each side.  In the center are the protection circuits.  There are two of these and there is a very good reason why they areESL-63 middle unit showing electrode rings needed!  As you can imagine, with up to 5000 volts of electrical potential between the electrodes, a spark between them would be like a thunder bolt blowing through the diaphragm!  Inside the pedestal is an antenna that detects when the air gets ionized just before sparking is about to occur. When this happens, the protection circuit short circuits the input of the speaker leaving a 1.5 Ohm load for the amplifier. Wow!  This sure gives the power amp a shock!  As well as that, there is a soft clipper that starts distorting the signal at about -3dB as a warning.  Because of this, some people say that the ESL-63's are not good for playing loud.  This may be true if you have a very large room, but I have never had a problem in any of my setups and I listen to loud rock music all the time.  My wife Susan usually tells me when I am going too loud and she always activates before either protection circuit!  When the protection circuit shorts the input of the speaker, in most cases when using a large power amp like the Technics SE-A5, the amp just keeps on going if it is not running at too high a level, otherwise the amp will activate it's own over current protection and there will be silence for a couple of seconds.  If the amp does not trip out, the signal can still be heard coming from the speakers but because the load is now so small at 1.5 Ohms the distortion becomes quite high so this can sound rather strange.  Usually, the only time the protection circuit will activate is if there is some spike on the mains power.  With such a large step up (almost 42 times with 120V AC) a high spike at the input could cause 1000's of extra volts to appear at the electrodes and potentially cause sparking..  This can happen if switching a motor on or off for example like a vacuum cleaner or a refrigerator on a circuit close to the speakers.  Some simple planning with regard to what is plugged in where and some basic filtering on the supply can prevent this problem.

Wanted:  Quad ESL-63 Speakers serial # 13009 & 13010

So says Earl - What a crock!Well, so now for the bad news.  In 2007 when we sold our house in Maryland I stupidly trusted Earle's Moving & Storage in Annapolis, an Allied Van Lines agent to look after a few boxes while we were getting our house in Florida ready.  When the shipment arrived later that year, the speakers were gone along with one of our sofa's and a bunch of other stuff!  Needless to say Earle and his cohorts are now no longer in business and I know exactly why.  Apart from not understanding their own  mission statement they didn't know how to count boxes.  On top of that, the Allied Van Lines claim service actually had the audacity to tell me that it was my fault for not checking through all the boxes on the day they arrived!  What all of them??  I have to say though, it was so$5000 of this for one pair of Quad ESL-63's! funny to be able to refer the claims agent to this web page that contained copies of all the receipts and the entire history of the speakers including pictures of them in the house where they were shipped from just five seconds after she smugly asked to see the receipt for a pair of 25 year old speakers!  Just look at that check to the right.  $5000.00 of that is for the now famous Quad ESL-63's serial numbers 13009 & 13010.  I guess they just don't know that Quad ESL-63's go for about $1300 to $1600 a pair on eBay...  But like I said to the claims agent, I don't want the money, I want my speakers back!  If you know where these speakers are and can return them to me in their original condition as of 2007, some of that $5000 will be yours!  Please let me know if you see them!

I did try a replacement pair of ESL-63's from eBay, serial numbers 13518 & 13518 but they just weren't the same as my original ones.  The protection circuits seemed to be cutting out all the time and I just didn't feel like messing around with them, so I sold them.  I did use them though as a reference for setting up my Technics SB-M1's that I now have to use as the main stereo pair as my beloved Quad's are gone and that was very helpful.

If they were still here or ever come back, the Quad ESL-63's will once again become my main front stereo speakers and form part of the home theatre system that has grown around them over that time.  Originally I had the Technics SE-A5 to power them back in 1983 and they were used together for more than ten years.  In 1994 when I needed more amplifier channels for the home theatre, I built a Velleman K4040 vacuum tube amplifier to use with the ESL-63's so that the Technics SE-A5 could be used with the center system.  Tube amps are almost as unusual as electrostatic speakers and they have been working perfectly together for the last ten years!  See my K4000 page for more usage details with the ESL-63 speakers.

Pictures and Reference

Unfortunately I have found it difficult to get any really good pictures of the ESL-63 speakers in their current setting because I have quite a coarse grill cloth (sock) on them to maintain sound quality.  The flash from the camera goes right through the cloth and then reflects on the dust cover and the diaphragm making them look nothing like they actually are!  The picture on the top right below is the only one taken with the flash on.

ESL-63's at Lovel road Cambridge England, 1987

Left side ESL-63 (with effects lights, camera & bubble machine!)

Right side ESL-63 (with effects lights & smoke machine!)

Right side ESL-63 taken with low flash

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