Sep 012013
 

Introduction

 

My involvement with music and audio goes back some 45 years. In those early days I could not afford to buy ready-made equipment (save, obviously, a record deck and cartridge) and had to build my own amplifier and speakers. However I read the audio press of the time (which were a better read than today’s audio ‘comics’) and knew of the manufacturers Quad, Leak, Radford, Rogers, Lowther and Tannoy, amongst others, and quickly became fascinated with one brand in particular: that of Quad.

 

The Quad ESL

 

Of all the Quad products this is probably their most famous. I should perhaps refer to it as the Quad 57 ESL (itself a misnomer: the design was announced to the public in 1955, but the error has become sufficiently well promulgated that even Quad themselves accept and use the designation), but I simply regard it as the Quad electrostatic. I became fascinated with the whole principle, theory and operation of electrostatic speakers, however until the Quad design, all preceding designs were either unsuccessful, or were used as tweeters only. Quad were the first to successfully design and market a full-range electrostatic speaker.

This was due in no small part to the work of F. V. Hunt who showed that a constant charge push-pull design would be free of distortion. However it was Peter Walker of Quad who realised that to provide a constant charge on the moving electrode, it would be better to decouple the electrode from the power supply, not through a high value series resistor, but to give the electrode itself a high surface sheet resistance. This would prevent the charge from “moving around” over the surface of the electrode. Quad were able to take advantage of the, then, recently developed polyethylene terephthalate (PET) polymer by ICI.

Once introduced the Quad electrostatic took the audio world by storm for its purity and neutrality, thanks to the lack of an enclosure with its concomitant colourations. Such qualities were immediately recognised by not only audio enthusiasts but by record companies, who used them in their quality control suites and by broadcast authorities. The BBC use (or used to use) Quad ESLs to monitor the quality of their overseas broadcasts.

The BBC Transcription Service’s listening room. Note the ‘remote control’ arrangement of the equipment.

 

As soon as I could afford to do so, I bought a pair in 1974 for the princely sum of £120. They were my second set of speakers (the first were a pair of Wharfdale 8/RS/DD 8″drivers built into 1.25 cubic foot distributed-port cabinets).

 

So, I have lived with and been thoroughly content with the Quads for nearly forty years and I can’t foresee me ever changing them.

No they aren’t perfect – far from it, but then what speaker is? None to date that I have heard! The Quad ESLs have many shortcomings – some might say failures, but I readily acknowledge them and live with them. What are they? Well here’s the list:

1 They don’t do bass. Agreed, they don’t go much below 50Hz and roll of at a rate that is asymptotic to 18dB/octave (i.e. fast).

But what bass they do is pure and clean without any “enhancement” (that is, frequency doubling) by any enclosure. Just listen to a 40Hz note played on an electric bass – it is so clean. And anyway I was never a bass freak – I have attended enough live rock concerts to know I don’t like to have my guts ‘churned’ by high volume bass notes. Nor am I a fan of the pipe organ, so do not miss the deep notes. (The beginning of R. Strauss’s [I]Also Sprach Zarathustra[/I] starts with a bass note of 32Hz, and with some recordings 16Hz. This comes across well enough on the Quads, though it doesn’t have the ‘weight’ that other speakers provide.) Peter Walker designed his speaker with domestic considerations in mind: he had no intention of foisting wardrobe-sized units on anyone. His design was a practical compromise between bass extension and size.

If you want to extend the bass performance, try stacking a pair of Quad ESLs (if you have the room), or use a sub-woofer (which is not without its own set of problems of integration).

2 They can’t be played loud. Agreed, and for many this is a serious shortcoming as it means the Quads cannot really impart a true sense of dynamics.

Without wishing to sidestep the issue, I have attended enough live concerts (especially orchestral concerts) to know that there are very few systems available that can truly reproduce dynamics without compromise. I’m happy with what the Quads can do – when the software allows it (!) I don’t play music loud enough so as to feel I’m having my ears battered. Again, I attended enough rock concerts in my youth to know I have had enough of loud music.

Overdriving the Quads in an attempt to increase the volume is a serious matter: they will be damaged by arcing between the motor and the stator electrodes, if they are fed with an audio signal of greater than 30V. In practice this means 20V rms or about 50W.

3 They are directional; they ‘beam’, so much so there is really only seat (the ‘hot seat’) where one can hear the superb imaging and soundstage. In other words they are anti-social speakers and have been likened to a giant set of headphones – only one listener can enjoy them.

True, and I have had friends complain of the sound staging, until that is, they sit in my chair, or alongside it. Sadly the directional properties, both in the vertical plane and horizontal plane are as a result of the layout of the ‘drivers’ in the speaker. Directionality in the vertical plane is due to all the drivers being ‘line drivers’, that is, consisting of a vertical strips, though this directionality has been somewhat ameliorated by making the drivers curve in a shallow arc. The vertical directivity can be reduced by either raising the speakers about 10″ off the floor or by tilting them forward by raising the rear leg by about 3″ (subject to experimentation). People sat in higher seats when the Quad ESL was designed. Nowadays, easy chairs allow people to sit lower down, so the treble ‘beam’ shoots over the listener’s head. Tilting them forward (at the risk of making them physically unstable) allows the treble beam to be directed at one’s ears. Beaming in the horizontal plane is due to either the width of the treble line driver, or to the interference pattern caused by the mid and bass driver pairs, which flank the central tweeter.

4 They are difficult to house and set up.

Being a doublet, or dipole design, almost as much sound comes from the rear as from the front. Despite some perfunctory sound absorption fitted to the rear of the speaker, behind the driver units, the speakers do need at least three foot of clearance (and preferably 6 foot) between the rear of the speakers and any parallel surface or wall. This means one needs a fairly large room, however Quads ESLs can be used in small rooms and can actually be positioned a couple of feet away from a rear wall, if sound absorbing material is used in between.

5 They are fussy of the amplifier used to drive them

As long as the amplifier is happy driving loads having a large capacitative reactance and driving low impedance loads (at high frequencies above 10kHz, the impedance of the Quad ESL drops to a couple of Ohms), then any amplifier will do. The speaker themselves do have a loading inductance fitted to a secondary winding of the audio transformer, but even so at frequencies above about 200Hz the reactance is capacitative. I have used Quad’s own amplifiers (both valve and solid state), Sugden, and Electrocompaniet solid state and Radford valve, and none have shown the slightest instability when driving the Quads. I am now using early Mark Levinson amplifiers, and these too drive the Quads like a dream.

What the Quads have going for them is a complete freedom from overhang; speed; superb attack and decay; complete absence of cabinet colouration (though there are some mild colourations around 7kHz and 10kHz due to the wooden support frame being insufficiently rigid); with wonderful focus, imaging and sound staging. Accurate rendition of the human voice, both spoken and sung, is very important to me and the Quads do this better than any other speaker I have heard – in fact most speakers sound coloured to me.

Quad electronics

 

At the time I bought the Quad ESLs the only amplifier I had to drive them was a home-built Sugden A21 power amp fed by a Sugden C51 preamp (don’t ask!). 12.5 watts (though it was probably less than that) was insufficient to drive the Quads fully; for a lot of the time the volume control was at near maximum. So the next Quad item acquired was the Quad 405 power amplifier, bought in 1978.

Since the C51 preamp takes it power supply from the power amp, I tapped-off the +50V supply rail of the Quad 405 and used it to supply the C51 via a simple Zener regulated 16V circuit.

When the Quad 405-1 was first introduced, there was much discussion as to how it actually worked, but the audio press generally gave it good reviews, however some commentators had their doubts about the sound quality. A large part of the criticism was directed at the quality of the op-amp used. It is a simple matter to replace this, as well as fitting the necessary by-pass capacitors required to maintain stability. Since then, my Quad 405-1 has been heavily modified, mostly as described in;

http://www.dc-daylight.ltd.uk/the-Hi-Fi-stuff.html

and http://quadrevisionspot.blogspot.co.uk/

With these modifications in place, the Quad 405 is a very good amplifier and an advance over the Sugden class-A designs (as well as the Series 2 Quad valve electronics).

The next Quad item acquired was a tuner: the Quad FM3. Since its arrival, the FM3 has been used every day when at home for the last 33 years. It has provided enormous pleasure listening to everything from Pick of the Pops, the BBC proms, Late Junction, as well as radio plays and documentaries.

I was not entirely happy with the C51 control unit, so for a while used a Hafler DH101 but as soon as it was made available I bought the Quad 44 preamp. This is a highly versatile design, whereby any of the five inputs can be customised through selection of the appropriate input cards. The pick-up input card has provision to adjust the sensitivity as well as the loading impedance. The same applies to the tape input card: allowing me to hook up an elderly Series Six Ferrograph reel-to-reel tape machine and later Uher and Nagra IV-S machines. Another attractive feature of the 44 is the ‘tilt’ control, which provides a 1 or 2dB tilt to the spectrum either up or down. I found this helpful in providing correction to some either dull or over-bright recordings; subtler than could be provided by the usual bass and treble controls of most pre-amps.

Quad 44 preamp (left) with Quad FM4 tuner (right)

 

I have always preferred to assemble my own cables: the choice of DIN connectors by Quad has not made this easy; one has to be adroit, neat and tidy when soldering DIN plugs but it does allow one to make up better leads than the ‘freebies’ provided. I use metal-clad Preh or Neutrik plugs with either Neumann microphone cable or RG 174 coaxial cable. (My system at that time used a mixture of RCA ‘phono’, DIN and ¼” jack plugs, more recently Canon XLR, Tuchel and CAMAC connectors have been added to the menagerie!)

Again the first version of the 44 suffered some problems. These were corrected in the second version; largely due to a redesign of the motherboard as well as improved quality components. The best version to buy is the last – only available in grey livery with grey buttons, it can be recognised by the additional +/-3dB setting on the tilt control and by the absence of the ‘cancel’ LED between the tilt control and the high frequency filter/slope control.

I have always found Quad gear to be reliable, but nothing is perfect. Because I cannot be without my system, I like to have replacements to fall back on, should and when the Quad gear needs attention. To this end I acquired a complete set of Series 2 valve electronics: a pair of Quad II power amps with Quad 22 preamplifier and Quad FM1 tuner many years ago for £75. It was interesting comparing the valve ‘sound’ with that of the Series 4 solid-state electronics. It was also amusing to try some tube ‘rolling’, but in the end the whole system was inconvenient to use; so I gave it away to a friend of mine (where they sounded very ‘nice’ feeding his Lowther Acousta horn-loaded speakers).

 

Copyright QuadTop: Quad II power amplifiers. Bottom: Quad 22 control unit (left) and FM1 tuner (right). [Image Copyright Quad]

 

To replace the Series 2 Quad valve electronics, I bought the Quad 33 with Quad 303 combination. I have always wanted a 33/303 since I first started getting involved with audio. When first introduced they were very well received by both audio enthusiasts and by professional users: The BBC used hundreds of them, as did groups like The Pink Floyd. They work superbly well into the Quad ESLs for a couple of reasons. First, despite having a fairly high output impedance of 0.1Ω, owing to the very low mass of the moving electrode of the Quad ESL, the amplifier has to provide very little damping (to stop the “tail wagging the dog”). Secondly, despite the Quad 303 using capacitor coupling, the series capacitance resonates with the inductance of the audio transformer of the speaker to flatten out the effective speaker impedance and extend the low frequency response.

Quad 33 preamp and Quad FM3 tuner fitted in the wooden sleeve.

 

The Quad 33 preamp design is “of its time” and now sounds dated – as do all other preamp designs of the mid-to-late ‘60s: be they Leak, Radford, Lowther or Sugden. Like all Series 3 electronics, specialist companies such as Dada and NET can improve both the 33 and 303. There is only so much improvement that can be done to the 33 (such as modifying one of the inputs to suit the output from a CD player and improving the power supply), more so with the 303: but even unmodified they produce a very smooth, satisfying and ‘comfortable’ sound (often referred to as “pipe and slippers”) devoid of ‘nasties’, if not the last word in resolution. Given the reasonable price of used units available on eBay, the 33/303 combination represents very good value for money. I have two 303 amplifiers: one fitted with the conventional sockets and a second fitted with Cannon XLR connectors.

 

Quad 303 power amplifier fitted with Cannon connectors

 

Quad 303

 

The 33/303 combination was used for a few years to relay the audio channels from my DVD player and digital TV decoder, running into Bowers & Wilkins DM2A speakers.

 

Quad 33 preamplifier, FM3 tuner, 405-1 (to the right on the record cabinet) and 303 (on floor) power amplifiers.

 

Before Quad introduced the 303 design, they had already designed a 50W solid-state single channel amplifier: the Quad 50E. This was intended for use by professional organisations only, such as recording studios, broadcast organisations (such as the BBC) and others (such as British Rail). It is an interesting design, in so far it was one of the first solid state power amp designs to use a regulated power supply with choke smoothing, but more importantly it uses an output transformer to couple to the speaker. On the 50E there are four 17V secondary windings and four 8.5V secondary windings. To configure the output to be suitable to drive Quad ESLs, the four 8.5V windings are connected in series as two pairs (to make two 17V), and these pairs connected in parallel with the four 17V windings. That way the ESLs are never subjected to more than 17V, which is within their operating specification. Of course by connecting the eight windings in other series/parallel combinations, speaker loads of anywhere between 5.8Ω and 200Ω can be accommodated, with maximum voltages of 17V to 102V respectively. The BBC was a major user of the 50Es as well as the customised 50D (which only had four 17V tappings, permitting 50W into loads of 8 -32Ω). Both of my Quad 50Es are ex-BBC – the only distinction being the replacement of the usual Bulgin 3-pin mains connector with a Cannon XLR type.

 

Quad 50E

 

One of the disadvantages of using either the 50E or 50D is the use of Plessey ‘Paignton’ connectors. These are no longer made, and whilst still available they are now very expensive.

The 50E can have its input configured to allow the use of a 600Ω – balanced line. This is achieved through the fitting of a transformer having a centre-tapped primary (such as the Sowter type 3654). I acquired a pair of 50Es to use as monoblocks, placed directly behind each speaker and connected to the preamp via balanced-line interconnects. I didn’t use the octal-base Sowter transformers, but used German studio-grade Beyer transformers: type TR/BV 3 061-060.

For the last three or so years the Quad FM3 tuner has been replaced with a Quad FM4. This was bought since I listen to more than one station (these being Radio 2, Radio 3, Radio 4 and sometimes Jazz FM and Classic FM), and liked the idea of being able to store these as presets. I also liked the idea of a tuner using a conventional tuning knob with a digital frequency display.

The FM4 is well regarded by many: the BBC selected it as being representative of a high quality tuner that their listeners might use, and with it they check the quality of their broadcasts. Compared to the FM3, the FM4 has a slightly ‘dryer’ sound, which I feel better suits the human voice. The inclusion of the FM4 completes the Series 4 electronics.

A couple of years ago I acquired a Quad AM3 and was given a Quad FM2 (valve) tuner. I very briefly tried the (European version) AM3 with a rudimentary ‘washing line’ aerial; mostly to listen to the World Service, but it now is no longer used and is kept as an objet d’art, along with a Quad AM1 tuner (also valve) I was given, the styling of the latter matching the Series 2 electronics. Compared to both the FM3 and FM4, the FM2 has a sweeter, warmer sound.

 

Quad AM3 tuner

 

Quad FM2 tuner

 

Top: Quad AM1 tuner (note that the company then was called “Acoustical”) Bottom: Quad AM3 tuner (European version). Both AM tuners employ valves

Lately I have bought two Quad 405-2 power amps: one being a late version with power switch and RCA phono connectors – necessary as I had replaced my preamplifier with one made by Mark Levinson; and the second, also a late version but fitted with NET dual-mono power supplies.

Finally, about four years ago I bought a Quad 520f power amplifier. This is a 150W/channel professional amplifier designed to be used in theatres, cinemas and recording studios. Again there are special versions of this amp customised for the BBC, and several of them are used for the sound reinforcement at the House of Commons.

 

Quad 520f power amplifier

Usually so-called professional power amplifiers are a case of superb reliability at the expense of sound quality. This is not the case with the 520f (the “f” stands for the provision to have a completely floating balanced-line input), it has enormous authority, yet is delicate, detailed and completely lacking in harshness or grain. I didn’t expect it to sound so good as it does. It now replaces the 33/303 combination used with the TV, where it is driven by a Mark Levinson ML10A preamp and runs into B&W DM2A speakers.

 

Summary

 

For the last forty years my listening pleasure has involved at least one Quad product or another. I hold Quad in very high regard, being one of the few British audio manufacturers that “got it right”; the Quad name is well respected worldwide and is something to be proud of. Their designs were the product of no-nonsense engineering, made by people who knew what musical instruments ought to sound like (Peter Walker played clarinet in a dance band) and priced reasonably. All Quad products are very reliable and although the company is now owned by the Chinese, all servicing is still carried out by engineers in Huntingdon who continue to provide a customer care service that is second to none.

Used samples of the series 2, 3 and 4 electronics all maintain their resale value, yet still represent excellent value for money. You get a lot of good quality sound for your pound.

As to the most recent Quad designs (the 909 power amp and CDP 99 player), these have also received good reviews, but there are reports filtering through the grapevine that the Chinese company are now using inferior home-sourced components (capacitors in particular) to the detriment of sound quality and, sad to say, to the reputation of the Quad name.

It might appear to some that I’m a bit of a “completist (?)” where it comes to Quad gear. True – I confess; I am a bit of a collector who admires the superb build quality and aesthetics of Quad gear, however there are many other enthusiasts out there who have far larger collections than I.

However lest you think I am a “dyed in the wool” Quad fanatic, I prefer to think of myself as a Quad enthusiast: my loyalties do have their limit – since the beginning of 2013, the amplification in my main system has been all Mark Levinson and I have recently been experimenting with a Radford STA15 Mk. III valve power amplifier.

 

Barry Hunt 

 

© Text Copyright and all photos 2013 Barry Hunt, except where noted and the Copyright there belongs with the named party. 

NB No part or portion of this article may be reproduced or quoted without written permission, failure to do so may result in legal proceedings.

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